Although we do not know the term exoplanet, so far, almost thousands of exoplanets that have been detected are less than 3,000 light years from Earth, that is, they are all located in the Milky Way. Now, astronomers have announced that the possible exoplanet M51-ULS-1b has been discovered for the first time and, if confirmed, will be the first exoplanet known to mankind.
Detecting exoplanets is a difficult task. Due to distance and technology, it is difficult to detect exoplanets directly. They are discovered primarily through indirect planetary transit or radial velocity methods. The first refers to when the planet passes in front of the mother star (telescope When looking back), the luminosity of the mother star will periodically decrease as the mother star darkens; the latter means that when the orbit of a massive planet reaches perihelion, the parent star will sway due to gravitational interaction and cause small changes in velocity. Astronomers These methods have confirmed the discovery of more than 4,000 exoplanets.
But astronomer Rosanne Di Stefano’s team from the Harvard-Smithsonian Center for Astrophysics has tried a different approach: observing changes in X-ray brightness in the binary X-ray star system and identifying candidate targets for exoplanets. The researchers said such systems produce bright X-rays in a small area, so if a planet passes by, it will basically block most or all of the X-ray output, making it easier to search for transits.
In this way, the team used the Chandra X-ray Observatory (CXO) and the XMM-Newton satellites to observe 55 systems in the M51 galaxy, 64 systems in the Messier 101 galaxy, and 119 systems in the Messier 104 galaxy. M51-ULS-1 about 23 million light years away, and there was an X-ray transit that lasted about 3 hours. During this period, the brightness of the X-rays suddenly dropped to zero and then returned to normal.
The researchers believe that the object causing the transit is an exoplanet, called M51-ULS-1b. It is estimated to be the same size as Saturn and orbits a black hole (or neutron star) with an orbital distance of about 10 from Earth. to the sun. ~ 100 times
If this discovery is confirmed by follow-up studies, M51-ULS-1b will become the first known extragalactic planet. However, the orbital path of M51-ULS-1b indicates that it will not pass through this position again for the next 70 years. It can be difficult for astronomers to accept the results in time.
The research team said that the M31 and M33 galaxies near the Milky Way are also interesting observing sites, which are convenient for astronomers to observe and have more opportunities to discover more exoplanets.paperPublished in the journal Nature Astronomy.
(Source of the first image:POT）
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