Posted on by Nancy Atkinson

New Search Technique May Lead to Discovery of Extra-solar Earth-Like Planets

The Holy Grail in the search for extra-solar planets would be to find an Earth-like world orbiting another star. A group of UK astronomers believe they have good chance of being the first to find such a planet with a revolutionary new camera called RISE. With RISE, scientists will search for extra-solar planets using a technique called “transit timing,” which may provide a short-cut to discovering Earth-like planets with existing technology.

The two primary techniques to find extra-solar planets are usually only sensitive to massive, gas giant planets in close orbit around their parent star, so-called “Hot Jupiters.” Firstly, planets can be found through their gravitational pull on the star they orbit – as the extra-solar planet moves the star wobbles back and forth, and by measuring this movement astronomers can deduce the presence of a planet. Secondly, the transit search technique looks for the changes in a star’s brightness as a planet passes in front of it.

But neither of these techniques is currently good enough to find small extra-solar planets similar to the Earth. With the new transit timing technique, the RISE camera will look for Earth-mass planets in orbit around stars already known to host Hot Jupiters.

Transit timing works on the principle that an isolated hot Jupiter planet orbiting its host will have a constant orbital period (i.e. its ‘year’ remains the same) and therefore it will block out the light from its parent star in a regular and predictable way. During the planet’s transit events, RISE can very accurately measure the rise and fall in the amount of light reaching the Earth from the parent star – the camera can be used to pinpoint the time of the centre of the event to within 10 seconds. RISE is a fast-read camera. It has a fixed “V+R” filter and reimaging optics giving a 7 x 7 acrminute field of view to maximize the number of comparison stars available. An e2V frame transfer detector is used to obtain a cycle time of less than 1 second.

Hot Jupiter planet. Image Credit: ESA

By observing and timing their transits, astronomers hope to detect small changes in the orbital periods of known hot Jupiters caused by the gravitational pull of other planets in the same system. In the right circumstances, even planets as small as the Earth could be found in this way.

“The potential of transit timing is the result of some very simple physics, where multi-planet systems will gravitationally kick one another around in their orbits – an effect often witnessed in our own Solar System,” said PhD student Neale Gibson of Queen’s University Belfast. “If Earth-mass planets are present in nearby orbits (which is predicted by current Hot-Jupiter formation theories) we will see their effect on the orbit of the larger transiting planets. RISE will allow us to observe and time the transits of extrasolar planets very accurately, which gives us the sensitivity required to detect the effect of even small Earth-mass planets.”

RISE was designed by astronomers at Queen’s University in collaboration with Liverpool John Moores University and is now installed on the 2 meter Liverpool Telescope on the Canary Island of La Palma. For more information about the RISE Camera, see Neale Gibson’s homepage.

Original News Source: NAM Press Release

Posted on by Nancy Atkinson

SuperWASP are Super Planet-Finding Observatories

The United Kingdom’s Wide Area Search for Planets, known as SuperWASP consists of two 8-camera robotic observatories that cover both hemispheres of the sky. In the past 6 months an international team of astronomers have used these unique observatories to discover 10 new extra-solar planets, making SuperWASP the most successful planet-hunting observatory in the world. The discovery of these planets was announced on April 1 by Dr. Don Pollacco of Queen’s University in Belfast at the Royal Astronomy Society’s National Astronomy Meeting in the UK.

All told, scientists have found more than 270 extrasolar planets since the the early 1990s. Most of these are detected through their gravitational influence on the star they orbit. As a planet orbits a star, it tugs the star back and forth. However, making these discoveries depends on looking at each star over a period of weeks or months, making the pace of discovery fairly slow.

But SuperWASP uses a different method. The two sets of cameras watch for events known as transits, where a planet passes directly in front of a star and blocks out some of the star’s light, so from the Earth the star temporarily appears a little fainter. The SuperWASP cameras work as robots, surveying a large area of the sky at once and each night astronomers have data from millions of stars that they can check for transits. The transit method also allows scientists to deduce the size and mass of each planet.

SuperWASP-North is located on the island of La Palma, just off the Northwestern coast of Africa, and SuperWASP-South is at the southern tip of Africa at the South African Astronomical Observatory near Sutherland, South Africa.

SuperWasp Cameras. Image Credit: SuperWASP project & David Anderson

The observatories are quite simple, but effective. They use 8 high quality digital cameras to take pictures of the sky and simply measure any changing brightness of the stars.

Each possible planet found using SuperWASP is then observed by astronomers working at the Nordic Optical Telescope on La Palma, the Swiss Euler Telescope in Chile and the Observatoire de Haute Provence in southern France, who use precision instruments to confirm or reject the discovery.

45 planets have now been discovered using the transit method, and since they started operation in 2004 the SuperWASP cameras have found 15 of them, which makes SuperWASP by far the most successful discovery instruments in the world. The SuperWASP planets have a variety of masses, between a middleweight 0.5 and a huge 8.3 times that of Jupiter. A number of these new worlds are quite exotic. For example, a year on WASP-12B (its orbital period) is just 1.1 days. The planet is so close to its star that its daytime temperature could reach a searing 2300 degrees Celsius.

Dr. Pollacco is delighted with the results. “SuperWASP is now a planet-finding production line and will revolutionize the detection of large planets and our understanding of how they were formed. It’s a great triumph for European astronomers.”

Original News Source: Royal Astronomy Society press release

Posted on by Nancy Atkinson

Planet Formation Revealed?

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One of the biggest unresolved questions of planet formation is how a thick disc of debris and gas surrounding young stars eventually evolves into a thin, dusty region with planets. This entire process, of course, has never actually been observed. But recently, and for the first time, a group of astrophysicists produced an image of material surrounding a star which seems to be coalescing into a planet.

The image was produced from a coronagraph attached to a telescope in Hawaii. It shows a horseshoe-shaped void in the disc of materials surrounding the star AB Aurigae, with a bright point appearing as a dot in the void.

“The deficit of material could be due to a planet forming and sucking material onto it, coalescing into a small point in the image and clearing material in the immediate surroundings,” said researcher Ben Oppenheimer, an astrophysicist at the American Museum of Natural History in New York. “It seems to be indicative of the formation of a small body, either a planet or a brown dwarf.”

A brown dwarf is considered a star that’s not massive enough to generate the thermonuclear fusion to create an actual star.

From what we know about planet formation, planets seem to be natural by-product of stars. But how does all this happen? Stars form when clouds of gas and dust contract under gravity, and if there’s enough compression and heat, sooner or later a nuclear reaction is triggered, and voilà: a star. If there’s any left-over material surrounding the young star, eventually the disc of dust and/or gas may congeal into planets. But the details of this process are unknown.

AB Aurigae is a well-studied star. It’s young, between one and three million years old, and can provide information on how stars and objects that orbit them form. And scientists hope that by studying this star, we can learn more about how planets form from the initial thick, gas-rich disk of debris that surrounds young stars. The observation of stars slightly older than AB Aurigae shows that at some point the gas is removed, but no one knows how this happens. AB Aurigae could be in an intermediate stage, where the gas is being cleared out from the center, leaving mainly dust behind.

“More detailed observations of this star can help solve questions about how some planets form, and can possibly test competing theories,” says Oppenheimer. And if this object is a brown dwarf, our understanding of them must be revamped as brown dwarfs are not believed to form in circumstellar materials, Oppenheimer said.

Original New Source: National Science Foundation Press Release

Posted on by Fraser Cain

Organic Molecules Seen in an Extrasolar Planet

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The Hubble Space Telescope has turned up evidence for organic molecules on a planet orbiting another star. Organic molecules? Like the stuff we’re made of? Yes, but wait, this isn’t the discovery of life. In fact, it’s just the tell-tale signature of methane in the atmosphere of a distant, superheated planet.

The Jupiter-sized extrasolar planet is called HD 189733b, and it orbits a star about 63 light-years away in the constellation Vulpecula. Astronomers discovered that the planet is a member of the “hot Jupiter” class of planets, orbiting so close to its parent star that it only takes 2 days to complete an orbit.

This close orbit, much closer than the orbit of Mercury, raises the planet’s temperature to a sweltering 900 degrees Celsius – about the same temperature as the melting point of silver.

Here’s a computer animated video of the planet.

The observations were made using the transit method. This is where the planet passes directly in front of the parent star from our perspective. As it passes in front, it dims the light from the star slightly. And there’s a special bonus. As the planet is making this transit, astronomers can measure its atmosphere.

Using a technique called spectroscopy, the astronomers were able to split the light coming from the planet to reveal the fingerprints of various chemicals in its atmosphere. They confirmed the existence of water, turned up by NASA’s Spitzer Space Telescope back in 2007. But now they also found methane.

Under the right circumstances, methane can play a key role in prebiotic chemistry – the chemical reactions considered necessary to form life as we know it. Methane has been discovered in other planets in our own Solar System, so it doesn’t mean there’s life on HD 189733b (especially with its extremely hot temperatures). But finding methane around another planet, orbiting another star is an exciting advancement.

So even though life is out of the question on HD 189733b, the technique is the major news here. Astronomers will eventually be peering at smaller, more Earth-sized planets, and will be using this method to find other chemicals of life within stellar habitable zones.

If the life’s out there, astronomers are getting closer and closer to finding it.

The discovery was published in the March 20th issue of the journal Nature.

Original Source: Hubble News Release

Posted on by Ian O'Neill

Could AA Tauri Hold the Biochemical Key to Extra-Terrestrial Life?

NASA’s Spitzer Space Telescope has measured huge quantities of water and organic compounds surrounding the star AA Tauri, 450 light years from Earth. AA Tauri is a young star, only a million years old, not too dissimilar to our Sun when it was a baby. What makes AA Tauri even more special is that it appears to have the “spectral fingerprint” for a system that could allow life to form. Finding a star system similar to our own, with organic compounds was always bound to cause excitement, but finding a star so close to us provides a fantastic opportunity to study AA Tauri. This will, in turn, help us understand the evolution of our own solar system and how life is able to form…

AA Tauri is slowly evolving. Gas and dust surrounds the star and recent observations suggest there are abundant organic chemicals (the ones responsible for binding together and creating amino acids). Although NASA’s announcement isn’t claiming that ET is out there (you can sit back into your seats), it is significant that a star should have all the building blocks for life as we know it laid out for the spectrometer on board Spitzer to observe.

The basic organic chemicals in question are possibly located within the “Goldilocks Zone” for planetary/life development from AA Tauri. Although AA Tauri is young, the surrounding flat disk of planetary-forming materials should eventually coalesce to form rocky bodies such as planets, asteroids and possibly gas giants (along the lines of “failed star” Jupiter). The abundance of organic chemicals and water will add to the intrigue surrounding the star.
A comparison between a model and observations of AA Tauri - water is present around the baby star (credit: NASA/JPL/CalTech/J. Carr/NRL)
These observations were collected by NASA’s Spitzer Space Telescope which is able to probe deep into the chemical structure of stars hundreds of parsecs from Earth. John Carr (Naval Research Laboratory, Washington) and Joan Najita (National Optical Astronomy Observatory, Tucson, Ariz.) are developing a new technique, applying Spitzer’s infrared spectrograph. The spectrograph is able to read the chemical composition of the dust contained within a protoplanetary disk. The team has been able to push Spitzer to a new level of precision by analysing the chemical composition of dust particles rather than the gas surrounding the star.

“Most of the material within the disks is gas, but until now it has been difficult to study the gas composition in the regions where planets should form. Much more attention has been given to the solid dust particles, which are easier to observe.” – John Carr of the Naval Research Laboratory, Washington.

So far abundances of hydrogen cyanide, acetylene, carbon dioxide and water vapour have been discovered, allowing scientists to see whether these organic chemicals are enriched or lost during the violent period of planetary formation. Observations such as these highly accurate measurements allow us a chance to glimpse back in time to see what our protoplanetary solar system may have looked like, clearly a very exciting time for the quest to find the origins of life in our galaxy.

Source: NASA/JPL

Posted on by Fraser Cain

Are There Planets Around Alpha Centauri?

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We’re holding out hope for the next generation of planet-finding observatories to locate Earth-sized planets orbiting other stars. But hold on, maybe we don’t need a super space observatory like ESA’s Darwin just yet. In fact, if our nearest neighbour Alpha Centauri has Earth-sized planets, we should be able to detect them with established techniques… right now, with the observatories we have today.

University of California researcher Javiera Guedes has developed a computer simulation that shows that Alpha Centauri B – the largest star in the nearby triple-star system – should have terrestrial planets orbiting within its habitable zone, where liquid water can exist.

They ran several simulations of the system’s first 200 million years. In each instance, despite different parameters, multiple terrestrial planets formed around the star. In every case, at least one planet turned up similar in size to the Earth, and in many cases this planet fell within the star’s habitable zone.

Guedes and co-author Gregory Laughlin think there are several reasons why Alpha Centauri B makes an excellent candidate for finding terrestrial planets. Perhaps the best reason is that Alpha Centauri is just so close, located a mere 4.3 light years away. But it’s also positioned well in the sky, giving it a long period of observability from the Southern Hemisphere.

Most of the 228 extrasolar planets discovered to date have been with the Doppler technique. This is where a planet pulls its parent star back and forth with its gravity. The star’s relative velocity in space changes the wavelength of light coming from it which astronomers can detect. Until now, only the largest planets, orbiting at extremely close distances from their parent stars have been discovered.

But with a nearby star like Alpha Centauri B, much smaller planets could be detected.

The researchers are proposing that astronomers dedicate a single 1.5-metre telescope to intensively monitor Alpha Centauri over a period of 5 years. In that time, any change in the star’s light should be detectable by this telescope.

“If they exist, we can observe them,” said Guedes.

Original Source: UCSC News Release

Posted on by Fraser Cain

Planet Hunter Prepped for Tests

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If you think the discoveries made by planet hunters is exciting already, just you wait. There are some missions in the works that are going multiply the number of planets discovered, and zoom in on the holy grail of finding habitable planets around other stars. The next planet hunter being readied for launch is NASA’s Kepler Mission. This week engineers conducted a series of tests on its image detectors – will it really be able to see planets?

Scheduled for launch in 2009, Kepler will detect planets using the transit method. This is where a planet passes in front of its parent star, briefly dimming the amount of light we see here on Earth. This has been done to detect Jupiter-scale planets, but nothing Earth-sized… yet.

Kepler will have sensitive enough instruments to be able to detect those slight variations in brightness, and determine just how many stars have planets in their habitable zones.

At the Ames Research Center, researchers have developed a Kepler Technology Demonstration test bed. This generates a field of stars that matches the part of the sky where mission scientists are planning to search for transits. The testing engineers can then modify the brightness of the artificial stars to mimic how transiting planets would look as they passed in front of stars.

“This is a major milestone for the Kepler mission,” said David Koch, deputy principal investigator for the Kepler Mission. “We will use hardware identical to what we will be flying on Kepler in the test bed at Ames. We will have the ability to create transits of a star so that we can see the change in the star’s brightness. By simulating transits, we will be able to demonstrate that the flight hardware will work,” Koch explained.

In the final mission, Kepler will be equipped with 42 CCD cameras attached to the spacecraft’s telescope. They make up a 30-cm square (1-foot) array; the largest that will have been flown in space to date. The spacecraft will be able to scan a region of the sky 30,000 times larger than Hubble is able to search.

This month’s test at AMES will have only a single CCD detector, measuring 2.5 cm by 5 cm (1-inch by 2-inches).

I’ll give you an update once the tests are run. Those habitable planets can’t hide forever.

Original Source: NASA News Release

Posted on by Nancy Atkinson

Rocky Planets May Form Around Most Sun-like Stars

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Astronomers have found numerous Jupiter-like planets orbiting other stars. But because of the limits of our current technology, they haven’t yet found any other terrestrial Earth-like planets out in the universe. But new findings from the Spitzer Space Telescope suggest that terrestrial planets might form around many, if not most, of the nearby sun-like stars in our galaxy. So perhaps, other worlds with the potential for life might be more common than we thought.

A group of astronomers led by Michael Meyer of the University of Tucson, Arizona used Spitzer to survey six sets of stars with masses comparable to our sun, and grouped them by age.

“We wanted to study the evolution of the gas and dust around stars similar to the sun and compare the results with what we think the solar system looked like at earlier stages during its evolution,” Meyer said. Our sun is about 4.6 billion years old.

They found that at least 20 percent, and possibly as many as 60 percent, of stars similar to the sun are candidates for forming rocky planets.

The Spitzer telescope does not detect planets directly. Instead, using its infrared capability, it detects dust — the rubble left over from collisions as planets form — at a range of infrared wavelengths. Because dust closer to the star is hotter than dust farther from the star, the “warm” dust indicates material orbiting the star at distances comparable to the distance between Earth and Jupiter.

Meyer said that about 10 to 20 percent of the stars in the four youngest age groups shows ‘warm’ dust, but not in stars older than 300 million years. That is comparable to the theoretical models of our own solar system, which suggests that Earth formed over a span of 10 to 50 million years from collisions between smaller bodies.

But the numbers are vague on how many stars are actually forming planets because there’s more than one way to interpret the Spitzer data. “An optimistic scenario would suggest that the biggest, most massive disks would undergo the runaway collision process first and assemble their planets quickly. That’s what we could be seeing in the youngest stars. Their disks live hard and die young, shining brightly early on, then fading,” Meyer said.

“However, smaller, less massive disks will light up later. Planet formation in this case is delayed because there are fewer particles to collide with each other.”

If this is correct and the most massive disks form their planets first and then the smaller disks take 10 to 100 times longer, then up to 62 percent of the surveyed stars have formed, or may be forming, planets. “The correct answer probably lies somewhere between the pessimistic case of less than 20 percent and optimistic case of more than 60 percent,” Meyer said.

In October 2007, another group of astronomers used similar Spitzer data to observe the formation of a star system 424 light-years away, with another possible Earth-like planet being created.

More definitive data on formation of rocky planets will come with the launch the Kepler mission in 2009, which will search to find if terrestrial planets like Earth could be common around stars like the sun.

Original News Source: JPL Press Release

Posted on by Fraser Cain

Another Solar System Found with Saturn and Jupiter-Sized Planets

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As the search for extrasolar planets continues, researchers are finding systems more and more like our own Solar System. And today researchers announced another significant find: a system with two planets smaller than Jupiter and Saturn. It’s almost starting to sound like home.

The report, due to be published in the February 15th edition of the journal Science discusses a series of observations made back on March 28, 2006. An experiment, known as the Optical Gravitational Microlensing Equipment (OGLE), detected the telltale signal of a microlensing event on a star 5,000 light-years away.

In case you weren’t up in the latest techniques for planetary discovery, a lensing event happens when two stars line up perfectly in the sky from our perspective on Earth. The closer star acts as a natural lens, magnifying the light from the more distant star.

The curve of light coming from the event is very specific, and astronomers know when they’re seeing a microlensing event, compared to something else like a nova or a variable star.

But there are special situations, where the light from the star brightens normally, but then has an additional distortion. The gravity from planets orbiting the closer star can actually create this additional distortion. And from this, astronomers can calculate their size (amazing!). Only 4 planets had been discovered this way so far.

Okay, enough back story.

The OGLE group announced their potential lensing event, and astronomers around the world sprung into action, gathering data for the entire time that the stars were lined up.

Researchers first calculated that there was a Saturn-sized planet orbiting the star, and then another group found that there had to be a Jupiter-sized planet as well.

“Even though we observed the micolensing effect of the Saturn for less than 0.3 percent of its orbit, the observations simply could not be explained without accounting for the orbit,�? said David Bennett, a research associate professor of astrophysics from the University of Notre Dame.

Unfortunately, viewing this planetary system was a one-time event. We’ll probably never see this star line up again, so there’s no way to perform any followup observations.

Original Source: University of Notre Dame News Release

Posted on by Fraser Cain

Lightweight Disk Could Harbour Planets

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Astronomers are looking for planets around other stars, but they’re also looking for the conditions where planets might be forming right now. Inside the disks of material that surround newly forming planets, they could be planets clearing paths through all the gas and dust. A team of Japanese astronomers have found the most lightweight stellar disk ever seen – a place where Earth-sized planets could be forming.

Using the powerful Subaru telescope, located atop Hawaii’s Mauna Kea, a team of astronomers from several Japanese universities have resolved a lightweight disk of material around a nearby, and relatively tiny star called FN Tau. It’s probably only 100,000 years old, and contains a mere 1/10th the mass of our own Sun.

Imaging the circumstellar disks around newly forming stars is difficult because they can be so dim. It’s harder still when the star itself is lightweight, and the disk is light too. All the disks seen to date have been around Sunlike stars. Until now, the lightest disk was still 7 times more massive than FN Tau.

In FN Tau, the astronomers report that we’re looking at the disk nearly face-on. Its radius is approximately 260 astronomical units (each AU is the distance from the Earth to the Sun). And as disks go, it’s relatively featureless, without any anomalies, rings, spirals, etc. But are there planets lurking in the disk?

Astronomers want to know what kinds of planets could form out of a disk like this. With a lightweight disk to total amount of gravity is much lower. This would make a thicker disk as you get further away from the star. Instead of the Jupiter-like planets turned up in extrasolar planet surveys so far, this environment might actually give a better chance of turning up Earth-mass planets instead.

According to their calculations, this disk should be able to form planets lighter than the Earth within 30 astronomical units of the parent star. The researchers are hoping to make followup observations with a newly commission instrument attached to the Subaru telescope. The HiCIAO will be able to resolve the detailed structure of disks and analyze the size and composition of the dust.

And these observations might help researchers know if FN Tau is a candidate for planetary formation.

Original Source: Subaru Telescope News Release