Among the discoveries: the smallest planet observed so far, as well as a planet roughly as distant as Jupiter from its sun
Avi Blizovsky
Jupiter outside the solar system
13 2002 June
Astronomers today announced the discovery of about a dozen new planets orbiting other stars. Among other things, a complete system reminiscent of our solar system was discovered.
After 15 years of searching, the scientists managed to discover a planetary system that reminds them of home. Geoffrey Marcy, a professor of astronomy at the University of California, Berkeley, and astronomer Paul Butler of Carnegie Mellon in Washington, D.C., announced the discovery of a Jupiter-like planet orbiting a Sun-like star at about the same distance as the real Jupiter orbits the Sun.
Astronomers have previously discovered planets similar in size to Jupiter, but all of them were in very close orbits to their parent star, so astronomers called them hot Jupiters. Also, their orbit was elliptical and not circular. "The new planet orbits its sun at roughly the same distance as Jupiter orbits the sun," Marcy says. "And that thing makes it interesting."
The star, 55 Cancri in the direction of Cancer was already known, because one planet around it had already been discovered by Butler and Marcy in 1996. This planet is a small giant just short of Jupiter. It orbits the star once every 14.6 days at a distance of one-tenth of an astronomical unit (an astronomical unit is the average distance between the Earth and the Sun - 150 million km). That is, the distance of the giant planet from its Sun is about one-tenth of the distance between the Earth and the Sun.
The newly discovered planet orbits 55 Cancri at a distance of 5.5 AU, compared to Jupiter which orbits the Sun at a distance of 5.2 AU. Its orbit around its sun takes about 13 years, compared to Jupiter's 11.86 years. Its mass is estimated between 3.5 and 5 Jupiter masses.
55 Cancri is 41 light-years away from us and is about the same age as the Sun - about 5 billion years. "To date, we have not found a system completely twinned to our solar system where a Jupiter-like star would have a circular orbit and a mass similar to that of Jupiter. However, this shows that we are getting close."
We are at the point of finding planets greater than 4 AU from their Sun. Butler says. "I think we'll find many of them in the 1,200 stars we track."
The team shared their findings with astronomer Greg Lapin of the University of California, Santa Cruz. His dynamic calculation shows that a planet the size of Earth could survive in a stable orbit between the two gas giants.
As for the foreseeable future, the very existence of such a planet around 55 Cancri will be speculative. "This star system will be a good candidate for direct photography when the Terrestrial Planet Finder spacecraft is launched later in the decade," says Berkeley astronomer Debra Fisher.
Marcy, Fisher and their teams also announced 13 new planets, including the smallest planet discovered to date – a planet orbiting HD49674 in the Origa system at a distance of 0.05 AU, or five percent of the distance from Earth to the Sun. Its mass is about 15 percent of the mass of Jupiter or 40 times that of Earth. This brings the number of known planets orbiting other planets to over ninety.
The news on the same subject by Tamara Traubman, Haaretz
15 new planets were discovered
by Tamara Traubman
Astronomers announced yesterday the discovery of 15 new planets located in solar systems located approximately 41 light years from Earth. According to the researchers, among the discovered planets is also a planet moving in an orbit similar in shape and distance from the Sun to the planet Jupiter. The new planet completes its orbit around its sun every about 13 years, which means that a year on this planet lasts about 13 years.
The star's mass is about four times that of Jupiter. It is in a solar system called CANCRI 55 So far, about 80 planets have been discovered outside our solar system, but none of them have been directly observed through a telescope. Researchers Dr. Jeff Marcy from the University of California at Berkeley, and Dr. Paul Butler from the Carnegie Institution in Washington, concluded the existence of the new planet based on fluctuations in the light emitted from the sun around which it is orbiting. Oscillations are caused by the mutual attraction between the sun and the planet.
At the end of this decade, the "terrestrial planet detector" should start working - a powerful telescope that astronomers hope will be able to directly observe distant planets.
In the picture: a simulation of the 55 Cnc system as it might have been seen by the human eye, but space artist Lynette Cook, in the digital simulation shows the sun and the inner planets in the background, as well as a moon circling that Jupiter-like planet.
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