solar system exception in milky way galaxy

Outer Space

Published on January 9th, 2014


Why is our solar system an exception in the Milky Way galaxy?

Planets that have characteristics similar to those of Earth, most often discovered by the U.S. telescope Kepler, are quite common in our galaxy, but do not exist in our own solar system, the Milky Way is considered an exception, announced paleontologists.

Over three quarters of potential planets detected by Kepler have a size ranging between the Earth and that of Neptune - nearly four times larger than our planet, informs AFP.


Such planets dominate the galactic census, but are absent in our solar system, astronomers have pointed out that they do not know the time nor the way they were formed and internal composition. They could be terrestrial, gaseous or made ​​up of water.

Paleontologists announced on Monday the results obtained after four years of observations made ​​with ground-based telescopes to confirm the discoveries made ​​by the Kepler on exoplanets. Their study was presented at the annual conference organized by the American Astronomical Society this week in Washington.

“This wonderful avalanche of data about the planet known as «mini -Neptunes», often reveal only their external shell structure”, said Geoff Marcy, professor of astronomy at the University of California at Berkeley, who led the summary analysis of the high-precision Doppler study.

“But now I deal with a difficult questions that we ask about how these enigmatic planets were formed and about why our solar system is devoid of such planets, given that they are quite numerous in our galaxy”, he added.

Using one of the most powerful ground-based telescopes, the Keck Observatory in Hawaii, scientists have confirmed the existence of 41 exoplanets discovered by Kepler and calculated the mass of 16 of them. Given the mass and diameter, American researchers were able to calculate the density of these planets, characterized as terrestrial, gas or a combination of the two.

Density measurement could lead to determine the composition of these strange planets. This suggests that the density measurement of these terrestrial “mini - Neptunes” have a core, but the proportions of hydrogen, helium, and hydrogen-rich molecules in the envelope surrounding that core vary dramatically, with some having no envelope at all.

The same scientists announced the discovery of five new terrestrial exoplanets with a size ranging between 110 % and 180 % of the size of the Earth, but none of them is inhabited. They are really too hot because they are too close to their stars.

The first results of mass analysis was made ​​on the ground, suggesting that many of the planets with a radius smaller than 1.5 times the Earth may be formed of silica, iron, nickel and magnesium - terrestrial elements found on the planets solar system.

Based on this information, scientists may discover those stars around which planets orbiting terrestrial considered Earth-like, which will take them closer to the discovery of a habitable environment outside the Solar System.

In November 2013, astronomers estimated at several billion Earth-sized number of planets orbiting other stars similar to the Sun in our galaxy that might be habitable.

According to the computer model used in that study, one-fifth of stars are similar to the Sun in the Milky Way, which has about 55 billion stars, is orbiting a planet whose size is similar or close to that of Earth, which is not too far nor too close to the star in it, allowing the occurrence of temperatures at which water could exist and thus become potentially  habitable.

Chart of Kepler planet candidates as of January 2014.
Image Credit: NASA Ames

The same researchers have based their calculations on the data reported in the first three years of operation of the telescope Kepler.

Kepler telescope - a mission of 600 million dollars - was launched by NASA in 2009 to monitor for at least four years, over 100,000 stars like our Sun, located in the constellation of the Swan and Lyra.

Kepler was placed on a safe trajectory in May 2013, after the failure of equipment designed to allow the telescope to move towards a given direction in the sky. Researchers at NASA could still continue to use Kepler for a number of scientific projects that do not require such precise positioning - search for asteroids, comets and other celestial bodies.

Source: AFP, NASA

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