Another Earth Like planet discovered

[Jan 26th 2006]

The International team of Astronomers claims discovery of another Earth like planet in the constellation Sagittarius not very far from core of our Galaxy. The discovered planet is the smallest ever found in the race for search for earth like planets. Earth like planet (OGLE-2005-BLG-390Lb) is orbiting around a red dwarf (A star with low surface temperature, around 3,000 degrees Celsius, and a diameter about half that of the Sun) at a distance comparable to that of a earth's orbit around sun.

The Team

The discovery of earth like planet is the joint effort of three independent microlensing campaigns: PLANET/RoboNet, OGLE (Optical Gravitational Lensing Experiment), and MOA (Microlensing Observations in Astrophysics), involving a total of 73 collaborators affiliated with 32 institutions in 12 countries ? France, the United Kingdom, Poland, Denmark, Germany, Austria, Chile, Australia, New Zealand, United States, South Africa and Japan.

Available data for Earth like Planet

Deemed Name : OGLE-05-390L b
Mass : 0.018 (± 0.01) MJ (5.5 times the mass of Earth)
Distance : 2.6 Astronomical Units (390 million kilometers from its star: if it were inside our Solar System, the planet would sit between Mars and Jupiter)
Orbital period : 3800 days (10 years to orbit its own sun)

What is Astronomical Unit?
Astronomical Units is a average distance between the Earth and Sun, equal to about 150 million kilometers
What is M Sin i?
In the case of extrasolar planets it is difficult to find the estimated mass of the planet. Because of limitations of the techniques used to find these planets, their precise mass M cannot be determined; what astronomers actually measure is the quantity M sin i, which is the mass times the sine of the orbital inclination, as seen from Earth. Since the orbital inclination is unknown, sin i can be anywhere from 0 to 1, so M sin i is a lower limit on the planet's mass. The planet's mass could be many times the value of M sin i, but statistically speaking, most of the time it will be less than twice that value.

The Technique used to find earth like planet

In most cases, new planets have been found using a technique called the Doppler shift, in which the wavelength of light emitted by a moving object is shifted due to its motion. Radiation is red shifted when an object is moving away from us and blue shifted when the object is moving toward us. Astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. As a giant planet orbits a star, it tugs it back and forth, producing a very small (meters per second) Doppler shift. However, using the Doppler shift method, most planets found have been giant gas planets.

In case of Earth like planet (OGLE-2005-BLG-390Lb) the team used a technique called microlensing, an idea that Albert Einstein came up with in 1936. By observing a particular star (A) on the sky, imagine another star (B) in the line of sight toward A. He showed that when A, B and the observer are exactly aligned, a ring-like image will be formed. Star B acts as a gravitational lens by bending the light of star A toward the observer. From there, objects, such as planets or white dwarfs, around A temporarily brighten star B.

In the case of newly found earth like planet, star A causes a characteristic brightening in star B that lasts about a month. Any planets orbiting star A can produce an additional signal, lasting days for giant planets down to hours for Earth-mass planets. The planet is not directly 'seen,' or even the star that it's orbiting, but its presence can be deduced from the effect of its gravity. In the case of the newly found planet, the extra brightening lasted about 12 hours. Microlensing is more sensitive to planets that orbit their star at distances that are in the range of the Earth sun separation. OGLE-2005-BLG-390Lb is only the third extra-solar earth like planet discovered so far from microlensing searches.

Is there a life?

"The search for a second Earth is the driving force behind our research," says Daniel Kubas at the European Southern Observatory in Santiago de Chile, Chile, part of the team that made the discovery. They are optimistic that the clever method they used to spot the planet could soon uncover an alien twin to our own world. But sadly this Earth-like body probably isn't crawling with life. Its dwarf star is so dim that the surface temperature of this planet is thought to be about - 220 °C.

The Next Earth like Planet

"That fact that we stumbled on one means there are thousands of them out there," said Kem Cook, an astronomer at the Lawrence Livermore National Laboratory who is also a member of PLANET, Probing Lensing Anomalies NETwork, a part of the group that made the discovery. "There must be lots of these out there," Cook said. "The microlensing technique is not going to find nearby planets. We're not going to discover planets to which NASA can fly. Microlensing can tell us how common planets are in distant parts of the galaxy and probe details of planetary formation that other techniques cannot."

The research appears in the Jan. 26 edition of the journal Nature.

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