27/10/1996
Merav Sherry
American astronomers published details of the eighth extraterrestrial planet discovered this weekend. The planet, larger than Jupiter, orbits a sun that is trillions (thousands of billions) of kilometers away from Earth. The discovery was presented at the meeting of the Planetary Sciences Division of the American Astronomical Society in Arizona, USA, and has the potential to shake up prevailing theories about the formation of planets.
Since 1989, eight extrasolar planets have been discovered. For more than two years, researchers from the University of Texas and San Francisco State University have been observing a solar star known as 16 Signi B located in the Cygnus, or Northern Cross, system. This star is similar in its mass and chemical composition to our sun.
The scientists calculated that the orbital speed of the star varies up to 160 km/h. Thus it was discovered that the Sun is orbited by a large planet, with a mass 1.6 times greater than the mass of Jupiter, and its distance from the Sun reaches about 250 million km.
In astronomical terms, says Prof. Zvi Maza, head of the Department of Astronomy and Astrophysics at Tel Aviv University, this distance is not much greater than the distance of the Earth from the Sun - 150 million kilometers. This discovery shocks previous theories about the formation of the giant planets. According to Maza, "In our solar system, all the giant planets - Jupiter, Saturn, Uranus and Neptune - are at a great distance from the Sun. In contrast, the small stars - Hema, Venus, Earth and Mars - are close to the sun. Based on this, the scientists formulated theories for the process of the formation of planets. But the latest findings are surprising, because some of the giant planets outside the solar system are at a relatively small distance from their sun."
According to Maza, the discovered planet has a very elliptical orbit, compared to an almost circular orbit for most of the planets in our solar system. This makes it difficult, in his estimation, for life to form there. "The distance of the planet from its sun increases and decreases five times and more, and this causes a radical change in the physical conditions that prevail in it. For example, the water in it may boil and freeze alternatively, and it is difficult to understand how life would be created under such conditions."
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