Observing a star 400 light-years away, astronomers have spotted signs of new planets forming. And it looks like a pair of these newborn worlds share the same orbit for two.
In the gravitational field of a system of two massive bodies, there are Lagrangian points where a third body can remain stationary: centrifugal forces and gravity cancel each other out. In some of these points in the orbits of many planets of the solar system are asteroids "Trojans": only at Jupiter they are known almost 10 thousand. Their clusters move ahead and behind the planets themselves at about 60 degrees, at points L4 and L5.
In theory, there may be other planets accompanying the "main" in its rotation around the star, but so far no such example has not been known. The first signs of such a system noticed Olga Balsalobre-Ruza (Olga Balsalobre-Ruza) and her colleagues, whose article is published in the journal Astronomy and Astrophysics.
The astronomers looked at the PDS 70 system using the ALMA radio telescope array. This young star is located in the constellation Centauri, 370 light-years from the Sun. It is surrounded by a gas and dust disk in which the formation of new planets continues. Earlier, two such newborn worlds were spotted in this cloud - the gas giants PDS 70 b and c.
Now scientists have taken a closer look at the dark ring cleared of dust by the planet PDS 70 b as it orbits the planet. After analyzing ALMA data collected between 2015 and 2018, the researchers noticed a light cluster of matter located at Lagrange point L5, 60 degrees behind the planet itself. This could indicate the formation of a "sister" planet in the same orbit as PDS 70 b.
Unfortunately, it is not yet possible to confidently announce the first detection of a pair of planets sharing a common orbit. ALMA's antennas are sensitive to the ranges of radio waves that are emitted by heated dust particles, not planets per se. But, according to estimates of the authors of the work, the total mass of the cluster noticed by them reaches a couple of masses of the Moon, which is quite enough for a full-fledged protoplanet. Final confirmation of such conclusions is yet to come.
Even if confirmation will be obtained, it is not clear how long the coexistence of two planets in the same orbit can last. The position of a massive body in the Lagrangian point is far from as stable as for small asteroids, and it is unlikely that the hypothetical planet - "partner" PDS 70 b will remain in its place for a long time.