A planetary system’s early days readily tell of turmoil. Giant planets are swept from distant birthplaces into sizzling orbits close to their host star. Others are blasted away from their star into the darkness of space. And smaller bodies, like asteroids and comets, are being traded around constantly.
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have seen the latter: swarms of Pluto-size objects turning to dust around a young star. And the image is remarkable.
“This system offers us the chance to study an intriguing time around a young, Sun-like star,” said coauthor Stuartt Corder and ALMA Deputy Director in a news release. “We are possibly looking back in time here, back to when the Sun was about 2 percent of its current age.”
The young star, HD 107146, is located roughly 90 light-years from Earth in the direction of the constellation Coma Berenices. Although the star itself is visible in any small telescope, ALMA can probe the star’s radically faint protoplanetary disk. This is the star’s dusty cocoon that coalesces into planets, comets and asteroids.
ALMA’s image revealed an unexpected bump in the number of millimeter-size dust grains far from the host star. This highly concentrated band spans roughly 30 to 150 astronomical units, the equivalent of Neptune’s orbit around the Sun to four times Pluto’s orbit.
So where is the extra dust coming from?
Typically, dust in the debris disk is simply left over material from the formation of planets. Early on, however, Pluto-size objects (otherwise known as planetesimals) will collide and blast themselves apart, also contributing to the dust. Certain models predict that this leads to a much higher concentration of dust in the most distant regions of the disk.
Although this is the case for HD 107146, “this is the opposite of what we see in younger primordial disks where the dust is denser near the star,” said lead author Luca Ricci from the Harvard-Smithsonian Center for Astrophysics. “It is possible that we caught this particular debris disk at a stage in which Pluto-size planetesimals are forming right now in the outer disk while other Pluto-size bodies have already formed closer to the star.”
Adding to this hypothesis is the fact that there’s a slight depression in the dust at 80 astronomical units, or twice Pluto’s average distance from the Sun. This could be a slight gap in the dust, where an Earth-size planet is sweeping the area clear of a debris disk.
If true, this would be the first observation of an Earth-size planet forming so far from its host star. But for now that’s a big if.
A team of Australian astronomers has been busy utilizing some of the world’s leading radio telescopes located in both Australia and Chile to carve away at the layered remains of a relatively new supernova. Designated as SN1987A, the 28 year-old stellar cataclysm came to Southern Hemisphere observer’s attention when it sprang into action at the edge of the Large Magellanic Cloud some two and a half decades ago. Since then, it has provided researchers around the world with a ongoing source of information about one of the Universe’s “most extreme events”.
Representing the University of Western Australia node of the International Centre for Radio Astronomy Research, PhD Candidate Giovanna Zanardo led the team focusing on the supernova with the Australia Telescope Compact Array (ATCA) in New South Wales. Their observations took in the wavelengths spanning the radio to the far infrared.
“By combining observations from the two telescopes we’ve been able to distinguish radiation being emitted by the supernova’s expanding shock wave from the radiation caused by dust forming in the inner regions of the remnant,” said Giovanna Zanardo of the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia.
“This is important because it means we’re able to separate out the different types of emission we’re seeing and look for signs of a new object which may have formed when the star’s core collapsed. It’s like doing a forensic investigation into the death of a star.”
“Our observations with the ATCA and ALMA radio telescopes have shown signs of something never seen before, located at the centre or the remnant. It could be a pulsar wind nebula, driven by the spinning neutron star, or pulsar, which astronomers have been searching for since 1987. It’s amazing that only now, with large telescopes like ALMA and the upgraded ATCA, we can peek through the bulk of debris ejected when the star exploded and see what’s hiding underneath.”
A video compilation showing Supernova Remnant 1987A as seen by the Hubble Space Telescope in 2010, and by radio telescopes located in Australia and Chile in 2012. The piece ends with a computer generated visualization of the remnant showing the possible location of a Pulsar. Credit: Dr Toby Potter, ICRAR-UWA, Dr Rick Newton, ICRAR-UWA
But, there is more. Not long ago, researchers published another paper which appeared in the Astrophysical Journal. Here they made an effort to solve another unanswered riddle about SN1987A. Since 1992 the supernova appears to be “brighter” on one side than it does the other! Dr. Toby Potter, another researcher from ICRAR’s UWA node took on this curiosity by creating a three-dimensional simulation of the expanding supernova shockwave.
“By introducing asymmetry into the explosion and adjusting the gas properties of the surrounding environment, we were able to reproduce a number of observed features from the real supernova such as the persistent one-sidedness in the radio images”, said Dr. Toby Potter.
So what’s going on? By creating a model which spans over a length of time, researchers were able to emulate an expanding shock front along the eastern edge of the supernova remnant. This region moves away more quickly than its counterpart and generates more radio emissions. When it encounters the equatorial ring – as observed by the Hubble Space Telescope – the effect becomes even more pronounced.
A visualization showing how Supernova1987A evolves between May of 1989 and July of 2014. Credit: Dr Toby Potter, ICRAR-UWA, Dr Rick Newton, ICRAR-UWA
“Our simulation predicts that over time the faster shock will move beyond the ring first. When this happens, the lop-sidedness of radio asymmetry is expected to be reduced and may even swap sides.”
“The fact that the model matches the observations so well means that we now have a good handle on the physics of the expanding remnant and are beginning to understand the composition of the environment surrounding the supernova – which is a big piece of the puzzle solved in terms of how the remnant of SN1987A formed.”
Deep within the Taurus Dark Cloud complex, one of the closest star-forming regions to Earth has just revealed one of its secrets – an umbilical cord of gas flowing from the expansive outer disc toward the interior of a binary star system known as GG Tau-A. According to the ESO press release, this never-before-seen feature may be responsible for sustaining a second, smaller disc of planet-forming material that otherwise would have disappeared long ago.
A research group led by Anne Dutrey from the Laboratory of Astrophysics of Bordeaux, France and CNRS used the Atacama Large
Millimeter/submillimeter Array (ALMA) to observe the distribution of
dust and gas in the unusual GG Tau-A system. Since at least half of
Sun-like stars are the product of binary star systems, these type of
findings may produce even more fertile grounds for discovering
exoplanets. However, the 450 light year distant GG Tau system is even more complex than previously thought. Through observations taken with the VLTI, astronomers have discovered its primary star – home to the inner disc – is part of a more involved multiple-star system. The secondary star is also a close binary!
“We may be witnessing these types of exoplanetary systems in the midst of formation,” said Jeffrey Bary, an astronomer at Colgate University in Hamilton, N.Y., and co-author of the paper. “In a sense, we are learning why these seemingly strange systems exist.”
Let’s take a look…
“Like a wheel in a wheel, GG Tau-A contains a large, outer disc
encircling the entire system as well as an inner disc around the main central star. This second inner disc has a mass roughly equivalent to that of Jupiter.” says the research team. “Its presence has been an intriguing mystery for astronomers since it is losing material to its central star at a rate that should have depleted it long ago.”
Thanks to studies done with ALMA, the researchers made an exciting discovery in these disc structures… gas clumps located between the two. This observation could mean that material is being fed from the outer disc to feed the inner. Previously observations done with ALMA show that a single star pulls its materials inward from the outer disc. Is it possible these gas pockets in the double disc GG Tau-A system are creating a sustaining lifeline between the two?
“Material flowing through the cavity was predicted by computer
simulations but has not been imaged before. Detecting these clumps
indicates that material is moving between the discs, allowing one to
feed off the other,” explains Dutrey. “These observations demonstrate that material from the outer disc can sustain the inner disc for a long time. This has major consequences for potential planet formation.”
As we know, planets are created from the materials leftover from
stellar ignition. However, the creation of a solar system occurs at a snail’s pace, meaning that a debris disc with longevity is required for planet formation. Thanks to these new “disc feeding” observations from ALMA, researchers can surmise that other multiple-star systems behave in a similar manner… creating even more possibilities for exoplanet formation.
“This means that multiple star systems have a way to form planets, despite their complicated dynamics. Given that we continue to find interesting planetary systems, our observations provide a glimpse of the mechanisms that enable such systems to form,” concludes Bary.
During the initial phase of planetary searches, the emphasis was placed on Sun-like, single-host stars. Later on, binary systems gave rise to giant Jupiter-sized planets – nearly large enough to be stars on their own. Now the focus has turned to pointing our planetary discovery efforts towards individual members of multiple-systems.
Emmanuel Di Folco, co-author of the paper, concludes: “Almost half the Sun-like stars were born in binary systems. This means that we have found a mechanism to sustain planet formation that applies to a significant number of stars in the Milky Way. Our observations are a big step forward in truly understanding planet formation.”
A new mystery of Titan has been uncovered by astronomers using their latest asset in the high altitude desert of Chile. Using the now fully deployed Atacama Large Millimeter Array (ALMA) telescope in Chile, astronomers moved from observing comets to Titan. A single 3 minute observation revealed organic molecules that are askew in the atmosphere of Titan. The molecules in question should be smoothly distributed across the atmosphere, but they are not.
The Cassini/Huygens spacecraft at the Saturn system has been revealing the oddities of Titan to us, with its lakes and rain clouds of methane, and an atmosphere thicker than Earth’s. But the new observations by ALMA of Titan underscore how much more can be learned about Titan and also how incredible the ALMA array is.
The ALMA astronomers called it a “brief 3 minute snapshot of Titan.” They found zones of organic molecules offset from the Titan polar regions. The molecules observed were hydrogen isocyanide (HNC) and cyanoacetylene (HC3N). It is a complete surprise to the astrochemist Martin Cordiner from NASA Goddard Space Flight Center in Greenbelt, Maryland. Cordiner is the lead author of the work published in the latest release of Astrophysical Journal Letters.
The NASA Goddard press release states, “At the highest altitudes, the gas pockets appeared to be shifted away from the poles. These off-pole locations are unexpected because the fast-moving winds in Titan’s middle atmosphere move in an east–west direction, forming zones similar to Jupiter’s bands, though much less pronounced. Within each zone, the atmospheric gases should, for the most part, be thoroughly mixed.”
When one hears there is a strange, skewed combination of organic compounds somewhere, the first thing to come to mind is life. However, the astrochemists in this study are not concluding that they found a signature of life. There are, in fact, other explanations that involve simpler forces of nature. The Sun and Saturn’s magnetic field deliver light and energized particles to Titan’s atmosphere. This energy causes the formation of complex organics in the Titan atmosphere. But how these two molecules – HNC and HC3N – came to have a skewed distribution is, as the astrochemists said, “very intriguing.” Cordiner stated, “This is an unexpected and potentially groundbreaking discovery… a fascinating new problem.”
The press release from the National Radio Astronomy Observatory states, “studying this complex chemistry may provide insights into the properties of Earth’s very early atmosphere.” Additionally, the new observations add to understanding Titan – a second data point (after Earth) for understanding organics of exo-planets, which may number in the hundreds of billions beyond our solar system within our Milky Way galaxy. Astronomers need more data points in order to sift through the many exo-planets that will be observed and harbor organic compounds. With Titan and Earth, astronomers will have points of comparison to determine what is happening on distant exo-planets, whether it’s life or not.
The report of this new and brief observation also underscores the new astronomical asset in the altitudes of Chile. ALMA represents the state of the art of millimeter and sub-millimeter astronomy. This field of astronomy holds a lot of promise. Back around 1980, at the Kitt Peak National Observatory in Arizona, alongside the great visible light telescopes, there was an oddity, a millimeter wavelength dish. That dish was the beginning of radio astronomy in the 1 – 10 millimeter wavelength range. Millimeter astronomy is only about 35 years old. These wavelengths stand at the edge of the far infrared and include many light emissions and absorptions from cold objects which often include molecules and particularly organics. The ALMA array has 10 times more resolving power than the Hubble space telescope.
The Earth’s atmosphere stands in the way of observing the Universe in these wavelengths. By no coincidence our eyes evolved to see in the visible light spectrum. It is a very narrow band, and it means that there is a great, wide world of light waves to explore with different detectors than just our eyes.
In the millimeter range of wavelengths, water, oxygen, and nitrogen are big absorbers. Some wavelengths in the millimeter range are completely absorbed. So there are windows in this range. ALMA is designed to look at those wavelengths that are accessible from the ground. The Chajnantor plateau in the Atacama desert at 5000 meters (16,400 ft) provides the driest, clearest location in the world for millimeter astronomy outside of the high altitude regions of the Antarctic.
At high altitude and over this particular desert, there is very little atmospheric water. ALMA consists of 66 12 meter (39 ft) and 7 meter (23 ft) dishes. However, it wasn’t just finding a good location that made ALMA. The 35 year history of millimeter-wavelength astronomy has been a catch up game. Detecting these wavelengths required very sensitive detectors – low noise in the electronics. The steady improvement in solid-state electronics from the late 70s to today and the development of cryostats to maintain low temperatures have made the new observations of Titan possible. These are observations that Cassini at 1000 kilometers from Titan could not do but ALMA at 1.25 billion kilometers (775 million miles) away could.
The prototype ALMA telescope was tested at the site of the VLA in New Mexico in 2003. That prototype now stands on Kitt Peak having replaced the original millimeter wavelength dish that started this branch of astronomy in the 1980s. The first dishes arrived in 2007 followed the next year by the huge transporters for moving each dish into place at such high altitude. The German-made transporter required a cabin with an oxygen supply so that the drivers could work in the rarefied air at 5000 meters. The transporter was featured on an episode of the program Monster Moves. By 2011, test observations were taking place, and by 2013 the first science program was undertaken. This year, the full array was in place and the second science program spawned the Titan observations. Many will follow. ALMA, which can operate 24 hours per day, will remain the most powerful instrument in its class for about 10 years when another array in Africa will come on line.
Watch out! Carbon monoxide gas is likely fleeing the disk of a young star like our Sun, producing an unusual signature in infrared. This could be the first time winds have been confirmed in association with a T Tauri star, or something else might be going on.
Because the observed signature of the star (called AS 205 N) didn’t meet what models of similar stars predicted, astronomers say it’s possible it’s not winds after all, but a companion tugging away at the gas.
“The material in the disk of a T Tauri star usually, but not always, emits infrared radiation with a predictable energy distribution,” stated Colette Salyk, an astronomer with the National Optical Astronomical Observatory who led the research. “Some T Tauri stars, however, like to act up by emitting infrared radiation in unexpected ways.”
T Tauri stars are still young enough to be surrounded by dust and gas that could eventually form planets. Winds in the vicinity, however, could make it difficult for enough gas to stick around to form Jupiter-sized gas giants — or could change where planets are formed altogether.
While it’s still unclear what’s going on in AS 205 N, the astronomers plan to follow up their work with observing other T Tauri stars. Maybe with more observations, they reason, they can better understand what these signatures are telling us.
What’s it like to spend a night at a huge telescope observatory? Jordi Busque recorded a brilliant timelapse of the Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA). What makes this video unique is not only the exotic location in Chile, but the use of sound in the area rather than music.
An international team of astronomers has obtained the best view yet of two galaxies colliding when the universe was only half its current age.
The team relied heavily on space- and ground-based telescopes, including the Hubble Space Telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), the Keck Observatory, and the Karl Jansky Very Large Array (VLA). But the greatest asset was a chance cosmic alignment.
“While astronomers are often limited by the power of their telescopes, in some cases our ability to see detail is hugely boosted by natural lenses created by the universe,” said lead author Hugo Messias of the Universidad de Concepción in Chile and the Centro de Astronomia e Astrofísica da Universidade de Lisboa in Portugal.
Such a rare cosmic alignment plays visual tricks, where the intervening lens (be it a galaxy or a galaxy cluster) appears to bend and even magnify the distant light. This effect, called gravitational lensing, allows astronomers to study objects which would not be visible otherwise and to directly compare local galaxies with much more remote galaxies, seen when the universe was significantly younger.
The distant object in question, dubbed H-ATLAS J142935.3-002836, was originally spotted in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). Although very faint in visible light pictures, it is among the brightest gravitationally lensed objects in the far-infrared regime found so far.
The Hubble and Keck images reveal that the foreground galaxy is a spiral galaxy, seen edge-on. Although the galaxy’s large dust clouds obscure part of the background light, both ALMA and VLA can observe the sky at longer wavelengths, which are unaffected by dust.
Using the combined data, the team discovered that the background system was actually an ongoing collision between two galaxies.
First, the team noticed that these two galaxies resembled a much closer system: the Antennae galaxies, two galaxies that have spent the past few hundred million years in a whirling embrace as they merge together. The similarity suggested a collision, but ALMA — with its high sensitivity and spatial resolution — was able to verify it.
ALMA has the unique ability to detect the emission from carbon monoxide, as opposed to other telescopes, which might only be able to probe the absorption along the line of sight. This allowed astronomers to measure the velocity of the gas in the more distant object. With this information, they were able to show that the lensed galaxy is indeed an ongoing galactic collision.
Such collisions naturally enhance star formation. Any gas within the galaxies will feel a headwind, much as a runner feels a wind even on the stillest day, and become compressed enough to spark star formation. Sure enough, ALMA shows that the two galaxies are forming hundreds of new stars each year.
“ALMA enabled us to solve this conundrum because it gives us information about the velocity of the gas in the galaxies, which makes it possible to disentangle the various components, revealing the classic signature of a galaxy merger,” said ESO’s Director of Science and coauthor of the new study, Rob Ivison. “This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst.”
The findings have been published in the Aug. 26 issue of Astronomy & Astrophysics and is available online.