We discovered a planet in another galaxy

The team of researchers found A new planet in another galaxy, 28 million light years from our Milky Way. First Exo-Exoplanet! Mathilde Fontez, Editor-in-ChiefEpsilon, New Science Magazine, looks back on this fascinating discovery.

franceinfo: Today, you announce the discovery of a planet in a galaxy that is not ours …

Mathilde Fontez: In the galaxy M51. It is a spiral galaxy that is very close to us, but still 28 million light years away. Yes, so this is the first time we have discovered a planet outside our Milky Way. If it is confirmed. This is because the signal collected by a team of international astronomers is very weak.

How was this planet discovered?

They targeted the stars with a space telescope. NASA’s Lunar Telescope. And they were looking for sharp drops in brightness. This is one of the main ways to detect planets, even in our own galaxy: when we see a star, a sudden drop of light means that something has passed between the telescope and the star. That something has obscured the light.

It was like an eclipse. Especially on a star, called ULS-1, the researchers found that the brightness decreases to zero for about 3 hours. According to their calculations, a giant planet the size of Saturn is attracted there.

And is it any wonder that there is a planet in another galaxy?

Well, not really. It has been a long time. Because planets, astronomers think are everywhere. Eight of them are in our solar system. Around the other stars, we found that there are 4,864 galaxies in our galaxy, according to the latest count.

There are planets of all kinds: as large as Jupiter; Small as Mars; Some too hot – too close to their star; Others may be moderate – like the earth.

These findings led astronomers to estimate that there are planets orbiting all or almost all the stars in the Milky Way. There will be tens and tens of billions. So there is no reason why it should not be in other galaxies. Besides, it’s incredibly difficult to care for because of the distance.

Because this drop in brightness is so low?

Yes. To view this exo-exoplanet: the first exoplanet outside the Milky Way, researchers had to target a particular type of star that was very bright in X-rays. And they can’t measure it any other way. Because according to their calculations, the orbit of the planet is very long. Will not go before the star again for 70 years. So we have to be satisfied with this data to confirm the existence of the planet … and try to find others.