Astronomers have found an exomoon that is much larger than Earth

(ORDO NEWS) — Usually satellites of planets are much smaller than our planet, but this time we are talking about such a large body that it looks like a very solid candidate for habitation.

An international team of astronomers has found a new celestial body in data from the Kepler space telescope. This is a satellite of a giant planet, but it is unusually large and, apparently, belongs either to the class of so-called super-Earths, or even to warm Neptunes.

Super-Earths, like warm Neptunes, are usually called planets that are noticeably larger than ours, but in the described case, we are not talking about a planet, but about a satellite. It seems that astronomical classification once again runs the risk of becoming a little more complicated. The corresponding article is published in Nature Astronomy .

The new body was named Kepler-1708 bi. The first part of the name means that it is in the system of the planet Kepler-1708 b, where “b” is the first planet discovered in the system of the star Kepler-1708. This is a sun-like star, around which at a distance of 1.6 times greater than the Earth from the Sun, the giant Jupiter-like planet Kepler-1708 b revolves.

The planet, like most known exoplanets, was found by the transit method. That is, astronomers recorded changes in the luminosity of the star Kepler-1708 and found that periodically it falls by the same amount.

However, a careful study of the luminosity graph showed that there are still some fluctuations in the depression in it, corresponding to the planet blocking the alien star. After a thorough analysis, the authors of the new work came to the conclusion that they should be explained by the presence of a moon near this planet, and an unusually large one at that.

Astronomers have found an exomoon that is much larger than Earth

To finally cast aside doubts, scientists tried to simulate such types of astrophysical activity of a star in the system under study, in which it could give similar fluctuations in the luminosity graph and lead the observer to a false conclusion that the planet of this system has a satellite.

In total, they conducted 200 simulation sessions, and only in two of them did they find signals that could really be confused with an exomoon like the one they discovered. This means that the probability of discovery being wrong is about 1%.

In other words, this time one of the most reliable candidates for large exomoons has been discovered. And Kepler-1708 bi is a really big moon: its diameter is about 2.61 times that of Earth. At the same time, it rotates at a distance of about a million kilometers from the giant host planet, that is, the latter should occupy a huge part of the visible sky on this planet – much larger than the Moon on Earth.

Previously, astronomers have found candidates for exomoons larger than the Earth, but quite few, and the probability of error there was noticeably higher than 1%. Therefore, many treated those data with distrust. A new discovery shows that giant exomoons are likely to be quite real.

Although the mechanisms for the formation of such large planetary satellites are still unclear. As well as why they are rare or why they are not in the solar system. Here, we recall, the largest satellites of giant planets are many times smaller than the Earth.

The question of the habitability of an open huge exomoon is currently unclear. In principle, a sufficiently massive body 240 million kilometers from a star like the Sun can be habitable if it has a sufficiently dense atmosphere. With dimensions 2.61 times larger than Earth’s, Kepler-1708 bi may indeed have a dense atmosphere, and possibly a magnetic field.

The combination of both can give the planet not only a temperature acceptable for life, but also protection from the radiation rings of its huge host planet. In the solar system, a number of satellites of Jupiter and Saturn, lying close to their radiation belts, are unsuitable for landing people, because they have a devastatingly high level of radiation danger.


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