'Newly found farout object might qualify as a dwarf planet' – Astronomer

The newly found object was announced Tuesday, 2 October, 2018 by the International Astronomical Union's Minor Planet Centre. A paper with the full details of the discovery has also been submitted to The Astronomical Journal. 2015 TG387 was nicknamed "The Goblin" by the discoverers, as its provisional designation contains TG and the object was first seen near Halloween.

Sputnik has discussed the newly-found object with one of the astronomers behind the discovery, David J Tholen, a co-researcher at the Institute for Astronomy of the University of Hawaii and Ph.D. in Solar System astronomy at the University of Arizona.

Sputnik: How did you manage to spot the space object? Why didn't we know about it before?

David J Tholen: We found the object by taking two pictures of the same piece of sky and then, inside a computer programme, it aligned the images, such that all the stationary objects such as stars and galaxies are in the same positions, and then anything that has moved is identified and we will verify that the detection is correct by looking at it visually, just to make sure that there are no artefacts that the computer might have been fooled by. And then we measured the position using the background stars as reference sources and started the process of computing the orbit. In this particular case, the object has only been observed for a little over a month. So the distance is known reasonably well but the orbit itself is fairly well unconstrained. In other words, we don't know the shape of the orbit. It could be circular. It could be a very skinny ellipse.

Sputnik; Now, you have obviously qualified your last answer, but what is it? Is it a planet or some of a type of other cosmic object?

David J Tholen: Well, we estimate the size of the object to be about 500 kilometres in diameter. So, that makes it a bit small to know for sure that it has enough mass to crush itself into a spherical shape, which is one of the criteria people like to use to call [something] planet. So probably a little bit small to be considered a planet, but it is comparable in size to some of the largest asteroids. For example, in the main asteroid belt between Mars and Jupiter, the asteroids Vesta, which was recently visited by the Dawn spacecraft, and Pallas, those are both roughly of the same size as we estimate this object to be. There is some uncertainty to the size, because we don't know how reflective the surface material is. So it could be anywhere from, say, 250 kilometres to perhaps a 1,000 kilometres. If it is up in the 1,000 kilometres size range, then yes, it might qualify as a dwarf planet.

Sputnik: What is Farout like? What do we know about its properties, qualities, and complexities? Is it similar to the other planets in the solar system? Is there any way of ascertaining that, or is it too difficult?

David J Tholen: There is not enough data right now to make comparisons with other objects. We did get some colour information on the object, so we know it is slightly redder than the sun, which is very common among other asteroids. So that's about the only indication we have of physical properties. And just the fact that it is very, very far from the sun means it is a cold object. So it would likely have icy material, such as water ice or carbon dioxide, methane, [or] other materials which are in solid form at such cold temperatures.

Sputnik: What are your next steps with regard to the next phase of planning to study for this particular "planet"? What would you look at as the next phase in depth of this particular finding?

David J Tholen: Well, I think the first step is to improve our knowledge of the orbit and that is simply going to take time. This thing takes about 1,000 years, roughly since we don't know the orbit, we don't have an exact orbital period, but it is going to take roughly 1,000 years to make one trip around the Sun. And so, it is going to take 2-3 years, maybe 4 years, to nail down the orbit to the point where we can say what the actual size and shape and orientation of the orbit is. And then that will be particularly interesting, because some of the other distant objects that we [have] found in the outer solar system tend to have orbits that are more or less aligned with one another. That alignment has led to the speculation that there is some massive object out there whose gravitational pull is kind of steering these smaller objects into similarly aligned orbits. So this object may help bolster the case for a massive object.