Evidence of a possible planet orbiting a star beyond the Milky Way galaxy has been spotted, NASA has revealed.
NASA’s Chandra X-ray Observatory made the discovery, allowing further studies of exoplanets further away than ever before, a statement posted on the US space agency’s website said. This possible candidate exoplanet is located in the spiral galaxy Messier 51 (M51), also known as the Whirlpool galaxy. It is located about 28 million light years from Earth.
These exoplanets are so called because they are positioned outside of our solar system. Most of the discovered and candidate exoplanets have been found just in the Milky Way galaxy, less than 3,000 light years from Earth. This M51 exoplanet could be thousands of times farther away than similar planets in the Milky Way.
NASA Chandra X-ray Images: Exoplanet Detection Performed At X-Ray Wavelengths
Rosanne Di Stefano, a scientist at Harvard and the Smithsonian Center for Astrophysics, who led the study published in Nature Astronomy, revealed that the search for exoplanets is done at the wavelengths of x-rays, which makes it possible to find planets further away from our galaxy.
The NASA statement said the results were based on transits, which are observed when a planet in front of a star obstructs some of the star’s light and generates that optical light drop. Astronomers using terrestrial or space telescopes, such as those on NASA’s Kepler and TESS missions, have also looked for such drops in optical light or electromagnetic radiation that humans can observe, making it possible to discover thousands of ‘exoplanets.
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Di Stefano told BBC News that his team’s approach is “the only currently implementable method for discovering planetary systems in other galaxies.” She added that this is a “unique method” that can find “planets around x-ray binaries at any distance from which we can measure a curve of light.”
Di Stefano’s team looked for optical light pits using the brightness of x-rays obtained from light x-ray binaries, NASA added. Such light systems typically include a neutron star or a black hole which sucks gas from a nearby star. Matter near the neutron star or black hole would become overheated, emitting glows in the form of x-rays.
Method revealed in the observation of the exoplanet M51
Since the area generating bright x-rays is small, a planet traversing in front of this region can obstruct most if not all of the x-rays, making the transit easier to detect because the x-rays can disappear from view entirely. This allows the detection of exoplanets at distances greater than the current analysis of optical light transit, which should spot small drops of light since the planet obstructs only a tiny fraction of the star.
NEW: Scientists may have detected for the first time evidence of a candidate planet orbiting a star outside of our Milky Way galaxy. The exoplanet could be about the size of Saturn: https://t.co/yoeFcGn2RK
– NASA (@NASA) 25 October 2021
Di Stefano’s team used this approach to locate the candidate exoplanet M51 in the binary system named M51-ULS-1. This binary system includes a neutron star or black hole that orbits a nearby star with a mass about 20 times our Sun. The x-ray transit the team discovered using Chandra lasted three hours, while the x-ray emission fell to zero.
Based on the study, scientists estimate that the candidate exoplanet is about the size of Saturn, which orbits the neutron star or black hole about twice the distance from Saturn to the Sun.
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