A powerful laser could create the conditions inside a giant exoplanet (Sunbeamtech)
[/caption]We’ve all heard that the Large Hadron Collider (LHC) will collide particles together at previously unimaginable energies. In doing so, the LHC will recreate the conditions immediately after the Big Bang, thereby allowing us to catch a glimpse of what particles the Universe would have been filled with at this time. In a way, the LHC will be a particle time machine, allowing us to see the high energy conditions last seen immediately after the Big Bang, 13.7 billion years ago.
So, if we wanted to understand the conditions inside a giant exoplanet, how could we do it? We can’t directly measure it ourselves, we have to create a laboratory experiment that could recreate the conditions in the core of one of these huge exoplanet gas giants. Much like the LHC will recreate the conditions of the Big Bang, a powerful laser intended to kick-start fusion reactions will be used in an effort to help scientists have a very brief look into the cores of these distant worlds…
The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California is ready for action. The facility will perform fusion experiments, hopefully making a self-sustaining nuclear fusion reaction a reality using an incredibly powerful laser (firing at a hydrogen isotope fuel). Apart from the possibility of finding a way to kick-start a viable fusion energy source (other laboratories have tried, but only sustained fusion for an instant before fizzing out), the results from the laser tests will aid the management of the US nuclear weapon stockpile (since there have been no nuclear warhead tests in 15 years, data from the experiments may help the military deduce whether or not their bombs still work).
Fusion energy and nuclear bombs to one side, there is another use for the laser. It could be used to recreate the crushing pressures inside a massive exoplanet so we can glean a better understanding of what happens to matter at these crushing depths.
The NIF laser can deliver 500 trillion watts in a 20-nanosecond burst, which may not sound very long, but the energy delivered is immense. Raymond Jeanloz, an astronomer at the University of California, Berkeley, will have the exciting task of using the laser, aiming it at a small iron sample (800 micrometres in diameter), allowing him to generate a moment where pressures exceed a billion times atmospheric pressure. That’s 1000 times the pressure of the centre of the Earth.
On firing the laser, the heat will vaporize the iron, blasting a jet of gas so powerful, it will send a shock wave through the metal. The resulting compression is what will be observed and measured, revealing how the metal’s crystalline structure and melting point change at these pressures. The results from these tests will hopefully shed some light on the formation of the hundreds of massive exoplanets discovered in the last two decades.
“The chemistry of these planets is completely unexplored,” says Jeanloz. “It’s never been accessible in the laboratory before.”
Technicians working inside the Astrotech Space Operations facility near NASA's Kennedy Space Center look over the Kepler spacecraft soon after it arrived in Florida in preparation for launch. Image credit: NASA/Tim Jacobs
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NASA’s Kepler spacecraft is ready to be moved to the launch pad today and will blast off within weeks, with a mission to address an age-old question: Are we alone?
Kepler is scheduled to blast into space from Florida’s Cape Canaveral Air Force Station aboard a Delta II rocket on March 5 at 10:48 p.m. eastern time (7:48 p.m. Pacific). It is the first mission with the ability to find planets like Earth — rocky planets that orbit sun-like stars in a warm zone where liquid water could be maintained on the surface. If Earth-sized and slightly larger planets are as common around other stars as some astronomers suspect, Kepler could spy hundreds of them within the next few years.
If so, “life may well be common throughout our universe,” said William Borucki, NASA’s principal investigator for Kepler science, who spoke about the mission Thursday afternoon at a NASA press conference. “If on the other hand we don’t find any, that will be another profound discovery. In fact it will mean there will be no Star Trek.”
The Kepler mission will spend three and a half years surveying more than 100,000 sun-like stars in the Cygnus-Lyra region of our Milky Way galaxy. Its telescope is specially designed to detect the periodic dimming of stars that planets cause as they pass by. Some star systems are oriented in such a way that their planets cross in front of their stars, as seen from our Earthly point of view. As the planets pass by, they cause their stars’ light to slightly dim, or wink.
The telescope can detect even the faintest of these winks, registering changes in brightness of only 20 parts per million. To achieve this resolution, Kepler will use the largest camera ever launched into space, a 95-megapixel array of charged couple devices, known as CCDs.
“If Kepler were to look down at a small town on Earth at night from space, it would be able to detect the dimming of a porch light as somebody passed in front,” James Fanson, Kepler project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a press release. During the briefing he added that the resolution is “akin to measuring a flea as it creeps across the headlight of an automobile at night. That’s the level of precision we have to achieve.”
Fanson added that Kepler, at a cost of about $500 million, is “the most complex piece of space flight hardware ever built” by the Boulder, Colorado-based Ball Aerospace & Technologies Corp.
The exoplanet research field has already proven exciting, Borucki said. Just over three hundred exoplanets have been detected so far, most of them gas giants like Jupiter and Saturn because those are the easiest to spot with pre-Kepler instruments. Already, the known exoplanets are an eclectic bunch.
“We’re finding planets that [would] float like foam on water,” Borucki said. “We’re finding planets with the density of lead.” And whereas researchers were expecting planet with orderly, circular orbits and sizes that increased with distances from stars, they’re finding a chaotic mix of behaviors — eccentric orbits, and giant, gaseous worlds so close to their parent stars that they complete full orbits within days.
By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles, allowing astronomers to confirm the presence of planets and use the Hubble and Spitzer space telescopes, along with ground-based telescopes, to characterize their atmospheres and orbits. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm the planets’ presence.
The first objects likely to be reported will be the Jupiter- and Saturn-sized planets, and gradually — as confirmations roll in and detections get more focused — Neptune and then Earth-sized detections will be more likely to emerge, said exoplanet hunter Debra Fischer of San Francisco State University in California, who is not directly involved with the mission.
“We have a good chance of finding Mars-size planets, and a possibility of finding Mercury-sized planets” with Kepler, she said. “We don’t think we can do better than that.”
The scientists are in no rush to announce new discoveries until they’re “bulletproof,” they said — which could translate into years of suspense for the world’s Trekkies.
“We don’t want to have false discoveries,” Borucki said. “We want to be sure when we say it’s an earth, its an earth.”
Exoplanets like the Earth might be more common than we think. Image Credit: ESO
With the upcoming launch in March of the Kepler mission to find extrasolar planets, there is quite a lot of buzz about the possibility of finding habitable planets outside of our Solar System. Kepler will be the first satellite telescope with the capability to find Earth-size and smaller planets. At the most recent meeting of the American Association for the Advancement of Science (AAAS) in Chicago, Dr. Alan Boss is quoted by numerous media outlets as saying that there could be billions of Earth-like planets in the Milky Way alone, and that we may find an Earth-like planet orbiting a large proportion of the stars in the Universe.
“There are something like a few dozen solar-type stars within something like 30 light years of the sun, and I would think that a good number of those — perhaps half of them would have Earth-like planets. So, I think there’s a very good chance that we’ll find some Earth-like planets within 10, 20, or 30 light years of the Sun,” Dr. Boss said in an AAAS podcast interview.
Dr. Boss is an astronomer at the Carnegie Institution of Washington Department of Terrestrial Magnetism, and is the author of The Crowded Universe, a book on the likelihood of finding life and habitable planets outside of our Solar System.
“Not only are they probably habitable but they probably are also going to be inhabited. But I think that most likely the nearby ‘Earths’ are going to be inhabited with things which are perhaps more common to what Earth was like three or four billion years ago,” Dr. Boss told the BBC. In other words, it’s more likely that bacteria-like lifeforms abound, rather than more advanced alien life.
This sort of postulation about the existence of extraterrestrial life (and intelligence) falls under the paradigm of the Drake Equation, named after the astronomer Frank Drake. The Drake Equation incorporates all of the variables one should take into account when trying to calculate the number of technologically advanced civilizations elsewhere in the Universe. Depending on what numbers you put into the equation, the answer ranges from zero to trillions. There is wide speculation about the existence of life elsewhere in the Universe.
To date, the closest thing to an Earth-sized planet discovered outside of our Solar System is CoRoT-Exo-7b, with a diameter of less than twice that of the Earth.
The speculation by Dr. Boss and others will be put to the test later this year when the Kepler satellite gets up and running. Set to launch on March 9th, 2009, the Kepler mission will utilize a 0.95 meter telescope to view one section of the sky containing over 100,000 stars for the entirety of the mission, which will last at least 3.5 years.
The prospect of life existing elsewhere is exciting, to be sure, and we’ll be keeping you posted here on Universe Today when any of the potentially billions of Earth-like planets are discovered!
With a target launch date of March 5, NASA’s Kepler mission is just weeks away from its tantalizing journey to peer at faraway stars and the Earth-like planets they may be hosting. Hundreds of astronomers from all over the world have a stake in the data. The United States participants hail from all the usual astronomy hubs, among them Arizona, California, Texas and … Iowa? Steve Kawaler, an astrophysicist at Iowa State University, took a moment to chat with Universe Today about his role in a less-publicized goal of the Kepler mission — and his research out of a less-publicized astronomy program.
Q. Why Iowa?
Kawaler: Iowa’s a great place. I’m originally a New Yorker, and went to grad school at the University of Texas, but landing at Iowa State (mostly by chance) still feels right.
(Still Kawaler:) You can get a lot of work done here. We’ve organized and run the Whole Earth Telescope from here for about 10 years. A few years ago [in 2004], the WET team showed a pulsating white dwarf (BPM 37093, but later dubbed the ‘Diamond Star’) may truly be crystalline. Finding one of the biggest diamonds in the cosmos and announcing it around Valentine’s Day was pretty fun! I’ve been part of some big collaborations where nearly all the work is done remotely, and that is important as we stare at the mountain of data we’re about to see.
Q. What’s your role in the Kepler mission?
Kawaler: I serve on the Steering Committee for the Kepler Asteroseismology Research Consortium. We’ll use the exquisite time-series measurements of the brightness of over 100,000 stars to measure their internal properties. The KASC has over 250 scientists involved, and the Steering Committee is charged with helping organize and coordinate their efforts in reducing and interpreting the data.
Q. What’s most exciting about the science in this mission?
Kawaler: The most exciting discovery will be the discovery of Earth-like planets around other stars. It’s what we all wonder about – are there other planets out there that host life? That said, most of the stars that Kepler examines won’t show any signs of planetary transits … but the data will provide a gold mine of information about how stars behave. From the point of view of my own research, the most exciting thing that will come out will be improvement, by a factor of almost 100, in the measure of brightness of over 100,000 stars. Asteroseismologists are drooling at this prospect, because we expect to find oscillations in many stars, but this huge increase in sensitivity is bound to reveal new phenomena that we can’t even guess at yet.
Q. A press release described part of your interest as “peering into stars.” Can you elaborate?
Kawaler: Until very recently, everything we know about stars, we learned from looking at the outsides. When you want to really need to know what’s going on, you need some sort of probe that goes beneath the surface. For the Earth, seismic waves generated by earthquakes give you that kind of probe. For stars, we have to measure their vibrations from (very!) far away. Those vibrations produce only tiny signals — very subtle brightness variations. We can also look at how the surfaces move up and down and use those as a measure of the oscillations that are going on inside. Once we do make those measurements, we use the tools that terrestrial seismologists have developed, along with some of our own that are adapted to the special circumstances within stars, to probe the insides of the stars.
Q. Why can’t we do this work from Earth?
Kawaler: The short answer is that we can, sort of, but Earth is a really poor place to do this kind of work. An astronomer can only look at a star for a couple hours a night before the star sets or the sun comes up. It’s kind of the equivalent of listening to Beethoven’s 5th Symphony and listening to every third note. You can sort of do it from the ground by putting together a network of telescopes. We’ve had some remarkable successes. But it’s much easier if you can observe from a platform that isn’t rotating. And if that platform is above the atmosphere, you get the added benefit of a direct line of sight to the star that doesn’t have the atmosphere degrading the image. With continuous views and no atmosphere, Kepler can do way, way better than we can from the ground.
6. Is this helping to realize a life-long ambition for you?
Kawaler: Absolutely – I’ve always been a space program ‘geek.’ I grew up in the 60s. My older brother grew up in the 50s, and he got caught up in the whole Sputnik thing. There were all these books and toys about space; I picked them up and was instantly fascinated. Later, I was just riveted to the TV all the time, watching Gemini and the Apollo missions. I guess I still haven’t grown out of it. My brother is one of the few rabbis that dresses as Captain Kirk on Purim, Jewish Halloween, so I guess he didn’t grow out of it, either. I’m actually heading down to Florida for the launch, with my father, so he can finally be convinced I didn’t have to be a ‘real doctor’ — I can be a PhD.
Artist's rendering of the Giant Magellan Telescope and support facilities at Las Campanas Observatory, Chile, high in the Andes Mountains. Photo by Todd Mason/Mason Productions
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Astronomy organizations in the United States, Australia and Korea have signed on to build the largest ground-based telescope in the world – unless another team gets there first. The Giant Magellan Telescope, or GMT, will have the resolving power of a single 24.5-meter (80-foot) primary mirror, which will make it three times more powerful than any of the Earth’s existing ground-based optical telescopes. Its domestic partners include the Carnegie Institution for Science, Harvard University, the Smithsonian Institution, Texas A & M University, the University of Arizona, and the University of Texas at Austin. Although the telescope has been in the works since 2003, the formal collaboration was announced Friday.
Charles Alcock, director of the Harvard-Smithsonian Center for Astrophysics, said the Giant Magellan Telescope is being designed to build on the legacy of a rash of smaller telescopes from the 1990s in California, Hawaii and Arizona. The existing telescopes have mirrors in the range of six to 10 meters (18 to 32 feet), and – while they’re making great headway in the nearby universe – they’re only able to make out the largest planets around other stars and the most luminous distant galaxies.
With a much larger primary mirror, the GMT will be able to detect much smaller and fainter objects in the sky, opening a window to the most distant, and therefore the oldest, stars and galaxies. Formed within the first billion years of the Big Bang, such objects reveal tantalizing insight into the universe’s infancy.
Earlier this year, a different consortium including the California Institute of Technology and the University of California, with Canadian and Japanese institutions, unveiled its own next-generation concept: the Thirty Meter Telescope. Whereas the GMT’s 24.5-meter primary mirror will come from a collection of eight smaller mirrors, the TMT will combine 492 segments to achieve the power of a single 30-meter (98-foot) mirror design.
In addition, the European Extremely Large Telescope is in the concept stage.
In terms of science, Alcock acknowledged that the two telescopes with US participation are headed toward redundancy. The main differences, he said, are in the engineering arena.
“They’ll probably both work,” he said. But Alcock thinks the GMT is most exciting from a technological point of view. Each of the GMT’s seven 8.4-meter primary segments will weigh 20 tons, and the telescope enclosure has a height of about 200 feet. The GMT partners aim to complete their detailed design within two years.
The TMT’s segmented concept builds on technology pioneered at the W.M. Keck Observatory in Hawaii, a past project of the Cal-Tech and University of California partnership.
Construction on the GMT is expected to begin in 2012 and completed in 2019, at Las Campanas Observatory in the Andes Mountains of Chile. The total cost is projected to be $700 million, with $130 million raised so far.
Artists concept of the Thirty Meter Telescope Observatory. Credit: TMT
Construction on the TMT could begin as early as 2011 with an estimated completion date of 2018. The telescope could go to Hawaii or Chile, and final site selection will be announced this summer. The total cost is estimated to be as high as $1 billion, with $300 million raised at last count.
Alcock said the next generation of telescopes is crucial for forward progress in 21st Century astronomy.
“The goal is to start discovering and characterizing planets that might harbor life,” he said. “It’s very clear that we’re going to need the next generation of telescopes to do that.”
And far from being a competition, the real race is to contribute to science, said Charles Blue, a TMT spokesman.
“All next generation observatories would really like to be up and running as soon as possible to meet the scientific demand,” he said.
In the shorter term, long distance space studies will get help from the James Webb Space Telescope, designed to replace the Hubble Space Telescope when it launches in 2013. And the Atacama Large Millimeter Array (ALMA), a large interferometer being completed in Chile, could join the fore by 2012.
COROT-exo-7b, bottom left dot shadows in front of his central star (artist's impression). Aufgrund der großen Nähe zu seiner Sonne vermuten Forscher Temperaturen von über 1000 Grad Celsius auf dem extrasolaren Planeten. Because of its proximity to large solar researchers suspect temperatures over 1000 degrees Celsius on the extrasolar planets. Bild: Klaudia Einhorn. Image: Klaudia Einhorn.
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The CoRoT satellite has found the smallest terrestrial exoplanet yet, — with a diameter just under twice that of Earth — complete with a rocky surface you could walk on and possibly even oceans to sail across. However, if you traveled there, you might want to bring some protection, as the temperature of this planet is likely very high. CoRoT-Exo-7b is located very close to its parent star, orbiting once every 20 hours. Astronomers estimate temperatures on the planet could be between 1000 and 1500°C and it possibly could be covered in lava or water vapor. This latest exoplanet was detected as it transited in front of its parent star, dimming the light from the star just enough to be noticeable.
The parent star lies about 140 parsecs from Earth, located about half way between the star Sirius in Canis Major and Betelgeuse, the red giant star in Orion.
The internal structure of CoRoT-exo-7b particularly puzzles scientists; they are unsure whether it is an ‘ocean planet’, a kind of planet whose existence has never been proved so far. In theory, such planets would initially be covered partially in ice and they would later drift towards their star, with the ice melting to cover it in liquid. COROT detects small, transiting exoplanet. Credits: CNES
“This discovery is a very important step on the road to understanding the formation and evolution of our planet,” said Malcolm Fridlund, ESA’s CoRoT Project Scientist. “For the first time, we have unambiguously detected a planet that is ‘rocky’ in the same sense as our own Earth. We now have to understand this object further to put it into context, and continue our search for smaller, more Earth-like objects with COROT,” he added.
About 330 exoplanets have been discovered so far, most of which are gas giants likeJupiter and Neptune. The density of COROT-Exo-7b is still under investigation: it may be rocky like Earth and covered in liquid lava. It may also belong to a class of planets that are thought to be made up of water and rock in almost equal amounts. Given the high temperatures measured, the planet would be a very hot and humid place.
“Finding such a small planet was not a complete surprise”, said Daniel Rouan, researcher at the Observatoire de Paris Lesia, who coordinates the project with Alain Léger, from Institut d’Astrophysique Spatiale (Paris, France). “CoRoT-Exo-7b belongs to a class of objects whose existence had been predicted for some time. COROT was designed precisely in the hope of discovering some of these objects,” he added.
Small terrestrial planets are difficult to detect, and so very few exoplanets found so far have a mass comparable to Earth, Venus, Mars, and Mercury. Most of the methods used to find planets are indirect and sensitive to the mass of the planet. The CoRoT spacecraft can directly measure the size of a planet’s surface, which is an advantage. In addition, its location in space allows for longer periods of uninterrupted observation than from ground.
Astronomers say this discovery is significant because recent measurements have indicated the existence of planets of small masses but their size remained undetermined until now. CoRoT (Convection Rotation and Transits) was launched in December 2006 and consists of a 27 cm-diameter telescope designed to detect tiny changes the brightness of nearby stars. The mission’s main objectives are to search for exoplanets and to study stellar interiors.
The planet HD80606b glows orange from its own heat in this computer-generated image. A massive storm has formed in response to the pulse of heat delivered during the planet's close swing past its star. The blue crescent is reflected light from the star. Image by D. Kasen, J. Langton, and G. Laughlin (UCSC).
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As mentioned in a previous article today about global warming, we on Earth worry about our planet’s atmosphere rising by a few degrees on average over the next century. But imagine living on a planet where temperatures could rise 700 degrees in just a few hours! A distant planet known as HD80606b, is a gas giant orbiting a star 200 light-years from Earth. It’s extremely eccentric orbit around the star takes it from a relatively comfortable distance in an Earth-like habitable zone to the blazing hot regions much closer than Mercury is to our Sun. Infrared sensors aboard NASA’s Spitzer Space Telescope measured the planet’s temperature as it swooped close to the star, observing a planetary heat wave that rose from 800 to 1,500 degrees Kelvin (980 to 2,240 degrees Fahrenheit) in just six hours. Wow!
And for those readers who like to complain about artist impressions images, the image here is a novel type of “photorealistic” image, created by a new computer program that calculates the radiative transfer processes in astrophysics.
“We can’t get a direct image of the planet, but we can deduce what it would look like if you were there. The ability to go beyond an artist’s interpretation and do realistic simulations of what you would actually see is very exciting,” said Gregory Laughlin, professor of astronomy and astrophysics at UCSC. Laughlin is lead author of a new report on the findings published this week in Nature.
“This is the first time that we’ve detected weather changes in real time on a planet outside our solar system,” said Laughlin “The results are very exciting because they give us important clues to the atmospheric properties of the planet.”
Spitzer observed the planet for 30 hours before, during, and just after its closest approach to the star. The planet passed behind the star (an event called a secondary eclipse) just before the moment of its closest approach. This was a lucky break for Laughlin and his colleagues, who had not known that would happen when they planned the observation. The secondary eclipse allowed them to get accurate measurements from just the star and thereby determine exact temperatures for the planet.
HD80606b has an estimated mass of about four times that of Jupiter and completes its orbit in about 111 days. At its closest approach to the star it experiences radiation about 800 times stronger than when it is most distant.
At the closest point, the sunlight beating down on the planet is 825 times stronger than the irradiation it receives at its farthest point from the star. “If you could float above the clouds of this planet, you’d see its sun growing larger and larger at faster and faster rates, increasing in brightness by almost a factor of 1,000,” Laughlin said.
“Even after finding nearly 200 planets, the diversity and oddness of these new worlds continues to amaze and confound me,” says Paul Butler of the Carnegie Institution for Science’s Department of Terrestrial Magnetism. Butler made the precision velocity measurements of the host star that allowed the planet’s orbit to be calculated. Butler’s work has uncovered about half of the known extra-solar planets.
Daniel Kasen, a Hubble postdoctoral fellow at UCSC, was able to generate the image with the new program. “It calculates the color and intensity of light coming from the glowing planet, and also how starlight would reflect off the surface of the planet,” Kasen said.
The resulting image shows a thin blue crescent of reflected starlight framing the night side of the planet, which glows cherry red from its own heat, like coals in a fire. “These images are far more realistic than anything that’s been done before for extrasolar planets,” Laughlin said.
The planet is expected to pass in front of its star when viewed from Earth on February, and the team will be watching again.
This artist's conception reveals the newly discovered Super-Neptune planet orbiting a star 120 light years away from Earth. Normally blue in color, its red hue is caused by the illumination from the nearby Red Dwarf star. Credit: David A. Aguilar (CfA)
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Another extrasolar planet has been found, this time a Neptune-sized world orbiting a star 120 light-years from Earth. It was found by a network of automated telescopes set up to search for other worlds, known as “HATNet,” which is operated by the Center in Arizona and Hawaii. This latest extrasolar world, called HAT-P-11b is the 11th planet found by HATNet, and the smallest yet discovered by any projects that are searching using the transit method. As a planet passes directly in front of (transits) its parent star, it blocks a small amount of light coming from the star. In this case, the planet blocked about 0.4 percent of the star’s light. This discovery puts the current extrasolar count at 335.
Transit detections are particularly useful because the amount of dimming tells the astronomers how big the planet must be. By combining transit data with measurements of the star’s “wobble” (radial velocity) made by large telescopes like Keck, astronomers can determine the mass of the planet.
While Neptune has a diameter 3.8 times that of Earth and a mass 17 times Earth’s, HAT-P-11b is 4.7 times the size of Earth and has 25 Earth masses.
A number of Neptune-like planets have been found recently by radial velocity searches, but HAT-P-11b is only the second Neptune-like planet found to transit its star, thus permitting the precise determination of its mass and radius.
The new-found world orbits very close to its star, revolving once every 4.88 days. As a result, it is baked to a temperature of around 1100 degrees F. The star itself is about three-fourths the size of our Sun and somewhat cooler.
There are signs of a second planet in the HAT-P-11 system, but more radial velocity data are needed to confirm that and determine its properties.
Another team has located one other transiting super-Neptune, known as GJ436b, around a different star. It was discovered by a radial velocity search and later found to have transits.
“Having two such objects to compare helps astronomers to test theories of planetary structure and formation,” said Harvard astronomer Gaspar Bakos, who led the discovery team.
HAT-P-11 is in the constellation Cygnus, which puts in it the field of view of NASA’s upcoming Kepler spacecraft. Kepler will search for extrasolar planets using the same transit technique pioneered by ground-based telescopes. This mission potentially could detect the first Earth-like world orbiting a distant star. “In addition, however, we expect Kepler to measure the detailed properties of HAT-P-11 with the extraordinary precision possible only from space,” said Robert Noyes, another member of the discovery team.
Artist's concept of the current mission configuration. Credit: JPL
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Two of the hottest and most engaging topics in space and astronomy these days are 1.) exoplanets – planets orbiting other stars – and 2.) dark matter—that unknown stuff that seemingly makes up a considerable portion of our universe. There’s a spacecraft currently in development that could help answer our questions about whether there really are other Earth-like planets out there, as well as provide clues to the nature of dark matter. The spacecraft is called SIM – the Space Interferometry Mission. “We’ll be looking for other Earths around other stars,” said Stephen Edberg, System Scientist for the mission, “and by making accurate mass measurements of galaxies, we should be able to measure dark matter, as well.”
The concept for this mission has been around for awhile, and the concept has changed over time, with the telescope going through different incarnations. Currently, the mission is being called SIM Lite, as the spacecraft itself has gotten smaller, however the mirrors for the interferometer have gotten bigger.
While interferometry at radio wavelengths has been done for over 50 years, optical interferometry has only matured recently. Optical interferometry combines the light of multiple telescopes to perform as a single, much larger telescope. SIM Lite will have two visible-wavelength stellar interferometer sensors – as well as other advanced detectors, that will work together to create an extremely sensitive telescope, orbiting outside of Earth’s atmosphere.
“These are instruments that can measure positions in the sky to almost unbelievable accuracy,” said Edberg. “Envision Buzz Aldrin standing on the moon. Pretend he’s holding a nickel between thumb and forefinger. SIM can measure the thickness of that nickel as seen by someone standing on the surface of the Earth. That is one micro arc second, a very tiny fraction of the sky.” Watch a video depicting this — (Quicktime needed)
Having the ability to make measurements like that with SIM, it will be possible to infer the presence of planets within about 30 light-years from Earth, and those planets can be as small and low mass as Earth. As of now, the SIM team anticipates studying between 65 and 100 stars over a five year mission, looking for Earth analogs, planets roughly the same mass as Earth orbiting their stars in the habitable zone, where liquid water could exist.
So, for example, SIM Lite would be able to detect a habitable planet around the star 40 Eridani A, 16 light-years away, known to fans of the “Star Trek” television series as the location of Mr. Spock’s home planet, Vulcan. See a movie depicting this possible detection — (QuickTime needed).
SIM will not detect a planet directly, but by detecting the motion it causes in the parent star. “That’s a difficult task, there’s no question,” said Edberg, “but it gets complicated, based on what we see with our own solar system and what we’ve seen in other planetary systems. We know there are other systems out there that have more than one planet. Multiple planets can confound the measurements.”
But SIM should be able to detect the different sized planets orbiting other stars. SIM Lite recently passed a double blind study conducted by four separate teams who confirmed that SIM’s technology will allow the detection of Earth-mass planets among multiple-planet systems, by having the ability to measure the mass of different sized planets, to as low as Earth-mass.
“With a few exceptions all the planets we know about were detected using a method called radial velocity,” said Edberg, “where we look at the periodic motion of the star coming toward us and moving away from us on a regular basis. But when you make measurements like that, when you have no other information, you don’t know the orientation of the planets’ orbit with respect to the star, or the mass of either the star or the planet.”
With the hottest stars, radial velocity can’t be used to look for planets. But SIM Lite will be able to look at stars clear across the diagram from the coolest to the hottest stars.
“It’s a big question mark in the other planets we know about now – I believe we know only about 10% of the masses of extrasolar planets,” said Edberg.
A second planet search program, called the “broad survey,” will probe roughly 2,000 stars in our galaxy to determine the prevalence planets the size of Neptune and larger. Graphic illustrating the mass and quantity of planets SIM Lite could potentially detect. Number of terrestrial planets assumes 40% of mission time divided evenly between 1-Earth mass and 2-Earth mass surveys. Credit: JPL
SIM will also be used to measure the sizes of stars, as well as distances of stars, and be able to do so several hundred times more accurately than previously possible. SIM Lite will also measure the motion of nearby galaxies, in most cases, for the first time. These measurements will help provide the first total mass measurements of individual galaxies. All of this will enable scientists to estimate the distribution of dark matter in our own galaxy and the universe.
“Dark matter is known for its gravitational affects,” said Edberg. “It doesn’t seem to interact with normal matter as we know it. To get more clues on it, we want to know where it is.”
SIM will measure on two different scales. One is within the Milky Way Galaxy, making measurements of stars and globular clusters, and making measurements of stars that have been torn out of smaller galaxies that orbit the Milky Way.
“We can do mass model of our galaxy and find out where that mass is, including what has to be a lot of dark matter,” said Edberg. “When we make measurements of how our galaxy rotates, you find that it rotates like a solid. Instead of being Keplerian, where you think of Mercury going around the sun faster than Pluto, from all the way inside the galaxy as close as we can measure to the center, out to beyond the sun’s distance, the Milky Way rotates like it’s a solid body. It’s not a solid body, but that means it must have a density that is constant all the way through and that means there is far more matter than we can see.”
“Another thing we’d like to know is the concentration of dark matter in cluster of galaxies,” Edberg continued. “The Milky Way is part of the Local Group of galaxies, and SIM has the capability to measure stars within the individual galaxies, which in turn can be modeled to tell us where the dark matter is within the Local Group. This is cutting edge. This is one of the big mysteries right now in astrophysics and cosmology.”
Extra solar planets and dark energy may seem like two completely different things for one spacecraft to be looking for, but Edberg said this is an example of how everything is tied together.
“To get planet masses we need to know the masses of the parent stars,” he said. “SIM will make measurements of stars, particularly binary stars, and determine the masses of stars for a wide variety of star types, and be able to estimate the sizes of the planets that are causing the reflex motion. To make the measurements, and because stars with planets are going to be scattered around the sky, we need to have a grid of stars that are the fixed points to give us latitude and longitude, so to speak. If you know exactly where St. Louis and Los Angeles are, then it’s much easier to triangulate where things between them are. We need to do this all around the sky, and to do that we tie that down to the stars, and SIM can do that. These are fundamental questions that we don’t know the answers to, but SIM will help us find the answers.”
So, SIM Lite will be searching from within our neighborhood to the edge of the universe.
What’s the status of this future spacecraft?
“We’re on hold right now,” said Edberg. “We recently passed the double blind test to show that SIM can find Earth-like planets in systems that have multiple planets. SIM is also undergoing a decadal review to make the case that the astronomical science community needs to have a mission like SIM to strengthen the foundations enormously.”
Technical work is being done to prepare to build the actual instruments, but due to budgetary reasons, NASA has not set a launch date. “We think we could be ready to launch by 2015 once we get the go-ahead from NASA,” said Edberg, “and the go ahead depends on the decadal review, and the reports should be out in about a year.”
SIM Lite would provide an entirely new measurement capability in astronomy. Its findings would likely stand firmly on their own, while complimenting the capabilities of our current, as well as other planned future space observatories.
For more information about SIM check out the mission website.
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In June of 2008, astronomers announced the finding of one of the smallest exoplanets yet around a normal star other than the Sun. The planet – believed to be a rocky exo-world — was found through a microlensing event, and was estimated to be 3.3 times the size of Earth, orbiting a brown dwarf star. But new analysis suggests the star may be larger than first thought, making the planet smaller than the original estimates. Astronomers say the exoplanet, called MOA-2007-BLG-192-L b could weigh just 1.4 Earths – less than half the original estimate. Observations over the next few months should be able to test the prediction.
Most known “exoplanets” are huge gas giants, hundreds of times Earth’s mass, and are discovered by detecting the wobble they induce in their parent stars.
But researchers found the planet and star using the gravitational microlensing technique. This is where two stars line up perfectly from our point of view here on Earth. As the two stars begin to line up, the foreground star acts as a lens to magnify and distort the light from the more distant star. By watching how this brightening happens, astronomers can learn a tremendous amount about the nature of both the foreground and background star.
In this case, there was an additional gravitational distortion from the planet orbiting the foreground star MOA-2007-BLG-192L, which astronomers were able to tease out in their data.
However, analyzing these events takes time, because there are so many variables to take into account, including the sizes of planet and star, their separation, and the distance from Earth.
Initially, the team believed that this host star was a brown dwarf – an object too small to sustain nuclear fusion, as normal stars do. That suggested MOA-2007-BLG-192-L b weighed 3.3 Earths.
But more recent observations suggest the parent star is actually heavier than first thought – a type of star called a red dwarf, team member Jean-Philippe Beaulieu of the Paris Astrophysical Institute reported last week at a meeting of the Royal Astronomical Society in London.
That suggests the planet weighs just 1.4 Earths. In size terms, that makes it a near twin of our own planet, closer in mass than any known planet except Venus.
“The result is important because this is the lowest-mass planet yet detected, and is extremely close to the mass of the Earth,” said Scott Gaudi of Ohio State University in Columbus. “Obviously, finding a true Earth-mass planet is one of the biggest goals of searches for exoplanets. We are very close to that goal now.” Very Large Telescope Facility. Credit: ESO
The team will attempt to get more data on the parent star in April or May using the Very Large Telescope in northern Chile.
If their analysis is confirmed, it is an unclear whether the tiny planet could host any life. Because its host is a very dim red dwarf, the planet is likely to be frozen – even though it orbits at about the same distance as Venus from our Sun.
However, if the planet boasts a thick, insulating hydrogen atmosphere, it could sustain a habitable surface temperature, capable of supporting life of some kind.
