Caltech just released a report that says there is possibly a large (10 earth mass) planet in a remote orbit (10 - 20 thousand year) that explains a lot of observations of Kuiper Belt objects. How long could it take for this to be confirmed or refuted observationally?

See this video

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    $\begingroup$ Pics or it didn't happen!” ;-) $\endgroup$
    – gerrit
    Commented Jan 20, 2016 at 18:46
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    $\begingroup$ 5 years according to this article: "Batygin and Brown are using Subaru to look for Planet X—and they are coordinating their efforts with their erstwhile competitors, Sheppard and Trujillo, who have also joined the hunt with Subaru. Brown says it will take about 5 years for the two teams to search most of the area where Planet X could be lurking." $\endgroup$ Commented Jan 21, 2016 at 1:36
  • $\begingroup$ Related: Why hasn't the "9th Planet" been detected already? $\endgroup$ Commented Jan 26, 2016 at 18:52
  • $\begingroup$ Nice update 1 year later on where we are: oklo.org/2017/01/21/planet-nine-a-one-year-update $\endgroup$ Commented Jan 22, 2017 at 23:18

2 Answers 2


Those are model calculations, which hint to the existence of a possible body of about 10-times the mass of Earth. Calling this a discovery would clearly be premature. The confidence level is just a little above the "evidence" level of 3 sigma, under the assumption, that the discoveries of the KBO objects leading to the inference aren't observationally biased. It's a long way to direct observation, since precise orbital data haven't been inferred. Another option is, that there has been a planet. But it might have left our Solar system. Hence predicting a date for direct observation doesn't appear reasonable at the moment.


Maybe the Gaia space telescope has already caught it? First data release in mid-2016.

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    $\begingroup$ That would be so awesome $\endgroup$ Commented Jan 21, 2016 at 5:50
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    $\begingroup$ Unless it's in the near part of its orbit, it'll be too faint for GAIA to see. A Neptune size object (slightly larger than this potential planet would be), would drop below GAIA's 20th magnitude limit at about 500 AU. I did the math as part of another answer. $\endgroup$ Commented Jan 21, 2016 at 18:52
  • $\begingroup$ @DanNeely I thought it could see more, but GAIA finding more KBO's along the suggested orbit of P9 should help test this. $\endgroup$
    – LocalFluff
    Commented Jan 21, 2016 at 21:01
  • $\begingroup$ LocalFluff has a good point, but an even broader point is that many discoveries actually have at least one "precovery" from years early. Pluto was this way. They found precovery photos from 1915 but no one noticed what it was (because it wasn't moving), thus the actual discovery by Clyde Tombough in 1930. The cite from wikipedia: en.wikipedia.org/wiki/Pluto#cite_note-Hoyt-34 So maybe we've already photoed it but just never noticed it moving (because it is really far away and therefore really slow in its orbit.) $\endgroup$
    – DrZ214
    Commented Jan 25, 2016 at 17:06

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