Other galactic planets first discovered?

Evidence of a planet the size of Saturn has been found in the swirling galaxy M51, called the Child Galaxy, 28 million light-years away. If confirmed as a planet, it is the first instance of a planet found in another galaxy. It is said that two X-ray observation satellites, NASA Chandra and ESA XMM-Newton, discovered this planet candidate using a planetary search technique called X-ray traffic method.

The transportation method used to discover extrasolar planets, such as the Kepler Space Telescope, finds planets by observing the periodic eclipse that occurs when a planet passes in front of the main star. However, this method can only be used for planets within the Milky Way galaxy. It doesn’t work in other galaxies, where it’s difficult to even tell a star very far away.

On the other hand, X-ray observation can specify objects in other galaxies because there are very few objects that emit strong X-rays. Some of the easiest to spot objects emit strong X-rays, forming so-called X-ray ductility in neutron stars or black holes. Afterwards, when a planet passes in front of it, it is possible to observe a decrease in the intensity of X-rays, and to find a candidate for a planet by the degree and motion of the object.

The researchers say the discovery is interesting, but says more data is needed to confirm that it is a planet. In addition, the decrease in X-rays that occurred in this observation was only about 3 hours. In other words, to get additional data, we need to predict and observe when this 3-hour timing will occur 70 years later.

However, if it can be confirmed that this is a planet, it would be an important discovery. It is almost certain that planets exist in other galaxies as well, but there is no evidence that they exist. In addition, in the search for future planets, not only the inside of the Milky Way galaxy, but also the relatively nearby Dran galaxy can be included in the investigation target. Related information can be found here.