Billions of planets
Billions of Earths in our galaxy
|Automatic translation||Updated June 01, 2013|
In our solar system, the Sun has captured 99.86% of the total mass of dust and gas of the original nebula. Jupiter, the largest planet in the system, has captured 71% of the remaining mass. The other planets have shared the residue of the gravitational evolution, i.e. 0.038% of the total mass. Even capturing 99.86% of the material of the original nebula of gas and dust, a star leaves enough material for seven planets and billions of terrestrial objects (asteroids, comets, dwarf planets) are developing. There is therefore no wonder that there will be many more planets than stars in galaxies. For there is no planet in a solar system, the star must capture the entire field of the nebula, which is unlikely. Still had to find a way to prove it. In July 2011, more than 1,200 exoplanets had been discovered by conventional methods of oscillations or variation of brightness. A team of scientists at the European Southern Observatory (ESO), has used the technique of gravitational microlensing, to evaluate the average number of planets around a star. After six years of observation, the team concludes that there is at least one planet around a star. The result of this study was published in the journal Nature of January 12, 2012. The search for exoplanets is to identify the oscillations of stars, with identical characteristics to the Sun. This chase is limited mainly to the planets giants that orbit their stars and more stars are new discoveries with cyclical oscillations. Another characteristic of the presence of planets around a star is the variation of brightness of this star. When a planet passes in front of its star, the brightness of the star shows a small variation.
This variation can reveal the size and other characteristics of the planet. Both techniques involve the large planets or planets close to their star, or both. But small planets the size of the Earth are invisible. The method used by the international team of astronomers is new, because it detects that any type of planets. This method is based on gravitational lens (see image opposite). In astrophysics, an illusion, whitch astronomers are familiar with, is the gravitational lensing or gravitational mirage. A massive object, a cluster of galaxies, for example, which is between an observer and a distant light source, prints a strong curvature in Spacetime. This has the effect of deflecting all light rays passing near the object, thereby distorting the images received by the observer. This amplification of light, a distant celestial object by a massive star in front, was predicted by the theory of general relativity in 1917. The massive objects modify the geometry of space and time in their neighborhood. The light on the other hand always takes the shortest path, but in a curved space modified by the presence of a huge mass, the shortest path is not straight. The light path is bent in the vicinity of massive stars.
Image: This gravitational lens shows a strange blue objects stretched. They are spread in a circle in this picture, but are only multiple views of a single ring galaxy.
To detect planets, astronomers have used the method of gravitational lens which amplifies the light from a star background. Indeed, the gravitational field of a system (star and its objects), acts as a magnifying glass, magnifying the light from a star behind. This increase in brightness varies when the system foreground has a planet or more.
This requires that the plane of the orbit of the planet is so aligned, that is seen edge-on (see the picture against).
Image: To detect the planet requires that the plane of the orbit of the planet is aligned with the star background.