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The case for, and against, the still-unseen Planet 9

16 Feb 2021, 19:48 UTC
The case for, and against, the still-unseen Planet 9
(200 words excerpt, click title or image to see full post)

A plot showing the relationship between the clustered orbits of several Trans-Neptunian Objects, or TNOs, in the extreme outer solar system as a result of gravitational interactions with an unseen world dubbed Planet 9. Image: Caltech/R. Hurt (IPAC)
For the past several years, astronomers have been searching for an unseen planet beyond the orbit of Pluto, a presumed world with 10 times the mass of Earth that could be responsible for the seemingly clustered orbits of small Trans-Neptunian Objects, or TNOs, in the extreme outer solar system. So far, “Planet 9” has eluded detection.
Dealing a possible blow to the theorised planet, a team of researchers led by Kevin Napier of the University of Michigan suggests selection bias may have played a role in the original justification for Planet 9.
TNOs are so distant and dim they can only be detected, if seen at all, when their orbits carry them relatively close to the inner solar system. Napier’s team analysed 14 other extreme TNOs discovered in three surveys and concluded their detection was based on where they happened to be at the time and the ability of the telescopes in question to detect them.
In other words, the clustering seen ...

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