25 Mar 2017

Astronomers find unexpected, dust-obscured star formation in distant galaxy

Pushing the limits of the largest single-aperture millimetre telescope in the world, and coupling it with gravitational lensing, University of Massachusetts Amherst astronomer Alexandra Pope and colleagues report that they have detected a surprising rate of star formation, four times higher than previously detected, in a dust-obscured galaxy behind a Frontier Fields cluster.

170323125453_1_900x600As Pope explains, "This very distant, relatively typical galaxy is known to us, and we knew it was forming stars, but we had no idea what its real star-formation rate was because there is so much dust surrounding it. Previous observations couldn't reach past that. Finding out that 75 percent of its star formation was obscured by dust is remarkable and intriguing. These observations clearly show that we have more to learn."

She adds, "Historians want to know how civilizations were built up, and we astronomers want to know where and how the elements in the universe were formed and where everything is made of, came from." The study is accepted for publication in The Astrophysical Journal.

The new tool that has made such revelations possible is the 50-meter Large Millimeter Telescope (LMT) which has been observing as a 32-meter telescope located on an extinct volcano in central Mexico in "early science mode" since 2013. Operated jointly by UMass Amherst and Mexico's Instituto Nacional de Astrofísica, Optical y Electronica (INAOE), it offers astonishing new power to peer into dusty galaxies, the astrophysicist says.

Pope, an expert at analysing how dust masks star formation, says tracing dust-obscured galaxies at early epochs offers good signposts for understanding how the universe became enriched with metals over time. "We know at the basic level that metals are formed in stars, but the rate of build-up over cosmic time we don't know," she points out. "We know what we see today but we don't know how it came about, and we want to fill in that picture."

Overall, she and colleagues write, "This remarkable lower-mass galaxy showing signs of both low metallicity and high dust content may challenge our picture of dust production in the early universe."

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Before the AzTEC camera on the LMT took observations of this galaxy, astronomers relied on Hubble Space Telescope images to study star formation, Pope says. But most star formation is obscured by dust, so the Hubble images could not make a complete census of the build-up of stars in this galaxy. "Previous millimetre observations have been limited to the most extreme dusty galaxies. With this study, we have detected a surprisingly high rate of dust-obscured star formation in a typical galaxy in the early universe."

With gravitational lensing, researchers use a foreground mass -- another galaxy or a galaxy cluster -- as a lens. As light from very distant, background galaxies passes through, it is magnified. "This technique offers a way to see things that are much fainter than your telescope can see," she notes. As traced in Hubble images, the lensed galaxy they studied in the Frontier Fields cluster showed it forming only about four solar masses of new stars per year, which is a "fairly typical" observation and unsurprising to astronomers today, Pope says. "But then the LMT observations revealed another 15 solar masses per year, which means we had been missing about three-quarters of the star formation going on."

She adds, "We are not yet at the level of detecting all of the star formation going on, but we are getting better. One of the big goals for us is to push observations at longer wavelengths and to trace these very dusty galaxies at early epochs. We are pushing observations in this direction and the fact that Hubble found only one quarter of the star formation in this distant normal galaxy is a huge motivation for doing a lot more studies like this."

As early as next year, Pope and her colleague Grant Wilson will install on the LMT a new state-of-the-art imaging system he is building, dubbed TolTEC. It will offer mapping speed 100 times faster than the LMT's current capability making it the fastest millimetre-wavelength polarimetric camera on Earth for conducting deep surveys of the universe, Wilson says. It should allow astronomers to create a census of star-forming galaxies, and observations that require five years to complete today will be done in a little over one week.

Pope says, "Currently, our census of dust-obscured star formation activity in galaxies is severely incomplete, especially in the distant universe. With TolTEC on the LMT, we will be able to make a complete census of dust-obscured star formation activity in galaxies over 13 billion years of cosmic time.

24 Mar 2017

NASA to slam a spaceship into an asteroid for practice

2-aidadoublemiNASA and the European Space Agency want to ram into an asteroid in a bid to save humanity from a “Deep Impact”-style catastrophe.

They want to see whether it’s possible to deflect a space rock from its course as part of a planetary defence mission.

Fears over potentially deadly asteroids are at an all time high after the White House issued an “emergency defence plan” in the event of a collision late last year.

Esteemed British astrophysicist and cosmologist Lord Martin Rees recently warned that the government should be spending “millions” on planetary defence.

The proposed mission will use two spacecraft, one to be launched by the ESA in 2020 and the other by NASA in 2021.

The first spaceship, dubbed AIM (for Asteroid Impact Mission) will orbit around 65803 Didymos, which was discovered in 1996.

The NASA spacecraft, called DART (Double Asteroid Redirection Test) will be timed to hit the rock a few months later, at a speed of nearly four miles per second.

AIM’s telescopes will monitor where stray pieces of rock end up.

The mission is to figure out whether deflection is the best defence from a stray space rock.

There’s a danger that crashing into the asteroid could cause fragments to break off and potentially speed up its trajectory.

untitledThe shrapnel could pose a risk to Earth, too.

“When we have a high-speed impact on an asteroid, you create a crater,” explained Andrew Cheng, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland said.

Cheng, who is lead investigator for the NASA side of the project, told Cosmos: “You blow pieces back in the direction you came from.”

The mission is yet to get the green light as it waits to confirm funding.

But planetary defence is a hot topic among scientists.

NASA have previously warned that Earth is “due an extinction level attack”.

But there’s little in place to stop one from causing absolute mayhem.

On the bright side, asteroids fly by Earth regularly and most are small enough to burn up in the atmosphere, completely unnoticed.

2 Mar 2017

There's a Massive, Glowing Blob in the Universe, and a Mystery Source Is Lighting It Up

lya-nebula_1024Astronomers have discovered a vast, glowing blob of gas in the distant Universe, and they can't figure out what's actually lighting it up.

This glowing nebula is located at the centre of an enormous 'protocluster' of early galaxies some 10 billion light-years from Earth, and is the brightest cosmic object of its kind ever found. And yet, there's no obvious source of its power.

The object, called an 'enormous Lyman-alpha nebula' (ELAN), is not only the brightest object of its kind found in the Universe - it's also one of the biggest, rivalling even the 'Slug Nebula', which stretches 2 million light-years through intergalactic space.

"It's extremely bright, and it's probably larger than the Slug Nebula, but there's nothing else visible except the faint smudge of a galaxy," says one of team, J. Xavier Prochaska, from the University of California, Santa Cruz.

"So it's a terrifically energetic phenomenon without an obvious power source."

Only a handful of ELANs have been discovered so far, and these accumulations of gas are thought to be part of a network of filaments that connect neighbouring galaxies to each other in the vast cosmic web of the Universe.

While other ELANs appear to be powered by the intense radiation given off by quasars, star formation, or supernovae, no such events could be found near this latest example, dubbed the MAMMOTH-1 nebula.

What we do know is the light has the same wavelength that's absorbed and emitted by hydrogen atoms as they cool down - a discharge known as Lyman-alpha radiation - but it's not clear what's been heating them up.

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The find recalls a discovery in 2000 of another ELAN, known as the Lyman-alpha blob 1, located in the southern constellation of Aquarius, some 11.5 billion light-years from Earth.

Stretching three times larger than our own Milky Way galaxy, this thing is ginormous and extremely green, but to this day, no one can say what's illuminating it.

Scientists have suggested that supermassive black holes swallowing matter in galaxies within the central region of the blob could be responsible, and now the team behind this new discovery suspect the same thing is happening to the MAMMOTH-1 nebula.

The MAMMOTH-1 nebula was found by a survey called Mapping the Most Massive Over densities Through Hydrogen (MAMMOTH), which was also responsible for finding the Slug Nebula back in 2014.

The protocluster it's found in is massive, hosting an unusually high concentration of galaxies in an area of about 50 million light-years across - all bound together by gravity.

While the galaxies are now mature, our telescopes are only just seeing them as they would have looked a mere 3 billion years after the Big Bang - the peak of galaxy formation in our Universe.

Several hypotheses have been put forward for how the MAMMOTH-1 nebula at the heart of this great protocluster got so bright, but the most likely ones revolve around radiation or discharges coming from something called an active galactic nucleus (AGN).

AGNs are compact regions at the centre of galaxies that have a much higher than normal luminosity. The team explains that AGNs are powered by a supermassive black hole actively feeding on gas in the centre of a galaxy, and are known for being extremely bright sources of light.

The intense radiation emitted by AGNs ionise the hydrogen gas in the space around it, and this could prompt the ELANs to emit super-bright Lyman-alpha radiation.

Quasars - the brightest objects in the Universe - are known for being the most luminous AGNs in visible light, except the MAMMOTH-1 nebula is not associated with a quasar, as far as the researchers can tell.

But that doesn't mean there isn't one lurking in the background.

"It has all the hallmarks of an AGN, but we don't see anything in our optical images. I expect there's a quasar that is so obscured by dust that most of its light is hidden," Prochaska says.

The team has its work cut out for it in trying to spot a single quasar some 10 billion light-years from Earth, and until then, the brightest known ELAN will remain a cosmic mystery.

The research has been accepted for publication in the Astrophysical Journal, and you can read it in full at the pre-print website, arXiv.org.

What Cassini's Daring Ring-Dive Around Saturn Could Tell Us About Uranus

Ashampoo_Snap_2017.03.02_02h17m12s_001_Glowing in pale blue, Uranus looks like a ghostly planet in pictures taken from the only spacecraft to ever visit it: Voyager 2. Due to the planet's great distance from Earth, follow-up studies of the planet began only in the late 1990s when telescope optics improved. Since then, Uranus has remained a low priority for observational institutions.

That's unfortunate for scientists looking to learn more about the faint rings of Uranus, discovered 40 years ago this year. Two airborne campaigns were set up to watch Uranus pass in front of a star in 1977. And both were taken aback when they found rings circling the planet. One of the teams missed three of the rings because they were so surprised by the find.

There are hopes that a spacecraft will fly to Uranus or Neptune in the 2020s or 2030s. NASA is undertaking early-stage feasibility studies. So it will remain to the plucky Cassini spacecraft, in orbit around Saturn since 2004, to show scientists what it can about the rings of Uranus by analogy with Saturn.

"At the time of the Uranian discovery, we had never seen narrow, dense rings before," said Mark Showalter, a planetary astronomer at the Search for Extra terrestrial Intelligence Institute. "The narrow rings of Saturn behave similarly to the rings of Uranus," he added, "so that has enabled us to understand dense rings a little bit better."

Cassini is in the final year of its epic mission, and is taking a rare close look at Saturn's rings in the coming weeks. The spacecraft is in the midst of performing 20 "ring-grazing orbits" that will allow for the best views of them since Cassini's arrival in 2004. The manoeuvres began in November and run through April.

"[W]e expect to see the rings, along with the small moons and other structures embedded in them, as never before," Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in California, said in a statement. "The last time we got this close to the rings was during arrival at Saturn in 2004, and we saw only their backlit side. Now we have dozens of opportunities to examine their structure at extremely high resolution on both sides."

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Following completion of the ring orbits, Cassini will perform unprecedented dives between Saturn and its rings between April and September. Then, on September 15, Cassini will make a suicidal plunge into Saturn itself to protect icy worlds like Enceladus from the small chance of Cassini crashing into and contaminating their surfaces.

But before that, Showalter points out, Cassini will provide more insights on what is happening within the Uranus system, even though the spacecraft is surveying a completely different planet. The wobbles in Saturn's narrow rings appear to move in similar ways that Uranian rings do, for example.

But there are still several mysteries that may take another Uranian mission to resolve.

For example, images from Voyager 2 depicted dust rings surrounding the main ring system of. Then, when Uranus reached its equinox (closest point in its orbit) in 2008, observations from the Keck Telescope imaged the rings when they were edge-on from Earth, making it easier to identify the presence of any dust. It appears that the dust has shifted 3,100 miles between the two observations, Showalter said. The reason for the shift remains poorly understood.

Another open question is the role that the moons Cornelia and Ophelia play in shepherding the outer ring of Uranus — a phenomena also seen around Saturn. But the rings around Uranus are more difficult to observe right now because the planet is in an area of the sky with fewer stars, Showalter said, meaning the planet remains obscure more than it did in the 1970s and 1980s.

Showalter has been very busy in the past few years working on both the New Horizons mission, which passed by Pluto in 2015, as well as Cassini. He says he hopes to pull out some older data on Uranus soon to learn more about the planet's ring system, and to provide some insight for whenever a spacecraft does visit the Blue World again.
 

28 Feb 2017

NASA study hints at possible change in water 'fingerprint' of comet

134387_webA trip past the sun may have selectively altered the production of one form of water in a comet - an effect not seen by astronomers before, a new NASA study suggests.

Astronomers from NASA's Goddard Space Flight Center in Greenbelt, Maryland, observed the Oort cloud comet C/2014 Q2, also called Lovejoy, when it passed near Earth in early 2015. Through NASA's partnership in the W. M. Keck Observatory on Mauna Kea, Hawaii, the team observed the comet at infrared wavelengths a few days after Lovejoy passed its perihelion - or closest point to the sun.

The team focused on Lovejoy's water, simultaneously measuring the release of H2O along with production of a heavier form of water, HDO. Water molecules consist of two hydrogen atoms and one oxygen atom. A hydrogen atom has one proton, but when it also includes a neutron, that heavier hydrogen isotope is called deuterium, or the "D" in HDO. From these measurements, the researchers calculated the D-to-H ratio - a chemical fingerprint that provides clues about exactly where comets (or asteroids) formed within the cloud of material that surrounded the young sun in the early days of the solar system. Researchers also use the D-to-H value to try to understand how much of Earth's water may have come from comets versus asteroids.

The scientists compared their findings from the Keck observations with another team's observations made before the comet reached perihelion, using both space- and ground-based telescopes, and found an unexpected difference: After perihelion, the output of HDO was two to three times higher, while the output of H2O remained essentially constant. This meant that the D-to-H ratio was two to three times higher than the values reported earlier.

"The change we saw with this comet is surprising, and highlights the need for repeated measurements of D-to-H in comets at different positions in their orbits to understand all the implications," said Lucas Paganini, a researcher with the Goddard Center for Astrobiology and lead author of the study, available online in the Astrophysical Journal Letters.

Changes in the water production are expected as comets approach the sun, but previous understanding suggested that the release of these different forms of water normally rise or fall more-or-less together, maintaining a consistent D-to-H value. The new findings suggest this may not be the case.

"If the D-to-H value changes with time, it would be misleading to assume that comets contributed only a small fraction of Earth's water compared to asteroids," Paganini said, "especially, if these are based on a single measurement of the D-to-H value in cometary water."

The production of HDO in comets has historically been difficult to measure, because HDO is a much less abundant form of water. Lovejoy, for example, released on the order of 1,500 times more H2O than HDO. Lovejoy's brightness made it possible to measure HDO when the comet passed near Earth, and the improved detectors that are being installed in some ground-based telescopes will permit similar measurements in fainter comets in the future.

The apparent change in Lovejoy's D-to-H may be caused by the higher levels of energetic processes - such as radiation near the sun - that might have altered the characteristics of water in surface layers of the comet. In this case, a different D-to-H value might indicate that the comet has "aged" into a different stage of its lifecycle. Alternatively, prior results might have ignored possible chemical alteration occurring in the comet's tenuous atmosphere.

"Comets can be quite active and sometimes quite dynamic, especially when they are in the inner solar system, closer to the sun," said Michael Mumma, director of the Goddard Center for Astrobiology and a co-author of the study. "The infrared technique provides a snapshot of the comet's output by measuring the production of H2O and HDO simultaneously. This is especially important because it eliminates many sources of systematic uncertainty."

27 Feb 2017

Black History Month: Benjamin Banneker (1731-1806)

rglogo1_SHARPEN projectsFor some years, Benjamin seems to have served as an indentured labourer on the Prince George’s County plantation of Mary Welsh, who had dealings with the Bannaky family and in 1773 executed her dead husband’s instructions to release several of her labour force, including “Negro Ben, born free age 43”.

Welsh was surely not Banneker’s grandmother, as argued by many biographers, but she did leave him a substantial legacy. He then lived alone as a tobacco farmer near the Patapsco River.

By tradition, Banneker received only a brief education from a Quaker schoolmaster. But he showed an early talent for mathematics and construction when, aged 21, he built a model of a striking clock, largely out of wood, which became renowned in his neighbourhood. He read widely and recorded his researches. His skills drew him into contact with a wealthy white family, the Ellicotts, who had established flour mills and an iron foundry on the outskirts of Baltimore in the mid-1770s.

In 1788, George Ellicott, a keen amateur astronomer, lent Banneker books and instruments that enabled him to construct tables predicting the positions of the stars and future solar and lunar eclipses. Three years later, Andrew Ellicott hired Banneker to assist him in surveying the boundaries of the ten-mile-square site of the future federal capital of Washington, DC.

In that year, too, Banneker won the backing of several Philadelphia supporters of the anti-slavery cause to print his work in the popular form of an almanac. Its 1792 publication, introduced by letters pointing out how Banneker’s accomplishments disproved the myth of Negro inferiority, was a considerable success and produced 27 further editions of Banneker’s Almanac over the next five years.

Banneker sent a manuscript copy of his work to Secretary of State Thomas Jefferson, along with a plea against the continuance of black slavery, and received a courteous, if evasive, reply. But Jefferson praised Banneker as “a very respectable mathematician” in forwarding the manuscript to the notice of the French Academy of Sciences. Banneker continued to live on his farm, in declining health, and died on October 9, 1806. Only fragments of his later writings survive, as most perished in a fire after his death. His life and work have become enshrouded in legend and anecdote.

But his achievements ranked him among other American scientists of the time, and they were the more remarkable as the product of patient, lifelong self- education, emerging out of humble origins.

Sources: Silvio Bedini, The Life of Benjamin Banneker (New York: Scribner’s, 1972); Charles A. Cerami, Benjamin Banneker: Surveyor, Astronomer, Publisher, Patriot (New York: Wiley, 2002); George Ely Russell, “Molly Welsh: Alleged Grandmother of Benjamin Banneker,” National Genealogical Society Quarterly, 94 (December 2006): 305-14

Radio telescope in Pune to detect faint objects from distant worlds

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The fully upgraded system of the Giant Metre wave Radio Telescope (GMRT), one of the largest telescopes in the world located near Pune, will be powerful enough to detect fainter objects in the universe that are yet to be observed, said Yashwant Gupta, dean, GMRT Observatory and senior professor, National Centre for Radio Astrophysics, on Sunday.

Speaking on the side-lines of the Science at the Sabha, organised by the Institute of Mathematical Sciences in the city, he said the up gradation of the GMRT by the end of this year will see its sensitivity increased threefold enabling astronomers to observe more objects and phenomena in the universe. "We are upgrading it to see over a much larger range of frequencies at any given time. It means we can get more data and see more details of the universe," he said.

Built in 1995, the GMRT is an array of 30 telescopes that observes radiation coming in from space with a wavelength in the order of radio frequencies. The resolution with which objects can be observed depends on the size of the telescope's antenna. "We are replacing the entire electronics of the antennas from the top all the way down to the end where the data is collected through receivers and analysed," he said.

The GMRT, which is used by astronomers in India and abroad, can study distant galaxies, black holes, high energy objects and events happening billions of light years away. "The upgrade is largely being carried out in India by experts who have gathered knowledge over the years. We are installing, testing and validating the systems." With GMRT, India has found new, highly magnetized, rapidly rotating neutron stars and identified new galaxies and their properties.

On the recent detection of seven earth-sized planets orbiting a star by NASA telescopes, Gupta said more such planets that are habitable would be found. "There are millions of stars like the sun in the galaxy and a solar system is expected to develop around each of them. With powerful transmitters and receivers, we may be able to establish communication with these planets," he said.

Minor planet named Bernard

170217095907_1_900x600_SHARPEN projectsA minor planet in the Solar System will officially be known as Bernard Bowen from today after Australian citizen science project the Skynet won a competition to name the celestial body.

The minor planet was named by the International Centre for Radio Astronomy Research (ICRAR) in honour of their founding chairman Dr Bernard Bowen.

Bernard Bowen sits in the asteroid belt between Mars and Jupiter and takes 3.26 Earth years to orbit the Sun.

The minor planet was discovered on October 28, 1991, and until now has been known as (6196) 1991 UO4.

Based at ICRAR, the Skynet has been running since 2011 and sees citizen scientists donating their spare computing power to help Australian astronomers uncover the mysteries of the Universe.

Its 50,000-odd volunteers entered an International Astronomical Union (IAU) contest to name planets beyond our Solar System.

Project founders ICRAR also won the right to name a minor planet within our Solar System.

Bernard Bowen was one of 17 minor planets to be christened today.

Other newly named minor planets include Kagura, after a traditional Shinto theatrical dance, and Mehdia, which is equivalent to the Arabic word for gift.

Dr Bowen has presided over scientific advances ranging from the oceans to the skies. He was instrumental in the establishment of ICRAR in 2009, and helped bring part of the Square Kilometre Array telescope to Western Australia.

A full list of the citation of the minor planets can be found at the IAU Minor Planet Circular. http://bit.ly/2lGgktg

Bernard Bowen on the Minor Planet Centre site, including an interactive showing its position in the Solar System. http://bit.ly/2kYXs72

Saturn's rings viewed in the mid-infrared show bright Cassini division

170224092557_1_900x600 bA team of researchers has succeeded in measuring the brightness's and temperatures of Saturn's rings using the mid-infrared images taken by the Subaru Telescope in 2008. The images are the highest resolution ground-based views ever made. They reveal that, at that time, the Cassini Division and the C ring were brighter than the other rings in the mid-infrared light and that the brightness contrast appeared to be the inverse of that seen in the visible light. The data give important insights into the nature of Saturn's rings.

The beautiful appearance of Saturn and its rings has always fascinated people. The rings consist of countless numbers of ice particles orbiting above Saturn's equator. However, their detailed origin and nature remain unknown. Spacecraft- and ground-based telescopes have tackled that mystery with many observations at various wavelengths and methods. The international Cassini mission led by NASA has been observing Saturn and its rings for more than 10 years, and has released a huge number of beautiful images.

Subaru Views Saturn

The Subaru Telescope also has observed Saturn several times over the years. Dr. Hideaki Fujiwara, Subaru Public Information Officer/Scientist, analysed data taken in January 2008 using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the telescope to produce a beautiful image of Saturn for public information purposes. During the analysis, he noticed that the appearance of Saturn's rings in the mid-infrared part of the spectrum was totally different from what is seen in the visible light

Saturn's main rings consist of the C, B, and A rings, each with different populations of particles. The Cassini Division separates the B and A rings. The 2008 image shows that the Cassini Division and the C ring are brighter in the mid-infrared wavelengths than the B and A rings appear to be. This brightness contrast is the inverse of how they appear in the visible light, where the B and A rings are always brighter than the Cassini Division and the C ring.

"Thermal emission" from ring particles is observed in the mid-infrared, where warmer particles are brighter. The team measured the temperatures of the rings from the images, which revealed that the Cassini Division and the C ring are warmer than the B and A rings. The team concluded that this was because the particles in the Cassini Division and C ring are more easily heated by solar light due to their sparser populations and darker surfaces.

On the other hand, in the visible light, observers see sunlight being reflected by the ring particles. Therefore, the B and A rings, with their dense populations of particles, always seem bright in the visible wavelengths, while the Cassini Division and the C ring appear faint. The difference in the emission process explains the inverse brightness's of Saturn's rings between the mid-infrared and the visible-light views.

Changing Angles Change the Brightness's

It turns out that the Cassini Division and the C ring are not always brighter than the B and A rings, even in the mid-infrared. The team investigated images of Saturn's rings taken in April 2005 with COMICS, and found that the Cassini Division and the C ring were fainter than the B and A rings at that time, which is the same contrast to what was seen in the visible light.

The team concluded that the "inversion" of the brightness of Saturn's rings between 2005 and 2008 was caused by the seasonal change in the ring opening angle to the Sun and Earth. Since the rotation axis of Saturn inclines compared to its orbital plane around the Sun, the ring opening angle to the Sun changes over a 15-year cycle. This makes a seasonal variation in the solar heating of the ring particles. The change in the opening angle viewed from the Earth affects the apparent filling factor of the particles in the rings. These two variations -- the temperature and the observed filling factor of the particles -- led to the change in the mid-infrared appearance of Saturn's rings.

The data taken with the Subaru Telescope revealed that the Cassini Division and the C ring are sometimes bright in the mid-infrared though they are always faint in visible light. "I am so happy that the public information activities of the Subaru Telescope, of which I am in charge, led to this scientific finding," said Dr. Fujiwara. "We are going to observe Saturn again in May 2017 and hope to investigate the nature of Saturn's rings further by taking advantages of observations with space missions and ground-based telescopes."

25 Feb 2017

Theoretical battle: dark energy vs. modified gravity

untitled_SHARPEN projectsTwo decades ago, scientists found that the Universe’s expansion is accelerating. This was the complete opposite of what had been expected: the expansion should be slowing down due to gravity, not speeding up.

At first, researchers didn’t know how to account for it. But they went back to Einstein’s equations for his General Theory of Relativity and discovered that a term he’d abandoned as his “biggest blunder”—the cosmological constant—actually described this expansion pretty well. There was only one problem: we can’t see the energy that’s driving the expansion. Nonetheless, researchers have gravitated to the idea that the energy is there, and they've labelled it dark energy. With time, dark energy has become a cornerstone of our current model of the Universe.

But not everyone was convinced. Some wondered if there was another way to explain the Universe’s accelerating expansion. One possibility is that gravity doesn’t work the same way on cosmological scales as it does on local scales. The idea is appealing in that it doesn’t require the existence of a vast amount of stuff that we can’t figure out how to observe. While the idea hasn't gained much traction, it also hasn't been ruled out.

The Speed of Gravity

dark_energy-4e8b278-introEarly last year, scientists at the upgraded LIGO facility ushered in a new era of astronomy when they detected gravitational waves. Among many other things, this opens the door for researchers to definitively measure the speed at which gravitational waves propagate. One way this could be done is by comparing the arrival times of gravitational waves to the arrival of light generated by the same event. A possible source of radiation associated with LIGO’s first gravitational wave source has been identified, but there’s controversy over whether the two are from the same event.

A team of researchers, expecting a measurement to be made soon, set to work on the theoretical side to determine what we can learn from the speed of gravity, which, it turns out, has consequences for the dark energy conundrum. If one of the modified gravity scenarios (the alternatives to dark energy) is true, it would have implications for the propagation of gravitational waves over cosmological scales.

Specifically, the researchers determine, a universe with dark energy would have the speed of gravity equal to that of light. If the two speeds are not the same, then there is no dark energy, and we need to come up with an alternative theory of gravity.

Conclusions

Not content to simply wait for LIGO to produce the data, the researchers proceeded to revaluate existing data to get an idea of how likely modified gravity scenarios are, given the speed restriction. If the Universe is able to accelerate itself through some modified gravity mechanism, we might be able to find some sign of it.

The researchers derived the minimum alterations to gravity that would cause the Universe to accelerate its expansion without dark energy. They then compared the consequences of that model to the data. They examined things like “geometric probes, [cosmic microwave background] data, and constraints from weak lensing, galaxy clustering, and the structure growth rate.” The overall conclusion? The likelihood of a modified gravity is pretty low, three standard deviations less likely than dark energy.

“Although marginally still possible, our result sets a challenge to the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity,” the authors conclude. They do mention the possibility of exotic alterations to gravity that could produce the same observations. But overall, the paper raises hard questions for the alternative gravity models.

Either way, Advanced LIGO could give us an additional test very soon, and it may have done so already—two events that are under analysis triggered an alert to other telescopes.

NASA ordered to return historic lunar bag, moon dust to highest bidder

920x920Nancy Lee Carlson will finally get her moon dust back.

A federal judge Friday ordered the Johnson Space Center to return the Illinois woman's lunar collection bag and the dusty specimens left inside from the historic 1969 moon landing.

The bag and its contents - a rare find that a NASA lawyer deemed a "national treasure" - had languished at the space centre for more than a year after scientists decided to keep it.
 
"There are no other lunar bags out there," said Joseph Gutheinz, a former NASA enforcement officer and moon rock hunter who supported Carlson's effort. "It's unique as all get out. And because of that, the value of that bag is incalculable."

U.S. District Judge Vanessa D. Gilmore in Houston ruled that Carlson is the bag's true owner, having bought it at a government auction for $995 in 2015.

The government may have erred in putting the bag up for sale, but government lawyers erred further by not appealing another judge's ruling on ownership, Gilmore concluded.

The bag is set to be covertly returned on Monday.

When the Apollo 11 capsule splashed down near Hawaii in July 1969, its celebrated crew came bearing loads of soil and rock stashed in specially designed collection bags.

The embroidered and zippered bag now owned by Carlson was among them, covered in microscopic moon dust and rock particles that NASA scientists discovered were difficult to remove.

Decades later, the round bag - about the size of a dinner plate - turned up in the home of a Kansas space museum's director, where it was seized by federal agents in an unrelated criminal case.

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The U.S. Marshal's office finally put it up for auction in 2014 as a "flown zippered lunar sample return bag with lunar dust. 11.5 [inches]. Tear at Center. Flown Mission Unknown."

The suggested opening bid was $20,000. Nobody bid on it.

When it went up for auction again in February 2015, Carlson was the highest bidder.

Carlson had watched the moon landing, like so many from her generation, as an awestruck 11-year-old in Marquette, Michigan.

"I just felt great that they left this planet and made it to the moon, but I felt even happier when they got back OK," Carlson said Friday at the Houston federal courthouse.

Carlson's parents pushed her and her sister to pursue their dreams, and the space program embodied those big dreams, she said.

The package arrived by UPS at her home in Inverness, Illinois, about 50 miles from Chicago. It arrived in a simple cardboard box, with the lunar bag wrapped in brown paper inside. She kept it in her bedroom closet for safekeeping.

A few months later, Carlson contacted Ryan Zeigler, the lunar sample curator at the Johnson Space Center, curious to know if the bag actually contained moon dust. He said he'd be glad to test it if she'd send it to him.

He confirmed that the bag contained lunar dust, and further tests revealed even more: It was an outer decontamination bag for the first lunar samples ever collected on the first manned mission to the moon.

That's when things got complicated.

Carlson and Zeigler exchanged emails over many months, ostensibly trying to arrange a time for her to retrieve her bag.

She eventually filed a federal lawsuit as part of the government's forfeiture action. A Kansas judge who got the case ruled the bag belonged to Carlson, but said a judge in the Houston region - where the Johnson Space Center is based – would have to oversee enforcement of the order.

Federal prosecutors in Kansas did not appeal the decision, presenting further problems for prosecutors in Houston.

NASA officials said late Friday that they consider the case closed.

"NASA is obviously disappointed by the decision of the court due to the fact that it was primarily through the unlawful activity of a third party that put this historical artefact into the public domain," according to a statement from William Jeffs, the NASA spokesman for the astromaterials division. "This artefact was never meant to be owned by an individual. Moreover, this artefact is important, not just for its scientific value, but also because it represents the culmination of a massive national effort involving a generation of Americans, including the astronauts who risked their lives in an effort to accomplish the most significant act humankind has ever achieved."

NASA officials have asked Carlson to consider allowing the bag to be displayed publicly.

Her lawyer, Christopher M. McHugh, said she will consider it. But first she wants to get it back in hand.

"Given that this bag is really a national treasure," McHugh told the judge, "I don't think it's possible for Ms. Carlson to just keep the bag at home. That's not going to happen. But I do think a transfer of ownership has to happen."

Carlson is also considering a quiet visit to the Johnson Space Center over the weekend while waiting to pick up her treasure.

Next-generation dark matter detector in a race to finish line

03_LUX_in_Water_Tank_with_LuizThe race is on to build the most sensitive U.S.-based experiment designed to directly detect particles of dark matter. Department of Energy (DOE) officials formally approved a key construction milestone that will propel the project named LUX-ZEPLIN (LZ) toward its goal for completion by April 2020.

“The science is highly compelling, so it’s being pursued by physicists all over the world,” said Carmen Carmona, assistant professor of physics at Penn State and member of the LZ collaboration. “It's a friendly and healthy competition, with the possibility of a major discovery at stake.”

The fast-moving schedule for LZ will help the U.S. stay competitive with similar next-generation experiments to directly detect dark matter, planned in Italy and China.

The LZ experiment passed a DOE review-and-approval stage on Feb. 9, known as Critical Decision 3 (CD-3), which accepts the final design and formally launches construction. The project, which will be built nearly a mile underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, is considered one of the best bets yet to determine whether theorized dark matter particles known as WIMPs (weakly interacting massive particles) actually exist. The LZ collaboration includes about 220 participating scientists and engineers who represent 38 institutions around the globe.

LZ will be at least 50 times more sensitive to finding signals from dark matter particles than its predecessor, the Large Underground Xenon experiment (LUX), which was removed from the SURF facility last year to make way for LZ. Successive generations of experiments have evolved to provide extreme sensitivity in the search that will at least rule out some of the likely candidates and hiding spots for dark matter, or may lead to a discovery. The new experiment will use 10 metric tons of ultra-purified liquid xenon to tease out possible signals of dark matter. Xenon, in its gas form, is one of the rarest elements in Earth’s atmosphere.

“The nature of dark matter — the invisible component or so-called ‘missing mass’ in the universe that would explain the faster-than-expected spins of galaxies and their motion in clusters observed across the universe — has eluded scientists since its existence was deduced through calculations by Swiss astronomer Fritz Zwicky in 1933,” said Luiz de Viveiros, assistant professor of physics at Penn State and member of the LZ collaboration. “The quest to find out what dark matter is made of, or to learn whether it can be explained by tweaking the known laws of physics in new ways, is considered one of the most pressing questions in particle physics.”

All of the components for LZ are painstakingly measured for naturally occurring radiation levels to account for possible false signals coming from the components themselves. A dust-filtering cleanroom is being prepared for LZ's assembly and a radon-reduction building is under construction at the South Dakota site. Radon is a naturally occurring radioactive gas that could interfere with dark matter detection.

“While WIMPs are the primary target for LZ and its competitors, LZ’s explorations into uncharted territory could lead to a variety of surprising discoveries,” said Carmona. “People are developing all sorts of models to explain dark matter. LZ is optimized to observe a heavy WIMP, but it’s sensitive to some less-conventional scenarios as well. It also can search for other exotic particles and rare processes.”

Above Image: We are the Dark Matter, Neutrinos and Particle Astrophysics Group at Penn State University.  Although we have only recently moved to Penn State, our group brings a long record and expertise in the design and construction of noble liquid TPC detectors and their operation in the search for dark matter, and is currently part of two dark matter direct detection experiments, LUX and LZ.

We are also involved in Project 8, an experiment aimed at measuring the neutrino mass by making precise measurements of the electron energy in beta decays, and on the development of novel rare-event detectors.  Visit our Research page for more details on these experiments and our work.

Carmona and de Viveiros are leading the LZ team at Penn State, which includes efforts to measure trace radon contamination levels present in the LZ components, and to develop real-time radon monitoring technologies suitable for use at liquid-xenon temperatures. These steps are necessary to remove background signals as much as possible.

A planned upgrade to the current XENON1T experiment at the National Institute for Nuclear Physics’ Gran Sasso Laboratory (the XENONnT experiment) in Italy, and China's plans to advance the work on PandaX-II, also are slated to be leading-edge underground experiments that will use liquid xenon as the medium to seek out a dark matter signal. Both of these projects are expected to have schedules and scales similar to LZ, though LZ participants are aiming to achieve a higher sensitivity to dark matter than these other contenders.

LZ is designed so that if a dark matter particle collides with a xenon atom, it will produce a prompt flash of light followed by a second flash of light when the electrons produced in the liquid xenon chamber drift to its top. The light pulses, picked up by a series of about 500 light-amplifying photomultiplier tubes (PMTs) lining the massive tank — over four times more than were installed in LUX — will carry the telltale fingerprint of the particles that created them.

“We are looking forward to seeing everything come together after a long period of design and planning,” said de Viveiros. “Preparations of the cavern where LZ will be housed are underway at SURF, and onsite assembly and installation will begin in 2018."

Major support for LZ comes from the DOE Office of Science’s Office of High Energy Physics, South Dakota Science and Technology Authority, the UK’s Science & Technology Facilities Council, and collaboration members in South Korea and Portugal.

24 Feb 2017

Official naming of surface features on Pluto and its satellites: First step approved by the I.A.U.

170223114747_1_900x600This high-resolution image was captured by NASA's New Horizons spacecraft on its Pluto flyby in 2015, combining blue, red, and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). The bright region in the west is part of Pluto's 'heart', and is rich in nitrogen, carbon monoxide, and methane ices.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

In 2015, in partnership with NASA's New Horizons mission and the SETI Institute, the International Astronomical Union (IAU) endorsed the Our Pluto naming campaign, which allowed the public to participate in the exploration of Pluto by proposing names for surface features on Pluto and its satellites that were still awaiting discovery. Each of the system's six worlds was designated a set of naming themes set out by the IAU's Working Group for Planetary System Nomenclature. The public responded with overwhelming enthusiasm, suggesting and voting on thousands of names within these categories, as well as proposing names not fitting the approved set of themes.

Working with the New Horizons team, the IAU has agreed to revised naming themes (listed below) for Pluto, and its largest moon, Charon. For its four smaller moons -- Styx, Nix, Kerberos, and Hydra -- the themes remain unchanged. Some of these themes build on the connection between the Roman god Pluto and the mythology of the underworld. Other themes celebrate the human spirit of exploration.

Pluto:
•Gods, goddesses, and other beings associated with the Underworld from mythology, folklore and literature.
•Names for the Underworld and for Underworld locales from mythology, folklore and literature.
•Heroes and other explorers of the Underworld.
•Scientists and engineers associated with Pluto and the Kuiper Belt.
•Pioneering space missions and spacecraft.
•Historic pioneers who crossed new horizons in the exploration of the Earth, sea and sky.

Charon:
•Destinations and milestones of fictional space and other exploration.
•Fictional and mythological vessels of space and other exploration.
•Fictional and mythological voyagers, travellers and explorers.
•Authors and artists associated with space exploration, especially Pluto and the Kuiper Belt.

Styx:
•River gods.

Nix:
•Deities of the night.

Kerberos:
•Dogs from literature, mythology and history.

Hydra:
•Legendary serpents and dragons.

Using the revised themes, the New Horizons team will now propose names for the surface features to the IAU, as the body responsible for the official naming of celestial bodies and their surface features. The IAU's Working Group for Planetary System Nomenclature will then decide on the formal names.

"I'm very happy with both the process and partnership that New Horizons and the IAU undertook that led to wonderful, inspiring, and engaging naming themes for surface features on Pluto and its moons," said Alan Stern, New Horizons principal investigator from Southwest Research Institute, Boulder, Colorado. "We look forward to the next step -- submitting actual feature names for approval."

Rita Schulz, Chair of IAU's WGPSN said "I am very pleased that the close collaboration of the WGPSN with the New Horizons Team led to these beautiful, inspirational categories for naming the features on Pluto and its satellites. We are ready now for receiving the proposals for names. Good things take time, but it will be worth it."

23 Feb 2017

EXCLUSIVE: NASA’s Last Discovery Observed from Morocco

exclusive-nasa’s-last-discovery-observed-from-moroccoNASA’s last discovery of seven Earth-size planets that could potentially harbour life came out of a crucial collaboration with the Observatory of Oukaimeden, near Marrakech in Morocco.
 
“Thanks to NASA’s Spitzer satellite installed in Oukeimeden and the dozens of observatories involved, we were able to determine the existence of seven planets,” Zouhair Benkhaldoun, the director of the observatory, proudly told Morocco World News.

The scientist explained that the observation project started four years ago when the Origins in Cosmology and Astrophysics group (OrCA), from Beligan University of Liège contacted Cadi Ayyad University to collaborate on a “research initiative concerning exoplanets.”

In terms of this partnership, the University of Liège installed the TRAPPIST North telescope, dedicated to the observation of exoplanets, at Oukaimeden in May 2016.

Then the Observatory contacted NASA asking it to steer the Spitzer Space Telescope (SST) on the observation system, added Benkhaldoun.

It was through the SST that this major discovery, detected by the OrCA group, was made possible.

“The results of the observation of the planets were scanned by Khalid Berkaoui, a second year doctorate student at Cadi Ayyad University,” said Benkhaldoune, adding that himself and Berkaoui are co-authors of the study on the discovered planets, which will appear in the journal Nature on February 23.

It is not the first time when the Observatory of Oukaimeden has established a discovery. It already made, indeed, several discoveries of small bodies of the solar system: four comets and five Near-Earth Asteroids.

“What you should know is that the Laboratory of Physics of High Energy and Astrophysics of Cadi Ayyad University is ranked first in terms of scientific production in Morocco,” explained the Moroccan scientist.

“We have a community of very enthusiastic young people taking interest in astronomy. The future can only be promising,” he concluded.

Sun-gazers in Tamil Nadu preserve century-old tradition

aa-Cover-d5ccijur5gg5bjdfv5obic4dq6-20170223140433_MediIn the early morning darkness, Devendran P. walks up a hill to a solar observatory in the southern hill town of Kodaikanal, trudging the same path his father and grandfather walked in a century-old family tradition of studying the sun.

Once inside, he pulls a rope to open shutters in the dome and positions a six-inch telescope used since 1899 to photograph the sun and preserve a daily record of its activity.

"The sun, like stars, has a lifetime of 10 billion years," Devendran said. "If you want to know about any small changes, you need to have a large amount of data."

The observatory, run by the Indian Institute of Astrophysics, has a key role in providing a continuous stream of data on the sun and its influence on Earth and surrounding space, said R. Ramesh, a professor at the institute. 

"Some of the discoveries made, based on data obtained in the Kodaikanal observatory, are so fundamental to solar physics that they vastly improved techniques used at observatories even today," Ramesh said.

mdi_fd_SHARPEN projects

In the observatory library, shelves stretch to the ceiling, packed with volumes of handwritten records and thousands of film plates of the sun. Authorities have launched a project to digitise and preserve the data collected over the past century.

Devendran's grandfather, Parthasarathy, joined the observatory in 1900, a year after it relocated from Chennai, the state capital, to Kodaikanal, situated more than 6,562 feet above sea level, offering ideal weather to study the sun.

Like his father and grandfather, Devendran has no formal education in astronomy. His interest was piqued during a visit to the observatory when he was a child.

He became a fulltime sun watcher in 1986 and says the six-inch ( telescope has never failed his family.

"It has never required any major overhaul, or change of parts, because we all take care of it," he said.

His 23-year-old son, Rajesh, expects to carry on the family tradition, but with one difference. He has a master's degree in physics.

"I get amazed by what my father does here," said Rajesh. "I think observing the Sun is in my blood."

Ultracool Dwarf and the Seven Planets

Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. According to the paper appearing today in the journal Nature, three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces.

Astronomers using the TRAPPIST–South telescope at ESO’s La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world [1], have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1 [2]. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth [3].

Dips in the star’s light output caused by each of the seven planets passing in front of it — events known as transits — allowed the astronomers to infer information about their sizes, compositions and orbits [4]. They found that at least the inner six planets are comparable in both size and temperature to the Earth.

Lead author Michaël Gillon of the STAR Institute at the University of Liège in Belgium is delighted by the findings: “This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!”

Comparing the TRAPPIST-1 planets

With just 8% the mass of the Sun, TRAPPIST-1 is very small in stellar terms — only marginally bigger than the planet Jupiter — and though nearby in the constellation Aquarius (The Water Carrier), it appears very dim. Astronomers expected that such dwarf stars might host many Earth-sized planets in tight orbits, making them promising targets in the hunt for extra-terrestrial life, but TRAPPIST-1 is the first such system to be found.

Co-author Amaury Triaud expands: “The energy output from dwarf stars like TRAPPIST-1 is much weaker than that of our Sun. Planets would need to be in far closer orbits than we see in the Solar System if there is to be surface water. Fortunately, it seems that this kind of compact configuration is just what we see around TRAPPIST-1!”

The team determined that all the planets in the system are similar in size to Earth and Venus in the Solar System, or slightly smaller. The density measurements suggest that at least the innermost six are probably rocky in composition.

The planetary orbits are not much larger than that of Jupiter’s Galilean moon system, and much smaller than the orbit of Mercury in the Solar System. However, TRAPPIST-1’s small size and low temperature mean that the energy input to its planets is similar to that received by the inner planets in our Solar System; TRAPPIST-1c, d and f receive similar amounts of energy to Venus, Earth and Mars, respectively.

All seven planets discovered in the system could potentially have liquid water on their surfaces, though their orbital distances make some of them more likely candidates than others. Climate models suggest the innermost planets, TRAPPIST-1b, c and d, are probably too hot to support liquid water, except maybe on a small fraction of their surfaces. The orbital distance of the system’s outermost planet, TRAPPIST-1h, is unconfirmed, though it is likely to be too distant and cold to harbour liquid water — assuming no alternative heating processes are occurring [5]. TRAPPIST-1e, f, and g, however, represent the holy grail for planet-hunting astronomers, as they orbit in the star’s habitable zone and could host oceans of surface water [6].

These new discoveries make the TRAPPIST-1 system a very important target for future study. The NASA/ESA Hubble Space Telescope is already being used to search for atmospheres around the planets and team member Emmanuël Jehin is excited about the future possibilities: “With the upcoming generation of telescopes, such as ESO’s European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope, we will soon be able to search for water and perhaps even evidence of life on these worlds.”

Astronomers explain unusual dune-like patterns on comet 67P

Astronomers-explain-unusual-dune-like-patterns-on-comet-67PResearchers in France have explained the large dune-like patterns found on the surface of comet 67P/Churyumov-Gerasimenko.

Images collected by the now-retired Rosetta probe and its OIRIS camera revealed the presence of dune-like patterns on the comet's two lobes and the neck connecting them. Images of the same location, photographed at different times, showed the dunes are on the move.

Dune formation requires two ingredients: sediment grains and wind. Previous studies have proven comet 67P's surface to be covered in a layer of loose, dusty sediment.

Now, new research suggests temperature and pressure differences between the sunlit and shadowed sides of the comet are significant enough to drive dune-forming winds.

Comet 67P doesn't have a thick, stable atmosphere like Earth. It's atmosphere is thin and tenuous, formed by gases sublimated as the comet gets closer to the sun. Researchers at the French National Center for Scientific Research and the Laboratory of Physics and Mechanics of Heterogeneous Environments at the University of Paris determined pressure gradients on the comet are stark enough to power winds along 67P's surface. Because the comet's gravity is extremely weak, its tiny grains are much easier to transport.

Researchers published their analysis in the journal PNAS.

"Our understanding of the coupling between hydrodynamics and sediment transport is able to account for bed form emergence in extreme conditions and provides a reliable tool to predict the erosion and accretion processes controlling the evolution of small solar system bodies," researchers wrote in their paper.

22 Feb 2017

Astronomers observe black hole producing cold, star-making fuel from hot plasma jets and bubbles.

galaxy-center-phoenix-clusterThe Phoenix cluster is an enormous accumulation of about 1,000 galaxies, located 5.7 billion light years from Earth. At its centre lies a massive galaxy, which appears to be spitting out stars at a rate of about 1,000 per year. Most other galaxies in the universe are far less productive, squeaking out just a few stars each year, and scientists have wondered what has fuelled the Phoenix cluster’s extreme stellar output.

Now scientists from MIT, the University of Cambridge, and elsewhere may have an answer. In a paper published today in the Astrophysical Journal, the team reports observing jets of hot, 10-million-degree gas blasting out from the central galaxy’s black hole and blowing large bubbles out into the surrounding plasma.

These jets normally act to quench star formation by blowing away cold gas — the main fuel that a galaxy consumes to generate stars. However, the researchers found that the hot jets and bubbles emanating from the centre of the Phoenix cluster may also have the opposite effect of producing cold gas, that in turn rains back onto the galaxy, fuelling further starbursts. This suggests that the black hole has found a way to recycle some of its hot gas as cold, star-making fuel.

“We have thought the role of black hole jets and bubbles was to regulate star formation and to keep cooling from happening,” says Michael McDonald, assistant professor of physics in MIT’s Kavli Institute for Astrophysics and Space Research. “We kind of thought they were one-trick ponies, but now we see they can actually help cooling, and it’s not such a cut-and-dried picture.”

The new findings help to explain the Phoenix cluster’s exceptional star-producing power. They may also provide new insight into how supermassive black holes and their host galaxies mutually grow and evolve.

McDonald’s co-authors include lead author Helen Russell, an astronomer at Cambridge University; and others from the University of Waterloo, the Harvard-Smithsonian Center for Astrophysics, the University of Illinois, and elsewhere.

Hot jets, cold filaments

imagesHACN1903

The team analysed observations of the Phoenix cluster gathered by the Atacama Large Millimeter Array (ALMA), a collection of 66 large radio telescopes spread over the desert of northern Chile. In 2015, the group obtained permission to direct the telescopes at the Phoenix cluster to measure its radio emissions and to detect and map signs of cold gas.

The researchers looked through the data for signals of carbon monoxide, a gas that is present wherever there is cold hydrogen gas. They then converted the carbon monoxide emissions to hydrogen gas, to generate a map of cold gas near the centre of the Phoenix cluster. The resulting picture was a puzzling surprise.

“You would expect to see a knot of cold gas at the centre, where star formation happens,” McDonald says. “But we saw these giant filaments of cold gas that extend 20,000 light years from the central black hole, beyond the central galaxy itself. It’s kind of beautiful to see.”

The team had previously used NASA’s Chandra X-Ray Observatory to map the cluster’s hot gas. These observations produced a picture in which powerful jets flew out from the black hole at close to the speed of light. Further out, the researchers saw that the jets inflated giant bubbles in the hot gas.

When the team superimposed its picture of the Phoenix cluster’s cold gas onto the map of hot gas, they found a “perfect spatial correspondence”: The long filaments of frigid, 10-kelvins gas appeared to be draped over the bubbles of hot gas.

“This may be the best picture we have of black holes influencing the cold gas,” McDonald says.

Feeding the black hole

MIT-Black-Hole-Bubbles_0

What the researchers believe to be happening is that, as jet inflate bubbles of hot, 10-million-degree gas near the black hole, they drag behind them a wake of slightly cooler, 1-million-degree gas. The bubbles eventually detach from the jets and float further out into the galaxy cluster, where each bubble’s trail of gas cools, forming long filaments of extremely cold gas that condense and rain back onto the black hole as fuel for star formation.

“It’s a very new idea that the bubbles and jets can actually influence the distribution of cold gas in any way,” McDonald says.

Scientists have estimated that there is enough cold gas near the centre of the Phoenix cluster to keep producing stars at a high rate for another 30 to 40 million years. Now that the researchers have identified a new feedback mechanism that may supply the black hole with even more cold gas, the cluster’s stellar output may continue for much longer.

“As long as there’s cold gas feeding it, the black hole will keep burping out these jets,” McDonald says. “But now we’ve found that these jets are making more food, or cold gas. So you’re in this cycle that, in theory, could go on for a very long time.”

He suspects the reason the black hole is able to generate fuel for itself might have something to do with its size. If the black hole is relatively small, it may produce jets that are too weak to completely blast cold gas away from the cluster.

“Right now [the black hole] may be pretty small, and it’d be like putting a civilian in the ring with Mike Tyson,” McDonald says. “It’s just not up to the task of blowing this cold gas far enough away that it would never come back.”

The team is hoping to determine the mass of the black hole, as well as identify other, similarly extreme star makers in the universe.

21 Feb 2017

Astronomers Planning To Map Family Tree Of Stars In The Galaxy

evolutionary-tree-of-near-by-stars-constructed-using-the-genetic-code-mega-and-17-different-chemical-elements-as-the-stellar-dna

 A study is being conducted in a bid to find out the ancestry of stars and map their family tree. Researchers are using principles from biology and archaeology to build this "tree of Life" for stars.  ( Amanda Smith | Institute of Astronomy )

In 1859, Charles Darwin published his path breaking theory "Origin of Species," which detailed that every life form on Earth shares a common ancestor.

The theory has opened numerous avenues in the field of evolutionary biology since then. Now, astronomers are applying the same theory to find out about the history of stars.

Dr. Paula Jofré from the Institute of Astronomy of University of Cambridge is drawing on Darwin's theory and is set to create a phylogenetic "tree of life," which will link a collection of stars with one another in the galaxy.

"Phylogenetic trees add an extra dimension to our endeavours which is why this approach is so special. The branches of the tree serve to inform us about the stars' shared history," says Jofré.

Researchers are lending principles from biology and archaeology to build this "tree of life" for stars. By studying of the chemical signatures of the stars in the galaxy, the astronomers are putting the tree together to see how stars are formed and how they are connected to each other.

The chemical signatures are akin to DNA sequences found in life forms on Earth. The team has selected 22 stars, which also include the Sun of our solar system. The chemical signature of these 22 stars has been cautiously measured by using data obtained from ground-based high-resolution spectra, captured by telescopes placed in northern Chile.

MilkyWayPinnacles_web_1024

As soon as the data was analysed and families of the stars were identified by using their chemical DNA, researchers went on to study its evolution. The study was conducted based on the stars' ages and their kinematical properties, which was obtained from space mission Hipparcos.

Violent explosions occurring in the gas clouds, present in the galaxy produce stars. It is very much possible that two stars sharing similar chemical compositions may have been formed from the same gaseous molecular cloud.

Some stars survive the hardships of the universe and provide fossil records of the gas they were formed from. Among the stars evaluated at Institute of Astronomy, the oldest was estimated to have been formed about 10 billion years ago, while the youngest star in the group is 700 million years old.

Stars, like living organisms, share a history of ancestry as they carry with them the chemical structure of their origin I.e. the gas clouds from which they were formed. Astronomers can apply the same phylogenetic methods biologists use to map out the descent of plants and animals, to discover the "evolution" of stars.

Changes of supermassive black hole in the centre of NGC 2617 galaxy

ngc2617wideMembers of the Sternberg Astronomical Institute of the Lomonosov Moscow State University have been studying changes in the appearance of emission from around the supermassive black hole in the centre of a galaxy known to astronomers as NGC 2617. The centre of this galaxy, underwent dramatic changes in its appearance several years ago: it became much brighter and things that had not been seen before were seen. This sort of dramatic change can give us valuable information for understanding what the surroundings of a giant black hole are like and what is going on near the black hole. The results of these investigations have been published in the Monthly Notices of the Royal Astronomical Society, one of the world's top-rated astronomical journals.

Most galaxies such as our own have a giant black hole in their central nuclei. These monstrous holes have masses ranging from a million to a billion times the mass of our sun. The black hole in our galaxy is inactive, but in some galaxies, the black hole is swallowing gas that is spiralling into it and emitting enormous amounts of radiation. These galaxies are called "active galactic nuclei" or AGNs for short. The energy output from around the black holes of these AGNs can exceed that of the hundreds of billions of stars in the rest of the galaxy. Just how these galaxies get their supermassive black holes is a major mystery.

ngc 2617_SHARPEN projectsThe nuclei of galaxies where the supermassive black holes are vigorously swallowing gas are classified into two types: those where we get a direct view of the matter spiralling into the black hole at a speed that is thousands of times faster than the speed of sound, and those where the inner regions are obscured by dust and we only see more slowly moving gas much further from the black hole.

For decades astronomers have wondered why we see the innermost regions of some active galactic nuclei but not others. A popular explanation of the two types of active galactic nuclei is that they are really the same but they appear to be different to us because we are viewing them from different angles. If they are face-on we can see the hot gas spiralling into the black hole directly. If the active galactic nucleus is tilted, then dust around the nucleus blocks our view and we can only see the more slowly moving gas a light year or more away.

The leader of the international research team involved in the investigation, Viktor Oknyansky, a Senior Researcher at the Sternberg Astronomical Institute of the Lomonosov Moscow State University says: "Cases of object transition from one type to the other turn out to be a definite problem for this orientation model. In 1984 we found a change in the appearance of another active galactic nucleus known as NGC 4151. It was one of few known cases of this kind in the past. We now know of several dozen active galactic nuclei that have changed their type. In our recent study we have focused on one of the best cases -- NGC 2617."

Oknyansky continues: "In 2013 a team of researchers in the US found that NGC 2617 had changed being an active galaxy where the inner regions were hidden to one where the inner regions were now exposed. We didn't not know how long it would remain in this new unveiled state. It could last for only a short period of time or, on the other hand, for dozens of years. The title of the paper by the US astronomers was "The man behind the curtain..." When we began our study we didn't know how long the curtain would remain open, but we've titled our paper "The curtain remains open...", because we are continuing to see into the inner regions of NGC 2617.

According to the authors there is no accepted explanation so far of what could cause us to start seeing down to the inner regions of an active galactic nucleus when it was previously hidden.

untitledViktor Oknyansky comments: "It's clear that this phenomenon isn't very rare, on the contrary, we think it's quite typical. We consider various possible explanations. One is that perhaps a star has come too close to the black hole and has been torn apart. However, the disruption of a star by a black hole is very rare and we don't think that such events can explain the observed frequency of type changes of active galactic nuclei. Instead we favour a model where the black hole has started swallowing gas more rapidly. As the material spirals in towards the black holes it emits strong radiation. We speculate that this intense radiation destroys some of the dust surrounding the nucleus and permits us to see the inner regions."

Oknyansky continues: "Study of these rapid changes of type is very important for understanding what is going on around supermassive black holes that are rapidly swallowing gas. So, what we have concentrated on is getting observations of the various types of radiation emitted by NGC 2617. This has involved a large-scale effort."

The observational data for the project were obtained using the MASTER Global Robotic Network operated by Professor Vladimir Lipunov and his team, the new 2.5-m telescope located near Kislovodsk, a 2-m telescope of the observatory in Azerbajan, the Swift X-ray satellite, and some other telescopes. This research has been conducted in cooperation with colleagues from Azerbaijan, the USA, Finland, Chili, Israel and the South Africa.