I just re-read a popular astronomy book that was published when I was a child, about 1973. It starts with an interview to Harold C. Urey where the interviewer asks about a hypothetical planet in our solar system called Biga.

Has a hypothetical planet ever been called "Biga" by its proponents, in the same way there was a proposed planet "Vulcan", or is this "Biga" name a printing or translation error?

If it's a mistake and there never was a "Biga" proposal, which is the proposed planet with the most similar name?

This link contains such interview, in Spanish. I will translate and quote its most relevant text:

Interviewer: At present, do we know all the planets of the Solar System, or is there the possibility of still unknown planets in our system?

H.C. Urey: We certainly know the nine usual planets. Recently there has been much talk of another object moving in space and supposed to be close to the Solar System, but I am not sure that it is a real hypothesis, and personally I think it is better to wait before deciding whether it is Not of a planet. I consider it sufficient to say that there are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the asteroidal belt.

Interviewer: When talking about this object, are you referring to the so-called planet Biga?

H.C. Urey: Yes, that's what I meant, but I'm not sure of its existence.

Please, remember:

1- This interview mas made about 45 yeras ago.

2- I'm not asking if this hypothesis is correct or even possible. Only want to know more about this hypothesis which was well known by H. C. Urey in the 70's.

3- I'm not asking if the name "Biga" is a correct proposal of a name for a planet in our Solar System accordind to current naming rules.

  • 1
    $\begingroup$ English translation: translate.google.com/translate?hl=en&sl=es&u=http://… $\endgroup$
    – userLTK
    Apr 23, 2017 at 0:21
  • 5
    $\begingroup$ Not sure if you're going to find an answer for this one. I tried to do some digging and literally the only existence of a hypothetical planet called Biga that I could find was in that interview. I couldn't find any reference to such a planet elsewhere. If it is a typo, I'm not sure what it was meant to be because there's no other planet/dwarf planet/potential planet that I know of that has a similar name. Either its a terribly bad typo, or an inconsequential part of history that has been lost to time. Perhaps a better researcher can find something though. $\endgroup$
    – zephyr
    Apr 23, 2017 at 4:41
  • $\begingroup$ never heard of it. $\endgroup$
    – user35971
    Oct 1, 2017 at 22:39
  • $\begingroup$ A planet Biga than expected $\endgroup$
    – Cheng
    Oct 10, 2022 at 3:54

2 Answers 2


This Wikipedia page doesn't say anything about a planet called Biga, and I couldn't find anything on the internet related to Harold Urey, and a possible tenth planet (netheir on Google nor on Wikipedia).

This page says that at that time, there was a theorized planet X, which might be what you are looking for, but lacking any references for Biga on the internet, it is hard to say anything.


If another planet in our solar system was to be named, I think that Biga wouldn't be the first name to come up, all of the known planets in our solar system are named after Roman deities and Biga is not a deity but rather a cart on which mostly Luna is depicted. I have never heard of this proposal and if the 'rules' are used for naming, it wouldn't be the first candidate.

  • $\begingroup$ Sorry to say this, but in my opinion your answer is quite useless. I'm not asking about rules for naming planets, and new planets hypothesis needn't to contain an orthodox name for its planet. Remember the so called "Planet X hypothesis" which was related to the discovery of Pluto or the current "Planet Nine" hypothesis. $\endgroup$
    – Ginasius
    Apr 22, 2017 at 12:55
  • $\begingroup$ I am sorry to hear that, I interpreted your question wrong then. $\endgroup$
    – Ian Ronk
    Apr 22, 2017 at 13:45
  • $\begingroup$ English is not my native language, so feel free to edit my question if you think is difficult to understand because of poor grammar. $\endgroup$
    – Ginasius
    Apr 22, 2017 at 13:53

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