:: OSEL.CZ :: - Planet from alien galaxy revealed by X-ray transit in extreme binary

An X-ray transit in an extreme binary star has revealed a planet from an alien galaxy

–

Did we find an extragalactic exoplanet in the X-ray binary? Credit: NASA / CXC / M. Weiss.

–

Many global media in covid autumn were fascinated by the news of “the first planet discovered in an alien galaxy.” However, as is often the case in similar cases, the reality is somewhat different from autumn dreaming. The words “possible” and “indirect detection” must be added to this report. At the same time, it is definitely not the first discovery of this type. We already know several indirect detections of extragalactic planets, and no direct ones so far.

Rosanne Di Stefano.

Credit: Harvard University.

–

Nevertheless, the discovery of a candidate for a planet that has already been designated M51-ULS-1b is very fascinating – because of the method used. Rosanne Di Stefano of the American Research Center Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, and her colleagues used data from the Chandra Space X-ray Observatory to track possible X-ray transit.

The candidate for the extragalactic exoplanet is located in the spiral galaxy M51 from the constellation Honic Dogs, which can only be praised. The galaxy, about 31 million light-years away, which is nicknamed the “Whirlpool Galaxy”, is one of the brightest galaxies, and it is also very beautiful.

As Di Stefan says, their discovery, especially if confirmed, could open a new field for exoplanet hunting, including the very distant ones. Many exoplanets have been discovered due to transits, ie the transitions of planets across the star’s disk from our point of view, which cause a temporary small decrease in the brightness of the star, usually in the visible region. Di Stefan’s team looked for transits elsewhere, in X-ray binary stars, in the area of harder X-rays.

–

Galaxy M51 with the location of the X-ray binary M51-ULS-1. Credit: NASA / CXC / SAO / R. DiStefano, et al .; Optical: NASA / ESA / STScI / Grendler.

–

They tend to be extreme binary stars where dramatic things happen. In this case, it should be a neutron star or a black hole stealing matter from a blue giant, about 20 Suns. In such a theft, the mass snatched from the star heats up immensely, creating a lot of radiation, including X-rays. The radiation comes from a relatively small area, so that a potential planet can block it almost completely. The transit of the possible planet M51-ULS-1b took about 3 hours, while the X-rays of the binary star completely disappeared.

The researchers deduced from the available data that the planet M51-ULS-1b, if it exists, should be about the size of our Saturn. It should orbit a neutron star or black hole, or “thief” of matter in this binary, about twice the distance of Saturn from the Sun. The existence of this planetary candidate will have to be confirmed by another X-ray transit. However, if Di Stefanová’s estimates are correct, such a transit should take place in about 70 years. Discovering exoplanets in distant orbits is usually a long-distance run.

Discoverers do not succumb to sadness and prefer to dream. If M51-ULS-1b is really a planet, then it must have a turbulent history. And also the future. She had to survive a supernova, and relatively soon another blue giant awaits her. That’s pretty much an explosion for one planet. Di Stefanova et al. examined a total of 55 similar binary stars in the galaxy M51, 64 in the galaxy M101 “Pinwheel” and 119 in the galaxy M104 “Sombrero”. They found the only candidate for the exoplanet. But they take it positively and continue their research. Chandra has usable data from at least 20 galaxies.

Video: Discovered: First Potential Planet Outside of Our Galaxy