So far, about 5,000 exoplanets worlds circling stars other than our Sun have been discovered, but they have all been found within the Milky Way galaxy. The probable Saturn-sized planet identified by NASA’s Chandra X-Ray Telescope resides in the Messier 51 galaxy. This is 28 million light-years distant from the Milky Way.
This new finding is based on transits, which occur when a planet passes in front of a star, blocking some of the star’s light and causing a distinctive drop in brightness that can be seen by telescopes. This broad method has previously been used to discover thousands of exoplanets.
The researchers looked for dips in the brightness of X-rays emitted by an object known as an X-ray bright binary. These objects often contain a neutron star or black hole that is sucking in gas from a nearby partner star. The material in the vicinity of a neutron star or black hole gets superheated and flashes at X-ray wavelengths. Because the zone of powerful X-rays is restricted, a planet passing in front of it may block most or all of the rays, making the transit easier to detect.
This approach was utilized by the team members to discover the exoplanet candidate in a binary system known as M51-ULS-1. The approach we created and used is the only currently implementable strategy for discovering planetary systems in other galaxies.
It is a one-of-a-kind strategy for discovering planets around X-ray binaries at any distance from which we can measure a light curve. This binary has a black hole or neutron star around a companion star with a mass roughly 20 times that of the Sun. A neutron star is the collapsing core of a large star.
The passage lasted around three hours, during which time the X-ray output dropped to zero. According to the calculations, the planet would be around the size of Saturn and would orbit the neutron star which is almost twice the distance Saturn is from the Sun.
The approaches that have been so effective in discovering exoplanets in the Milky Way, according to Dr. Di Stefano, fail when seen in other galaxies. This is due, in part, to the large distances involved, which restrict the quantity of light that reaches the telescope and, in addition, to the fact that many objects are crowded into a tiny space, making it difficult to discern individual stars.
With X-rays, we may only need a few dozen sources distributed throughout the whole galaxy to resolve them. Furthermore, a subset of them is sufficiently luminous in X-rays that we can quantify their light curves. Finally, the massive X-ray emission is caused by a tiny area that can be significantly or completely blocked by a passing planet.
One difficulty is that the planet candidate’s enormous orbit implies it will not cross in front of its binary companion again for some 70 years, thereby ruling out any attempts to perform a follow-up observation shortly. Another possibility that the astronomers investigated was that the dimming was produced by a cloud of gas and dust passing in front of the X-ray source.
However, they believe this is implausible because the event’s features do not match those of a gas cloud.