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Artist concept of the newly discovered dwarf planet, nicknamed The goblin (aka 2015 TG387). Image via Roberto Molar Candanosa / Scott Sheppard / Carnegie.
Astronomers have found a leprechaun in the confines of the external solar system. No, it's not a mythical space creature. The goblin is the nickname given to a new dwarf planet in the external solar system. This is an exciting discovery in itself and The Goblin's orbit also supports the possible existence of the much sought-after, and much larger, planet X.
Scott Sheppard of the Carnegie Institute of Science, Chad Trujillo of Northern Arizona University, and David Tholen of the University of Hawaii announced the discovery on October 2, 2018 via an electronic flyer from the IAU Minor Planet Center. A document was submitted to the The astronomical journal. In other words, astronomers just found this object.
They found it during an intensive search on Planet X. These astronomers said:
… the most thorough and comprehensive survey of its kind to date.
The orbit of the new dwarf planet places it in a group of small distant worlds that astronomers call Inner Oort Cloud Objects. In other words, it lies in Oort's cloud – a giant spherical shell of icy objects surrounding our sun, considered the realm of comets, far beyond the orbits of Pluto and the objects less distant from the Kuiper belt.
The goblin, also known as the 2015 TG387, is about 80 astronomical units (AU) of the sun, an AU being defined as the distance between the sun and the Earth. In comparison, Pluto is at 34 AU from the sun, so The Goblin is about two and a half times farther of the sun like Pluto, now.
It is thought to be quite small, about 300 km in diameter. Its orbit is very elongated, never approaching the object of the sun as 65 AU. In addition to the 2015 TG387, the only other objects with a more distant perihelion – that is, points farther from the sun – are the VP133 and Sedna 2012, at 80 and 76 AU respectively.
However, the Goblin's orbital half-major axis is larger than that of the 2012 VP113 and Sedna, which means that it moves much further from the sun than its orbit around its orbit. At its furthest point, it's an incredible 2300 AU of the sun.
The Goblin's orbit is comparable to that of some other Inner Oort Cloud objects. Image via Roberto Molar Candanosa / Scott Sheppard / Carnegie Institution for Science.
As Scott Sheppard explained:
These so-called Inner Oort Cloud objects such as 2015 TG387, 2012 VP113 and Sedna are isolated from most of the known mass of the solar system, which makes them extremely interesting. They can serve as probes to understand what is happening at the edge of our solar system.
Sheppard and Trujillo also discovered the 2012 VP113 in 2014. The discovery of such objects means that there are probably many more left over. According to David Tholen:
We think there may be thousands of small bodies like the 2015 TG387 on the periphery of the solar system, but their distance makes their search very difficult. Currently, we only detect 2015 TG387 when it is close to its closest approach to the sun. For about 99% of its 40,000-year-old orbit, it would be too weak to see it.
Graphic illustrating the distances of the planets and the Kuiper belt from The Goblin (not to the scale). Image via Roberto Molar Candanosa / Scott Sheppard / Carnegie Institution for Science.
But it is not only the objects themselves that interest astronomers. These distant objects could also point the way to locating another major planet in our solar system. As Sheppard noted:
These distant objects are like breadcrumbs that lead us to Planet X. The more we find, the better we can understand the outer solar system and the possible planet that we believe is shaping their orbit – a discovery that would redefine our knowledge of the evolution of the solar system.
An important clue that the goblin could be a proof of the largest planet X is that the location in the sky where 2015 TG387 reaches perihelion is similar to that of 2012 VP113, Sedna and most other trans objects. -neptunians known far away; this could be explained by something that would "push" them into similar types of orbits. To test this further, Chad Trujillo and Nathan Kaib of the University of Oklahoma conducted computer simulations to determine the impact of various hypothetical X-ray orbits in the 2015 TG387 orbit. As most previous estimates of the size of the planet X indicated that it was much larger than the Earth, the simulations included a super-terrestrial planet of several hundred AU in an elongated orbit, as proposed by Konstantin Batygin and Michael Brown of Caltech in 2016.
Discovery footage of the Goblin (2015 TG387) taken by Subaru's 8-meter telescope on Mauna Kea in Hawaii on October 13, 2015. Both images were taken approximately 3 hours apart. Image via Scott Sheppard.
So what was the result? Most simulations suggested that not only was TG387's 2015 orbit stable for the entire solar system, but it was actually guided by the gravity of Planet X – which would allow the TG387 of 2015, much smaller, to get away from the much more massive Planet X. the gravitational shepherd – similar to the way Saturn's smaller moons "shepherd" her rings – could also explain why these far-flung objects of the solar system have all a similar orbit. According to Trujillo:
What makes this result really interesting is that Planet X seems to affect 2015 TG387 in the same way as all other extremely distant objects in the solar system. These simulations do not prove that there is another gigantic planet in our solar system, but they are further proof that something big might exist.
If Planet X is confirmed, it may well be, as some scientists suggest, a super-Earth, a rocky planet larger than Earth but smaller than Uranus or Neptune. Many worlds of this type have already been found in other solar systems, so it would be very exciting to discover here a world previously unknown.
Conclusion: Although the elusive planet X has not been found yet, the discovery of The Goblin is intriguing and provides another clue than Planet X should be there, waiting to be detected by terrestrial telescopes.
Via Carnegie Institution for Science
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