<p>Of course; how would we find it otherwise? This is how we look for it: image one part of the sky with a telescope, about where the planet is presumed. At another time we image the same part again and see whether a star moved or is no longer there. This star is the wandering star = planet we're looking for.</p>
<p>The hypothetical object has a very elliptical orbit, and perhaps can even be seen with the naked eye when at perihelion since it may be a primordial black hole (which itself isn't visible but its accretion disc would be). About 4,000 years ago, when the black hole (if it is one) was closer to perihelion, the Sumerians  may have seen it and called it <em>Nibiru</em>. But we dunno whether that's the currently looked-for Planet IX.</p>

CC BY-SA 4.0
2020-07-15T17:54:51.750Z
@antispinwards How would we learn? Maybe the Sumerians just called Uranus and Neptune differently.
Ioannes
CC BY-SA 4.0
2020-07-16T04:43:51.703Z
@antispinwards In case Planet IX is a primordial black hole, the ancient Babylonians might have seen its accretion disc. Such a disc is flat while a pillar-like bar emanates from the poles of the black hole. From the distance, without a telescope, it might look like a dot, star-like.
Ioannes
CC BY-SA 4.0
2020-07-15T17:00:44.853Z
2020-07-16T04:55:33.813Z
2020-07-16T04:55:33.813Z
Ioannes
<p>If they knew exactly where to point Mr. Hubble, then yes, it should be easily visible, though at that distance, it would still be blurry, not a clean image.</p>

<p>The estimated <a href="https://en.wikipedia.org/wiki/Apparent_magnitude">apparent magnitude</a> of Planet Nine varies based on which website you believe, Google provides ranges from 20 to 25 with <a href="https://en.wikipedia.org/wiki/Planet_Nine">Wikipedia</a> saying >22.  Higher numbers mean less visible.</p>

<p>Hubble can see things up to apparent magnitudes of about <a href="https://lcogt.net/spacebook/what-apparent-magnitude/">30</a>, so, yes, it should be easily visible by Hubble or (perhaps) even more visible by an infra-red telescope or radio telescope that knows where to look.  But in any case, with current technology all images would still be blurry.   Hubble's pictures of Pluto are blurry and Pluto's much closer.  </p>

CC BY-SA 3.0
2016-06-26T22:40:30.907Z
2016-06-26T22:40:30.907Z
userLTK
<p>Is so-called Planet Nine (given it exists) observable in principle? By "observable in principle", I mean "if we knew <em>exactly</em> where to look, would we be able (from a technological standpoint) to get an image of the purported celestial body"?</p>

<observational-astronomy><9th-planet>
Is Planet Nine observable in principle?
Michael Smith
# Is Planet Nine observable in principle?

(Asked by: username_0 on 2016-06-26)

Is so-called Planet Nine (given it exists) observable in principle? By "observable in principle", I mean "if we knew *exactly* where to look, would we be able (from a technological standpoint) to get an image of the purported celestial body"?

**Tags:** observational-astronomy, 9th-planet


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## 2 answers

### Answer by username_2 on 2016-06-26. Score: 8 | Accepted answer

If they knew exactly where to point Mr. Hubble, then yes, it should be easily visible, though at that distance, it would still be blurry, not a clean image.

The estimated [apparent magnitude](https://en.wikipedia.org/wiki/Apparent_magnitude) of Planet Nine varies based on which website you believe, Google provides ranges from 20 to 25 with [Wikipedia](https://en.wikipedia.org/wiki/Planet_Nine) saying >22. Higher numbers mean less visible.

Hubble can see things up to apparent magnitudes of about [30](https://lcogt.net/spacebook/what-apparent-magnitude/), so, yes, it should be easily visible by Hubble or (perhaps) even more visible by an infra-red telescope or radio telescope that knows where to look. But in any case, with current technology all images would still be blurry. Hubble's pictures of Pluto are blurry and Pluto's much closer.


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### Answer by username_1 on 2020-07-15. Score: -4

Of course; how would we find it otherwise? This is how we look for it: image one part of the sky with a telescope, about where the planet is presumed. At another time we image the same part again and see whether a star moved or is no longer there. This star is the wandering star = planet we're looking for.

The hypothetical object has a very elliptical orbit, and perhaps can even be seen with the naked eye when at perihelion since it may be a primordial black hole (which itself isn't visible but its accretion disc would be). About 4,000 years ago, when the black hole (if it is one) was closer to perihelion, the Sumerians may have seen it and called it *Nibiru*. But we dunno whether that's the currently looked-for Planet IX.

> **Comments:**
> **username_1**: @antispinwards How would we learn? Maybe the Sumerians just called Uranus and Neptune differently.  
> **username_1**: @antispinwards In case Planet IX is a primordial black hole, the ancient Babylonians might have seen its accretion disc. Such a disc is flat while a pillar-like bar emanates from the poles of the black hole. From the distance, without a telescope, it might look like a dot, star-like.  

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