The Goblin: How does it support the idea that a giant is hiding farther away?

Its orbit, according to the team who discovered it, supports the existence of Planet X, or Planet 9 — distant and elusive, presumed to be the ninth planet of the Solar System.

Written by Kabir Firaque | New Delhi | Published: October 4, 2018 12:58:56 am
The orbits of Goblin and two other objects, 2012 VP113 and Sedna, as compared with the rest of the Solar System. Illustration by Roberto Molar Candanosa and Scott Sheppard. (Source: Carnegie Institution for Science)

A newly discovered dwarf planet, nicknamed ‘The Goblin’ and charting a lonely orbit far beyond Pluto, has caught the attention of the scientific community. Its orbit, according to the team who discovered it, supports the existence of Planet X, or Planet 9 — distant and elusive, presumed to be the ninth planet of the Solar System.

Planet 9

Estimated to be 10 times as massive as Earth, it has been predicted in a series of studies over the years. It is believed to be influencing the behaviour of many known objects — behaviour that would be difficult to explain if it did not exist. In 2016, CalTech researchers Konstantin Batygin and Michael Brown argued that Planet 9 could be responsible for the peculiar alignment of objects on the outskirts of the Solar System. The same year, another team held Planet Nine responsible for the “wobble” in the orbital plane of the eight planets, which is aligned six degrees off from the Sun’s equatorial plane. Earlier this year, University of Michigan PhD student Juliette Becker and colleagues reported a new discovery — an object called 2015 BP519 — and argued that Planet 9 was causing the extreme tilt of BP519’s orbital plane, aligned at 54° to the orbital plane of the eight planets.

A comparison of the Goblin at 65 AU with the known planets. (Adapted from an illustration by Roberto Molar Candanosa & Scott Sheppard © Carnegie Institution for Science)

The latest find

Why ‘The Goblin’? Two reasons: one, its provisional name, 2015 TG387, contains the initials TG; two, it was discovered close to Halloween. At the time of discovery, announced Tuesday, the Goblin was 80 astronomical units (AU) from the Sun (1 AU is equal to the distance between the Earth and the Sun). At its closest, the Goblin is 65 AU from the Sun. It orbits the Sun once in 40,000 years.
It is part of a region called the Inner Oort Cloud, along with the objects 2012 VP113 and Sedna. When VP113 was discovered, scientists noticed similarities in the orbits of several distant Solar System objects, and proposed this was because of the influence of Planet 9. “These distant objects are like breadcrumbs leading us to Planet X,” the Carnegie Institution for Science quoted researcher Scott Sheppard as saying. Fellow researcher Chad Trujillo (Northern Arizona University) said: “Planet X seems to affect 2015 TG387 the same way as all the other extremely distant Solar System objects.”

Hunt goes on

How much more evidence is required before it is certain that Planet 9 exists? Sheppard told The Indian Express, by email: “We need to double the sample of smaller extremely distant objects in order to be sure they are showing signs of being shepherded by a much larger planet sized object… I’m about 85% sure the planet exists.” CalTech’s Batygin, on the other hand, had told The Indian Express last May that “the false-alarm probability with the current set of objects is about 0.1%.” This was after the discovery of BP519. But Becker, who had led the research paper on BP519, had said: “The only way to prove the existence of Planet Nine is to directly detect it…”


Telling Numbers: Bru tribals in Tripura – 47% jump in a decade marked by flight from Mizoram, 14% in next decade

Between 1991 and 2001, the population of Bru (Reang) tribals in Tripura had increased by nearly half (47%), from under 1.12 lakh to over 1.65 lakh, Census figures compiled by the Tripura government show. It was during this period — in the wake large-scale violence in 1997 — that thousands of Bru tribals had fled Mizoram and taken shelter in Tripura. Their displacement has come into focus again amid reports (The Indian Express, October 3) that they have stopped receiving assistance and free rations in their camps in Tripura.

These have stopped following a July agreement between the two state governments to resettle 32,000 of the Bru tribals in Mizoram, but only 180 of them have actually been resettled. Others had been resettled in previous batches, including over 8,500 in a process that started in 2010. And between 2001 and 2011, Tripura’s Bru population rose moderately — by 14%, to 1.88 lakh.


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