Extrasolar planet, definition and study. A-Z index of Cognitio.

An Extrasolar or exo planet is a planet not belonging to the solar system, orbiting around a star other than the Sun.

Sun, definition and study. A-Z index of Cognitio.

Sun

At 29 October 2017 there are 3,691 Extrasolar planet known in 2,766 different planetary systems; furthermore 2,422 is the number of candidate planets and other 206 possible planets are waiting for confirmation or controversy. The full list of known extra solar planets can be found in the list of confirmed extra sets and in the unconfirmed or controversial list of extra solar planets. Completely confirmed only in 1995, the existence of extraterrestrial planets was long believed to be more plausible so that scientific speculations of this type date back to at least the beginning of the eighteenth century: the first hypothesis of the existence of these celestial bodies was formulated , by Isaac Newton in 1713.

Planets, in comparison to the stars, emit much less light in the cosmos.

For this reason, direct detection of extra solar planets is extremely difficult: under normal visibility conditions, planets usually have a brightness of about one million times less than that of a star. In addition to this intrinsic detection difficulty, the greater brightness of the stars, around which the orbits of the planets, causes a glow that tends to cover the light weakly reflected by the celestial bodies of the respective system. For these reasons, current telescopes can only provide indirect information on the physical and orbital parameters of the exo planets and their presence can only be detected in extraordinary circumstances using indirect investigation techniques. Specifically, it is possible to identify the largest planets (considerably larger than Jupiter), sufficiently distant from their star and recent formation (so that being warmer they are capable of intense emissions in the infrared spectrum). Six methods of indirect observation of extra solar planets were determined by 2008. Most of the known exo planets have been discovered with such techniques.

Astrometry

Astrometry is the precise measurement of the position of a star in the sky and the observation of how this position changes over time. If the star has a planet, then the gravitational influence of the planet itself will cause the star a slight circular movement or elliptical orbit around a common mass center. This movement is determined by the Doppler effect.

Astrometry

Astrometry

Radial speeds

The variations in the speed with which the star approaches or departs from Earth – this speed is defined as the radial velocity of the star compared to the Earth – can infer the presence of a planet due to star-spectrum imbalances. Over time, this has become the most productive technique used by “planets hunters”. With this method you can determine the mass and weight of an extra solar planet.

Radial speeds

Radial speeds

 

Variations in Pulsar Emission Ranges

A pulsar, rotating, emits radio waves at extremely regular intervals. Light emission abnormalities can be used to trace changes in pulsar motion caused by the presence of one or more planets.

Variations in Pulsar Emission Ranges

Variations in Pulsar Emission Ranges

 

Transit method

If a planet crosses (or passes) in front of its star then observes a reduction in the brightness of the eclipse star. The amount of variation depends on the size of the planet and the star itself. The extra solar planets are distinguished by the variable stars at eclipse that in the first light curve there is only one variation; in the second there are two variations. With this method you can determine the dimensions of the extra solar planet.

Transit method

Transit method

 

Gravitational micro lent

The effect of the gravitational lens occurs when the gravitational fields of two celestial bodies cooperate to focus the light of a distant star. If the first celestial body (the closest to the observer) is a planet, this means that it has a gravitational field that contributes significantly to the effect of the gravitational micro lent.

Gravitational micro lent

Gravitational micro lent

 

Circular and protoplanets disks

Powder clouds surround many stars, and they can be identified as they can absorb stellar light and re-transmit it in the form of infrared radiation. By carefully analyzing dust clouds, it is possible to identify elements that suggest the presence of planets.

Circular and protoplanetic disks

Circular and protoplanets disks

 

For the future, many space missions are planned to improve the detection techniques of Extrasolar planets. Astronomical measurements made by space allow for greater sensitivity than those made on Earth’s surface; in fact, the distorting effect of the Earth’s atmosphere is canceled, and infrared instruments can also detect the radiation that is blocked by the atmosphere.

Atmosphere, definition and study. A-Z index of Cognitio.

Atmosphere

Some of these missions should be able to identify terrestrial planets. Large space telescopes, finally, could get direct images of the exo planets.

Space telescope, definition and study. A-Z index of Cognitio.

Space telescope

 

Extrasolar planet, definition and study. A-Z index of Cognitio.

© ALL RIGHTS RESERVED

 

To open the video  click on the image, good view from your Alessandro Brizzi.



Extrasolar planet, definition and study. A-Z index of Cognitio.

Extrasolar planet