The search for extrasolar planets has expanded outside the Milky Way. Using NASA’s Chandra X-ray Observatory, astronomers have discovered what could be the first hints of a planet in another galaxy.
In the Messier 51 (or M51) galaxy, 28 million light-years away, the scientists discovered dips in X-ray brightness that point to a planet transiting in front of a star.
The achievement was made feasible by the sheer nature of stars. The transit was much easier to observe because the researchers had to focus on X-ray binary systems with a small region of bright rays. Because a planet may only block a modest quantity of light from a given star, conventional detection of nearby stars requires far higher sensitive light detection.
The dimming was not thought to be caused by gas clouds or dust, as these aren’t consistent with the event observed in M51. A planet, on the other hand, would match the data.
The problem, as you can expect, is confirming that information. Because of the planet’s enormous orbit, astronomers may not be able to see another transit in the coming 70 years, and it’s unclear when they’ll have to look. This planet candidate’s three-hour transit did not give a big window.
However, if there is ever a confirmation, the revelation would be huge. While there is no doubt that planets exist in other galaxies, proof of their existence would be valuable. This could also broaden the scope of future planetary searches to include the entire galaxy, rather than just nearby stars.