from Hacker News

Possible new dwarf planet found in our solar system

by ddahlen on 5/21/25, 6:32 PM with 99 comments

• by astroalex on 5/21/25, 8:51 PM

  I found the preamble at the beginning of the announcement charmingly dated:

  > The Minor Planet Electronic Circulars contain information on unusual minor planets, routine data on comets and natural satellites, and occasional editorial announcements. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. > > Prepared using the Tamkin Foundation Computer Network

  Looking up the Tamkin Foundation Computer Network: https://www.minorplanetcenter.net/iau/Ack/TamkinFoundation.h...

  > The OpenVMS cluster consists of nine single-CPU workstations and one four-CPU server. All the machines are running the extremely robust and secure OpenVMS operating system. The twelve Alpha-based machines are arranged as an OpenVMS Cluster, allowing all machines to share disk storage, execution and batch queues and other resources, as well as simplifying system management.

  Assuming "Alpha-based machines" is referring to the DEC Alpha, these computers are ~30 years old. https://en.wikipedia.org/wiki/DEC_Alpha

• by ddahlen on 5/21/25, 6:32 PM

  The minor planet center is the clearing house of observations of objects in our solar system. They have announced a new dwarf planet today.

  This object appears to be in a very eccentric orbit (0.948), and with an H magnitude of 3.55, so it is likely hundreds of km in diameter. Ceres for reference has a H magnitude of 3.33 (smaller H is bigger diameter).

  If you want to know what H means: https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_Syste...

• by ChuckMcM on 5/21/25, 7:41 PM

  "That's no moon" :-). But more seriously, just another giant lump of stuff swinging around the solar system. I am not an astronomer, so I'm not sure about some of the things I'm reading in that report but to me, it seems to be in the solar ecliptic. But its far enough away even at perigee that the only thing of note it might interact with would be Pluto.

  I suppose that flying through the Oort cloud it might periodically launch ice balls into the inner solar system.

• by d_silin on 5/21/25, 9:04 PM

  For the curious.

  Periapsis, au: 45.241

  Apoapsis, au: 1714.759

  Period, years: 26106.07

• by ddahlen on 5/21/25, 8:57 PM

  I got a bit too excited with this one, this is may not be a full on dwarf planet, but it is a very large object. There are only a small number (about 10-20) objects in our solar system of this size. Its the first big one we have found in a number of years.

• by java-man on 5/21/25, 7:15 PM

  Sorry for a stupid question: could it be "the planet X", or is it too light / in a wrong orbit?

• by tomcam on 5/21/25, 11:26 PM

  They prefer to be called little planets

• by calmbell on 5/22/25, 3:58 AM

  Here is the arXiv preprint: https://arxiv.org/abs/2505.15806

• by jsnider3 on 5/22/25, 4:45 AM

  Welcome to the neighborhood!