The discovery of the first planet outside our Milky Way | science and planet

Our solar system contains eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. In addition, scientists have now found nearly 5,000 so-called exoplanets. They all orbit other stars in our Milky Way. Most of them lie within 3,000 light-years (a light-year is about 9.47 trillion km), which is “around the corner” in terms of space.

To find such distant planets, scientists do not look at the planets themselves, because they are too small and too far to see. Instead, they measure the light and X-rays that come from the stars. When a planet flies “through the frame”, the radiation becomes slightly less bright for a while. See this US Chandra space telescope at M51-ULS-1. This is a binary star in the Messier 51 galaxy, also known as the Whirlpool Galaxy. It is about 28 million light years from Earth.

M51-ULS-1 consists of a star with a mass about twenty times the mass of our Sun, orbited by a neutron star or black hole. The star’s X-rays were obscured by the suspected planet for hours. Based on this, the researchers estimated that the size of the planet is about the same size as Saturn, and its distance from its star is twice as far as Saturn is from our sun. Because of its long orbit, the candidate planet is likely to pass in front of its star again after 70 years. Only then can it be confirmed whether it is indeed a planet. This makes researchers cautious in their conclusions.

The discovery will be published Monday in the important scientific journal Nature Astronomy. Scientists looked at a total of 238 stars in three galaxies, and revealed one possible planet. There is no chance of life on this planet: it is almost certainly exposed to unbearable radiation.

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