Astronomers discover the first possible planets outside the Milky Way

Astronomers discover the first possible planets outside the Milky Way
kmpkt 28 million light years away

Astronomers may have discovered the first planet outside our galaxy

illustration of a spiral galaxy

Quayle: Getty Images/Science Photo Library – Mark Garlick.

Astronomers have long known that there are planets outside our solar system. But are there planets outside our galaxy as well? A mysterious celestial body, 28 million light-years away, provides the first clue.

vFor decades our imagination has been driven by the idea of ​​discovering new planets outside the Solar System: from “Star Wars” and “Star Trek” to “The Great Game” and “Dune.” Astronomers have already identified some of these exoplanets in the Milky Way, orbiting stars other than the Sun. but now scientists Harvard-Smithsonian Center for Astrophysics Discovered a planet in a completely different galaxy.

Astronomers locate mysterious celestial body in the so-called Whirlpool galaxy – a spiral galaxy 28 million light-years away from Earth. in expert journal nature astronomy Researchers explain how they came across the object and what it could possibly be.

The Whirlpool Galaxy (NGC 5194) and a companion galaxy (NGC 5195) in the constellation Canes Venetisi.

The Whirlpool Galaxy (NGC 5194) and a companion galaxy (NGC 5195) in the constellation Canes Venetisi

Quayle: Getty Images/Stocktrek Images

Astronomy: Extragalactic celestial body orbiting a double star

The key to the celestial body puzzle is the double star around which the extragalactic planet candidate orbits. It consists of two objects: a compact star in the form of a black hole or neutron star, and a massive companion star. The compact object tears off the matter from its companion, collecting it as a disk around itself and heating it to several million degrees. This causes X-ray light to be emitted from the binary star.

Such star systems also exist in our galaxy. Their radiation enables astronomers to discover planets and other celestial bodies. The whole thing works according to the “transit method”: if an object stands between Earth and the star during its transit, it can block the star’s X-ray light. Such a change can be observed with an X-ray telescope accordingly.

illustration of a double star

Quayle: Getty Images/Stocktrek Images/Corey Ford

Harvard scientists Rosanne Di Stefano and Nia Imara already said in 2018 that the “transit method” could also be used for planets outside the Milky Way. astrophysical journal suggested. Now two astronomers have proved that the strategy works: Together with other collaborators, they found a double star whose X-rays were blocked for three hours.

exoplanet, brown dwarf or star

How can this observation be explained? Possibility number one: The double star itself is less bright. Space objects are very variable in this aspect – sometimes they can even go completely black. However, this theory seems impossible to the researchers because then not only the intensity but also the spectral color of the X-ray light would have changed.

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Possibility number two: Clouds of dust and gas have formed in front of the double star. In this case, however, the X-ray telescope would still have captured a diffuse light on Earth. So the explanation is out there too.

Only option number three remains: a space object with a clearly defined surface has blocked the X-rays of the neutron star or black hole and its companion star. Theoretically, it could be an exoplanet, a star, or a so-called brown dwarf (celestial bodies that have no hydrogen fusion and are therefore not counted as stars). But as model calculations by astrophysicists show, the last two celestial bodies will be much larger. Therefore only a planet the size of Saturn will come under question.

The Milky Way, as you can see it in Patagonia, Argentina

The Milky Way, as you can see it in Patagonia, Argentina

Source: Getty Images/abandoned superlertsophon

Will have to wait for some time now for the verification of the planet hypothesis

For Harvard researchers, the extragalactic discovery is a sensational event. “It’s always a pleasure to find something first of its kind,” said Di Stefano. NBC News.

When we found the first planets around us, it seemed obvious that there are planets in other galaxies as well. But this is really exciting.

However, it may take some time to verify the planetary hypothesis. The Harvard team suspects that the distance between the occult identified double star and the celestial body is several dozen times greater than the distance between the Sun and Earth. By your estimates, one orbit of a candidate planet could take about 70 years—in other words, seven decades could pass before X-ray light would re-envelop it and we learn more about a potential extrasolar planet. Huh.

In the meantime, luckily there are other celestial subjects that can be just as inspiring. If you want to continue your space odyssey, we recommend this article:

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