# What is the farthest reported distance from observer from which a solar system body has occulted a star?

I originally wrote "...farthest distance from Earth..." but changed to "observer" in case the occultation was observed from a space telescope. It may not matter much but I didn't want to over-constrain or burden the answer.

The occultation of a roughly 13th magnitude star by a roughly 40 km diameter object in the Kuiper Belt; 2014 MU69 has been successfully observed! I'm hoping to be able to look up the star's name direct. On 2017-Jun-03 03:07 UTC it was about 43.294 AU from the Sun, and 42.435 AU from Earth, (using the JPL Horizons ephemeris.)

I'm wondering if this is the farthest distance from which a solar system body would have been seen to occult a star?

• In theory, any object in the solar system could occult stars, especially given the density of the star field. However, mikebrownsplanets.com/2010/11/shadowy-hand-of-eris.html disagrees w/ me and also points out Eris occulted a magnitude 17 star, though I'm not sure how far it was (perihelion = 37.911 AU so maybe less far). I'd be willing to bet Sedna (or anything in the solar system) will occult a star "soon". – user21 Jun 28 '17 at 18:16
• occult.mit.edu/research/occultations/kbo/Sedna/Sedna.20130110/… notes that Sedna itself has occulted a star, so that probably qualifies. – user21 Jun 28 '17 at 18:49
• @barrycarter I found this page but it's not clear to me if this counts as a verified observation of an occultation. Since 2014 MU69 is now confirmed, perhaps it's the current record holder? If there's a reasonable answer, I'm happy to accept it. – uhoh Dec 18 '17 at 3:47
• @NilayGhosh There hasn't been much activity here, perhaps you can post that as an answer? – uhoh Nov 12 '20 at 21:52
• I have added an answer as per your request. – Nilay Ghosh Nov 13 '20 at 4:27

Wikipedia lists some of the most farthest objects from the sun in the solar system. The third farthest object "Eris" was the subject of one of the most distant stellar occultations observed from Earth. From this occultation, its diameter, density and albedo was calculated.

On 6 November 2010, Eris occulted a faint star (V $$\sim$$ 17.1) which was observed from Chile. The following data was recorded from the occultation:

1. Radius, RE = 1163 $$\pm$$ 6 km
2. Density, $$\rho$$ = 2.5 $$\pm$$ 0.05 g/cm3
3. Albedo, $$p_V$$ = $$0.96 ^{+0.09} _{-0.04}$$
4. Distance, ~98 AU

Eris is now near its aphelion (at 97.6 AU), and is the most remote body presently observed in the solar system. With an orbital period of almost 560 years, it will take more than 240 years from now to reach its perihelion, at 37.8 AU.

Reference:

1. Sicardy, B., Ortiz, J., Assafin, M. et al. A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation. Nature 478, 493–496 (2011). https://doi.org/10.1038/nature10550 (PDF)