Six exoplanets in close orbit around far-flung star
By Jason Palmer Science and technology reporter, BBC News
|Kepler measures stars' "light curves" as planets that pass in front block some of their light|
BBC-A solar system including six planets around a star 2,000 light-years away has been spotted by astronomers.
The planets range between two and four-and-a-half times the radius of Earth, and between two and 13 times its mass.
Five of the planets orbit the star closer than Mercury orbits our Sun.
The find, published in Nature, is the first from the latest data release from the Kepler space telescope - which includes details of more than 1,000 additional exoplanet candidates.
The planets are likely to have atmospheres made of light gases, but also likely to be too hot to support life.
The Kepler team released the raw data that led to the discovery as part of its commitment to making its findings publicly available.
Kepler has already yielded evidence of a three-planet system, Kepler-9, and in January the team announced it had spotted the first definitively rocky exoplanet, Kepler-10.
The newly-discovered solar system, around the star Kepler 11, is a rich "laboratory" for studying planetary formation. Its surprising number of planets orbiting so closely together gives astrophysicists a unique system to refine their theories of how planets form.
The find is different from the planetary system HD10180, first announced in August 2010, in which a rich exoplanet system comprising at least five planets orbits a star 127 light-years away. In that study, the "wobble" that the planets' gravity caused on their host star was used to infer their presence; a sixth and seventh planet are yet to be confirmed.
The Kepler telescope, by contrast, performs a more direct observation, measuring the minuscule dimming that occurs when planets pass in front of their host star.
Typically, in these "transit" measurements, the dimmings merely suggest planets; their presence is confirmed by ground-based telescopes that look for the "wobble" - a method known as radial velocity measurements.
In the case of Kepler-11, the planets orbit their host star so close to one another that they have noticeable gravitational effects on each other. These effects rhythmically change the time that each needs to orbit the star, and the authors were able to work out the masses of the planets.
All of the planets orbit their host star closely - five of them closer to their star than Mercury is to our Sun, and the sixth just beyond that distance. Two orbit at a distance just one-tenth as far as the Earth is from the Sun.
What is surprising is that all the planets are comparatively large; the system has a total of 10 times the mass of the Earth inside the radius of Mercury's orbit; here in our Solar System, there are only about two Earth masses contained in a radius five times that of the Earth's orbit.
"Large planets very close in orbit around a single star were just totally unexpected," said lead author of the study Jack Lissauer of Nasa's Ames Research Center.
"We think this is the biggest thing in exoplanets since the discovery of 51 Pegasi - the first exoplanet - in 1995."
Moreover, the fact that six planets could be spotted around the Kepler-11 star means that all of the planets must lie in an almost completely flat plane, flatter even than our own Solar System, and aligned edge-on to the Earth - otherwise Kepler would not have been able to spot all six passing in front of the star.
Dr Lissauer explained that the find challenges the notion that planets form by coalescing from discs of debris around young stars, bumping into each other violently in the later stages, casting them into irregular elliptical and out-of-plane orbits.
"I come from a planet formation theory perspective, and this has sent me back to the drawing board," he said.
More to come
Study co-author Jonathan Fortney of the University of Santa Cruz in California said that rather than upending current theory, the Kepler-11 system will be a boon to astrophysicists exploring a fuller range of planet formation scenarios.
"Planetary science is very comparative - planets are so different from one another, you need them to be in similar environments and then compare them to each other," Dr Fortney said.
"In the Kepler-11 system, we have a fantastic laboratory - better than any planetary system yet found - to look at the planets and compare them to one another to understand how they've evolved over time."
David Latham of the Harvard-Smithsonian Center for Astrophysics told BBC News that the Kepler-11 system was just the leading edge of a wave of results from Kepler, which will regularly be releasing the data it gathers by staring fixedly at over 150,000 stars.
With the new crop of candidate planets, and recent suggestions that candidates are likely to be confirmed eventually as planets, the catalogue of known exoplanets looks set to explode.
"This tells us about the architecture of planetary systems and gives us a context for trying to understand our own Solar System," he said.
"The 'holy grail' is to find something enough like the Earth that you could live there, but in the meantime I'm very distracted by these multiple [exoplanet systems]."
Watch video and read more of this story, from BBC.
Ok, so what now?
Note from SW: As a senior astrophysicist at Harvard University, Howard Smith claims we are alone in the universe after an analysis showed that of all the 500 planets discovered so far, none can support life. Smith went on to say that the extreme conditions found on planets outside our solar system are likely to be the norm.
"We have found that most other planets and solar systems are wildly different from our own. They are very hostile to life as we know it."
Pointing to stars such as HD10180, which is orbited by a planet of similar size and appearance to Earth, although roasting hot with radiation.
"Life as we know it."
I have to disagree with Howard Smith and anyone who thinks like he does. With all the billions upon billions of stars [Carl Sagan, bless you] and countless, thus unknown solar systems in our vast universe, the odds are very good at finding planets not unlike our own.
Who is to say that life did not evolve completely different from our own, on other worlds? Can you say "looking through a key hole, using both eyes"? He should have waited until all the facts are uncovered and all evidence presented. That may take a long time.
Just my 2 cents, you understand...
Now pay attention. Anything is possible when you consider how old our universe is and that it is still growing [OK, expanding]. We don't know 'everything' and we're still 'discovering'! Take for instance:
Hubble discovery may be oldest galaxy ever spotted
|This NASA image shows a presumed galaxy that existed 480 million years after the Big Bang, 13 billion years ago. (G. Illingworth/ AFP/ Getty Images)|
Boston.com- WASHINGTON — Hubble’s still got it.
The aging beauty of a space telescope has glimpsed a presumed galaxy that astronomers say might just be the oldest thing ever seen, a small, hot affair that blazed to life during the childhood of the cosmos.
Age of Hubble: almost 21.
Age of the possible galaxy: 13 billion years, give or take.
Although NASA’s Hubble has offered a generation’s worth of spectacular images — sparkling galaxies, billowing nebulae, stunning star clusters — its latest quarry lacks charisma. The presumed oldest galaxy is but a faint smudge on Hubble’s Ultra Deep Field image, the astronomical equivalent of a days-long staring contest.
In 2009, Hubble’s operators turned the telescope toward a dark pocket in the southern sky and “bored a hole,’’ in the words of one Hubble enthusiast, funneling a trickle of light thrown off by the most ancient stuff we’ve ever seen.
The Ultra Deep Field displays a roiling zoo of galaxies — thin ones, fat ones, cigars, pinwheels, discs, and clouds. But the oldest galaxy is nothing but a smear.
Still, this “candidate’’ galaxy — so-called because it could turn out to be something much less exciting — marks the latest entry in a quickening deep-space race among astronomers to bag and tag ever older objects.
Hubble’s new wide field camera 3, installed during a tense 2009 spacewalk, has sparked the race, peering into the heavens with 40 times the sensitivity of its predecessor.
“The idea that you can detect something from the beginning of cosmic time by looking at a patch of sky for 87 hours is just wild,’’ says Rychard Bouwens, an astronomer from Leiden Observatory in the Netherlands, who led the team that made the discovery.
Daniel Fabricant, an astronomer at Harvard University, said, “If true, the discovery would be a very big deal.’’
Writing in the journal Nature, Bouwens and his team say they are 80 percent certain the object is, in fact, an ancient galaxy. They won’t know for sure until new telescopes come online over the next few years, particularly the James Webb Space Telescope, slated to replace Hubble in 2015.