Talk:Interstellar object

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A fact from Interstellar object appeared on Wikipedia's Main Page in the Did you know column on 3 March 2009, and was viewed approximately 2,109 times (disclaimer). The text of the entry was as follows: Did you know... that Jupiter is the only planet capable of pulling an interstellar comet into a Sun-centered orbit? A record of the entry may be seen at Wikipedia:Did you know archive/2009/March.

If Jupiter can capture a interstellar comet every 60 million years, could this mean the majority of the moons of Jupiter are in fact these comets? - User:62.8.126.181

• No. They go into orbit around the Sun, not around Jupiter. What happens is that the interstellar comet is moving too fast initially for it to remain in the solar system. But occasionally Jupiter's gravity can take enough of the speed off the comet for it to settle into orbit around the Sun. Reyk _YO! 12:34, 10 March 2010 (UTC)Reply

The article Pan-STARRS has a link entitled Interstellar debris to here. Quote "During the formation of a planetary system it is thought that a very large number of objects are ejected due to gravitational interactions with planets (as many as 10¹³ such objects in the case of the Solar System). Objects ejected by planetary systems around other stars might plausibly be flying throughout the galaxy". Are all such objects interstellar comets, if not should there be a new article on debris? John a s (talk) 08:18, 4 April 2013 (UTC)Reply

I suppose a lot of those objects would be rocky rather than icy, and so it might not be right to call them comets. Maybe they could be put in as a subsection of this article, if there are sources for it. Later on if it turns out that there's as much material on interstellar debris as there is on just interstellar comets, we can think about renaming the page. What do you think? Reyk _YO! 21:19, 4 April 2013 (UTC)Reply

I think the page is fine, it describes a theoretical object that is likely to exist. I note that it should be possible to distinquish one from a comet that came from the Oort cloud (which I read is also a theory) due to its trajectory, so lets hope one appears soon! John a s (talk) 07:41, 5 April 2013 (UTC)Reply

distinquish? 35.129.197.5 (talk) 04:28, 12 September 2022 (UTC)Reply

Why is there a picture of Comet Hyakutake heading this article, as it is not an interstellar comet? Maybe an artists impression is needed. John a s (talk) 07:36, 5 April 2013 (UTC)Reply

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• Sekanina, Zdenek (1976). "A probability of encounter with interstellar comets and the likelihood of their existence". Icarus. 27: 123. Bibcode:1976Icar...27..123S. doi:10.1016/0019-1035(76)90189-5.

• Sen, A. K; Rama, N. C (1993). "On the missing interstellar comets". Astronomy and Astrophysics. 275: 298. Bibcode:1993A&A...275..298S.

• Stern, S. Alan (1990). "On the number density of interstellar comets as a constraint on the formation rate of planetary systems". Publications of the Astronomical Society of the Pacific. 102: 793. Bibcode:1990PASP..102..793S. doi:10.1086/132704.

• Valtonen, M. J; Innanen, K. A (1982). "The capture of interstellar comets". Astrophysical Journal. 255: 307. Bibcode:1982ApJ...255..307V. doi:10.1086/159830.
• Cook, Nathaniel V; Ragozzine, Darin; Granvik, Mikael; Stephens, Denise C (2016). "Realistic Detectability of Close Interstellar Comets". The Astrophysical Journal. 825: 51. Bibcode:2016ApJ...825...51C. doi:10.3847/0004-637X/825/1/51.{{cite journal}}: CS1 maint: unflagged free DOI (link)

• Fogg, Martyn J (1990). "Interstellar Planets". Communications in Astrophysics. 14: 357. Bibcode:1990ComAp..14..357F.

• Valtonen, Mauri J; Zheng, Jia-Qing; Mikkola, Seppo (1992). "Origin of oort cloud comets in the interstellar space". Celestial Mechanics and Dynamical Astronomy. 54: 37. Bibcode:1992CeMDA..54...37V. doi:10.1007/BF00049542.

• Finney, B. R; Jones, E. M (1983). "Interstellar nomads". IN: Space manufacturing 1983; Proceedings of the Sixth Conference: 357. Bibcode:1983spmf.conf..357F.
• Napier, W. M (1990). "Dusty Objects in the Universe". Dusty Objects in the Universe. Proceedings of the Fourth International Workshop of the Astronomical Observatory of Capodimonte [OAC 4]. Astrophysics and Space Science Library. 165: 103. Bibcode:1990ASSL..165..103N. doi:10.1007/978-94-009-0661-7_13. ISBN 978-94-010-6782-9. {{cite journal}}: |chapter= ignored (help)CS1 maint: extra punctuation (link) CS1 maint: periodical has ISBN (link)

• Weissman, P. R (1994). "Why are there no interstellar comets?". Bulletin of the Astronomical Society. 26: 1021. Bibcode:1994BAAS...26.1021W.

• Strigari, Louis E; Barnabè, Matteo; Marshall, Philip J; Blandford, Roger D (2012). "Nomads of the Galaxy". Monthly Notices of the Royal Astronomical Society. 423 (2): 1856. Bibcode:2012MNRAS.423.1856S. doi:10.1111/j.1365-2966.2012.21009.x.

• Kresak, Lubor (1992). "Are there any comets coming from interstellar space?". Astronomy and Astrophysics. 259: 682. Bibcode:1992A&A...259..682K.

• Engelhardt, Toni; Jedicke, Robert; Vereš, Peter; Fitzsimmons, Alan; Denneau, Larry; Beshore, Ed; Meinke, Bonnie (2017). "An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets". The Astronomical Journal. 153 (3): 133. Bibcode:2017AJ....153..133E. doi:10.3847/1538-3881/aa5c8a.{{cite journal}}: CS1 maint: unflagged free DOI (link)

• Jura, M (2011). "An Upper Bound to the Space Density of Interstellar Comets". The Astronomical Journal. 141 (5): 155. Bibcode:2011AJ....141..155J. doi:10.1088/0004-6256/141/5/155.
• "Interstellar comets How many we shouldhave seen and when we will see them".

• "Setting an Observational Upper Limit to theNumber Density of Interstellar Objects" (PDF).

The following citations were removed during a recent re-write of the introduction, which had become a mess. It wasn't clear exactly what facts they were meant to substantiate, but they are related to the distinction between exoplanets and exocomets. Jess_Riedel (talk) 18:16, 6 November 2018 (UTC)Reply

• "'Exocomets' Common Across Milky Way Galaxy". Space.com. 7 January 2013. Archived from the original on 16 September 2014. Retrieved 8 January 2013. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help) (Previous ref name="Space-20130107")

• Beust, H.; Lagrange-Henri, A.M.; Vidal-Madjar, A.; Ferlet, R. (1990). "The Beta Pictoris circumstellar disk. X – Numerical simulations of infalling evaporating bodies". Astronomy and Astrophysics. 236: 202–216. Bibcode:1990A&A...236..202B. (Previous ref name="Beust1990")

• Sanders, Robert (7 January 2013). "Exocomets may be as common as exoplanets". University of California, Berkeley. Retrieved 8 January 2013. (Previous ref name="Berkeley-20130107")

Given that substellar objects includes asteroids and comets and what-have-you, it seems odd to exclude substellar object in the initial definition of what an interstellar object is. Was it meant to say low mass stars perhaps? RhinoMind (talk) 20:29, 20 December 2017 (UTC)Reply

As I understand it a substar is a failed star, being not quite big enough for nuclear fusion, but the Substellar object article claims that the definition includes anything smaller than a star, including planets (and presumably coconuts and suchlike). I'd suggest that the opening paragraph of this article is specifically referring to failed stars, and the other article needs rewriting. I'll alter the opening paragraph to read, "An interstellar object is a body other than a star or substar located in interstellar space, and not gravitationally bound to a star." (It will still be linked.) It might be a good idea to tidy up the other article since, as far as I know, asteroids and comets (and coconuts) are not classed as substellar objects. nagualdesign 20:49, 20 December 2017 (UTC)Reply

Hi. Good idea. I don't know what "substellar object" is supposed to mean really, so I didn't dare mingling with that article on my own. RhinoMind (talk) 21:00, 20 December 2017 (UTC)Reply

It's entirely possible that there's more than one definition of substellar object, or rather, that there are two not-quite-related concepts that both employ the same phrase, and the Substellar object article is erroneously mixing the two. There's nothing wrong with Wikipedia adopting a working definition and sticking with that. Alternatively, the two concepts could be given different articles (Substellar object and Substar?), though that would probably be confusing. If you check through the references and see which ones use which definition, we could rewrite the article to specifically mean failed stars (unless others disagree) with a subsection to explain other uses of the phrase if necessary. To be honest, I don't think that any astronomers consider terrestrial planets to be substellar objects, or if they do then they don't consider substellar object and substar to be synonyms. nagualdesign 21:59, 20 December 2017 (UTC)Reply

I've just added a line regarding the PNG bolide, tucked in under the existing section for 'Oumuamua. It occurs to me that it and the previously mentioned four other candidate objects probably deserve a section of their own, but I see we have no articles about the other four objects, and I've found no real extra information regarding them online to warrant a new section. It's not ideal, but for now I've left them all lumped together. If anyone can find any other references and wants to move that content to the new section, please do. Cadar (talk) 15:49, 20 April 2019 (UTC)Reply

From when this article was started until November 2017, it was about interstellar comets. An interstellar object can be anything not bound to the Sun. It would be good to move this article to a more appropriate name as stars are also traveling among the stars. -- Kheider (talk) 19:28, 27 September 2019 (UTC)Reply

For consideration/discussion - Copied the following below (in part) from Talk:ʻOumuamua - hope it helps in some way - in any case - Stay Safe and Healthy !! - Drbogdan (talk) 12:39, 12 April 2022 (UTC)Reply

FWIW - seems an interstellar object may currently be on Earth - recent news^{[1][2][3][4][5]} may be of possible interest to some I would think - iac - Stay Safe and Healthy !! - Drbogdan (talk) 20:33, 9 April 2022 (UTC)Reply

BRIEF Followup - Updated the lede of the 'Oumuamua article as follows => *ʻOumuamua is a known interstellar object detected passing through the Solar System.(+ref) It is possibly the second interstellar object known; the first being a purported interstellar meteor that impacted Earth in 2014.(+refs)" - seems better - comments welcome of course - in any case - Stay Safe and Healthy !! - Drbogdan (talk) 22:35, 11 April 2022 (UTC)Reply

FURTHER Updates (also for consideration/discussion) - originally in the "Interstellar object" article as follows:

• Interstellar object - LEDE

The first interstellar object which was discovered traveling through our Solar System was 1I/ʻOumuamua in 2017. The second was 2I/Borisov in 2019. They both possess significant hyperbolic excess velocity, indicating they did not originate in the Solar System. Earlier, in 2014, an interstellar object was purported to have impacted Earth, based on its estimated initial high velocity.^[1][2][3][4]

• Interstellar object#January 8, 2014 meteor

In 2019, a preprint was published suggesting that a 0.45 meter meteor of interstellar origin, did burn up in the Earth's atmosphere on January 8, 2014.^[6][7][1][2] It had a heliocentric speed of 60 km/s and an asymptotic speed of 42.1±5.5 km/s, and it exploded at 17:05:34 UTC near Papua New Guinea at an altitude of 18.7 km.^[3] After declassifying the data in April 2022,^[8] the U.S. Space Command confirmed the detection through its planetary protection sensors.^[9][4]

• Interstellar object#Candidates

In April 2022, astronomers reported the possibility that a meteor that impacted Earth in 2014 may have been an interstellar object due to its estimated high initial velocity.^[1][2][3][4]

There are 6 listed source in the 2017 interstellar meteor section. 5 of them are authored by the same person. The only other source is a summary of some of those sources from Vice and notes that the primary source--a published paper--was not peer reviewed. It mostly interviews the two authors of the primary source and has one other source that does not support the conclusions.

I am arguing that this does not match normal expectations of sourcing considering how this paragraph is presented and considering the immediate objections to the 2014 interstellar meteor candidate. I think it should either be removed or the fact that this paragraph fundamentally comes from a single source highlighted in the text in some way, since the multiple "sources" cited and the framing here implies otherwise. If no other source than the authors of the original paper, including one who has had their work consistently questions and frequently disputed, makes this claim about CNEOS 2017-03-09 then I don't think Wikipedia should be making this claim at all, or at least not without a clear article-level caveat. Phifty (talk) 19:42, 3 December 2024 (UTC)Reply

Two quotes from the article:

• An interstellar comet can probably, on rare occasions, be captured into a heliocentric orbit while passing through the Solar System. Computer simulations show that Jupiter is the only planet massive enough to capture one, and that this can be expected to occur once every sixty million years.
• A paper by Torbett indicated that the density was no more than 10¹³ (10 trillion) comets per cubic parsec.

The source for that is Torbett (1986),[2] which is outdated, based on bad assumptions, and also isn't quite doing what we say.

Torbett uses an upper bound for the number density of interstellar objects (${\displaystyle <10^{13}{\text{ pc}}^{-3}}$) that he takes from Whipple (1975),[3] and which Whipple assumes (quote) "liberally". His upper bound for the number density is both an order of magnitude higher than the upper bound from Francis (2005) cited elsewhere in this Wikipedia article, and also two orders of magnitude lower than estimates by Jewitt&Seligman (2023) [4] from actual observations of interstellar objects.[5] The formula Torbett derives to estimate that time (formulas 27 and 28, slightly adjusted) is ${\displaystyle T=1/R=1/(n\sigma v_{\infty })}$, with assumed values of ${\displaystyle n=10^{13}{\text{ pc}}^{-3}}$ (the number density), ${\displaystyle \sigma =5A_{J}}$ (cross section for capture, found to be about 5 times the cross area of Jupiter), and ${\displaystyle v_{\infty }=20{\text{ km/s}}}$ (the approach velocity of the comet).[6] Note that Torbett uses his upper bound for the number density as an estimate for the value of ${\displaystyle n}$, and assumes that all objects approach the Sun at a velocity of ${\displaystyle 20{\text{ km/s}}}$. That velocity is very slow, well below that of the three real interstellar comets that have been observed so far.

To demonstrate how sensitive that formula is to models and assumptions, consider this: If one uses the upper bound for the number density of ${\displaystyle <10^{12}{\text{ pc}}^{-3}}$ from the (also outdated) Francis (2005), that time increases by a factor of 10, to at least 600 million years. On the other hand, if one instead uses the much larger number density of ${\displaystyle 0.1{\text{–}}0.2{\text{ AU}}^{-3}}$ from Jewitt&Seligman (2023), and the average approach velocity for interstellar comets of ${\displaystyle \approx 50{\text{ km/s}}}$ from Fig. 1 in Hopkins et al. (2025),[7], that time drops to between 140,000 and 280,000 years.[8] That's a difference of 3 to 4 orders of magnitude. And that's before one looks at all the simplifications made in the derivation of Torbett's formula -- like the assumption that interstellar objects arrive from all directions with equal probability.

Whipple himself doesn't actually give a number density, but an estimate for the space density of interstellar comets of ${\displaystyle 2\cdot 10^{-26}{\text{g/cm}}^{3}}$, which – as the author proudly exclaims – is within an order of magnitude of the then-latest upper bound of ${\displaystyle 10^{-25}{\text{g/cm}}^{3}}$. He probably rightly assumed his back-of-the-envelop calculation to be much more uncertain than within one order of magnitude. Torbett doesn't state how he arrives at his number density from this; I believe he assumes an average radius of about ${\displaystyle 2{\text{ km}}}$, and a density of ${\displaystyle 1.5{\text{ g/cm}}^{3}}$, for typical comets.[9] That assumed radius is probably way too high, which may explain all the discrepancies with more modern estimates. Note that the radius goes into this as ${\displaystyle r^{3}}$, so the number density increases by a factor of 8 if one instead assumes an average radius of ${\displaystyle 1{\text{ km}}}$, and by a factor of 8,000 for a radius of ${\displaystyle 100{\text{ m}}}$. We do not know the actual sizes of the three known interstellar objects with good precision, let alone what's the actual average across the population of all such objects.

A side note: One consequence of Torbett's formula ${\displaystyle R=n\sigma v_{\infty }}$ is that the rate of capture by Jupiter increases as the hyperbolic excess velocity of the comet gets larger. I would have expected the opposite, that a capture is more likely for objects that approach the Solar System at low velocities. But what do I know...

If we want to keep historic estimates for that number density, we should probably also cite Stern (1990),[10] who finds an upper bound for the number density of ${\displaystyle 1.2\cdot 5.7\cdot 10^{-4}{\text{ AU}}^{-3}}$, with a stated uncertainty of "a factor of 2-3". Like all other estimates, a key part of this was the lack of any interstellar objects in the catalog. Stern's upper limit is in line with other estimates made before the discovery of the first interstellar object. It is about 150–300 times less than the actual density found by Jewitt&Seligman (2023).

So, what do we do with this? I think we should

1. remove the statement about the rate of capture, as outdated and based on uncertain/bad assumptions,
2. add a reference to Whipple (1975) if we want to keep the historic number density from Torbett (1986), and
3. put less emphasis overall on estimates made before the discovery of the first interstellar object, and more on models derived from actual observations. Renerpho (talk) 21:57, 15 August 2025 (UTC)Reply

I tend to agree as long as we can find a more recent estimate of rate of capture and perhaps consider an "early work" section.©Geni (talk) 21:13, 31 August 2025 (UTC)Reply

@Geni: There are a couple of studies that we could use. The most promising may be a series of three papers from 2020 and 2022, about the capture of interstellar comets. [11] (Hands and Dehnen, 2020), who use Torbett as a comparison to their own - different - conclusions; [12] (Dehnen and Hands, 2022), who call out a massive error in Torbett's calculations in a footnote (quote: This contradicts the claim by Torbett (1986) that Jupiter is the only planet in the Solar system able to capture an object with asymptotic speed v∞ = 20 km s−1 . This suggests an error in Torbett’s analysis, who used the same approximation but assumed a circular planet orbit, when we still find v∞,max = 31.6 km s−1 and 21.6 km s−1 for Jupiter and Saturn, respectively -- comment from me: that the planet orbits were assumed to be circular doesn't account for the difference, Torbett's math was probably just wrong); and [13] (Dehnen, Hands and Schönrich, 2022), who don't cite Torbett at all, but further develop the ideas of the two previous papers.

"On the Capture of Interstellar Objects by Our Solar System" [14] (Napier, Adams and Batygin, 2021) doesn't cite Torbett, but they study a similar problem and this may also be a useful reference.

Despite their apparently wrong calculations and ambiguous assumptions/conclusions, Torbett's paper is cited in a number of studies about the capture rate of interstellar comets from the 2010s, who mostly take it at face value. An example would be [15] (Engelhardt et al., 2017), who cite Torbett on the first page, although they arrive at a very different capture rate themselves. But, as I have already explained in my comment above, any such capture rate (1 in 60 million years, 1 in 400 million years, or whatever) is meaningless, and I strongly suggest we avoid making similar claims. It is interesting that Dehnen and Hand's second paper is the only paper I could find that actually explicitly states that Torbett was wrong. Renerpho (talk) 00:38, 1 September 2025 (UTC)Reply

Look you are clearly vastly more familiar with the literature than I am or will ever be. So I'm not in a position to argue most of this. One thing I will say is that we may be the reason that Torbett has stuck around as long as it has so it may be worth building an Early work section based on Whipple (1975) Torbett (1986) and Dehnen and Hand explaining early density and capture estimates and that they have explicitly been disproven.©Geni (talk) 01:50, 1 September 2025 (UTC)Reply

Sounds reasonable to me. I'll see if I find the time to write it in the day! Renerpho (talk) 02:00, 1 September 2025 (UTC)Reply

I've tagged the two questionable parts of the article as "dubious" for now, until I find the time to work on properly rewriting it. It is a pity that the one thing about the topic that ever made it to the Main Page ("Did you know... that Jupiter is the only planet capable of pulling an interstellar comet into a Sun-centered orbit?") turns out to be nonsense; you may be right about the "we may be the reason that Torbett has stuck around as long as it has" part. Renerpho (talk) 18:30, 9 October 2025 (UTC)Reply

I believe this description is wrong, it is not 'ruled out' - it is considered highly unlikely, as there is no direct proof and other possible explanations are more likely because they do not require previously unobserved phenomena, but 'ruled out' is simply too stark. 46.29.241.16 (talk) 13:20, 9 October 2025 (UTC)Reply

It has been "ruled out" by astronomers that are not trying to self-promote and do not have a conflict of interest. Any astronomer **COULD SPECULATE** that 240P/NEAT is a spaceship that launched a probe (240P-B) towards Earth around 3 October 2025. -- Kheider (talk) 13:40, 9 October 2025 (UTC)Reply

Effectively ruled out. We don't need to cover every theoretical possibility as if it was a serious option; see WP:FRINGE. Renerpho (talk) 18:16, 9 October 2025 (UTC)Reply

While reading the lead, I noticed it mentioned the discussion of the objects being "alien spaceships". I don't really think this is worthy of being in the lead. There are virtually no scientists who actually believe it, and unlike stuff such as Vaccine and climate change skepticism (where in which it's notable because of the political discourse), this doesn't really have any significance, at least in my opinion. I'd like to hear some other people's thoughts on this though, since I feel like it might be a tad contentious. Gaismagorm (talk) 19:23, 18 February 2026 (UTC)Reply

Quick addendum, it looks like there aren't really any mentions of it beyond the lead. Perhaps a small section discussing the theories could be added, obviously with the information that researchers don't take it seriously. Gaismagorm (talk) 19:24, 18 February 2026 (UTC)Reply

Information about the interstellar object is here: https://en.wikipedia.org/wiki/CNEOS_2014-01-08 Mtshomskyieee (talk) 19:29, 1 April 2026 (UTC)Reply

I see, it's not IM1... due to confirmation issues. It is in the uncomfirmed section Mtshomskyieee (talk) 19:44, 1 April 2026 (UTC)Reply