Posted on by Nancy Atkinson

Another (Better) Opportunity to Send Your Name to Space

Kepler spacecraft. IMage credit: NASA

It’s a great idea, so all the missions might as well join in. Earlier today, Ian reported on how the Lunar Reconnaissance Orbiter mission is offering the chance for the public to ‘ride along’ to the moon by sending their names to be added to a computer chip which will be embedded on the spacecraft. Well, not to be outdone, the upcoming Kepler mission that will search for Earth-sized exoplanets is offering the same chance. But this is no sluff opportunity where you just fill in your name and you’re done: you’ve got to work a little and be creative! The Kepler folks would like you to also state in 100 words or less why you think the Kepler mission is important. I think that’s a great idea, and I’m going to add my name and statement right away. But there’s more reasons why I prefer the Kepler mission’s approach to sending your name to space:

Your name will be in an exciting Earth-trailing heliocentric orbit, going around the sun every 372.5 days.

This activity is done in association with the International Year of Astronomy 2009.

Your name will be on the spacecraft that will likely identify the first Earth-sized or smaller planet orbiting another star.

Your name will be launched on board a Delta II rocket.

Your name will be part of the mission that will determine the frequency of terrestrial and larger planets in or near the habitable zone of a wide variety of spectral types of stars.

Oh, the list goes on, but as you can see the Kepler mission will be THE mission to have your name be included.

So, here’s where you can add your name, as well as your statement of the importance of the Kepler mission. The deadline is November 1, 2008. And learn more about the mission here. Current plans are for a February 2009 launch for Kepler.

Original News Source: JPL press release

Posted on by Fraser Cain

How Big Do Planets Get?

Artist's impression of Gliese 436 c

Question: How Big Can Planets Get?

Answer: Here in the Solar System, we have three kinds of planets: the inner terrestrial planets, the gas giants, and the ice planets. Sadly, Pluto is no longer a planet, so we won’t deal with that here. We know how big our planets are, but how big can planets actually get in other Solar Systems. What are the biggest possible planets?

Let’s start with terrestrial planets, like our Earth. We’ll set the size of the Earth and 1 Earth radius, and the mass as 1 Earth mass. We’ve seen that terrestrial planets can get smaller, with Mars and Mercury, and astronomers have detected larger terrestrial planets orbiting other stars.

The largest known rocky planet is thought to be Gliese 436 c. This is probably a rocky world with about 5 Earth masses and 1.5 times our planet’s radius. Amazingly, this planet is thought to be within its star’s habitable zone.

What’s the largest possible rocky planet? For this I put in an email to Dr. Sean Raymond, a post doctoral researcher at the Center for Astrophysics and Space Astronomy (CASA) at the University of Colorado. Here’s what he had to say:

“The largest “terrestrial” planet is generally considered the one before you get too thick of an atmosphere, which happens at about 5-10 Earth masses (something like 2 Earth radii). Those planets are more Earth-like than Neptune-like.”

Gas giants, of course, can come much larger. Jupiter is 317 times more massive than Earth, and 11 times larger. You could fit 1,400 Earths inside Jupiter.

Thebiggest planet in the Universe (at the time of this writing) is TrES-4, which is located 1,400 light years away in the constellation Hercules. The planet has been measured to be 1.4 times the size of Jupiter, but it only has 0.84 times Jupiter’s mass. With such a low density, the media was calling TrES-4 the puffy planet.

And once again, how large can they get? Again, here’s Dr. Raymond:

“In terms of gaseous planets, once they reach 15 Jupiter masses or so there is enough pressure in the core to ignite deuterium fusion, so those are considered “brown dwarfs” rather than planets.”

What is the biggest planet in the Solar System?

Posted on by Fraser Cain

Why Haven’t Planets Been Detected Around Alpha Centauri?

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Artist impression of Alpha Centauri

Question: Why aren’t astronomers looking for planets around nearby stars like Alpha Centauri?
Answer: That’s a great question. Since Alpha Centauri is only a little over 4 light-years away, why aren’t astronomers studying it for planets, instead of the more distant stars.

Astronomers have included stars like Alpha Centauri in their search for extrasolar planets, they just haven’t found them yet. That’s because the techniques used to find extra solar planets require very large planets orbiting very close to their parent stars.

The first technique is called the radial velocity method. This is where the gravity of the planet yanks its parent star back and forth. The changes in the star’s velocity are measurable in the light that reaches the Earth.

The second technique looks for transits. This is where the planet passes in front of the parent star, dimming it slightly. By measuring the amount the light dims, astronomers are able to know if there’s a planet there, calculate its size and even determine what’s in its atmosphere.

A third technique detects microlensing events. A closer star focuses the light from a more distant star with its gravity. From Earth, we see a flare in brightness as the two stars line up perfectly. If the closer star has a planet orbiting it, that will change the light curve that astronomers detect, allowing them to calculate the size of the planet.

Most of the planets discovered to date are known as Hot Jupiters. These are planets much larger than Jupiter that orbit within the orbit of Mercury.

A team of astronomers led by Javiera Guedes from the University of California think that an Earth-sized planet should be detectable orbiting Alpha Centauri. They’re working to get a single dedicated telescope to watch the star, and work out if there are planets there. According to their calculations, it should only take about 5 years of intense observations by a dedicated telescope to work out the answer.

Posted on by Nancy Atkinson

Using Laser Combs to Find Exoplanets

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We’ve run a couple of articles recently about new techniques to find Earth-like extra-solar planets. Here’s one more, but this new technique is really quite exciting. A new device, called a laser comb, uses femto-second (one millionth of one billionth of a second) pulses of laser light coupled with an atomic clock to provide a precise standard for measuring wavelengths of light. Also known as an “astro-comb,” these devices should give astronomers the ability to use the Doppler shift method with incredible precision to measure spectral lines of starlight up to 60 times greater than any current high-tech method, according to a new paper in the journal Nature.

Astronomers have been using the Doppler shift method to find exoplanets for the past 10 years. Current technology can measure spectral lines with a precision of 60 centimeters per second, which works good enough to find a planet 5 times the mass of Earth in a Mercury-like orbit around a Sun-like star. To find an Earth-mass planet in an Earth-like orbit, a precision of less than 5 cm per second is necessary, and the researchers believe they ultimately can achieve 1 cm per second precision.

The combs work by creating regular spikes of laser light that are evenly spaced in wavelength ”like the teeth of a comb” and can be projected onto a spectrograph.

One of the authors of the paper, Ronald Walsworth from the Harvard-Smithsonian Center for Astrophysics said the group should begin testing its prototype system in June 2008 at the Multi-Mirror Telescope (MMT) Observatory on Mount Hopkins in Arizona. And in 2009 the researchers plan to set up a planet-spotting system at the 4.2-metre William Herschel Telescope on La Palma, in the Canary Islands, in collaboration with the Geneva Observatory.

The inventors of the laser comb, John L. Hall and Theodor W. Hansch shared half of the 2005 Nobel Prize in Physics. This technology has previously been used in chemical sensing and telecommunications. If used with larger telescopes, researchers believe the astro comb could possibly make direct measurements of dark energy.

Original News Sources: Nature, and Nature News

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