A ring discovered around the dwarf planet Haumea

Artist's concept of Haumea with its ring (Image courtesy IAA-CSIC/UHU)
Artist’s concept of Haumea with its ring (Image courtesy IAA-CSIC/UHU)

An article published in the journal “Nature” describes the discovery of a ring around the dwarf planet Haumea. A team led by astronomers at the Astrophysical Institute of Andalucía (Instituto de Astrofísica de Andalucía, IAA-CSIC) in Spain used observations of several telescopes to find the ring, the first located around a trans-neptunian object, and to get better estimates of other Haumea characteristics.

Discovered in 2004, Haumea was classified as a dwarf planet in 2008. Its distance from the Sun is currently about 50 times the Earth’s and is year is about 284 Earth’s years. Among its peculiar characteristics there’s a rotation of only 3.9 hours, faster not only than any other planet or dwarf planet of the solar system but also of other celestial bodies with a diameter greater than 100 km. This explains why its shape is so elongated, very oval.

After its discovery, further observations made it possible to discover the presence of two moons, which were called Hi’iaka and Namaka. Despite its high brightness, its distance makes it difficult to study it but occasionally comes the help of the stellar occultation phenomenon. In essence, it’s an eclipse that occurs when an object passes in front of a star allowing higher quality observations for a period that can be of very few minutes.

ESA’s Gaia satellite has been mapping the sky with details never before and among the benefits there’s the possibility to predict star occultations with remarkable precision. Thanks to the data collected, it was possible to establish that this phenomenon would occur on January 21, 2017, allowing to observe the dwarf planet Haumea and ten European observatories participated in this study campaign thanks to their favorable position during the occultation.

José Luis Ortiz of the IA-CSIC, the article’s lead author, coordinated the observatories’ efforts for that brief but intense period. Because of the slightly different perspective in the various nations, the duration was as different and provided slightly different measures that allowed to reconstruct more precisely the dwarf planet Haumea’s size and shape.

The surprise, however, came from the discovery of the presence of a thick and thin ring around Haumea. At about 2,300 kilometers of altitude for a thickness of about 70 kilometers, the ring lies on the dwarf planet’s equatorial plane, like its moon Hi’iaka. It could have formed after a collision with an asteroid or Haumea’s high rotation speed might have pushed into space materials that were on its surface.

We’re used to the presence of rings around giant planets but in 2014 the existence of rings around the asteroid Chariklo was announced, so the one around the dwarf planet Haumea is not that strange. It’s the first discovered around a trans-neptunian object and was found thanks to an international collaboration that involved several small telescopes, proving their usefulness in an excellent scientific work.

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