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We Found the Planets, but Are There Any Aliens?55 Cancri A |
By Gabriel Gache, Science News Editor
7th of November 2007, 07:52 GMT
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After 18 years of careful observation conducted on the 55 Cancri planetary system, scientists announced yesterday the confirmation of the discovery of the fifth planet, making 55 Cancri the biggest planetary system known today.
55 Cancri is a binary system composed of two components: a yellow dwarf star similar to the Sun named 55 Cancri A and a red dwarf star named 55
Cancri B separated by more than 1000 astronomical units. Certain studies suggest that 55 Cancri B could be itself a double star, but the theory has not been yet confirmed. The newly found planet, like the other previously four planets found, orbit the main components of the binary system, 55 Cancri A. It is located 41 light-years away from Earth, in the direction of the Cancer constellation and is visible with a pair of binoculars.
The 55 Cancri resembles many features of our own solar system, but the planets found so far are more massive than our own by a factor of 5 to 10, somewhere the size of Neptune or bigger, meaning they are most probably gas giants. It appears to have a similar configuration to the solar system, with four inner planets, separated by a huge gap from the outer planet.
The newly found planet is about 45 times more massive than Earth and might be similar to Saturn in composition and appearance.
"We haven't found a twin of our solar system, because the four planets close to the star are all the size of Neptune or bigger," Geoffrey Marcy said.
So far over 250 planets outside our solar system have been detected; only one other star is known to have four planets. Technical improvement will greatly multiply the discovery of new planets. The planets of 55 Cancri A are well within the area around the star, in which water can exist in its liquid state, but so far this information is without use, since no rocky planet has been discovered. Marcy believes that within five years, a rocky planet will be detected in the big gap between the inner and outer planets.
The prediction is based on observations on the solar system, in which such huge gaps between two planets are actually not empty, but filled with some kind of rocky planet, or in our solar system's case, an asteroid belt. The newly found planet could have a natural satellite, which is quite common in our solar system, a rocky surface, liquid water or possibly even life.
The planets were found using the Lick Observatory and W.M. Keck Observatory in Hawaii, using a technique that involves measuring the radial velocity, or "wobble" of the star. Planets around a star affect the gravitational field of the star. Usually detecting such a "wobble" reveals that a large gas planet is orbiting the star, but as technology advances, certain techniques will be able to detect even small rocky planets.
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