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New Analysis Of The Second Most Distant TNOs (225088) 2007 OR10

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New Analysis Of The Second Most Distant TNOs (225088) 2007 OR10

Using analysis provided by NASA’s Kepler space telescope — K2 extended mission — and thermal infrared data provided by ESA’ Herschel Space Observatory, a team of scientists found that (225088) 2007 OR10 is likely to be larger in size and darker than previously thought.

Trans-Neptunian objects (TNOs) are known as the most pristine types of bodies orbiting in the Solar System — TNOs are objects in our Solar System that orbits the Sun at a greater average distance than Neptune is. The most famous Trans-Neptunian objects is Pluto, a dwarf planet discovered over 60 years before any other TNOs. Studying these objects could help us to understand both the formation of our planetary system and the circumstellar material, debris disks orbiting other stars.

Discovered in 2007, (225088) 2007 OR10 is the second most distant known TNO to date, following Eris. Its situated at a distance of at least 87AU and still moving further away up to its aphelion at 100AU. It has high orbital eccentricity, so upon perihelion, it comes nearly as close as Neptune.

Ground-based observations revealed a corresponding diameter of 2007 OR10 as 1535 km which places (225088) 2007 OR10 in the biggest top three trans-Neptunian objects. The infrared thermal spectra measurements taken with the Herschel Space Observatory revealed the presence of water ice and a characteristic red color for this object — the red color of 2007 OR10 is likely to be due to the retain of methane, carbon monoxide and nitrogen on the surface.

You get to see this nice picture of what once was an active little world with water volcanoes and an atmosphere, and it’s now just frozen, dead, with an atmosphere that’s slowly slipping away,

Mike Brown, of Caltech, said.

The newly derived diameter of 2007 OR10 is notably larger than the previously obtained value in 2012. This new value would place 2007 OR10 as the third largest dwarf planet after Pluto and Eris. Due to its large size, 2007 OR10 has likely a shape close to spherical that may be altered by rotation ~ leading to a shape of a MacLaurin spheroid.

Jacobi ellipsoid

MacLaurin spheroid. ©

  The Kepler space telescope has been designed to continuously observe, discover and characterize transiting exoplanets. After the failure of the reaction wheels in 2013, the new mission called K2 has been initiated and commissioned.

In this extended mission, Kepler can be relevant collecting data for the study of “supernova explosions, star formation and Solar-System bodies such as asteroids, comets and TNOs.

K2 was used intensely to study 2007 OR10, leading astronomers to find some intriguing physical proprieties of this object. They determined that it has rotation period significantly shorter than earlier estimation (22.40 or 44.81 h). The slow rotation of 2007 OR10 can be caused by tidal synchronization, similar to the object 2010WG9, a slow rotation superseded by a very few objects only.

For four and a half billion years, 2007 OR10 has been sitting out there, slowly losing its atmosphere, and now there’s just a little bit left.

Researchers hope to use even bigger telescopes to scrutinize the dwarf planet further. To mention that all of the data presented in the paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, under NASA contract. The paper was uploaded on arxiv servers.


  1. Laszlo Molnar

    “it has rotation period significantly shorter than earlier estimation” – you mean significantly slower. Or shockingly slow, as Mike Brown himself put it:

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