In the long distances of the solar system, along the orbit of Neptune, things are becoming more and more difficult and complicated. Directly depicting small objects in the darkness of the Kuiper belt – where Pluto resides – is really difficult, which makes the recent discovery even more exciting.
If you know where something is, you can watch it, waiting for it to pass in front of distant stars. This is called occultation and astronomers use it to study all kinds of trans-Neptunian objects.
But when astronomers used occultism in 2018 to study such an object, which they have been observing for nearly two decades, they discovered something really unexpected – a piece of the moon relative to the orbiting body. A study describing their findings has already been accepted Astronomy and astrophysics, and was first covered by Jonathan O̵
The object caught to sport this moon is the probable dwarf planet (84522) 2002 TC302. It was first discovered in 2002, after which it was identified in earlier observations.
Between 2000 and 2018, astronomers collected at least 126 observations of the object at different wavelengths (including the Hubble Space Telescope); using this information, they calculated the potential orbit, size and color of the dwarf planet.
They found that it was about 584 kilometers in diameter (363 miles) and had an orbital period of 417 years – in a 2: 5 orbital resonance with Neptune.
That’s pretty great. This means 2002 TC302 almost meets the requirements for a dwarf planet – it orbits the Sun (but not another planet); has not cleared its orbital quarter; and it must have sufficient mass to achieve hydrostatic equilibrium or round shape.
But we are not quite sure. When forecasts for its orbit indicated an occult event on January 28, 2018, observatories across Europe turned their attention to TC TC 2002.302neighborhood to try to understand its physical properties, such as size and shape.
Telescopes in Italy, France, Slovenia and Switzerland made 12 positive discoveries at the occult event, as well as four negative discoveries. This gave the best observation of a trans-Neptunian object we have received so far, the researchers say.
Adding them together allowed researchers to obtain a new, more accurate measurement of the object’s diameter: 500 kilometers (311 miles).
So how do we account for the missing 84 kilometers calculated from the other observations? Well, there is a really interesting answer to that. If 2002 TC302 had a moon about 200 kilometers (124 miles) in diameter and only 2,000 kilometers (1,243 miles) from the probable dwarf planet, it could produce the signal that other astronomers interpreted as a slightly larger 2002 TC302,,
It’s insanely close. The moon, for context, is 384,400 kilometers (238,900 miles) from Earth (average). In such close proximity, 2002 TC302The satellite will be extremely difficult to depict – even images from the Hubble Space Telescope taken in 2005 could not solve it individually.
If a potential dwarf planet does have a satellite, it may help us learn about the early solar system. Things in the Kuiper belt have changed very little since the formation of the solar system, and as such these objects are considered time capsules.
Two objects, extremely close to each other, can help us better understand the close interactions when the solar system is forming. Since planets are thought to have formed through growth – more and more things are sticking together – this can be an important clue to how smaller bodies grow.
Of interest is Arrokoth, the strange snowman-shaped rock visited by the New Horizons spacecraft in 2015. The data provided by this fly showed us that planetary growth may be a more sparing process than we thought.
2002 TC302 is much larger than Arrokoth, but could be at a later stage of the process – which would be really helpful in merging the stages in which it happens. In any case, it is clear that we should probably look at it a little more and try to understand what its deal is. Exciting!
The study was accepted Astronomy and astrophysics, and is available on arXiv.