Although we are not unfamiliar with the term exoplanet, so far, almost thousands of exoplanets that have been detected are less than 3,000 light-years away from the earth, that is to say, they are all located in the Milky Way. Now, astronomers have announced that the candidate exoplanet M51-ULS-1b has been discovered for the first time. If confirmed, it will be the first exoplanet known to mankind.
Detecting exoplanets is a difficult task. Due to the influence of distance and technology, it is difficult to directly image and detect exoplanets. It is mainly discovered through the indirect planetary transit method or the radial velocity method. The former refers to when the planet passes in front of the parent star (telescope Seeing the past from an angle), the luminosity of the parent star will be periodically reduced by blocking the parent star; the latter means that when the orbit of a massive planet reaches the perihelion, the parent star will shake due to gravitational interactions and cause slight speed changes. Astronomers These methods have confirmed the discovery of more than 4,000 exoplanets.
But the team of astronomer Rosanne Di Stefano at the Harvard-Smithsonian Center for Astrophysics has tried a different approach: observing the changes in X-ray brightness in the X-ray binary star system and identifying candidate targets for exoplanets. Researchers said that such systems produce bright X-rays in a small area, so if a planet passes in front, it will basically block most or all of the X-ray output, making it easier to spot transits.
In this way, the team used the Chandra X-ray Observatory (CXO) and 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. , From the M51-ULS-1 system about 23 million light-years away from us, there was an X-ray transit that lasted about 3 hours. During this period, the X-ray brightness suddenly dropped to zero and then returned to normal.
Researchers believe that the object causing the transit phenomenon is an exoplanet, named M51-ULS-1b. It is estimated to be the same size as Saturn and orbit around a black hole (or neutron star) with an orbital distance of about 10 from the 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 in the next 70 years. It may be difficult for astronomers to accept the results within time.
The research team said that the M31 and M33 galaxies near the Milky Way are also interesting observation sites, which are convenient for astronomers to observe and have more opportunities to discover more exoplanets. The new paper was published in the journal Nature Astronomy.
(First image source: NASA)
