Beyond Pluto: Hunt for elusive Planet Nine set to intensify

With Vera Rubin Observatory due to start ops in mid-2024, astronomers hope to solve the mystery

- DEVANGSHU DATTA

How many planets are there in the Solar System? We know about eight and, of course, there's poor Pluto, which has been downgraded to "dwarf planet" status along with several other dwarfs. But one of the astronomers responsible for the Pluto downgrade believes there is another large planet out there, in the outer reaches of the Solar System. When the Vera Rubin Telescope is commissioned later this year, it's hoped the Planet Nine hypothesis will be confirmed.

In 2016, Mike Brown, professor at the California Institute of Technology who is nicknamed "Pluto-killer" for advocating the downgrade, co-authored "Evidence for a distant giant planet in the solar system" with his colleague Konstantin Batygin.

For years, Brown, Batygin and other astronomers had been puzzled by the movements of multiple large objects beyond the orbit of Neptune - the socalled Trans-Neptunian Objects (TNO).

They had found at least 13 large TNOS, which didn't orbit as expected. One explanation was that the gravitational attraction of a large, invisible planet was influencing these movements.

If at all, this Planet Nine exists, it might have a very long orbit and it may be at its most distant point from the sun, which would make it hard to see.

Moreover, while astronomers have looked for it, they may not have been looking in the right places. Alternatively, it has been seen but not recognised as a planet. The Vera Rubin Observatory in the Atacama Desert of Chile is due to start operating in mid-2024. It will run the Large Synoptic Survey Telescope (LSST), with a three-mirror system that should be able to pick close to 90 per cent of near-Earth objects and catalogue at least 10,000 TNOS.