Rogue planets in the Milky Way.
Researchers have found new evidence for rogue planets that fly freely in space, rather than revolving around parent stars such as the Sun. In particular, they found four candidates that are suitable for this criterion, the mass of which is comparable to the mass of rocky planets, similar to Earth.
Finding dark rogue planets in the Milky Way is an incredible accomplishment
1. The Kepler Space Telescope, a hunter for distant exoplanets, completed its challenging mission in 2018. However, astronomers still continue to analyze the data they collected. More than 2,000 distant planets have been discovered thanks to Kepler, and many of the candidates identified with its help are awaiting confirmation.
2. Recently, this list was replenished with four more orphan planets in the region of the center of the Milky Way.
3. Rogue planets are thrown out of the parent system under the influence of gravity from their massive neighbors and are making a more or less free flight in interstellar space. It is assumed that this once happened in the solar system, and indeed such objects are extremely common in our Galaxy, although estimates of their number differ.
4. It is especially difficult to detect a dark rogue planet: for this, it is necessary to notice the moment of its accidental passage against the background of more distant stars and to fix the gravitational microlensing of their radiation – distortion by the attraction of an object invisible directly.
5. In search of such signals, an international team of astronomers led by Iain McDonald of the University of Manchester looked to data from the Kepler K2 mission from 2016.
6. Kepler observed stars in an area of 3.7 degrees in the bulge (central bright ellipsoidal component) of the Galaxy. As a result, 27 short microlensing signals were detected, when an invisible object distorts the light of background stars and galaxies, while simultaneously increasing their brightness.
7. The duration of these events varied from one hour to ten days. The four shortest signals correspond to objects the size of which is comparable to the Earth. At the same time, short signals were not accompanied by longer ones, which could confirm the presence of some parent stars nearby.
8. In this regard, scientists came to the conclusion that this event could indicate the presence of freely flying planets in the Galaxy. Presumably, such objects originally formed in the protoplanetary cloud before they were ejected by the gravitational pull of heavier planets.
9. The study also suggests that about one in a million stars in the Milky Way are exposed to microlensing, yet only a few percent of these events are caused by planets. Despite the fact that the Kepler telescope was not a good instrument for observing microlensing in a dense field of objects in the center of the Galaxy, the researchers used a new software for processing photometric data, which allowed detecting both known microlensing events and new ones.
10. Unlike bodies revolving around stars in a regular orbit, it is hardly possible to repeat such observation for free-flying planets, so they will forever remain in the rank of “candidates”. It is impossible to clarify the conditions on them. Most likely, these worlds are icy lifeless deserts, although, according to some reports, even rogue planets can be heated by their own bowels to quite acceptable temperatures.
References: Phys.org