Talk:C/2014 UN271 (Bernardinelli–Bernstein)

Most distant comet activity
Seeing the assumption of no comet activity I was curious about the largest distances were that activity has been detected. Comet C/2010 U3 (Boattini) was active in precovery images to 25.8 au. Comet C/2017 K2 (PANSTARRS) was active in precovery images to 23.7 au. A model of the rate of expansion of Comet C/2017 K2 (PANSTARRS)'s coma estimated it became active as distant as 35 au. Comet C/1995 O1Hale-Bopp was active at 25.7 au and possible active, though it had a stellar appearance, at 30.7 au. Given that these were either unusual comets, or in the case of Hale-Bopp a well studied comet that was followed to large distances, I believe that it is safe assuming no recent cometary activity on 2014 UN271. Agmartin (talk) 18:03, 20 June 2021 (UTC)
 * I see no reason given to automatically assume 2014 UN271 will be any different than the above samples. We need a reliable source to claim it is HUGE because if it has any kind of a coma it will turnout to be much smaller. -- Kheider (talk) 18:20, 20 June 2021 (UTC)
 * Image with no observed coma in this tweet.Agmartin (talk) 00:53, 21 June 2021 (UTC)


 * Since this object was just noticed about a month ago, I think we should wait for a proper paper before declaring *as fact* that this object "only observed by one telescope (W84)" is in fact not outgassing in anyway and therefore truly 100+ km in diameter. As it stands I would not be surprised to find out it is only a more common ~60 km diameter as such objects are simply more common. -- Kheider (talk) 01:20, 21 June 2021 (UTC)

I checked the ephemeris of C/2014 UN271 for 24 August 2019 around when PANSTARRS observed it at mag ~20.5. It was at 22.63 au from the sun and 22.15 au from earth. Using this data I calculate its absolute magnitude at that time as 7.0. Perhaps this indicates that activity began in 2019. Agmartin (talk) 20:04, 24 June 2021 (UTC)

I read that the Hubble Space Telescope is back online so we may find out big the nucleus actually is soon. Agmartin (talk) 21:56, 19 July 2021 (UTC)


 * I am also hoping we get a better estimate that limits it to more of 30-120km range instead of the 200+ km estimates that are almost certainly wrong because of the early assumptions of asteroidal behavior and absmag (H) size estimates. -- Kheider (talk) 00:00, 20 July 2021 (UTC)

Possible picture for use
In the SkyGems reference Kheider gave, I see that Luca claims the object shows clear cometary activity of 15 arcseconds. He also goes on to include this picture. I am unfamiliar with how free use works for this Italian observatory/agency as compared to NASA images, so I don't know if this image will be available for Wikimedia Commons use. Sir Trenzalore (talk) 16:55, 22 June 2021 (UTC)


 * It might fall under Non-free content criteria until an observatory offers a free use image. -- Kheider (talk) 17:27, 22 June 2021 (UTC)

Las Cumbres Observatory
Las Cumbres Observatory's offices are in California, the telescope used for the observations is in Sutherland, South Africa. Astronomer's Telegram refers to 1-m Sutherland-LCOGT C (observatory code K93) which is located at the South African Astronomical Observatory. Agmartin (talk) 01:14, 25 June 2021 (UTC)

Bernardinelli-Bernstein paper on arxiv
C/2014 UN271 (Bernardinelli-Bernstein): the nearly spherical cow of comets

A couple of relevant twitter threads: https://twitter.com/phbernardinelli/status/1440497364934873098 https://twitter.com/benmontet/status/1440477176164335623 now off to read the paper. Agmartin (talk) 17:45, 22 September 2021 (UTC)
 * I read this from section 4 "It is apparent that the coma was already present in the PS1 images at rh = 22.6 au, indeed also for most of the DES observations, albeit not at a level that precludes our attribution of the PSF-fitting fluxes to the nucleus." as indicting that the observed cometary activity should not affect their estimates of the size of the nucleus.Agmartin (talk) 19:07, 22 September 2021 (UTC)

Orbital Period
Could someone explain the orbital period estimate on this page? I'm seeing estimates from other sources ranging from 600,000 years to 3 million. Since this appears to be the largest comet ever to be witnessed by man, it might be important to have an accessible explanation of the orbital period. The current reference source is filled with quite technical data. B1db2 (talk) 02:45, 21 November 2021 (UTC)


 * The inbound and outbound orbital period are never exactly the same as the orbit changes as a result of planetary perturbations. So it really depends on what date (epoch) you use to define the solution. For an object like UN271 you do NOT want to define the solution while it is inside the the orbit of the planets as the solution (potentially ~600,000 years) simply is not real-world accurate. So it is useful to define the orbit many decades (say the year 1950) before and many decades (say the year 2100) after leaving the planetary region. JPL lists 1E+09 days for 1950 (roughly 3 million years) for the inbound and 1.6E+9 days (roughly 4 million years) for the year 2100. I would take all of these solutions with a grain of salt as we do not really known what perturbed the object while it was more than 1500au from the Sun. For the lay person it is only important to know that it was millions of years inbound and slightly more outbound. And comet 95P/Chiron is larger, even though it does not come directly from the Oort cloud. -- Kheider (talk) 10:32, 21 November 2021 (UTC)
 * Thanks for the overview, especially the distinction about inside vs outside the orbit of the planets. News articles are confusing this distinction, along with its blanket description as the largest comet. It would be helpful if someone would add a description like yours to the article in order to inform the general public. B1db2 (talk) 04:20, 23 November 2021 (UTC)

Orphaned references in C/2014 UN271 (Bernardinelli-Bernstein)
I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of C/2014 UN271 (Bernardinelli-Bernstein)'s orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "EarthSky": From ALESS 073.1:  From 2016 AJ193:  From (231937) 2001 FO32:  

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 07:07, 18 February 2022 (UTC)