You can often hear the question of which of the known planets is the largest. The largest planet in the solar system is Jupiter. However, in density it is inferior to many planets. For example, the density of the Earth is four times greater. This fact allowed scientists to conclude that Jupiter consists mainly of gases, does not have a solid core. Also, Jupiter is the largest planet in the solar system in terms of radius, and, accordingly, volume, surface and other characteristics associated with size.
If we include in this competition the size of the planets found in other star systems, the so-called "exoplanets", then Jupiter will turn out - 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 must be at least 15 times larger in order for nuclear fusion reactions to 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 planets around othersstars. The results achieved in recent decades have shown that the solar system is only one of many planetary systems. Connected with these explorations is humanity's long-standing hope of finding other habitable worlds. The first exoplanet was discovered in 1992, and now several hundred exoplanets are known. Most exoplanets known today are giants the size of Jupiter or larger.
Planets orbiting distant stars are extremely difficult to detect as they don't emit their own
light and are in close proximity to the central star of the corresponding system. To get around these difficulties, scientists use a variety of methods to capture subtle effects that indicate the presence of a planet near a particular star. The most common method for finding planets around distant stars is to observe radial velocity modulations. This method is based on the fact that the planet has the smallest influence on the motion of a star that can be captured using very precise 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. Extraterrestrial life is most likely to be found on Earth-like planets orbiting in a belt adapted to create and sustain life.
Unfortunately, the detection of such planets presents an extraordinary difficulty for ground-based telescopes. To this end, it is planned to launch orbital telescopes, the sensitivitywhich will be sufficient to observe terrestrial exoplanets.
One of these orbiting Kepler observatories is able to detect exoplanets comparable to the size of 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 there is life on it is not the greatest. The planet of the solar system, similar in characteristics to this exoplanet - Mercury. But the fact that Kepler-37b is definitely solid rock is a remarkable and reassuring fact.
