Astronomers Capture Best View Ever Of Disintegrating Comet

Astronomers have captured the sharpest, most detailed observations of a comet breaking apart 67 million miles from Earth, using NASA’s Hubble Space Telescope. The discovery is published online in Astrophysical Journal Letters.

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In a series of images taken over three days in January 2016, Hubble showed 25 fragments consisting of a mixture of ice and dust that are drifting away from the comet at a pace equivalent to the walking speed of an adult, said UCLA astrophysicist David Jewitt, who led the research team.

The images suggest that the roughly 4.5-billion-year-old comet, named 332P/Ikeya-Murakami, or comet 332P, may be spinning so fast that material is ejected from its surface. The resulting debris is now scattered along a 3,000-mile-long trail, larger than the width of the continental United States.

These observations provide insight into the volatile behavior of comets as they approach the sun and begin to vaporize, unleashing powerful forces.

“We know that comets sometimes disintegrate, but we don’t know much about why or how,” Jewitt said. “The trouble is that it happens quickly and without warning, so we don’t have much chance to get useful data. With Hubble’s fantastic resolution, not only do we see really tiny, faint bits of the comet, but we can watch them change from day to day. That has allowed us to make the best measurements ever obtained on such an object.”

The three-day observations show that the comet shards brighten and dim as icy patches on their surfaces rotate into and out of sunlight. Their shapes change, too, as they break apart. The icy relics comprise about four percent of the parent comet and range in size from roughly 65 feet wide to 200 feet wide. They are separating at only a few miles per hour as they orbit the sun at more than 50,000 miles per hour.

The Hubble images show that the parent comet changes brightness frequently, completing a rotation every two to four hours. A visitor to the comet would see the sun rise and set in as little as an hour, Jewitt said.

The comet is much smaller than astronomers thought, measuring only 1,600 feet across, about the length of five football fields.

Comet 332P was discovered in November 2010, after it surged in brightness and was spotted by two Japanese amateur astronomers.

Based on the Hubble data, the research team suggests that sunlight heated the surface of the comet, causing it to expel jets of dust and gas. Because the nucleus is so small, these jets act like rocket engines, spinning up the comet’s rotation, Jewitt said. The faster spin rate loosened chunks of material, which are drifting off into space. The research team calculated that the comet probably shed material over a period of months, between October and December 2015.

Jewitt suggested that some of the ejected pieces have themselves fallen to bits in a kind of cascading fragmentation. “We think these little guys have a short lifetime,” he said.

Hubble’s sharp vision also spied a chunk of material close to the comet, which may be the first salvo of another outburst. The remnant from still another flare-up, which may have occurred in 2012, is also visible. The fragment may be as large as comet 332P, suggesting the comet split in two. But the remnant wasn’t spotted until Dec. 31, 2015, by a telescope in Hawaii.

That discovery prompted Jewitt and colleagues to request Hubble Space Telescope time to study the comet in detail.

“In the past, astronomers thought that comets die when they are warmed by sunlight, causing their ices to simply vaporize away,” Jewitt said. “But it’s starting to look like fragmentation may be more important. In comet 332P we may be seeing a comet fragmenting itself into oblivion.”

The researchers estimate that comet 332P contains enough mass for 25 more outbursts. “If the comet has an episode every six years, the equivalent of one orbit around the sun, then it will be gone in 150 years,” Jewitt said. “It’s just the blink of an eye, astronomically speaking. The trip to the inner solar system has doomed it.”

The icy visitor hails from the Kuiper belt, a vast swarm of objects at the outskirts of our solar system. As the comet traveled across the system, it was deflected by the planets, like a ball bouncing around in a pinball machine, until Jupiter’s gravity set its current orbit, Jewitt said.

Co-authors include Harold Weaver Jr., research professor at the Johns Hopkins University Applied Physics Laboratory.

Explaining Why The Universe Can Be ‘Transparent’: Universe’s Reionization Is Based On A Galaxy’s Dust Content

Two papers published by an assistant professor at the University of California, Riverside and several collaborators explain why the universe has enough energy to become transparent.

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The study led by Naveen Reddy, an assistant professor in the Department of Physics and Astronomy at UC Riverside, marks the first quantitative study of how the gas content within galaxies scales with the amount of interstellar dust.

This analysis shows that the gas in galaxies is like a “picket fence,” where some parts of the galaxy have little gas and are directly visible, whereas other parts have lots of gas and are effectively opaque to ionizing radiation. The findings were just published in The Astrophysical Journal.

The ionization of hydrogen is important because of its effects on how galaxies grow and evolve. A particular area of interest is assessing the contribution of different astrophysical sources, such as stars or black holes, to the budget of ionizing radiation.

Most studies suggest that faint galaxies are responsible for providing enough radiation to ionize the gas in the early history of the universe. Moreover, there is anecdotal evidence that the amount of ionizing radiation that is able to escape from galaxies depends on the amount of hydrogen within the galaxies themselves.

The research team led by Reddy developed a model that can be used to predict the amount of escaping ionizing radiation from galaxies based on straightforward measurements on how “red,” or dusty, their spectra appear to be.

Alternatively, with direct measurements of the ionizing escape fraction, their model may be used to constrain the intrinsic production rate of ionizing photons at around two billion years after the Big Bang.

These practical applications of the model will be central to the interpretation of escaping radiation during the cosmic “dark ages,” a topic that is bound to flourish with the coming of 30-meter telescopes, which will allow for research unfeasible today, and the James Webb Space Telescope, NASA’s next orbiting observatory and the successor to the Hubble Space Telescope.

The research ties back to some 400,000 years after the Big Bang, when the universe entered the cosmic “dark ages,” where galaxies and stars had yet to form amongst the dark matter, hydrogen and helium.

A few hundred million years later, the universe entered the “Epoch of Reionization,” where the gravitational effects of dark matter helped hydrogen and helium coalesce into stars and galaxies. A great amount of ultraviolet radiation (photons) was released, stripping electrons from surrounding neutral environments, a process known as “cosmic reionization.”

Reionization, which marks the point at which the hydrogen in the Universe became ionized, has become a major area of current research in astrophysics. Ionization made the Universe transparent to these photons, allowing the release of light from sources to travel mostly freely through the cosmos.

The data for this research was acquired through the low resolution imaging spectrograph on the W.M. Keck Observatory.

The collaborators of this research are Charles Steidel (Caltech), Max Pettini (University of Cambridge), Milan Bogosavljevic (Astronomical Observatory, Belgrade) and Alice Shapley (UCLA).

Discovery Nearly Doubles Known Quasars From The Ancient Universe

Quasars are supermassive black holes that sit at the center of enormous galaxies, accreting matter. They shine so brightly that they are often referred to as beacons and are among the most-distant objects in the universe that we can currently study. New work from a team led by Carnegie’s Eduardo Bañados has discovered 63 new quasars from when the universe was only a billion years old.

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This is the largest sample of such distant quasars presented in a single scientific article, almost doubling the number of ancient quasars previously known. The findings will be published by The Astrophysical Journal Supplement Series.

“Quasars are among the brightest objects and they literally illuminate our knowledge of the early universe,” Bañados said.

But until now, the population of known ancient quasars was fairly small, so scientists’ ability to glean information from them was limited. One of the main challenges is finding these distant quasars, which are extremely rare. Scientists have searched for them for decades, but the effort is comparable to finding a needle in a haystack.

The quasars discovered by Bañados and his team will provide valuable information from the first billion years after the Big Bang, which is a period of great interest to astronomers.

Why?

The universe was created in the Big Bang and hot matter exploded everywhere. But then it cooled off enough for the first protons and electrons to form and then to coalesce into hydrogen atoms, which resulted in a dark universe for a long time. It wasn’t until these atomic nuclei formed larger structures that light was able to shine once again in the universe. This happened when gravity condensed the matter and eventually formed the first sources of illumination, which might have included quasars.

There is still a lot about this era when the universe’s lights were turned back on that science doesn’t understand. But having more examples of ancient quasars will help experts to figure out what happened in those first billion years after the Big Bang.

“The formation and evolution of the earliest light sources and structures in the universe is one of the greatest mysteries in astronomy,” Bañados said. “Very bright quasars such as the 63 discovered in this study are the best tools for helping us probe the early universe. But until now, conclusive results have been limited by the very small sample size of ancient quasars.”

The coming years will see a great improvement in what we know about the early universe thanks to these discoveries.

Ripples In Fabric Of Space-time? Hundreds Of Undiscovered Black Holes

New research by the University of Surrey published today in the journal Monthly Notices of the Royal Astronomical Society has shone light on a globular cluster of stars that could host several hundred black holes, a phenomenon that until recently was thought impossible.

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Globular clusters are spherical collections of stars which orbit around a galactic centre such as our Milky-way galaxy. Using advanced computer simulations, the team at the University of Surrey were able to see the un-see-able by mapping a globular cluster known as NGC 6101, from which the existence of black holes within the system was deduced. These black holes are a few times larger than the Sun, and form in the gravitational collapse of massive stars at the end of their lives. It was previously thought that these black holes would almost all be expelled from their parent cluster due to the effects of supernova explosion, during the death of a star.

“Due to their nature, black holes are impossible to see with a telescope, because no photons can escape,” explained lead author Miklos Peuten of the University of Surrey. “In order to find them we look for their gravitational effect on their surroundings. Using observations and simulations we are able to spot the distinctive clues to their whereabouts and therefore effectively ‘see’ the un-seeable.”

It is only as recently as 2013 that astrophysicists found individual black holes in globular clusters via rare phenomena in which a companion star donates material to the black hole. This work, which was supported by the European Research Council (ERC), has shown that in NGC 6101 there could be several hundred black holes, overturning old theories as to how black holes form.

Co-author Professor Mark Gieles, University of Surrey continued, “Our work is intended to help answer fundamental questions related to dynamics of stars and black holes, and the recently observed gravitational waves. These are emitted when two black holes merge, and if our interpretation is right, the cores of some globular clusters may be where black hole mergers take place.”

The researchers chose to map this particular ancient globular cluster due to its recently found distinctive makeup, which suggested that it could be different to other clusters. Compared to other globular clusters NGC 6101 appears dynamically young in contrast to the ages of the individual stars. Also the cluster appears inflated, with the core being under-populated by observable stars.

Using computer simulation, the team recreated every individual star and black hole in the cluster and their behaviour. Over the whole lifetime of thirteen billion years the simulation demonstrated how NGC 6101 has evolved. It was possible to see the effects of large numbers of black holes on the visible stars, and to reproduce what was observed for NGC6101. From this, the researchers showed that the unexplainable dynamical apparent youth is an effect of the large black hole population.

“This research is exciting as we were able to theoretically observe the spectacle of an entire population of black holes using computer simulations. The results show that globular clusters like NGC 6101, which were always considered boring are in fact the most interesting ones, possibly each harbouring hundreds of black holes. This will help us to find more black holes in other globular clusters in the Universe. ” concluded Peuten.

Loneliest Young Star Seen By Spitzer And WISE

Alone on the cosmic road, far from any known celestial object, a young, independent star is going through a tremendous growth spurt.

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The unusual object, called CX330, was first detected as a source of X-ray light in 2009 by NASA’s Chandra X-Ray Observatory while it was surveying the bulge in the central region of the Milky Way. Further observations indicated that this object was emitting optical light as well. With only these clues, scientists had no idea what this object was.

But when Chris Britt, postdoctoral researcher at Texas Tech University in Lubbock, and colleagues were examining infrared images of the same area taken with NASA’s Wide-field Infrared Survey Explorer (WISE), they realized this object has a lot of warm dust around it, which must have been heated by an outburst.

Comparing WISE data from 2010 with Spitzer Space Telescope data from 2007, researchers determined that CX330 is likely a young star that had been outbursting for several years. In fact, in that three-year period its brightness had increased by a few hundred times.

Astronomers looked at data about the object from a variety of other observatories, including the ground-based SOAR, Magellan, and Gemini telescopes. They also used the large telescope surveys VVV and the OGLE-IV to measure the intensity of light emitted from CX330. By combining all of these different perspectives on the object, a clearer picture emerged.

“We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere,” said Britt, lead author of a study on CX330 recently published in the Monthly Notices of the Royal Astronomical Society.

The lone star’s behavior has similarities to FU Orionis, a young outbursting star that had an initial three-month outburst in 1936-7. But CX330 is more compact, hotter and likely more massive than the FU Orionis-like objects known. The more isolated star launches faster “jets,” or outflows of material that slam into the gas and dust around it.

“The disk has probably heated to the point where the gas in the disk has become ionized, leading to a rapid increase in how fast the material falls onto the star,” said Thomas Maccarone, study co-author and associate professor at Texas Tech.

Most puzzling to astronomers, FU Orionis and the rare objects like it—there are only about 10 of them—are located in star-forming regions. Young stars usually form and feed from their surrounding gas and dust-rich regions in star-forming clouds. By contrast, the region of star formation closest to CX330 is over a thousand light-years away.

“CX330 is both more intense and more isolated than any of these young outbursting objects that we’ve ever seen,” said Joel Green, study co-author and researcher at the Space Telescope Science Institute in Baltimore. “This could be the tip of the iceberg—these objects may be everywhere.”

In fact, it is possible that all stars go through this dramatic stage of development in their youth, but that the outbursts are too short in cosmological time for humans to observe many of them.

How did CX330 become so isolated? One idea is that it may have been born in a star-forming region, but was ejected into its present lonely pocket of the galaxy. But this is unlikely, astronomers say. Because CX330 is in a youthful phase of its development—likely less than 1 million years old—and is still eating its surrounding disk, it must have formed near its present location in the sky.

“If it had migrated from a star-forming region, it couldn’t get there in its lifetime without stripping its disk away entirely,” Britt said.

CX330 may also help scientists study the way stars form under different circumstances. One scenario is that stars form through turbulence. In this “hierarchical” model, a critical density of gas in a cloud causes the cloud to gravitationally collapse into a star. A different model, called “competitive accretion,” suggests that stars begin as low-mass cores that fight over the mass of material left in the cloud. CX330 more naturally fits into the first scenario, as the turbulent circumstances would theoretically allow for a lone star to form.

It is still possible that other intermediate- to low-mass stars are in the immediate vicinity of CX330, but have not been detected yet.

When CX330 was last viewed in August 2015, it was still outbursting. Astronomers plan to continue studying the object, including with future telescopes that could view it in other wavelengths of light.

Outbursts from a young star change the chemistry of the star’s disk, from which planets may eventually form. If the phenomenon is common, that means that planets, including our own, may carry the chemical signatures of an ancient disk of gas and dust scarred by stellar outbursts.

But as CX330 is continuing to devour its disk with increasing voracity, astronomers do not expect that planets are forming in its system.

“If it’s truly a massive star, its lifetime is short and violent, and I wouldn’t recommend being a planet around it,” Green said. “You could experience some pretty intense heat for a few centuries.”

The Role Of Magnetic Fields In Star Formation

The star forming molecular clump W43-MM1 is very massive and dense, containing about 2100 solar masses of material in a region only one-third of a light year across (for comparison, the nearest star to the Sun is a bit over four light years away).

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Previous observations of this clump found evidence for infalling motions (signaling that material is still accumulating onto a new star) and weak magnetic fields. These fields are detected by looking for polarized light, which is produced when radiation scatters off of elongated dust grains aligned by magnetic fields. The Submillimeter Array recently probed this source with high spatial resolutions and found evidence for even stronger magnetic fields in places. One of the outstanding issues in star formation is the extent to which magnetic fields inhibit the collapse of material onto stars, and this source seems to offer a particularly useful example.

CfA astronomers Josep Girart and TK Sridharan and their colleagues have used the ALMA submillimeter facility to obtain images with spatial scales as small as 0.03 light years. Their detailed polarization maps show that the magnetic field is well ordered all across the clump, which itself is actually fifteen smaller fragments, one of which (at 312 solar masses) appears to be the most massive fragment known.

The scientists analyze the magnetic field strengths and show that, even in the least massive fragment the field is not strong enough to inhibit gravitational collapse. In fact, they find indications that gravity, as it pulls material inward, drags the magnetic field lines along. They are, however, unable to rule out possible further fragmentation. The research is the most precise study of magnetic fields in star forming massive clumps yet undertaken, and provides a new reference point for theoretical models.

Scientists Observe A Superluminous Supernova That Appears To Have Exploded Twice

Supernovae are among the most violent phenomena in the universe. They are huge explosions that end the lives of certain types of stars. These explosions release immense amounts of energy, so much that some can be observed from Earth with the naked eye, appearing as points of light that are briefly brighter than all the millions of stars in the galaxies where they are found. Following an intense burst of light lasting a few weeks, supernovae start to fade gradually until they have effectively burned out.

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There are several types of supernovae. The astronomers classify them by their observable characteristics, which give clues about their origin. Among the most well known are those of type Ia .When a white dwarf, the final state of a star slightly more massive than the sun, absorbs mass from another nearby star or merges with another white dwarf, its mass grows until it becomes unstable and a thermonuclear explosion occurs. As these events produce a characteristic luminosity, they can be used by astronomers as “standard candles” to measure large distances in the universe, like sailors to inferring the distance of a known lighthouse at night by estimating its brightness.

The other types of supernovae are produced when very massive stars exhaust their fuel, so that nuclear fusion in their interiors comes to an end. This fusion not only causes stars to emit light and heat, but keeps them in equilibrium so that they don’t collapse under their own gravity. When the fusion stops, the centre of the star collapses and the outer layers are flung outwards with violence, causing a supernova, while the centre implodes, leaving a neutron star—or for very massive stars, a black hole.

In recent years, a new type of supernova has been discovered, about which very little is yet known, and which are brighter and longer-lasting. Astronomers call them superluminous supernovae (SLSN). Although only about a dozen of them are known, an international group of researchers has used the Gran Telescopio CANARIAS (GTC) to observe a superluminous supernova almost from the moment it occurred. The research has revealed surprising behaviour, because this supernova showed an initial increase in brightness that later declined for a few days, and then increased again much more strongly. The scientists have combined from the GTC with other observations in order to try to explain the origin of the phenomenon.

“Superluminous supernovas are up to a hundred times more energetic than type 1a supernovae because they can remain bright for up to six months before fading, rather than just a few weeks,” explains Mathew Smith, a postdoctoral researcher at the University of Southampton (UK) and the person directing this study, whose results have been published in the specialized journal The Astrophysical Journal Letters. “What we have managed to observe, which is completely new, is that before the major explosion, there is a shorter, less luminous outburst, which we can pick out because it is followed by a dip in the light curve, and which lasts just a few days.”

It is the first time that something like this has been observed in a supernova. “From our data, we have tried to determine if this is a characteristic unique to this object, or whether it is a common feature of all superluminous supernovae, but has not been observed before, which is perfectly possible given their unpredictable nature,” says the scientist.

This new, intriguing object, given the cryptic name of DES14X3taz by the astronomers, was discovered on December 21, 2014 by the Dark Energy Survey, an international project that surveys the night sky, making precision measurements of over 300 million galaxies that are situated thousands of millions of light years from Earth, and incidentally detecting thousands of supernovae and other transient phenomena. The objective of this survey is to explain the expansion of the universe, and to find clues to the nature of dark energy. To do this, astronomers are using an extremely sensitive 570 megapixel digital camera on the four metre Victor M. Blanco telescope at the Inter-American Observatory at Cerro Tololo (Chile).

Once DES14X3taz had been identified as a possible superluminous supernova, an immediate observation was requested on the GTC, which turned its powerful eye toward it over two nights of observation, January 26 and February 6, 2015. GTC devotes some of its observing time to “targets of opportunity,” so that other programmed observations can postponed to prioritize such transient phenomena, which may offer unrepeatable opportunities.

“The GTC, with its huge 10.4m mirror, and its OSIRIS instrument, is the ideal tool to observer this SNSL, which is at a vast distance and because we are looking for information in the visible and the near infrared,” says Smith, who is a participant in the Dark Energy Survey. Thanks to the observations made with the GTC and other telescopes, Smith and his collaborators could reconstruct the evolution of the brightness of DES14X3taz from almost the moment of its detection. They have also determined its absolute brightness with great precision, as well as its distance, some 6,400 million light years.

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After comparing their observations with several physical models, the astronomers concluded in their article that the most plausible explanation is that the mechanism causing this supernova is the birth of a “magnetar,” a neutron star that rotates very rapidly on its axis. In the data, the initial peak of the brightness graph is followed by rapid cooling of the object, after which there is a quicker rise in brightness. This is consistent with the emission of a huge bubble of material into the surrounding space, which cools rapidly as it grows in size.

“We think that a very massive star, some 200 times the mass of the Sun, collapses to form a magnetar. In the process, the first explosion occurs, which expels into space a quantity of matter equivalent to the mass of our sun, and this gives rise to the first peak of the graph. The second peak occurs when the star collapses to form the magnetar, which is a very dense object rotating rapidly on its axis, and which heats up the matter expelled from the first explosion. This heating is what generates the second peak in the luminosity,” explains Smith.

This understanding may allow us to “standardize” superluminous supernovae as has occurred for the type Ia supernovae for use as a reference source for distance measurement on large scales in the universe. Its high luminosity may make these objects useful for calculating distances on larger scales, and with greater accuracy than current techniques. However, before we get to that point, we need a much deeper understanding of their origin and their nature.

Another mystery about this new type of supernova is that, until recently, all the examples detected have been in small galaxies with low metallicity (low content in heavy elements), which is not well understood. “It is a part of the mystery of these objects,” says Smith, and adds that among future priorities, we need to detect more superluminous supernovae and observe them from the moment they explode in real time with a telescope the size of the GTC.