Earth like planet discovered outside solar system

[June 13th 2005]

Team of astronomers announced discovery of Most Earth like planet outside our solar system. This planet is about seven and a half times in mass compared to earth and twice in radius, smallest ever detected planet which revolves round a star (red dwarf) Gliese 876. Such a rocky star only twice in radius to earth and revolving round a dim star not very different from our sun is a very close configuration to earth like planets, at least the closest ever found.

Discovery of this earth like planet is based on observations from high resolution spectrophotometer (HIRES) at keck observatory hawaii. All the other extrasolar planets (planets outside our solar system) discovered around normal stars to date are all larger than Uranus. Uranus is a ice giant planet in our solar system that is about 15 times massive than earth.

Newly discovered Earth like planet revolves around Gilese 876 a red dwarf is nearly 15 light years away from us. Besides this earth like planet star also posses two larger Jupiter sized planets which orbits Gilese 876 in resonance. Being very close to the Gilese 876, the newly discovered planet completes one revolution around the star in just 2 days compared to earths 365 days and probably has dayside temperature of around 200 to 400 degree celsius.

Gliese 876 is smaller than the Sun, only about 1/3 as mass of our sun, and a dim star to be seen without a telescope. But it is known to be one of the nearest stars, only 15 light-years distant in constellation Aquarius. Butler and Marcy detected the first planet there in July 1998. They discovered two Planets in 1998 orbiting around Gilese 876. Both this planets were gas giant planets about twice as mass of Jupiter and revolving in resonating motions around the star. The outer planet was taking approx 61 days around double than inner planet. Lissauer and Rivera of NASA Ames Research Center have been analyzing data on the Gliese 876 system from keck observatory in order to model the unusual resonating motions of two known planets, and three years ago got an vague understanding that there might be a smaller, third planet orbiting the star. It was the unusual resonating motions of two planets orbiting around the red dwarf that lead to research into existence of 3rd planet.

"We had a model for the two planets interacting with one another, but when we looked at the difference between the two-planet model and the actual data, we found a signature that could be interpreted as a third planet," Lissauer said. A three-planet model consistently gave a better fit to the data, added Rivera. "But because the signal from this third planet was not very strong, we were very cautious about announcing a new planet until we had more data," he said.

Such a high precision observations can be recorded only due to high resolution spectrometer (HIRES) at keck Observatory Hawaii. Keck Observatory is in news again after its observations on Andromeda galaxies outer arm making its size six times bigger than what we have learned in schools.

There were recent improvements done (in last august) to the CCD (charged coupled device, one of the type of image sensors which converts light into electrons, we use these in digital cameras) of spectrometer at Keck observatory. These improvements are done at lick observatory laboratory at University of California by Steven Vogt who initially designed and build this high resolution spectrometer (HIRES).

This improved CCD detectors can maintain a precision of 1 meter per second in Doppler velocity (its a radial velocity of astronomical objects based on phase measurement of pulses, red signals indicates far from radar and blue indicates nearer). Precision at this level will allow researchers to analyze more interesting areas like gravitational effect.

"We are pushing a whole new regime at Keck to achieve one meter per second precision, triple our old precision, that should also allow us to see Earth-mass planets around sun-like stars within the next few years," said Paul Butler one of the researcher on the project from Carnegie Institution of Washington.
"It is the higher precision data from the upgraded HIRES that gives us confidence in this result," Butler said.
"In a two-day orbit , it's about 200 degrees Celsius too hot for liquid water," Butler said. "That tends to lead us to the conclusion that the most probable composition of this thing is like the inner planets of this solar system--a nickel-iron rock, a rocky planet, a terrestrial planet."
"A planet seven and a half times the mass of the Earth could easily hold onto an atmosphere," noted Laughlin, an assistant professor of astronomy at UC Santa Cruz. "It would still be considered a rocky planet, probably with an iron core and a silicate mantle. It could even have a dense steamy water layer. I think what we are seeing here is something that's intermediate between a true terrestrial planet like the Earth and a hot version of the ice giants Uranus and Neptune."
After the milestone of discovering New Most Earth like planet the team is planning to analyze data on other 150 odd planets around normal stars which they observe regularly. They are planning to do this with improved computer software and ccd's.
"So far we find almost no Jupiter-mass planets among the M dwarf stars we've been observing, which suggests that, instead, there is going to be a large population of smaller mass planets," Butler noted.

Milestone in finding another earth ?

"We keep pushing the limits of what we can detect, and we're getting closer and closer to finding Earths," said team member Steven Vogt, a professor of astronomy and astrophysics at the University of California, Santa Cruz.
"This is the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets," said team member Paul Butler of the Carnegie Institution of Washington. "It's like Earth's bigger cousin."
"This planet answers an ancient question," said team leader Geoffrey Marcy, professor of astronomy at the University of California, Berkeley. "Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star."
"Today's results are an important step toward answering one of the most profound questions that mankind can ask: Are we alone in the universe?" said Michael Turner, head of the Mathematical and Physical Sciences directorate at the National Science Foundation (NSF), which provided partial funding for the research.
Press conference at National science foundation, Arlington is really sounds like a good kick to the old common curiosity among all of us.
Nevertheless, this discovery has definitely increased the chances and confidence of finding more smaller earth like planets outside our solar system.

The team's work, conducted at the Keck Observatory in Hawaii, was also supported by the National Aeronautics and Space Administration (NASA), the University of California and the Carnegie Institution of Washington.
Marcy, Butler, theoretical astronomer Jack Lissauer of NASA's Ames Research Center, and post-doctoral researcher Eugenio J. Rivera of the University of California Observatories/Lick Observatory at UC Santa Cruz presented their findings today (Monday, June 13) during a press conference at NSF in Arlington, Va.
A paper detailing their results has been submitted to The Astrophysical Journal. Coauthors on the paper are Steven Vogt and Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz; Debra Fischer of San Francisco State University; and Timothy M. Brown of NSF's National Center for Atmospheric Research in Boulder, Colorado.

You can find the original story at NSF Arlington. and a paper detailing these results has been submitted to The Astrophysical Journal