An image of the dwarf plant 2002 TC302, as observed by astronomers in 2005. Image Credit: Michael Brown / Caltech / Hubble Space Telescope.

Distant Moon Detected in the Outer Solar System; Here’s What You Should Know

Astronomers have likely detected the existence of a distant moon closely orbiting a dwarf planet called 2002 TC302 in the solar system’s Kuiper Belt.

In the outermost reaches of our solar system, in the darkness of the Kuiper belt, a distant moon has been found orbiting a small dwarf planet discovered in 2002 by astronomer Mike Brown and his team at the Palomar Observatory. The dwarf planet is designated (84522) 2002 TC302 and is considered a trans-Neptunian object (TNO).

Not long after its discovery, observations revealed a probable diameter of around 1,145 kilometers, which would have made it one of the largest dwarf planets in the solar system. This was not the case, and the observations in 2018 enabled astronomers to study the object, which reveals an oval-shaped body, with dimensions of around 500 kilometers in diameter.

But there are many distant objects in the Kuiper Belt. What makes this one different?

The observations done in 2018 helped determine the diameter of the dwarf planet from the occultation of a 15.3 magnitude star.  When the Spitzer Space Telescope studied the dwarf planet in 2008, it determined an estimated diameter of 584.1/ +105.6 −88.0 km. However, the observations in 2018 showed a different diameter; 499.6 km.

The difference of around 84 kilometers is significant and could indicate that the dwarf planet may not be alone in its journey around the sun. Astronomers believe that 2002 TC302 has a moon, with a possible size range of 100 and 300 kilometers.

The existence of the satellite and observations of the dwarf planet imply that the moon orbits the Dwarf planet in close proximity, probably at a distance not greater than 2000 km.

The discrepancy of 84 kilometers that turned up during the 2018 observations could be explained by a moon around the dwarf planet. 

However, since the satellite probably orbits its dwarf parent at a distance that is around 2,000 km, imaging it is nearly impossible, and not even images taken by the Hubble Space Telescope back in 2005 (see featured image) could resolve it. However, if the existence of this moon is really confirmed, it would help a great deal to understand the early solar system.

Since both the planet and its potential moon are within the so-called Kuiper Belt, this area of space has remained largely unchanged since our star system came into existence. Because things in the Kuiper belt are really, really old, they essentially act as cosmic time capsules that can help us better understand the formation of our solar system, our planet, life on Earth, but also show other, distant star systems function.

There are quite a few interesting objects in the solar system, especially in the Kuiper Belt. One such object-of-interest was visited by NASA’s New Horizons spacecraft back in 2015, as it swung by a peculiar object known as Arrokoth. Of course, 2002 TC302 is much larger than Arrokth, but both objects can help us understand the process involved in the formation of cosmic bodies in the solar system.

Arrokoth can answer questions that dwarf planet 2002 TC3402 can’t and the other way around. Understanding such dwarf planets and their moons is essentially gathering pieces of a giant puzzle.

Written by Curiosmos


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