(55637) 2002 UX 25 1

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(55637) 2002 UX 25 1
20131105 2002 UX25 hst.png
Image from 2002 UX 25 and S / 2007 (55637) 1 (left) by the Hubble Space Telescope (2005).
Central body (55637) 2002 UX 25
Properties of the orbit
Major semi-axis 4770 ± 40 km
Periapsis 3959 km
Apoapsis 5581 km
eccentricity 0.170 ± 0.030
Orbital time 8.3090 ± 0.0002 d
Physical Properties
Medium diameter km
Medium density 0.82 g / cm 3
discovery
Explorer

Michael E. Brown
Terry – Ann Suer

Date of discovery August 26, 2005

(55637) 2002 UX 25 1 is a moon of the trans-Neptunian object (55637) 2002 UX 25 , which is classified as Cubewano (according to another source, Detached Object) in terms of orbital dynamics . The companion is about a third the diameter of the mother planetoid.

Discovery and naming

(55637) 2002 UX 25 1 was discovered by Mike Brown and Terry – Ann Suer on 2002 UX 25 images taken with the Hubble Space Telescope on August 26, 2005. Both components of the system could be recognized as clearly separated by the recordings. The discovery was announced on February 22, 2007, the moon was given the provisional designation (55637) 2002 UX 25 1 .

The companion was found by the discoverers on the Hubble images at a distance of 0.164 ± 0.003 arc seconds, with an apparent brightness that was 2.5 ± 0.2 m weaker .

Orbital simulation of 2002 UX 25 and (55637) 2002 UX 25 1 (mutual distance: 4770 km).

Track properties

(55637) 2002 UX 25 1 orbits the common barycentre in an elliptical orbit at an average distance of 4770 km from the planetoid, that is 14.34 2002 UX 25 radii and 49.43 (55637) 2002 UX 25 1 radii . It takes 8 days 7 hours 25 minutes to complete one cycle, which corresponds to around 12176 cycles in a 2002 UX 25 year. The orbital eccentricity is 0.170. The inclination of the companion is currently unknown. (As of January 2019)

In this binary system, a month accordingly lasts 13.87 2002 UX 25 days .

Physical Properties

The diameter of (55637) 2002 UX 25 1 is currently estimated at 193 km, based on an estimated reflectivity of 10.7%, analogous to the mother planetoid. The discovery of the moon does not seem to have any significant influence on the determination of the size of the mother planetoid, which, according to current estimates, is still 665 km in size. Thus, S / 2007 (55637) 1 should have about 29% of the diameter of 2002 UX 25 . However, if the companion only has half of the albedo (a typical assumed albedo of 5% for "cold" Cubewanos ), the size of the two bodies could well amount to 260 km and 640 km, respectively, making the relative size of S / 2007 (55637) 1 would increase UX 25 to 40.6% over 2002 .

The total mass of the system is 1.25 ± 0.03  ·  10 20  kg. With a density of only 0.82 g / cm³, 2002 UX 25 is one of the largest solid celestial bodies in the solar system, the density of which is lower than that of water. Larger Kuiper belt objects should actually have a significant proportion of silicates and metals and thus have a higher density. If the composition of the two bodies is similar to that of other large KBOs, their internal structure would have to be extremely porous, which seems very unlikely in view of the flowability of water ice. Hence, this low density still amazes astronomers.

Determination of the diameter for (55637) 2002 UX 25 1
year Dimensions km source
2013 210.0 ± 30.0 Fornasier et al. a.
2013 190.0 Brown
2014 193.0 ± 10.0 Vilenius et al. a.
2017 230.0 ± 19.0 Brown et al. a.
The most precise determination is marked in bold .

See also

Individual evidence

  1. ↑ Marc W. Buie: Orbit Fit and Astrometric record for 55637. SwRI (Space Science Department), accessed January 30, 2019 .
  2. ^ Wm. R. Johnston: (55637) 2002 UX25 . Johnston's Archives. September 20, 2014. Accessed January 30, 2019.
  3. ^ Daniel WE Green: IAUC 8812: Sats of 2003 AZ 84, (50000), (55637), (90482); V1281 Sco; V1280 Sco . Central Bureau for Astronomical Telegrams. February 22, 2007. Accessed January 30, 2019.
  4. ^ A b c M. E. Brown : The density of mid-sized Kuiper belt object 2002 UX25 and the formation of the dwarf planets . In: The Astrophysical Journal . 778, No. 2, November 14, 2013, p. L34. arxiv : 1311.0553 . bibcode : 2013ApJ ... 778L..34B . doi : 10.1088 / 2041-8205 / 778/2 / L34 .
  5. ↑ a b Ron Cowen: Astronomers surprised by large space rock less dense than water . Nature. November 13, 2013. Retrieved January 30, 2019.
  6. ↑ S. Fornasier et al. a .: TNOs are cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of 9 bright targets at 70-500 μm . In: Astronomy & Astrophysics . 564, No. A35, May 2, 2013, p. 18. arxiv : 1305.0449 . bibcode : 2013A & A ... 555A..15F . doi : 10.1051 / 0004-6361 / 201321329 .
  7. ↑ E. Vilenius et al. a .: "TNOs are Cool": A survey of the trans-Neptunian region. X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations . In: Astronomy & Astrophysics . 564, No. A35, March 25, 2014, p. 18. arxiv : 1403.6309 . bibcode : 2014A & A ... 564A..35V . doi : 10.1051 / 0004-6361 / 201322416 .
  8. ^ ME Brown, BJ Butler: The density of mid-sized Kuiper belt objects from ALMA thermal observations . In: The Astronomical Journal . 154, No. 1, February 23, 2017. arxiv : 1702.07414 . bibcode : 2017AJ .... 154 ... 19B . doi : 10.3847 / 1538-3881 / aa6346 .