Is the planet x bigger than the earth

American astronomers used the Hubble space telescope to re-measure the diameter of the "10th planet" in 2003 UB313: its diameter is 2385 kilometers and is therefore only slightly larger than the 2274 kilometer Pluto.

Washington / Pasadena (USA) - Earlier measurements had provided a diameter of about 3000 kilometers for UB313. Meanwhile, celestial researchers still disagree on whether UB313 should be counted as a real planet - or whether Pluto will lose its planetary status instead.

"Hubble is the only telescope that is currently able to measure the diameter of UB313 in visible light," explains planetary researcher Michael Brown from Caltech in Pasadena. Brown and his team had discovered the celestial body, provisionally christened "Xena", last year and were also involved in the new observations. As long as the status of the celestial body is not clarified, UB313 cannot be given a definitive name.

2003 UB313 is a member of the so-called Kuiper Belt, which extends from the orbit of Neptune over the orbit of the ninth planet Pluto far into space. Since 2003 UB313 is larger than Pluto, many astronomers believe that the celestial body also deserves the status of a planet. On the other hand, the scientists suspect that there could still be many objects in the Kuiper Belt that are larger than Pluto. Some astronomers would therefore rather withdraw the planetary status of Pluto and simply list the previous ninth planet as a Kuiper belt object in their books.

The new Hubble observations also show that UB313 has an extremely bright surface. After Saturn's moon Enceladus, it has the second largest reflectivity of all celestial bodies in the solar system. The surface of Enceladus is presumably covered by fine ice crystals and is therefore so bright. The researchers suspect frozen methane on the surface of Xena. The celestial body may have a thin atmosphere when it is closer to the sun. UB313 is currently near the point of its orbit furthest from the sun and the atmosphere has frozen out. One orbit of Xena around the sun takes around 560 years.