2024-02-21 03:46:00
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So far no one has seen the alleged “Planet 9”. (Artist’s impression) © Caltech/R. Hurt (IPAC)
The mysterious “Planet 9” in our solar system has still not been found – but a research team can now report success anyway.
Pasadena – When it comes to searching for previously unknown planets, astronomy often uses the so-called “transit” method. The light from a star is observed over a longer period of time. If a planet passes in front of the star, the starlight is slightly shadowed for a short time – an indication of a planet that researchers can then investigate further. This method works well for exoplanets, i.e. planets that orbit stars outside our solar system – more than 5,500 exoplanets have been discovered so far, many of which have been revealed by their transits.
But in the solar system it is difficult to discover planets using this method. After all, only two planets pass in front of our sun from an earthly perspective: Venus and Mercury. A ninth planet, which has been searched for in our solar system for several years, should move well outside the orbit of Neptune. From the Earth’s perspective it can therefore never be seen in front of the sun. That’s why the researchers who are hunting for the mysterious “Planet 9” only have one thing left: they have to infer the properties of “Planet 9” based on the movements of other celestial bodies.
On the hunt for the mysterious “Planet 9”
Over time, some of the properties that researchers have attributed to “Planet 9” have come together without ever having seen it. For example, the unknown planet is said to have around 6.6 times the mass of Earth. Researchers have also long since worked out its possible orbit. The only problem is: the region in the solar system where “Planet 9” could be is huge, distant and dark. So it’s not easy to look for the planet that many researchers assume exists.
In a new study, a research team has now taken data from the PanSTARRS telescope and searched it for the planet. Michael E. Brown (California Institute of Technology) and his research colleagues didn’t find anything – but they can now rule out almost 80 percent of the possible locations where “Planet 9” could be located. “We have significantly reduced the search region,” explains Brown opposite Universe Today.
The areas of the sky that have not yet been examined will be largely covered by the Vera Rubin Observatory, the team writes in its study. The dignity published on the pre-print server ArXiv and from the specialist magazine The Astronomical Journal accepted for publication. The observatory is a giant reflecting telescope currently being built in Chile.
“Planet 9” would be the fifth largest planet in the solar system
The researcher Brown is known as the person who discovered the dwarf planet Eris together with a team in 2005. The discovery ensured that the new class “dwarf planet” was defined – whereupon Pluto was demoted from planet to dwarf planet. Brown has been trying to find “Planet 9” for many years now.
“This would be the fifth largest planet in our solar system and the only one with a mass between Earth and Uranus,” explains Brown, why he is looking for the previously unseen planet. “Such planets are common around other stars and we would suddenly have the chance to study one in our solar system.”
“Planet 9” explains much of what is happening in the outer solar system
Another reason to look for the planet is its effects on the outer solar system, which are obvious to Brown: “‘Planet 9’ explains many things about the orbits of objects in the outer solar system that would otherwise be inexplicable and would each require their own explanations,” emphasizes Brown, meaning, among other things, strongly inclined and retrograde orbits of objects in the outer solar system. “None of these should occur in the solar system, but all are easily explained as an effect of ‘Planet 9’.”
Of course, it is a possibility that “Planet 9” does not exist at all, the research team writes in the study, but points out again that other explanations for phenomena in the outer solar system would then be needed. The research group states in its work: “As long as such explanations are not available, we continue to consider ‘Planet 9’ to be the most likely hypothesis.” (tab)
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