exoplanets Archives

January 7, 2013December 23, 2015 by Jason Major

Kepler Finds Hundreds of New Exoplanet Candidates

Artist’s depiction of the Kepler 10 system, which contains planets 2.2 and 1.4 times the size of Earth. (NASA/Ames/JPL-Caltech)

Kepler mission scientists announced today the discovery of literally hundreds of new exoplanet candidates — 461, to be exact — orbiting distant stars within a relatively small cross-section of our galaxy, bringing the total number of potential planets awaiting confirmation to 2,740. What’s more, at least 4 of these new candidates appear to be fairly Earth-sized worlds located within their stars’ habitable zone, the orbital “sweet spot” where surface water could exist as a liquid.

Impressive results, considering that NASA’s planet-hunting spacecraft was launched a little under 4 years ago (and watching 150,000 stars to spot the shadows of planets is no easy task!)

“… the ways by which men arrive at knowledge of the celestial things are hardly less wonderful than the nature of these things themselves.”

— Johannes Kepler

Since the last official announcement of Kepler candidates in Feb. 2012 the number of smaller Earth- and super-Earth-sized worlds observed has risen considerably, as well as the identification of multi-planet systems that are organized more-or-less along a flat plane… just like ours.

“There is no better way to kickoff the start of the Kepler extended mission,” said Kepler scientist Christopher Burke, “than to discover more possible outposts on the frontier of potentially life bearing worlds.”

From the NASA press release:

Since the last Kepler catalog was released in February 2012, the number of candidates discovered in the Kepler data has increased by 20 percent and now totals 2,740 potential planets orbiting 2,036 stars. The most dramatic increases are seen in the number of Earth-size and super Earth-size candidates discovered, which grew by 43 and 21 percent respectively.

The new data increases the number of stars discovered to have more than one planet candidate from 365 to 467. Today, 43 percent of Kepler’s planet candidates are observed to have neighbor planets.

The most dramatic increases are seen in the number of Earth-size and super Earth-size candidates discovered, which grew by 43 and 21 percent respectively. (NASA)

Although some of the new candidates announced today are large Neptune-sized planets, more than half are Earth- to super-Earth sized worlds less than twice the radius of our own planet.

In order for Kepler candidates to be “officially” called exoplanets, they must be observed 3 times on a regular orbit — that is, their signature dimming of the light from their home star must occur as predicted once their presence and then orbital period is calculated. Only then is an exoplanet confirmed.

To date Kepler has confirmed 105 exoplanets.

The longer the mission continues, the better the chance that Kepler will be able to confirm smaller Earth-sized worlds in longer-period orbits.

“The analysis of increasingly longer time periods of Kepler data uncovers smaller planets in longer period orbits — orbital periods similar to Earth’s,” said Steve Howell, Kepler mission scientist. “It is no longer a question of will we find a true Earth analogue, but a question of when.”

Scientists analyzed more than 13,000 transit-like signals called ‘threshold crossing events’ to eliminate known spacecraft instrumentation and astrophysical false positives, phenomena that masquerade as planetary candidates, to identify the potential new planets. Watch the video below to see how Kepler observes the light-curve of transit events.

Read more on the NASA press release, and learn more about the Kepler mission here.

January 7, 2013December 23, 2015 by Nancy Atkinson

Nearly All Sun-Like Stars Have Planetary Systems

A new analysis examined the frequencies of planets of different sizes based on findings from NASA's Kepler spacecraft, correcting for both incompleteness and false positives. The results show that one in six stars has an Earth-sized planet in a tight orbit. Credit: F. Fressin (CfA)

The latest analysis of data from the Kepler planet-hunting spacecraft reveals that almost all stars have planets, and about 17 percent of stars have an Earth-sized planet in an orbit closer than Mercury. Since the Milky Way has about 100 billion stars, there are at least 17 billion Earth-sized worlds out there, according to Francois Fressin of the Harvard-Smithsonian Center for Astrophysics (CfA), who presented new findings today in a press conference at the American Astronomical Society meeting in Long Beach, California. Moreover, he said, almost all Sun-like stars have planetary systems.

The holy grail of planet-hunting is finding a twin of Earth – a planet of about the same size and in the habitable zone around similar star. The odds of finding such a planet is becoming more likely Fressin said, as the latest analysis shows that small planets are equally common around small and large stars.

While the list of Kepler planetary candidates contains majority of the knowledge we have about exoplanets, Fressin said the catalog is not yet complete, and the catalog is not pure. “There are false positives from events such as eclipsing binaries and other astrophysical configurations that can mimic planet signals,” Fressin said.

By doing a simulation of the Kepler survey and focusing on the false positives, they can only account for 9.5% of the huge number of Kepler candidates. The rest are bona-fide planets.

This artist's illustration represents the variety of planets being detected by NASA's Kepler spacecraft. Credit: C. Pulliam & D. Aguilar (CfA)

Altogether, the researchers found that 50 percent of stars have a planet of Earth-size or larger in a close orbit. By adding larger planets, which have been detected in wider orbits up to the orbital distance of the Earth, this number reaches 70 percent.

Extrapolating from Kepler’s currently ongoing observations and results from other detection techniques, it looks like practically all Sun-like stars have planets.

The team then grouped planets into five different sizes. They found that 17 percent of stars have a planet 0.8 – 1.25 times the size of Earth in an orbit of 85 days or less. About one-fourth of stars have a super-Earth (1.25 – 2 times the size of Earth) in an orbit of 150 days or less. (Larger planets can be detected at greater distances more easily.) The same fraction of stars has a mini-Neptune (2 – 4 times Earth) in orbits up to 250 days long.

Larger planets are much less common. Only about 3 percent of stars have a large Neptune (4 – 6 times Earth), and only 5 percent of stars have a gas giant (6 – 22 times Earth) in an orbit of 400 days or less.

The researchers also asked whether certain sizes of planets are more or less common around certain types of stars. They found that for every planet size except gas giants, the type of star doesn’t matter. Neptunes are found just as frequently around red dwarfs as they are around sun-like stars. The same is true for smaller worlds. This contradicts previous findings.

“Earths and super-Earths aren’t picky. We’re finding them in all kinds of neighborhoods,” says co-author Guillermo Torres of the CfA.

Planets closer to their stars are easier to find because they transit more frequently. As more data are gathered, planets in larger orbits will come to light. In particular, Kepler’s extended mission should allow it to spot Earth-sized planets at greater distances, including Earth-like orbits in the habitable zone.

Kepler detects planetary candidates using the transit method, watching for a planet to cross its star and create a mini-eclipse that dims the star slightly.

Sources: Harvard Smithsonian CfA, AAS Press Conference

November 12, 2012December 23, 2015 by Jason Major

Here There Be Planets: Stellar Disk Gap May Reveal Newborn Worlds

HiCIAO near-infrared image of the protoplanetary disk around PDS 70. The circular mask hides the star itself, as well as a smaller internal disk structure. (Credit: NAOJ)

Over the past couple of decades astronomers have figured out several methods for finding planets around other stars in our galaxy. Some have revealed their presence by the slight “wobble” they impart to their host stars as they orbit, while others have been discovered as they pass in front of their stars from our perspective, briefly dimming the light we see.

Now, some astronomers think they may have identified the presence of multiple planets, based on a large gap found in the disk of gas and dust surrounding a Sun-like star 460 light-years from Earth.

Using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) mounted on Japan’s 8.2-meter optical-infrared Subaru telescope atop Mauna Kea in Hawaii, an international team of astronomers targeted PDS 70, a young star (10 million years old) about the same mass as the Sun located 460 light-years away in the constellation Centaurus.

The near-infrared observations made by HiCIAO reveal a protoplanetary disk surrounding PDS 70. This disk is composed of gas and dust and extends billions of miles out from the star. Quite literally the stuff that planets are made of, it’s a disk much like this that our solar system likely started out as over 4.6 billion years ago.

“Thanks to the powerful combination of the Subaru Telescope and HiCIAO, we are able to probe the disks around Sun-like stars. PDS 70 shows how our solar system may have looked in its infancy. I want to continue this kind of research to understand the history of planetary formation.”

– Team Leader Jun Hashimoto (NAOJ)

Within PDS 70’s disk are several large gaps positioned at varying distances from the star itself, appearing as dark regions in the near-infrared data. These gaps — especially the largest, located about 70 AU from the star — are thought to be the result of newly-formed planets having cleared the surrounding space of dust and smaller material. It’s also believed that multiple planets may be present since, according to the team, “no single planet, regardless of how heavy or efficient it is in its formation, is sufficient to create such a giant gap.”

In addition to the large disk structure and outer gap, PDS 70 also has a smaller disk located only 1 AU away. (This disk is obscured by the HiCIAO mask in the image above.)

Further observations will be needed to locate any actual exoplanets directly, since the light from the star and scattered light within the disk makes it difficult — if not impossible with current technology — to detect the incredibly faint light reflected by planets.

Still, it’s fascinating to come across what may very well be a solar system in its infancy, giving us a glimpse back in time to our own formation.

“Direct imaging of planets in the process of forming in protoplanetary disks would be ideal so that we can learn when, where, and how planets form,” said team leader Ruobing Dong of Princeton University.

Read more on the NAOJ website for the Subaru Observatory here.

The goal of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) Project is to study the disks around less massive stars like the Sun.

Inset image: Artist’s rendition of PDS 70 and its two protoplanetary disks (NAOJ)

November 7, 2012December 23, 2015 by Nancy Atkinson

Want to Name an Exoplanet? Uwingu Has a Plan

Screenshot from the Uwingu exoplanet naming website.

Astronomers have now discovered nearly 1,000 planets orbiting other stars, and right now these exoplanets all have boring, license-plate-like names, such as HD85512 and GJ 436 instead of endearing, “real” planet names that might offer hints of what that world could be like. And recall the recent extrapolation of how many habitable planets might be in the Milky Way? A team using the ESO’s HARP’s spectrograph determined there might be upwards of 160 billion worlds out there for us to find, and perhaps eventually name. How might we come up with that many names?

Uwingu, a startup company that is hoping to use innovative ways to fund space and astronomy research, has an idea of how to do that. Their first commercial project is to challenge people to create a ‘baby book of planet names’ for all these planets, as suggestions for future names for other worlds.

“The many, many planets discovered across the galaxy in past 20 years are a tribute to our natural human desire to explore beyond the horizon,” said noted planet hunter Dr. Geoff Marcy of the University of California at Berkeley, who is also an advisor for Uwingu. “Now people all over the world can participate in these discoveries in a new way, giving identities and even personality to billions of planets in our galaxy for the first time.”

How does this raise money for space science? Submitting suggestions for names cost $.99 each, and Uwingu will use proceeds from this project and future ones to create funds for grants that space researchers, space educators, and project teams can apply to use.

Uwingu’s first project is technically now in “beta testing,” and in a press release, the organization said the public can participate immediately, helping to generate a new source of funds for space exploration, research, and education.

But it doesn’t end with just suggestions. People can vote on the top names (each vote also costs $.99), and as Uwingu CEO and founder Alan Stern told Universe Today, they are hoping the voting goes viral among the social media savvy.

“This is a way for people everywhere to connect with space,” he said. “You can suggest a name and tell all your friends to vote, and the top names will be the first to be used. If you nominate the name of someone famous, hopefully they’ll get in on the excitement and ask their fans to vote, too.”

The Uwingu team suggests nominating planet names for your favorite town, state, or country, your favorite sports team, music artist, or hero, your favorite author or book, your school, your company, for your loved ones and friends, or even for yourself.

The names won’t be officially approved by the International Astronomical Union, but Stern said they will be are similar to the names given to features on Mars by the mission science teams (such as the “Jake Matijevic” rock recently analyzed by the Curiosity rover) that everyone ends up using. This also solves the problem of how to come up with names, a task that the IAU has yet to discuss.

Initial reactions to the planet naming project – and to Uwingu itself — have been mixed. During their Indigogo fundraising, the Uwingu team didn’t disclose what types of things they would be selling or doing to raise funds, which was a concern to some in the space and astronomy community who normally support almost any space-related initiative. In a previous interview with UT, Stern said being secretive was a way to generate interest and likened it to how Apple announces a new product.

While there seems to be excitement about the opportunity to suggest names for exoplanets (as of this writing 74 names had been nominated, with numerous votes for each name), some early reactions have been that this might be similar to the ‘name a star’ registries that are unofficial and quite expensive.

IAU’s stance on naming exoplanets has been that since it appears there are going to be so many of them, naming them will be difficult. However, in an email reply, the former president of the IAU Planetary Systems Science body, Karen Meech said that at the IAU meeting in Beijing this summer there was discussion about the need to set up a group to look into the issue of exoplanet names.

And Meech did confirm that since the IAU is the only scientifically recognized arbiter of astronomical names, any contests for names from the public will not be officially recognized by the scientific community.

But if the problem is in the amount of names that will be required, that’s where Uwingu’s crowd sourcing idea seems to fit the need.

And for those who are critical of Uwingu’s methods, Uwingu is so far the only group or organization to step forward with innovative, out-of-the-box ways to try and solve what seems to be a continuous, perennial problem: how to fund creative space and astronomy projects and move beyond the old tried and not always true methods of relying on government grants and subsidies or angel donors.

Uwingu is at least trying something different, and it will be interesting to see how this plays out. Stern said earlier that Uwingu’s projects would appeal to the general public, not just the space and astronomy community, to provide a bigger marketplace for their projects. He indicated Uwingu will be coming out with another project in a few months.

We humans love to name things: we name our cars, spacecraft and rocks, craters and hills on other planets. NASA has had contests to name missions, rovers, and modules on the ISS, all of which has generated excitement among the public. Science and science fiction fans have expressed disappointment at the names given to exoplanets so far (they certainly aren’t as intriguing as names we’ve come to love like Tatooine, Pandora, Vulcan or Hoth.) Uwingu is using that innate need/love of naming things to try and move space science and astronomy into a new era.

September 10, 2012April 26, 2016 by Nancy Atkinson

Possible Subterranean Life Means More Exoplanets Could Harbor Life

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.

Artistic representation of the current five known potential habitable worlds. Will this list broaden under a new habitability model? Credit: The Planetary Habitability Laboratory (PHL)

When we think of life on other planets, we tend to imagine things (microbes, plant life and yes, humanoids) that exist on the surface. But Earth’s biosphere doesn’t stop at the planet’s surface, and neither would life on another world, says a new study that expands the so-called ‘Goldilocks Zone’ to include the possibility of subterranean habitable zones. This new model of habitability could vastly increase where we could expect to find life, as well as potentially increasing the number of habitable exoplanets.

We know that a large fraction of the Earth’s biomass is dwelling down below, and recently microbiologists discovered bacterial life, 1.4 kilometers below the sea floor in the North Atlantic, deeper in the Earth’s crust than ever before. This and other drilling projects have brought up evidence of hearty microbes thriving in deep rock sediments. Some derive energy from chemical reactions in rocks and others feed on organic seepage from life on the surface. But most life requires at least some form of water.

“Life ‘as we know it’ requires liquid water,” said Sean McMahon, a PhD student from the University of Aberdeen’s (Scotland) School of Geosciences. “Traditionally, planets have been considered ‘habitable’ if they are in the ‘Goldilocks zone’. They need to be not too close to their sun but also not too far away for liquid water to persist, rather than boiling or freezing, on the surface. However, we now know that many micro-organisms—perhaps half of all living things on Earth—reside deep in the rocky crust of the planet, not on the surface.”

Location in the night sky of the stars with potential habitable exoplanets (red circles). There are two in Gliese 581. Click the image for larger version. CREDIT: PHL @ UPR Arecibo and Jim Cornmell.

While suns warm planet surfaces, there’ also heat from the planets’ interiors. Crust temperature increases with depth so planets that are too cold for liquid water on the surface may be sufficiently warm underground to support life.

“We have developed a new model to show how ‘Goldilocks zones’ can be calculated for underground water and hence life,” McMahon said. “Our model shows that habitable planets could be much more widespread than previously thought.”

In the past, the Goldilocks zone has really been determined by a circumstellar habitable zone (CHZ), which is a range of distances from a star, and depending on the star’s characteristics, the zone varies. The consensus has been that planets that form from Earth-like materials within a star’s CHZ are able to maintain liquid water on their surfaces.
But McMahon and his professor, John Parnell, also from Aberdeen University who is leading the study now are introducing a new term: subsurface-habitability zone (SSHZ). This denote the range of distances from a star within which planets are habitable at any depth below their surfaces up to a certain maximum, for example, they mentioned a “SSHZ for 2 km depth”, within which planets can support liquid water 2 km or less underground.

If this notion catches on – which it should – it will have exoplanet hunters recalculating the amount of potentially habitable worlds.

The research was presented at the annual British Science Festival in Aberdeen.

Source: University of Aberdeen

August 17, 2012December 23, 2015 by Jason Major

What If All of Kepler’s Exoplanets Orbited the Same Star?

That’s exactly the scenario shown by a mesmerizing animation called “Worlds” by Alex Parker — a single system containing 2299 multiple-transit planetary candidates identified to date by NASA’s Kepler space telescope, which is currently scrutinizing a field of view within the constellation Cygnus to detect the oh-so-faint reductions in brightness caused by planets passing in front of their stars.

The search requires patience and precision; it’s not really this crowded out there.

Alex’s animation takes 2299 candidates that have been observed multiple times, each shown to scale in relation to their home star, and puts them in orbit around one star, at their relative distances.

The result, although extravagantly impossible, is no less fascinating to watch. (I suggest going full screen.)

“The Kepler observatory has detected a multitude of planet candidates orbiting distant stars,” Alex writes on his Vimeo page. “The current list contains 2321 planet candidates, though some of these have already been flagged as likely false-positives or contamination from binary stars. This animation does not contain circumbinary planets or planet candidates where only a single transit has been observed, which is why ‘only’ 2299 are shown.

“A fraction of these candidates will likely be ruled out as false positives as time goes on, while the remainder stand to be confirmed as real planets by follow-up analysis,” Alex adds.

The white ellipses seen when the animation pulls back are the relative sizes of the orbits of Mercury, Venus and Earth.

At this time the Kepler mission has identified 2321 planetary candidates, with 74 exoplanets confirmed. See more on the Kepler mission here.

Animation: Alex Parker. Image: Kepler mission planet candidates family portrait (NASA Ames/Jason Rowe/Wendy Stenzel)

August 14, 2012December 23, 2015 by Jon Voisey

Two “b”‘s in the Beehive

Praesepe (aka. the Beehive Cluster)

As astronomers near the 800 mark for confirmed extra solar planets, it seems that notable milestones are becoming fewer and further between. Multi-planet systems aren’t even worth mentioning. Planets less massive than Earth? Already heard about it. Detecting atmospheres? Old news.

But a recent paper manages to sneak in one new first: The first detection of hot Jupiters in an open cluster. This discovery is not simply notable due to the novelty, but clusters have special characteristics that can help astronomers determine more of the history of the system.

The discovery was made by astronomers at Georgia State University using the “wobble” method in which they looked for the spectroscopic wiggle of spectral lines as planets tugged their parent stars around in orbit. The Beehive Cluster was chosen because it is a nearby cluster with over 1,000 member stars, many of which are similar in mass to the Sun. Additionally, the cluster is known to have an above average metallicity which is known to be correlated with planetary systems.

Searches of other open clusters have largely come up empty. Only two stars in open clusters have so far been found to have planets and both of those are around giant stars and as such, the planets are in wide orbits. This paucity is odd since stars are expected to form in clusters, and as such, the frequency of planets in clusters should be nearly the same as isolated stars.

The team used the 1.5-m Tillinghast Reflector at the Fred L. Whipple Observatory on Mt. Hopkins, Arizona observing a total of 53 stars in the cluster. Their results uncovered two new hot Jupiter planets in tight orbits around the parent, main-sequence stars. The first has an estimated mass of 0.54 times that of Jupiter while the second weighs in at 1.8 Jupiter masses.

The discovery helps to place constraints on how planets form and migrate in fledgling systems. Since massive planets such as these would need to form further out in colder parts of the circumstellar cloud, such planets would have to move inwards. The time period in which this happens has been a difficult question for astronomers to pin down. But since the Beehive cluster is only 600 million years old and these new planets are already in tight orbits, this helps to demonstrate that such migration is possible on short timescales.

While these are the first of their kind discovered in open clusters, this discovery puts the number of hot Jupiters in open clusters in rough agreement with expectations based on the number of such systems of stars that are no longer bound in clusters. This finding bridges the gap between formation and isolated stars that previous searches of open clusters had left open.

July 20, 2012December 23, 2015 by Jason Major

Exoplanet Gliese 581g Makes the Top 5

Exoplanet Gliese 581g is back, and “officially” ranking #1 on a list of potentially habitable worlds outside of our solar system thanks to new research from the team that originally announced its discovery in 2010.

Orbiting a star 20 light-years away, the super-Earth is now listed alongside other exoplanets Gliese 667Cc, Kepler-22b, HD85512 and Gliese 581d in the University of Puerto Rico at Arecibo’s Habitable Exoplanets Catalog as good places to look for Earthlike environments… and thus the possibility of life.

First announced in September 2010 by a team led by Steven S. Vogt of UC Santa Cruz, the presence of Gliese 581g was immediately challenged by other astronomers whose data didn’t support its existence. Vogt’s team conducted further analysis of the Gliese system in which it appeared that the orbits of the planets were circular, rather than elliptical, and it was in this type of scenario that a strong signal for Gliese 581g once again appeared.

Read: Could Chance For Life on Gliese 581g Actually Be “100%”?

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt.

And, located near the center of its star’s habitable “Goldilocks” zone and receiving about the same relative amount of light as Earth does, Gliese 581 g isn’t just on the list… it’s now considered the best candidate for being an Earthlike world — knocking previous favorite Gliese 667Cc into second place.

Read: Billions of Habitable Worlds Likely in the Milky Way

The announcement was made on the PHL’s press site earlier today by Professor Abel Méndez, Director of the PHL at UPR Arecibo.

Diagram of the Gliese system. The green area is the habitable zone, where liquid water can exist on a planet’s surface. (PHL @ UPR Arecibo)

“The controversy around Gliese 581g will continue and we decided to include it to our main catalog based on the new significant evidence presented, and until more is known about the architecture of this interesting stellar system”

– Prof. Abel Méndez, UPR Arecibo

July 10, 2012December 23, 2015 by John Williams

Sifting Starlight, Finding New Worlds

These two images show HD 157728, a nearby star 1.5 times larger than the sun. The star is centered in both images, and its light has been mostly removed by an adaptive optics system and coronagraph belonging to Project 1640, which uses new technology on the Palomar Observatory’s 200-inch Hale telescope near San Diego, Calif., to spot planets. Credit: Project 1640

Looking directly at stars is a bad way to find planets orbiting faraway suns but using a new technique, scientists can now sift the starlight to find new exoplanets millions of times dimmer than their parent stars.

“We are blinded by this starlight,” says Ben R. Oppenheimer, a curator in the American Museum of Natural History’s Department of Astrophysics and principal investigator for Project 1640. “Once we can actually see these exoplanets, we can determine the colors they emit, the chemical compositions of their atmospheres, and even the physical characteristics of their surfaces. Ultimately, direct measurements, when conducted from space, can be used to better understand the origin of Earth and to look for signs of life in other worlds.”

Using indirect detection methods, astronomers have found hundreds of planets orbiting other stars. The light stars emit, however, is tens of millions to billions of times brighter than the light reflected by planets.

Project 1640 is an advanced telescope imaging system, made up of the world’s most advanced adaptive optics system, instruments and software. The project operates at the 200-inch Hale Telescope at California’s Palomar Observatory. Engineers at the American Museum of Natural History, California Institute of Technology, and NASA’s Jet Propulsion Laboratory worked more than six years developing the new system.

Earth’s atmosphere wreaks havoc with starlight. The heating and cooling of the atmosphere produces turbulence that creates a twinkling effect on the point-like light from a star. Optics within a telescope also warp light. The instruments that make up Project 1640 manipulate starlight by deforming a mirror more than 7 million times a second to counteract the twinkling. This produces a crystal clear infrared image of the star with a precision smaller than one nanometer; about 100 times smaller than a typical bacteria.

“Imaging planets directly is supremely challenging,” said Charles Beichman, executive director of the NASA ExoPlanet Science Institute at the California Institute of Technology. “Imagine trying to see a firefly whirling around a searchlight more than a thousand miles away.”

A coronagraph, built by the American Museum of Natural History, optically dims the star leaving other celestial objects in the field of view. Other instruments help create an “artificial eclipse” inside Project 1640. Only about half a percent of the original light remains in the form of a speckled background. These speckles can still be hundreds of times brighter than the dim planets. The instruments control the light from the speckles to further dim their brightness. What the instrument creates is a dark hole where the star had been while leaving the light reflected from any planets. Coordination of the system is extremely important, say the researchers. Even the smallest light leak would drown out the incredibly faint light from planets orbiting a star.

For now Project 1640, the world’s most advanced and highest contrast imaging system, is focusing on bright stars relatively close to Earth; about 200 light-years away. Their three-year survey includes plans to image hundreds of young stars. The planets they may find are likely to be very large, Jupiter-sized bodies.

“The more we learn about them, the more we realize how vastly different planetary systems can be from our own,” said Jet Propulsion Laboratory astronomer Gautam Vasisht. “All indications point to a tremendous diversity of planetary systems, far beyond what was imagined just 10 years ago. We are on the verge of an incredibly rich new field.”

Read more about Project 1640: http://research.amnh.org/astrophysics/research/project1640

Image Caption: Two images of HD 157728, a nearby star 1.5 times larger than the Sun. The star is centered in both images, and its light has been mostly removed by the adaptive optics system and coronagraph. The remaining starlight leaves a speckled background against which fainter objects cannot be seen. On the left, the image was made without the ultra-precise starlight control that Project 1640 is capable of. On the right, the wavefront sensor was active, and a darker square hole formed in the residual starlight, allowing objects up to 10 million times fainter than the star to be seen. Images were taken on June 14, 2012 with Project 1640 on the Palomar Observatory’s 200-inch Hale telescope. (Courtesy of Project 1640)

July 5, 2012December 23, 2015 by Jason Major

The Case of the Disappearing Dust

Astronomy has always taught us that planets form from vast clouds of dust and gas orbiting young stars. It’s a gradual process of accretion that takes hundreds of thousands, perhaps even millions, of years… or does it?

During a 1983 sky survey with the Infrared Astronomical Satellite (IRAS) astronomers identified a young Sun-like star with a large cloud of dust surrounding it. The star, named TYC 8241 2652 1, is 450 light years away and what they had found around it was thought to be the beginnings of a solar system – the protoplanetary disc from which planets form.

Fast forward to 2008. Astronomers observed at the same star with a different infrared telescope, the Gemini South Observatory in Chile. What was observed looked a lot like what was previously seen in ’83.

Then, in 2009, they looked again. Curiously, the brightness of the dust cloud was only a third of what it was the year before. And in WISE observations made the very next year, it had disappeared entirely.

“It’s like the classic magician’s trick: now you see it, now you don’t. Only in this case we’re talking about enough dust to fill an inner solar system, and it really is gone.”

– Carl Melis, lead author and postdoctoral fellow at UC San Diego

Abracadabra?

“It’s as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared,” said study co-author and circumstellar disk expert Ben Zuckerman of UCLA.

It’s always been thought that planets take some time to form, in the order of hundreds of thousands of years. Although that may seem like forever to humans, it’s quick in cosmic time scales. But if what they’ve seen here with TYC 8241 is in fact planetary formation, well… it may happen a lot faster than anyone thought.

On the other hand, the star could have somehow blown all the dust out of the system. More research will be needed to see if that was the case.

The really interesting thing here is that astronomers have traditionally looked for these kinds of dust clouds around stars to spot planetary formation in action. But if planets form quicker than we thought, and the dust clouds are only fleeting features, then there may be a lot more solar systems out there that we can’t directly observe.

“People often calculate the percentage of stars that have a large amount of dust to get a reasonable estimate of the percentage of stars with planetary systems, but if the dust avalanche model is correct, we cannot do that anymore,” said study co-author Inseok Song, assistant professor of physics and astronomy at the University of Georgia. “Many stars without any detectable dust may have mature planetary systems that are simply undetectable.”

Top image: Gemini Observatory/AURA artwork by Lynette Cook.