Astronomers have discovered an exoplanet that is located incredibly far from the Solar system. Besides, it is close to the Earth at the same time the weight and size of the orbit, and such worlds are able to open extremely rare.
The achievement is described in a scientific paper published in the Astronomical Journal.
For today mankind knows more than four thousand exoplanets. The vast majority of them are less than a thousand light-years from us because to detect a planet at large distances is too difficult. For comparison, the diameter of the milky Way is about one hundred thousand light-years.
This time, astronomers are fortunate. They opened up the world, located in more than 24700 light-years from the Sun, near the bulge of the milky Way. It’s almost a record. Known to just a handful of more distant exoplanets.
The heavenly body was discovered the only way to observe the planets at such distances: the gravitational microlensing method.
Explain what it’s about. When a star passes between a distant light source and observer, its gravity works as a lens, bending the rays of light. As a result, the background brightness of the object suddenly increases. Sometimes the subtle details of this change can be understood that the star lenses are the planet, and even to determine its characteristics.
This phenomenon is extremely rare. In each moment of time, only one star in a million feels the effect of gravitational microlensing. In addition, such events are not repeated. Light once worked for the observer as a gravitational lens, most likely, won’t repeat this trick too unlikely that it will pass exactly between Earth and a distant star. So to open so the planet can only be by happy accident.
There are entire networks of telescopes hunting for microlensing events. This, in particular, KMTNet, consisting of three identical instruments in Chile, Australia, and South Africa. Every 15 minutes this telescope measures the brightness of a hundred billion stars. There are single instruments with the same objective. For example, the OGLE project uses a single telescope in Chile.
“In these experiments detected about 3000 microlensing events per year, most of which are associated with lensing of a single (no observed satellites — approx. edition) stars,” says co-author Michael Albrow (Michael Albrow) from the University of Canterbury in New Zealand.
The event OGLE-2018-BLG-0677 was recorded in 2018, observers of both projects. Processed data, astronomers realized that the star-the lens has a planet.
The mass of this exoplanet is estimated at 1.3 to 9.8 earth (the most probable value of 3.96). Thus, the open world is a super-earth or a sub-Neptune.
The celestial body is located at a distance of 0.63-0.72 astronomical units from the parent star (one AU equals the distance from the Earth to the Sun). But, since the mass of this luminary is only 0.04-0.26 solar, the year on this planet is longer than ours: 611 Earth days.
It would be practically impossible to open such a planet in other ways, even if it were near a star close to the Sun. Indeed, classical approaches, such as the transit method and the radial velocity method, require the exoplanet to make at least three turns around its star in front of astronomers. That is, it would be required to observe the system for 1833 days.
Usually, observers cannot afford to spend so much time in one area of the sky. Therefore, worlds with such a long year open up very, very rarely.
Thus, discovering a planet with an almost terrestrial orbital period is an amazing success for astronomers.
It is difficult to say anything definite about the potential habitability of this exoplanet. Her parent star is too far away to analyze its spectrum and find out which class it belongs to. And this is necessary in order to calculate how much heat the planet receives from its sun.
By the way, earlier Vesti.Nauka (nauka.vesti.ru) talked about how gravitational lensing made it possible to open planets in another galaxy. We also wrote about the first exoplanet, located outside the plane of the Galaxy