The story of KIC 8462852 appears far from over. You’ll recall NASA’s Kepler mission had monitored the star for four years, observing two unusual incidents, in 2011 and 2013, when its light dimmed in dramatic, never-before-seen ways. Models to explain its erratic behavior were so lacking that some considered the possibility that alien megastructures built to capture sunlight around the host star (think Dyson Spheres) might be the cause.
Shattered comets and asteroids were also suggested as possible explanations — dust and ground-up rock would be at the right temperature to glow in the infrared — but Kepler could only observe in visible light where any debris would be invisible or swamped by the light of the star. So researchers looked through older observations made in 2010 by the Wide Field Infrared Survey Explorer (WISE) space telescope. Unfortunately, WISE observed the star before the strange variations were seen and therefore before any putative dust-busting collisions.
Not to be stymied, astronomers next checked out the data from NASA’s Spitzer Space Telescope, which like WISE, is optimized for infrared light. Spitzer just happened to observe KIC 8462852 much more recently in 2015.
“Spitzer has observed all of the hundreds of thousands of stars where Kepler hunted for planets, in the hope of finding infrared emission from circumstellar dust,” said Michael Werner, the Spitzer project scientist and the lead investigator of that particular Spitzer/Kepler observing program.
I’d love to report that Spitzer tracked down glowing dust but no, it also came up empty-handed. This makes the idea of an asteroidal smash-up very unlikely, but not one involving comets according to Massimo Marengo of Iowa State University (Ames) who led the new study. Marengo proposes that cold comets are responsible. Picture a family of comets traveling on a very long, eccentric orbit around the star with a very large comet at the head of the pack responsible for the big fading seen by Kepler in 2011. Later, in 2013, the rest of the comet family, a band of various-sized fragments lagging behind, would have passed in front of the star and again blocked its light. By 2015, the comets would have moved even farther away on their long orbital journey, leaving no detectable infrared excess.
“This is a very strange star,” said Marengo. “It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after ‘Little Green Men.'”
Clearly, more long-term observations are needed. And frankly, I’m still puzzled why cold or less active comets might still not be detected by their glowing dust. But let’s assume for a moment the the comet idea is correct. If so, we should expect to see similar dips in KIC 8462852’s light as the comet swarm swings around again.
Astronomers have been arguing over just how many spiral arms our Galaxy exhibits. Is the Milky Way a four or two-armed spiral galaxy? Astronomers had often assumed the Milky Way was potentially a four-armed spiral galaxy, but comparatively recent observations from NASA’s Spitzer telescope implied the Galaxy had two spiral arms. In 2013, astronomers mapped star forming regions and argued they had found the two missing arms, bringing the total number of arms back to four.
The case for a four-armed Milky Way may have just gotten stronger.
“Despite efforts aimed at improving our understanding of the Galaxy’s structure, questions remain. There is no consensus regarding the number and shape of the Galaxy’s spiral arms.”, noted lead author D. Camargo. He added that the Sun’s location within the obscured disc of the Galaxy was a principal factor hindering our understanding of the Milky Way’s broader structure. In other words, we do not have a bird’s eye view of our Galaxy.
The team remarked that young embedded clusters are excellent tracers of the Galaxy’s structure, “The present results indicate that the Galaxy’s embedded clusters are predominantly located in the spiral arms.” They noted that star formation may occur after the collapse and fragmentation of giant molecular clouds found within spiral arms, and consequently the young embedded star clusters that subsequently emerge are excellent probes of Galactic structure as they have not displaced far from their birthplace.
The team used data from NASA’s WISE infrared telescope to identify young clusters still embedded in their natal clouds, which are often encompassed by significant dust. Infrared stellar light is less obscured by dust than visible light, giving the astronomers an unprecedented view. Indeed, the group discovered 7 new embedded clusters, several of which (designated Camargo 441-444) may belong to a larger aggregate that resides in the Perseus arm. They suggested that a giant molecular cloud was compressed by the spiral arm which may have triggered star formation in several clumps, and numerous star clusters with similar ages emerged (an alternative or concurrent scenario is sequential formation).
The team also used near-infrared data from the 2MASS survey to determine distances for the star clusters, once the objects were identified in the WISE images. A primary goal of their work was to establish accurate fundamental cluster parameters, which would bolster any resulting conclusions concerning the Galaxy’s overall structure. An innovative algorithm was therefore adopted to minimize contamination by foreground and background stars along the sight-line, which may otherwise appear as cluster members and degrade the reliability of any distant estimates.
“The embedded clusters in the present sample are distributed along the Sagittarius-Carina, Perseus, and Outer arms.”, concluded the team. They likewise noted that the search for new embedded clusters throughout the entire Galaxy must continue unabated, since such targets may foster our understanding of the Galaxy’s structure.
The discoveries are described in a new study by D. Camargo, C. Bonatto, and E. Bica that is entitled “Tracing the Galactic spiral structure with embedded clusters”. The research has been accepted for publication, and will appear in a forthcoming issue of the Monthly Notices of the Royal Astronomical Society (MNRAS). A preprint of the work is available on arXiv.
Beam us up, Scotty. There’s no signs of intelligent life out there. At least, no obvious signs, according to a recent survey performed by researchers at Penn State University. After reviewing data taken by the NASA Wide-field Infrared Survey Explorer (WISE) space telescope of over 100,000 galaxies, there appears to be little evidence that advanced, spacefaring civilizations exist in any of them.
First deployed in 2009, the WISE mission has been able to identify thousands of asteroids in our solar system and previously undiscovered star clusters in our galaxy. However, Jason T. Wright, an assistant professor of astronomy and astrophysics at the Center for Exoplanets and Habitable Worlds at Penn State University, conceived of and initiated a new field of research – using the infrared data to assist in the search for signs of extra-terrestrial civilizations.
And while their first look did not yield much in the way of results, it is an exciting new area of research and provides some very useful information on one of the greatest questions ever asked: are we alone in the universe?
“The idea behind our research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths,” said Wright, “exactly the radiation that the WISE satellite was designed to detect for other astronomical purposes.”
This logic is in keeping with the theories of Russian astronomer Nikolai Kardashev and theoretical physicist Freeman Dyson. In 1964, Kardashev proposed that a civilization’s level of technological advancement could be measured based on the amount of energy that civilization is able to utilize.
To characterize the level of extra-terrestrial development, Kardashev developed a three category system – Type I, II, and III civilizations – known as the “Kardashev Scale”. A Type I civilization uses all available resources on its home planet, while a Type II is able to harness all the energy of its star. Type III civilizations are those that are advanced enough to harness the energy of their entire galaxy.
Similarly, Dyson proposed in 1960 that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. Believing that a sufficiently advanced civilization would be able to enclose their parent star, he believed it would be possible to search for extraterrestrials by looking for large objects radiating in the infrared range of the electromagnetic spectrum.
These thoughts were expressed in a short paper submitted to the journal Science, entitled “Search for Artificial Stellar Sources of Infrared Radiation“. In it, Dyson proposed that an advanced species would use artificial structures – now referred to as “Dyson Spheres” (though he used the term “shell” in his paper) – to intercept electromagnetic radiation with wavelengths from visible light downwards and radiating waste heat outwards as infrared radiation.
“Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” said Wright. “This same basic physics causes your computer to radiate heat while it is turned on.”
However, it was not until space-based telescopes like WISE were deployed that it became possible to make sensitive measurements of this radiation. WISE is one of three infrared missions currently in space, the other two being NASA’s Spitzer Space Telescope and the Herschel Space Observatory – a European Space Agency mission with important NASA participation.
WISE is different from these missions in that it surveys the entire sky and is designed to cast a net wide enough to catch all sorts of previously unseen cosmic interests. And there are few things more interesting than the prospect of advanced alien civilizations!
To search for them, Roger Griffith – a postbaccalaureate researcher at Penn State and the lead author of the paper – and colleagues scoured the entries in the WISE satellites database looking for evidence of a galaxy that was emitting too much mid-infrared radiation. He and his team then individually examined and categorized 100,000 of the most promising galaxy images.
And while they didn’t find any obvious signs of a Type II civilization or Dyson Spheres in any of them, they did find around 50 candidates that showed unusually high levels of mid-infrared radiation. The next step will be to confirm whether or not these signs are due to natural astronomical processes, or could be an indication of a highly advanced civilization tapping their parent star for energy.
In any case, the team’s findings were quite interesting and broke new ground in what is sure to be an ongoing area of research. The only previous study, according to the G-HAT team, surveyed only about 100 galaxies, and was unable to examine them in the infrared to see how much heat they emitted. What’s more, the research may help shed some light on the burning questions about the very existence of intelligent, extra-terrestrial life in our universe.
“Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes,” said Wright. “That’s interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognize them.”
Alas, it seems we are no closer to resolving the Fermi Paradox. But for the first time, it seems that investigations into the matter are moving beyond theoretical arguments. And given time, and further refinements in our detection methods, who knows what we might find lurking out there? The universe is very, very big place, after all.
The research team’s first research paper about their Glimpsing Heat from Alien Technologies Survey (G-HAT) survey appeared in the Astrophysical Journal Supplement Series on April 15, 2015.
It’s hard to believe it now looking at Mars’ dusty, dessicated landscape that it once possessed a vast ocean. A recent NASA study of the Red Planet using the world’s most powerful infrared telescopes clearly indicate a planet that sustained a body of water larger than the Earth’s Arctic Ocean.
If spread evenly across the Martian globe, it would have covered the entire surface to a depth of about 450 feet (137 meters). More likely, the water pooled into the low-lying plains that cover much of Mars’ northern hemisphere. In some places, it would have been nearly a mile (1.6 km) deep.
Now here’s the good part. Before taking flight molecule-by-molecule into space, waves lapped the desert shores for more than 1.5 billion years – longer than the time life needed to develop on Earth. By implication, life had enough time to get kickstarted on Mars, too.
Using the three most powerful infrared telescopes on Earth – the W. M. Keck Observatory in Hawaii, the ESO’s Very Large Telescope and NASA’s Infrared Telescope Facility – scientists at NASA’s Goddard Space Flight Center studied water molecules in the Martian atmosphere. The maps they created show the distribution and amount of two types of water – the normal H2O version we use in our coffee and HDO or heavy water, rare on Earth but not so much on Mars as it turns out.
In heavy water, one of the hydrogen atoms contains a neutron in addition to its lone proton, forming an isotope of hydrogen called deuterium. Because deuterium is more massive than regular hydrogen, heavy water really is heavier than normal water just as its name implies. The new “water maps” showed how the ratio of normal to heavy water varied across the planet according to location and season. Remarkably, the new data show the polar caps, where much of Mars’ current-day water is concentrated, are highly enriched in deuterium.
On Earth, the ratio of deuterium to normal hydrogen in water is 1 to 3,200, but at the Mars polar caps it’s 1 to 400. Normal, lighter hydrogen is slowly lost to space once a small planet has lost its protective atmosphere envelope, concentrating the heavier form of hydrogen. Once scientists knew the deuterium to normal hydrogen ratio, they could directly determine how much water Mars must have had when it was young. The answer is A LOT!
Only 13% of the original water remains on the planet, locked up primarily in the polar regions, while 87% of the original ocean has been lost to space. The most likely place for the ocean would have been the northern plains, a vast, low-elevation region ideal for cupping huge quantities of water. Mars would have been a much more earth-like planet back then with a thicker atmosphere, providing the necessary pressure, and warmer climate to sustain the ocean below.
What’s most exciting about the findings is that Mars would have stayed wet much longer than originally thought. We know from measurements made by the Curiosity Rover that water flowed on the planet for 1.5 billion years after its formation. But the new study shows that the Mars sloshed with the stuff much longer. Given that the first evidence for life on Earth goes back to 3.5 billion years ago – just a billion years after the planet’s formation – Mars may have had time enough for the evolution of life.
So while we might bemoan the loss of so wonderful a thing as an ocean, we’re left with the tantalizing possibility that it was around long enough to give rise to that most precious of the universe’s creations – life.
To quote Charles Darwin: “… from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
At first glance, you wouldn’t think Hawaii has any connection at all with asteroid 2004 BL86, the one that missed Earth by 750,000 miles (1.2 million km) just 3 days ago. One’s a tropical paradise with nightly pig roasts, beaches and shave ice; the other an uninhabitable ball of bare rock untouched by floral print swimsuits.
But Planetary Science Institute researchers Vishnu Reddy and Driss Takir would beg to differ.
Using NASA’sInfrared Telescope Facility on Mauna Kea, Hawaii they discovered that the speedy “space mountain” has a composition similar to the very island from which they made their observations – basalt.
“Our observations show that this asteroid has a spectrum similar to V-type asteroids,” said Reddy. “V-type asteroids are basalt, similar in composition to lava flows we see in Hawaii.
The researchers used a spectrograph to study infrared sunlight reflected from 2004 BL86 during the flyby. A spectrograph splits light into its component colors like the deli guy slicing up a nice salami. Among the colors are occasional empty spaces or what astronomers call absorption lines, where minerals such as olivine, pyroxene and plagioclase on the asteroid’s surface have removed or absorbed particular slices of sunlight.
These are the same materials that not only compose earthly basalts – all that dark volcanic rock that underlies Hawaii’s reefs and resorts – but also Vesta, considered the source of V-type asteroids. It’s thought that the impact that hollowed out the vast Rheasilvia crater at Vesta’s south pole blasted chunks of mama asteroid into space to create a family of smaller siblings called vestoids.
So it would appear that 2004 BL86 could be a long-lost daughter born through impact and released into space to later be perturbed by Jupiter into an orbit that periodically brings it near Earth. Close enough to watch in wonder as it inches across the field of view of our telescopes like it did earlier this week.
The little moonlet may or may not be related to Vesta, but its presence makes 2004 BL86 a binary asteroid, where each object revolves about their common center of gravity. While the asteroid is unlikely to become future vacation destination, there will always be Hawaii to satisfy our longings for basalt.
Imagine a single mission that would allow you to explore the Milky Way and beyond, investigating cosmic chemistry, hunting planets, mapping galactic structure, probing dark energy and analyzing the expansion of the wider Universe. Enter the Sloan Digital Sky Survey, a massive scientific collaboration that enables one thousand astronomers from 51 institutions around the world to do just that.
At Tuesday’s AAS briefing in Seattle, researchers announced the public release of data collected by the project’s latest incarnation, SDSS-III. This data release, termed “DR12,” represents the survey’s largest and most detailed collection of measurements yet: 2,000 nights’ worth of brand-new information about nearly 500 million stars and galaxies.
One component of SDSS is exploring dark energy by “listening” for acoustic oscillation signals from the the acceleration of the early Universe, and the team also shared a new animated “fly-through” of the Universe that was created using SDSS data.
The SDSS-III collaboration is based at the powerful 2.5-meter Sloan Foundation Telescope at the Apache Point Observatory in New Mexico. The project itself consists of four component surveys: BOSS, APOGEE, MARVELS, and SEGUE. Each of these surveys applies different trappings to the parent telescope in order to accomplish its own, unique goal.
BOSS (the Baryon Oscillation Spectroscopic Survey) visualizes the way that sound waves produced by interacting matter in the early Universe are reflected in the large-scale structure of our cosmos. These ancient imprints, which date back to the first 500,000 years after the Big Bang, are especially evident in high-redshift objects like luminous-red galaxies and quasars. Three-dimensional models created from BOSS observations will allow astronomers to track the expansion of the Universe over a span of 9 billion years, a feat that, later this year, will pave the way for rigorous assessment of current theories regarding dark energy.
At the press briefing, Daniel Eistenstein from the Harvard-Smithsonian Center for Astrophysics explained how BOSS requires huge volumes of data and that so far 1.4 million galaxies have been mapped. He indicated the data analyzed so far strongly confirm dark energy’s existence.
APOGEE (the Apache Point Observatory Galactic Evolution Experiment) employs a sophisticated, near-infrared spectrograph to pierce through thick dust and gather light from 100,000 distant red giants. By analyzing the spectral lines that appear in this light, scientists can identify the signatures of 15 different chemical elements that make up the faraway stars – observations that will help researchers piece together the stellar history of our galaxy.
MARVELS (the Multi-Object APO Radial Velocity Exoplanet Large-Area Survey) identifies minuscule wobbles in the orbits of stars, movements that betray the gravitational influence of orbiting planets. The technology itself is unprecedented. “MARVELS is the first large-scale survey to measure these tiny motions for dozens of stars simultaneously,” explained the project’s principal investigator Jian Ge, “which means we can probe and characterize the full population of giant planets in ways that weren’t possible before.”
At the press briefing, Ge said that MARVELS observed 5,500 stars repeatedly, looking for giant exoplanets around these stars. So far, the data has revealed 51 giant planet candidates as well as 38 brown dwarf candidates. Ge added that more will be found with better data processing.
SEGUE (the Sloan Extension for Galactic Understanding and Exploration) rounds out the quartet by analyzing visible light from 250,000 stars in the outer reaches of our galaxy. Coincidentally, this survey’s observations “segue” nicely into work being done by other projects within SDSS-III. Constance Rockosi, leader of the SDSS-III domain of SEGUE, recaps the importance of her project’s observations of our outer galaxy: “In combination with the much more detailed view of the inner galaxy from APOGEE, we’re getting a truly holistic picture of the Milky Way.”
One of the most exceptional attributes of SDSS-III is its universality; that is, every byte of juicy information contained in DR12 will be made freely available to professionals, amateurs, and lay public alike. This philosophy enables interested parties from all walks of life to contribute to the advancement of astronomy in whatever capacity they are able.
As momentous as the release of DR12 is for today’s astronomers, however, there is still much more work to be done. “Crossing the DR12 finish line is a huge accomplishment by hundreds of people,” said Daniel Eisenstein, director of the SDSS-III collaboration, “But it’s a big universe out there, so there is plenty more to observe.”
DR12 includes observations made by SDSS-III between July 2008 and June 2014. The project’s successor, SDSS-IV, began its run in July 2014 and will continue observing for six more years.
Here is the video animation of the fly-through of the Universe:
In the reeds that line the banks of the celestial river Eridanus, you’ll find Hebe on the prowl this month. Discovered in 1847 by German amateur astronomer Karl Ludwig Hencke , the asteroid may hold the key to the origin of the H-chondrites, a large class of metal-rich stony meteorites found in numerous amateur and professional collections around the world. You can now see this interesting minor planet with nothing more than a pair of binoculars or small telescope.
The first four asteroids – Ceres, Pallas, Juno and Vesta – were discovered in quick succession from 1801 to 1807. Then nothing turned up for years. Most astronomers wrongly assumed all the asteroids had been found and moved on to other projects like measuring the orbits of double stars and determining stellar parallaxes. Nothing could have been further from the truth. Hencke, who worked as a postmaster during the day, doggedly persisted in sieving the stars for new asteroids in his free time at night. His systematic search began in 1830. Fifteen years and hundreds of cold nights at the eyepiece later he turned up 5 Astrae (asteroid no. 5) on Dec. 8, 1845, and 6 Hebe on July 1, 1847.
Energized by the finds, astronomers returned to their telescopes with renewed gusto to join in the hunt once again. The rest is history. As of November 2014 there are 415,688 numbered asteroids and a nearly equal number of unnumbered discoveries. Fittingly, asteroid 2005 Hencke honors the man who kept the fire burning.
At 120 miles (190 km) across, Hebe is one of the bigger asteroids (officially 33rd in size in the main belt) and orbits the Sun once every 3.8 years. It will be our guest this final month of the year shining at magnitude +8.2 in early December, +8.5 by mid-month and +8.9 when you don your party hat on New Year’s Eve. All the while, Hebe will loop across the barrens of Eridanus west of Orion. Use the maps here to help track it down. I’ve included a detailed color map above, but also created a “black stars on white” version for those that find reverse charts easier to use.
In more recent times, Hebe’s story takes an interesting turn. Through a study of its gravitational nudges on other asteroids, astronomers discovered that Hebe is a very compact, rocky object, not a loosey-goosey pile of rubble like some asteroids. Its high density provides strong evidence for a composition of both rock and iron. Scientists can determine the approximate composition of an asteroid’s surface by studying its reflectance spectrum, or what colors or wavelengths are reflected back from the object after a portion is absorbed by its surface. They use infrared light because different minerals absorb different wavelengths of infrared light. That data is compared to infrared absorptions from rocks and meteorites found on Earth. Turns out, our friend Hebe’s spectrum is a good match to two classes of meteorites – the H-chondrites, which comprise 40% of known meteorites – and the rarer IIE silicated iron meteorites.
Because Hebe orbits close to an unstable zone in the asteroid belt, any impacts it suffers are soon perturbed by Jupiter’s gravity and launched into trajectories than can include the Earth. When you spot Hebe in your binoculars the next clear night, you might just be seeing where many of the more common space rocks in our collections originated.
Crazy things can happen when galaxies collide, as they sometimes do. Although individual stars rarely impact each other, the gravitational interactions between galaxies can pull enormous amounts of gas and dust into long streamers, spark the formation of new stars, and even kick objects out into intergalactic space altogether. This is what very well may have happened to SDSS1133, a suspected supermassive black hole found thousands of light-years away from its original home.
Seen above in a near-infrared image acquired with the Keck II telescope in Hawaii, SDSS1133 is the 40-light-year-wide bright source observed 2,300 light-years out from the dwarf galaxy Markarian 177, located 90 million light-years away in the constellation Ursa Major (or, to use the more familiar asterism, inside the bowl of the Big Dipper.)
The two bright spots at the disturbed core of Markarian 177 are thought to indicate recent star formation, which could have occurred in the wake of a previous collision.
“We suspect we’re seeing the aftermath of a merger of two small galaxies and their central black holes,” said Laura Blecha, an Einstein Fellow in the University of Maryland’s Department of Astronomy and a co-author of an international study of SDSS1133. “Astronomers searching for recoiling black holes have been unable to confirm a detection, so finding even one of these sources would be a major discovery.”
Interactions between supermassive black holes during a galactic collision would also result in gravitational waves, elusive phenomena predicted by Einstein that are high on astronomers’ most-wanted list of confirmed detections.
Watch an animation of how the suspected collision and subsequent eviction may have happened:
But besides how it got to where it is, the true nature of SDSS1133 is a mystery as well.
The persistently bright near-infrared source has been detected in observations going back at least 60 years. Whether or not SDSS1133 is indeed a supermassive black hole has yet to be determined, but if it isn’t then it’s a very unusual type of extremely massive star known as an LBV, or Luminous Blue Variable. If that is the case though, it’s peculiar even for an LBV; SDSS1133 would have had to have been continuously pouring out energy in a for over half a century until it exploded as a supernova in 2001.
To help determine exactly what SDSS1133 is, continued observations with Hubble’s Cosmic Origins Spectrograph instrument are planned for Oct. 2015.
“We found in the Pan-STARRS1 imaging that SDSS1133 has been getting significantly brighter at visible wavelengths over the last six months and that bolstered the black hole interpretation and our case to study SDSS1133 now with HST,” said Yanxia Li, a UH Manoa graduate student involved in the research.
And, based on data from NASA’s Swift mission the UV emission of SDSS1133 hasn’t changed in ten years, “not something typically seen in a young supernova remnant” according to Michael Koss, who led the study and is now an astronomer at ETH Zurich.
Regardless of what SDSS1133 turns out to be, the idea of such a massive and energetic object soaring through intergalactic space is intriguing, to say the least.
The study will be published in the Nov. 21 edition of Monthly Notices of the Royal Astronomical Society.
In a test of its new high resolution capabilities, the Atacama Large Millimeter/submillimeter Array (ALMA) is happily sharing some family snapshots with us. Astronomers manning the cameras have captured one of the best images so far of a newly-forming planet system gathering itself around a recently ignited star. Located about 450 light years from us in the constellation of Taurus, young HL Tau gathers material around it to hatch its planets and fascinate researchers.
Thanks to ALMA images, scientists have been able to witness stages of planetary formation which have been suspected, but never visually confirmed. This very young star is surrounded by several concentric rings of material which have neatly defined spacings. Is it possible these clearly marked gaps in the solar rubble disc could be where planets have started to gel?
“These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.
“When we first saw this image we were astounded at the spectacular level of detail. HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets. This one image alone will revolutionize theories of planet formation,” explained Catherine Vlahakis, ALMA Deputy Program Scientist and Lead Program Scientist for the ALMA Long Baseline Campaign.
Let’s take a look at what we understand about solar system formation…
Through repeated research, astronomers suspect that all stars are created when clouds of dust and gas succumb to gravity and collapse on themselves. As the star begins to evolve, the dust binds together – turning into “solar system soup” consisting of an array of different sized sand and rocks. This rubble eventually congeals into a thin disc surrounding the parent star and becomes home to newly formed asteroids, comets, and planets. As the planets collect material into themselves, their gravity re-shapes to structure of the disc which formed them. Like dragging a lawn sweeper over fallen leaves, these planets clear a path in their orbit and form gaps. Eventually their progress pulls the gas and dust into an even tighter and more clearly defined structure. Now ALMA has shown us what was once only a computer model. Everything we thought we knew about planetary formation is true and ALMA has proven it.
“This new and unexpected result provides an incredible view of the process of planet formation. Such clarity is essential to understand how our own solar system came to be and how planets form throughout the universe,” said Tony Beasley, director of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, which manages ALMA operations for astronomers in North America.
“Most of what we know about planet formation today is based on theory. Images with this level of detail have up to now been relegated to computer simulations or artist’s impressions. This high resolution image of HL Tauri demonstrates what ALMA can achieve when it operates in its largest configuration and starts a new era in our exploration of the formation of stars and planets,” says Tim de Zeeuw, Director General of ESO.
The major reason astronomers have never seen this type of structure before is easy to envision. The very dust which creates the planetary disc around HL Tau also conceals it to visible light. Thanks to ALMA’s ability to “see” at much longer wavelengths, it can image what’s going on at the very heart of the cloud. “This is truly one of the most remarkable images ever seen at these wavelengths. The level of detail is so exquisite that it’s even more impressive than many optical images. The fact that we can see planets being born will help us understand not only how planets form around other stars but also the origin of our own solar system,” said NRAO astronomer Crystal Brogan.
How does ALMA do it? According to the research staff, its new high-resolution capabilities were achieved by spacing the antennas up to 15 kilometers apart. This baseline at millimeter wavelengths enabled a resolution of 35 milliarcseconds, which is equivalent to a penny as seen from more than 110 kilometers away. “Such a resolution can only be achieved with the long baseline capabilities of ALMA and provides astronomers with new information that is impossible to collect with any other facility, including the best optical observatories,” noted ALMA Director Pierre Cox.
The long baselines spell success for the ALMA observations and are a tribute to all the technology and engineering that went into its construction. Future observations at ALMA’s longest possible baseline of 16 kilometers will mean even more detailed images – and an opportunity to further expand our knowledge of the Cosmos and its workings. “This observation illustrates the dramatic and important results that come from NSF supporting world-class instrumentation such as ALMA,” said Fleming Crim, the National Science Foundation assistant director for Mathematical and Physical Sciences. “ALMA is delivering on its enormous potential for revealing the distant universe and is playing a unique and transformational role in astronomy.”
Pass them baby pictures our way, Mama ALMA… We’re delighted to take a look!
Surprise! Three planets believed to be good candidates for having water vapor in their atmosphere actually have much lower quantities than expected.
The planets (HD 189733b, HD 209458b, and WASP-12b) are “hot Jupiters” that are orbiting very close to their parent star, at a distance where it was expected the extreme temperatures would turn water into a vapor that could be seen from afar.
But observations of the planets with the Hubble Space Telescope, who have temperatures between 816 and 2,204 degrees Celsius (1,500 and 4,000 degrees Fahrenheit), show only a tenth to a thousandth of the water astronomers expected.
“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside our solar system, and we can now say with much greater certainty than ever before that we’ve found water in an exoplanet,” stated Nikku Madhusudhan, an astrophysicist at the University of Cambridge, England who led the research. “However, the low water abundance we have found so far is quite astonishing.”
This finding, if confirmed by other observations, could force exoplanet formation theory to be revised and could even have implications for how much water is available in so-called “super-Earths”, rocky planets that are somewhat larger than our own, the astronomers said.
That theory states that planets form over time as small dust particles stick to each other and grow into larger bodies. As it becomes a planet and takes on an atmosphere from surrounding gas bits, it’s believed that those elements should be “enhanced” in proportion to its star, especially in the case of oxygen. That oxygen in turn should be filled with water.
“We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth),” Madhusudhan stated.
The research will be published today (July 24) in the Astrophysical Journal.