You can often hear the question of which of the known planets is the largest. The planet of the solar system with the largest mass is Jupiter. However, in density it is inferior to many planets. For example, the density of the Earth is four times higher. This fact allowed scientists to conclude that Jupiter consists mainly of gases, does not have a solid core. Jupiter is also the largest planet in the solar system in terms of radius, and, accordingly, volume, surface and other characteristics related to size.
If we include in this competition the
sizes of the planets found in other stellar systems, the so-called "exoplanets", then Jupiter will turn out to be - this is far from a record holder. For example, the planet TrES-4 is 1.4 times larger than the largest planet in the solar system. According to calculations, the gas cloud should be at least 15 times larger so that
nuclear fusion
reactions begin inside. It is the presence of this process that distinguishes stars and planets.
New methods of observation allow astrophysicists to discover more and more new planets around other stars. The results achieved in recent decades have shown that the solar system is only one of many planetary systems. Connected with these studies is the long-standing hope of mankind to find other inhabited worlds. The first exoplanet was discovered in 1992, and now several hundred exoplanets are already known. Most now known exoplanets are giants the size of Jupiter or more.
Planets orbiting distant stars are extremely difficult to detect since they do not emit their own
light and are in close proximity to the central star of the corresponding system. To circumvent these difficulties, scientists use various methods that allow you to catch subtle effects that show the presence of a planet near a star. The most common method for finding planets in distant stars is
to observe radial velocity modulations. This method is based on the fact that the planet has the smallest effect on the motion of a star, which can be captured using very accurate spectral measurements. This method is most likely to find the most massive planets that are too close to the star. The chances of these worlds being inhabited are minimal. The greatest probability is to find extraterrestrial life on terrestrial planets, rotating in a belt adapted to create and maintain life.
Unfortunately, the discovery of such planets presents an extraordinary difficulty for ground-based telescopes. For this purpose, it is planned to launch orbital telescopes, the sensitivity of which will be sufficient to observe Earth-type exoplanets.
One of these Kepler orbital observatories is capable of detecting exoplanets comparable in size to the Earth and even smaller. For example, the
planet Kepler-37b, found in the system in the
constellation Lyra, is comparable in size to the moon. It is completely devoid of atmosphere and heated to enormous temperatures, and the likelihood that it has life is not the greatest. The planet of the solar system, similar in characteristics to this exoplanet - Mercury. But the fact that Kepler-37b definitely consists of hard rock is a wonderful and encouraging fact.