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Classical Kuiper belt object

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486958 Arrokoth, the first classical Kuiper belt object visited by a spacecraft.
The orbits of various cubewanos compared to the orbit of Neptune (blue) and Pluto (pink)

A classical Kuiper belt object, also called a cubewano, is a Kuiper belt object (KBO) that has an orbit that is beyond Neptune's, does not have a high eccentricity, and does not have an orbital resonance with Neptune. Their orbits have semi-major axes between 40 and 50 astronomical units. Unlike Pluto, they do not cross Neptune's orbit. They have orbits with low eccentricity and mostly low inclination, like the major planets.

The name "cubewano" comes from the first trans-Neptunian object (TNO) found after Pluto and Charon: 15760 Albion. Before January 2018, it was only called (15760) 1992 QB1.[1] Objects similar to it that were found later were often called "QB1-os", or "cubewanos". However, scientists mostly use the word "classical" instead of "cubewano".

Cubewanos include:

136108 Haumea was first marked as a cubewano by the Minor Planet Center in 2006,[3] but they found out it had an orbital resonance with Neptune.[2]

'Hot' and 'cold' cubewanos

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Semimajor axis and inclination of cubewanos (blue) compared to resonant TNOs (red).

There are two types of classical Kuiper Belt objects: those that have calm, almost circular orbits farther out ('cold' cubewanos), and those that are closer to the Sun and have more eccentric orbits ('hot' cubewanos).

Most cubewanos are between the 2:3 orbital resonance with Neptune (the plutinos' orbit) and the 1:2 resonance. For example, 50000 Quaoar has an orbit that is almost a circle and close to the ecliptic. Plutinos, however, have more eccentric orbits, bringing some of them closer to the Sun than Neptune.

Most cubewanos, the cold population, have low inclinations (< 5°) and almost circular orbits that are between 42 and 47 AU. A smaller population (the hot population) has more inclined and eccentric orbits.[4] The words 'hot' and 'cold' have nothing to do with the actual temperatures, but actually mean orbits of the objects. They use an analogy comparing orbits to gas molecules, which move faster as they heat up.[5]

The Deep Ecliptic Survey found the inclinations of both populations. The cold population's inclinations were centered around 4.6° and the hot population's inclinations were larger than 30° (Halo).[6]

Distribution

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Most cubewanos (more than two-thirds) have inclinations less than 5° and eccentricities less than 0.1. They mostly orbit in the middle of the Kuiper Belt. Smaller objects further out are more likely to get caught in an orbital resonance and stop being cubewanos.

Cubewanos make a clear 'belt' outside Neptune's orbit, but the plutinos approach, or even cross Neptune's orbit. When scientists compare orbital inclinations, 'hot' cubewanos can be easily found by their higher inclinations. This high inclination of 'hot' cubewanos has not been explained.[7]

Left: TNO distribution of cubewanos (blue), twotinos (red), SDOs (grey) and sednoids (yellow). Right: The orbits of cubewanos, plutinos, and Neptune (yellow) are compared.

Cold and hot populations: physical characteristics

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The two populations are not just different in orbits, they are different in how they look.

The difference in colour between the red cold population, such as 486958 Arrokoth, and more heterogeneous hot population was observed as early as in 2002. Since 2002, scientists have seen that cold population cubewanos are more red than the bluish-colored hot population.[8] Newer studies confirm this, saying that it is true that cold population bodies are redder than the hot population.[9]

Another difference between the low-inclination (cold) and high-inclination (hot) classical objects is the number of binary systems (two objects orbiting each other and the Sun at the same time). Low-inclination classical objects are more likely to be binary systems, and the brightness of both objects in the binary system are close to being the same. On the other hand, binary systems are rarer in lower-inclination cubewanos, and the brightness difference is higher. This observation, and the differences in colour, show that the cubewanos belong to at least two different populations, with different physical properties and history.[10]

Families

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The first known collisional family—a group of objects that might be leftovers from when a larger object broke apart—in the classical Kuiper belt is the Haumea family.[11] It includes Haumea, its moons, 2002 TX300 and seven smaller bodies.[a] The objects have similar orbits and physical characteristics. They have large amounts of water ice (H2O) and have colors between red (cold classical objects) and blue (hot classical objects)[12][13] Some other collisional families could be in the classical Kuiper belt.[14][15]

Exploration

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New Horizons trajectory and the orbits of Pluto and 486958 Arrokoth

Only one classical Kuiper belt object has ever been visited by spacecraft. Both Voyager spacecraft passed through the area before the Kuiper belt was found, but New Horizons was the first mission to visit a classical KBO.[16] After its explored the Pluto system in 2015, the NASA spacecraft traveled to the small cubewano 486958 Arrokoth. It arrived there on January 1, 2019.[17]

List

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Main article: List of trans-Neptunian objects § List

As of July 2023, there are about 870 objects that are between 40 and 48 astronomical units.[18] Some of them are in the list below.

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References

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  1. ↑ Jewitt, David. "Classical Kuiper Belt Objects". UCLA. Retrieved 1 July 2013.
  2. ↑ 2.0 2.1 2.2 2.3 Brian G. Marsden (30 January 2010). "MPEC 2010-B62: Distant Minor Planets (2010 FEB. 13.0 TT)". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Archived from the original on 4 September 2012. Retrieved 26 July 2010.
  3. ↑ "MPEC 2006-X45: Distant Minor Planets". IAU Minor Planet Center & Tamkin Foundation Computer Network. 12 December 2006. Retrieved 3 October 2008.
  4. ↑ Jewitt, D.; Delsanti, A. (2006). "The Solar System Beyond The Planets" (PDF). Solar System Update : Topical and Timely Reviews in Solar System Sciences (PDF). Springer-Praxis. ISBN 978-3-540-26056-1. Archived from the original (PDF) on 29 January 2007. Retrieved 2 March 2006.)
  5. ↑ Levison, Harold F.; Morbidelli, Alessandro (2003). "The formation of the Kuiper belt by the outward transport of bodies during Neptune's migration". Nature. 426 (6965): 419–421. Bibcode:2003Natur.426..419L. doi:10.1038/nature02120. PMID 14647375. S2CID 4395099.
  6. ↑ J. L. Elliot; et al. (2006). "The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population". Astronomical Journal. 129 (2): 1117–1162. Bibcode:2005AJ....129.1117E. doi:10.1086/427395. ("Preprint" (PDF). Archived from the original (PDF) on 23 August 2006.)
  7. ↑ Jewitt, D. (2004). "Plutino". Archived from the original on 19 April 2007.
  8. ↑ A. Doressoundiram; N. Peixinho; C. de Bergh; S. Fornasier; P. Thebault; M. A. Barucci; C. Veillet (October 2002). "The Color Distribution in the Edgeworth-Kuiper Belt". The Astronomical Journal. 124 (4): 2279. arXiv:astro-ph/0206468. Bibcode:2002AJ....124.2279D. doi:10.1086/342447. S2CID 30565926.
  9. ↑ Peixinho, Nuno; Lacerda, Pedro; Jewitt, David (August 2008). "Color-inclination relation of the classical Kuiper belt objects". The Astronomical Journal. 136 (5): 1837. arXiv:0808.3025. Bibcode:2008AJ....136.1837P. doi:10.1088/0004-6256/136/5/1837. S2CID 16473299.
  10. ↑ K. Noll; W. Grundy; D. Stephens; H. Levison; S. Kern (April 2008). "Evidence for two populations of classical transneptunian objects: The strong inclination dependence of classical binaries". Icarus. 194 (2): 758. arXiv:0711.1545. Bibcode:2008Icar..194..758N. doi:10.1016/j.icarus.2007.10.022. S2CID 336950.
  11. ↑ Brown, Michael E.; Barkume, Kristina M.; Ragozzine, Darin; Schaller, Emily L. (2007). "A collisional family of icy objects in the Kuiper belt" (PDF). Nature. 446 (7133): 294–6. Bibcode:2007Natur.446..294B. doi:10.1038/nature05619. PMID 17361177. S2CID 4430027. Archived (PDF) from the original on 2018-07-23.
  12. ↑ Pinilla-Alonso, N.; Brunetto, R.; Licandro, J.; Gil-Hutton, R.; Roush, T. L.; Strazzulla, G. (2009). "The surface of (136108) Haumea (2003 EL61), the largest carbon-depleted object in the trans-Neptunian belt". Astronomy and Astrophysics. 496 (2): 547. arXiv:0803.1080. Bibcode:2009A&A...496..547P. doi:10.1051/0004-6361/200809733. S2CID 15139257.
  13. ↑ Pinilla-Alonso, N.; Licandro, J.; Gil-Hutton, R.; Brunetto, R. (2007). "The water ice rich surface of (145453) 2005 RR43: a case for a carbon-depleted population of TNOs?". Astronomy and Astrophysics. 468 (1): L25 – L28. arXiv:astro-ph/0703098. Bibcode:2007A&A...468L..25P. doi:10.1051/0004-6361:20077294. S2CID 18546361.
  14. ↑ Chiang, E.-I. (July 2002). "A Collisional Family in the Classical Kuiper Belt". The Astrophysical Journal. 573 (1): L65 – L68. arXiv:astro-ph/0205275. Bibcode:2002ApJ...573L..65C. doi:10.1086/342089. S2CID 18671789.
  15. ↑ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (11 February 2018). "Dynamically correlated minor bodies in the outer Solar system". Monthly Notices of the Royal Astronomical Society. 474 (1): 838–846. arXiv:1710.07610. Bibcode:2018MNRAS.474..838D. doi:10.1093/mnras/stx2765. S2CID 73588205.
  16. ↑ Stern, Alan (28 February 2018). "The PI's Perspective: Why Didn't Voyager Explore the Kuiper Belt?". Retrieved 13 March 2018.
  17. ↑ Lakdawalla, Emily (24 January 2018). "New Horizons prepares for encounter with 2014 MU69". Planetary Society. Retrieved 13 March 2018.
  18. ↑ "q > 40 AU and Q < 48 AU". IAU Minor Planet Center. minorplanetcenter.net. Harvard-Smithsonian Center for Astrophysics. Retrieved 31 July 2023.

Other websites

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