When a star amplifies the light from another star enter general relativity

With astrometric, velocimetric and transit methods already in use, a new and original technique for finding exoplanets emerged. It is based upon an application of Einstein's theory of general relativity, according to which lightrays are bent in the vicinity of very massive objects. This effect was confirmed during the total solar eclipse of 1919, when astronomers accurately measured 2.10 The gravitational microlensing method 35 The principle of gravitational microlensing. The observer on Earth...

First attempts at detection and first disappointments

In the nineteenth century, astronomers began to find evidence of the presence of smaller companions to stars when they detected slight periodic motions of those Edward Emerson Barnard (1857-1923) Piet van de Kamp (1901-1995). In 1964 was one of the greatest observers of his day. van de Kamp announced his discovery of a He discovered the fifth moon of Jupiter, planet orbiting Barnard's Star, but in 1973 it Amalthea, in 1892, and is also remembered was demonstrated that the star has no for the...

A great variety of giant planets may exist within extrasolar planetary systems

Although they are usually listed together as 'giant planets', the gas giants and the ice giants are very different from each other. Jupiter, at a heliocentric distance of 5.2 AU, is the most massive and the largest, as well as being the giant nearest to the Sun. Its diameter is about a tenth that of the Sun, and its mass about a thousandth of a solar mass. Situated just beyond the ice line, Jupiter was best placed to capture the greatest number of planetesimals, and rapidly grew larger. How...

First results from velocimetry

In the early 1990s, several teams of astronomers embarked upon systematic searches for low-mass companions of nearby Sun-like stars. Their targets were not only exoplanets, but also brown dwarfs - embryonic stars that have insufficient mass (less than 0.08 times the mass of the Sun) to trigger the fusion reaction to 'burn' hydrogen into helium. This mass is equivalent to about 80 times the mass of Jupiter, and so brown dwarfs are a priori less difficult to find than exoplanets. The velocimetric...

A question as old as astronomy itself

From Democritus and Epicurus to Aristotle and Seneca, Greek and then Roman philosophers often aired the question of the plurality of worlds. For Lucretius, 'there are, in other regions of space, Earths other than ours, different races of men, and different wild creatures.' Diogenes Laertius wrote 'The Universe is infinite of it, one part is a plenum, and the other a vacuum. He Leucippus also says that the elements, and the worlds which are derived from them, are infinite, and are dissolved...

Conditions and conclusions

What is the probability of being able to observe a planetary transit across a star at distance a If the star were indeed a point source, the transit would occur only if the star, the planet and the observer were in exact alignment. However, since the star has a definite radius R*, calculation shows that the probability of transit is expressed by R* a. Simple logic the nearer a planet is to its star, the greater the possibility of a transit and the larger the star, the greater the chance that...

Naming exoplanets

The names of exoplanets are hardly poetic. Lei us take the star HD 38529 as an example. The first exoplanet discovered orbiting this star is designated HD 38529 b, the next HD 38529 c, and so on. HD 38529 itself derives its name from its number In the star catalogue of Henry Draper, Most of the stars observed by the veloci metric method will be nearby stars such as HD 38529, already listed in various catalogues, or e Eridani, the fifth brightest star in apparent magnitude in the constellation...