Using the Kepler telescope, researchers were able to find four new orphan planets the size of Earth. These objects are not gravitationally connected to any star, and it is not yet clear how they ended up so close to each other.
Finding planets around bright stars even today is not always easy. Now astrophysicists have been able to find several planets left without a parent star and wandering in outer space
Until recently, astronomers could only use telescopes to find stars, galaxies and their clusters – very bright objects. Observing planets around other stars was out of the question – it seemed to require telescopes with exorbitant resolution. But improvements in optical technology and computer algorithms for data processing have made it possible to discover exoplanets “in packs”, and to date there are almost 4000 confirmed objects of this kind.
Observing planets moving around stars becomes possible largely due to the luminosity of the stars themselves. But there are also orphan planets that are not attached to any of the stars. To detect them, astrophysicists have to use an effect called gravitational microlensing. It consists of distorting light from a distant object by a body that is between the radiation source and the observer.
If a small object passes in front of the source, the brightness of the light increases briefly, and this can be seen from Earth. Using this effect, scientists using the Kepler telescope were able to detect 27 short-lived signals from potential objects – their duration ranged from an hour to 10 days. Many of these were also seen in earlier data, but the four shortest events were new. They corresponded to objects of terrestrial mass.
In the area where the objects are located, scientists did not notice longer signals indicating the presence of a host star. This means that the planets are “orphans”-they are not gravitationally connected to any massive body. Researchers do not yet know exactly how these four celestial bodies in relative proximity came to be, but suggest that they were previously formed around one star and then ejected by the gravity of more massive neighboring planets.