Astronomers have discovered an exoplanet candidate orbiting a low-mass star. The discovery is interesting because this system is moving at a tremendous speed through the center of our galaxy and may leave it in the future.
Mysterious microlensing
Astronomers first discovered signs of the pair’s existence while studying data from the MOA (Microlensing Observations in Astrophysics) project, which is dedicated to searching for microlensing events. They occur when the gravitational field of an object closer to us, like a lens, concentrates and amplifies light from a more distant background source.
In 2011, MOA recorded a microlensing event caused by a pair of celestial bodies. Scientists determined that the mass of one of them was about 2,300 times the mass of the other. But because of the unknown distance to the Earth, the exact value of their masses remained unknown.
The authors of the discovery suggest that the microlensed objects are either a star whose mass is about 20% of the solar mass and the exoplanet orbiting around it is 29 times heavier than Earth, or a closer rogue planet about four times as massive as Jupiter with a moon smaller than Earth.
Fleeing star
To find out which explanation is more believable, astronomers analyzed data from the Keck Observatory in Hawaii and the Gaia spacecraft. They were able to detect a suspicious star located about 24,000 light years away. It is part of the bulge, a spherical compaction of stars at the center of the Milky Way. By comparing the star’s estimated location in 2011 to 2021, the team calculated its speed.
It turns out that the star moves through the center of the Milky Way at a speed of 540 km/s. This is twice the speed of the solar system. But that’s just its two-dimensional movement. If the star also moves toward or away from us, the speed may be even higher. It may well exceed the escape velocity (600 km/s), enough to leave the Milky Way forever in the future.
As for the exoplanet orbiting around it, it is a so-called super-Neptune. If it were in the Solar System, its orbit would lie between the orbits of Venus and Earth. As the exoplanet orbits a dim red dwarf, it receives too little heat and light for water to exist in liquid form on its surface.
The researchers intend to repeat the observations to make sure the star moves in the right direction. If confirmed, the pair would set a record as the fastest moving exoplanet system known to exist. If observations show that the star remains in the same position, it means that the microlensing event was not caused by it, and the most likely scenario is a rogue planet and its companion.
According to NASA
