Does this discovery of 'The Goblin make 'Planet 9' more likely? Yes I’d say so. It’s looking really strange. I’m beginning to be won around to the idea :). There is plenty of space for planets to exist beyond Neptune. No known big gas giants to get in their way. And - objects get far far fainter the further they are from the sun. It was hard to find, even though it was only 80 au from the Sun - at it's furhest it would be 2300 au away. They spotted it first in 2015 and it's taken since then to figure out its orbit.

Its full name is 2015 TG378 (the letters and numbers indicate its position in the list of minor bodies found so far that year) and it gets its name from the initial leters TG. Astronomy Now reports it like this:

The newly discovered body, known as 2015 TG387, was discovered by Carnegie’s Scott Sheppard, Chad Trujillo of Northern Arizona University and David Tholen of the University of Hawaii. They first observed TG387 in 2015 using the Japanese Subaru 8-metre telescope in Hawaii. But it is so distant, so dim and moving so slowly it took additional observations over three years using Carnegie’s Las Campanas Observatory in Chile and the Discovery Channel Telescope in Arizona to pin down TG387’s orbit.

The thing is that our telescopes can spot even small objects easily out to about the distance of Pluto. But beyond there it rapidly gets very hard to see anything. It’s because of the way brightness falls off with distance. If something is ten times further away, it is visually 100 times smaller in the sky, and what’s more, it gets only a hundredth of the sunlight, and combining those two effects makes it 10,000 times fainter to our telescopes. Something a hundred times the distance of Pluto would be a hundred million times fainter. At its furthest point in its orbit, this new object will be 683,000 times fainter than it is now.

You can also look at it another way. If it is ten times further away its diameter has to be 100 times larger to be the same brightness (would make it 10,000 times larger in cross section to compensate for being 10,000 times fainter).

“Where we think the planet is—hundreds of AU away, if not 1,000 AU—something even as big as Neptune would be fainter than most telescopes could see,” Sheppard told Space.com. (In case this sounds odd or incongruous: The Goblin was discovered near perihelion, at about 80 AU from the sun.)

“And most of our surveys to date do not go that faint, do not go that deep. We’ve covered very little of the sky to the depth that’s needed to be covered to find something this faint,” he added. “You can hide a very big thing in the outer solar system very easily.” Newfound World "The Goblin" May Lead to Mysterious Planet Nine

From that same article, it was found at a distance of 80 au and has an estimated diameter of 300 km approximately (they don’t know for sure as it depends on whether it is light or dark coloured, they just know its total overall brightness). At it's furthest point in its orbit, 2,300 au,, then it would need to have a diameter of 250,000 km to be similar in brightness - even Jupiter (diameter 139,822 km) would be fainter at that distance..

If it was at a distance of 800 au, it would need to have a diameter of 30,000 km to have the same brightness. “Planet 9” if it exists would be 13,000 to 26,000 km in diameter and expected to be up to 1,200 au away. That would make it significantly fainter than Goblin. So, 'Planet 9', if it exists it is just on the edge of what is possible for our biggest telescopes to spot. Also, a more distant object would be moving much more slowly in the sky, both because of its distance, and because planets that are further away from the sun orbit at a slower speed relative to the sun too - so would be even harder to figure out. If it is there, it's probably not going to be the easiest of things to discover despite its vast size.

Artist’s impression of distant “planet 9” which the Goblin may be hinting at Introducing ‘The Goblin’: A new, distant dwarf planet bolsters evidence for planet 9

This shows its orbit

This shows some of the other objects found so far - “the Goblin” would be in an orbit stretching off to the left in this picture. It’s striking to look at, nearly all of them except 2013 FT28 are in orbits in that direction.

Postulated orbit of ‘Planet 9’ in green and the detached objects - note how the newly discovered objects cluster on one side of the sun - this could be due to the influence of a big heavy planet in the postulated orbit.

The theory is that the big planet 9 makes orbits in the other directions unstable over very long time periods - though you won’t notice anything in a single orbit. It’s not like the discovery of Neptune - we don’t see any anomalies in the movements of these objects

The only anomaly is that they are in these very elliptical orbits that cluster to one side of the sun. The orbits themselves, are normal enough; the anomaly is more about what we don’t find. Why haven’t we yet found any similar objects in ellipses pointing in the opposite direction?

Another possibility is that the orbits are clustered this way because of the gravitational bunching up of smaller objects circling the sun in the Kuiper belt. To model that is computationally expensive - you have to add in the mass of hundreds of objects, then the effects on each other as well as the effects on these larger trans Neptunian objects. But it seemed to be possible to explain some of the effects in this way. That was a result of a new study by an undergraduate Flesig at CU Boulder whose study got a lot of attention earlier this year. It doesn't explain everything, the tilt of the orbits particularly, but it does give a way that lots of smaller objects could create orbits of larger objects bunched up in a similar way.

What About Mars Or Earth Sized 'Goblin's?

Also notice that these objects were only discovered because they were at the closest part of their orbit to the sun.

Close up of some of the detached objects showing their positions at the time of discovery.

Co-discoverer Tholen says (as reported in Astronomy Now)

...there could be thousands of small bodies like 2015 TG387 out on the solar system’s fringes, but their distance makes finding them very difficult. Currently we would only detect 2015 TG387 when it is near its closest approach to the Sun. For some 99 percent of its 40,000-year orbit, it would be too faint to see.”

It’s not remotely likely they all happened to be close to the sun by coincidence at the very moment in time that astronomers started looking for them. This means that for each one we've spotted, there must be dozens, through to a hundred or more of each of these objects in a similar orbit - but currently much further from the sun. We must be seeing only a small selection from a vast population of hundreds of these objects. And then when you take account of others that never get quite as close to the sun as the ones we've found, and that we are also still discovering them and have only surveyed a small part of the sky with suffiicient senstivity to spot the fainter ones - surely there must be thousands of themin total that we haven't found yet.

And when even very large objects in the population are hard to spot - and there are so many objects of a few hundred kilometers in diameter up to a few thousands - you’d expect to find a few larger ones too. So - there may well be larger Mars and Earth sized planets out there in similar orbits to these ones as well.

Mike Brown hypothesized that in a talk about Sedna soon after its discovery - that there are probably several Mercury, Mars and maybe even Earth sized objects out there in similar orbits to Sedna. These haven’t been found yet - but they would be even harder to spot than “Planet 9”. Though it doesn’t get mentioned much, this option is also surely very much in the air still. There has to be a largest object in these families and it is not at all likely we have found it yet - so how large is it?

So -we have perhaps this huge 'Planet 9' on one side of the sun (for most of its orbit) and then we have probably thousands of objects on the other side of the sun t(for most of their orbits) and they have sizes ranging from hundreds of kilometers through to the 1800 km of Sedna- maybe there are Mars and Earth sized objects on that side of the sun?

There's also the possibility that 'Planet 9' is not one object but severl objects.

So - we may eventually find not just ‘Planet 9’ but ‘Planet’s 10, 11, 12, …’. And - some of them - way out there beyond Pluto - may be as large as Mercury or as large as Mars or even Earth. The IAU will want to say they aren’t planets because they don’t “clear their orbits”. But I think we will surely call them planets and re-open that whole debate again.

This picture shows some of those objects again, but I like it because it gives an idea of our solar neighbourhood. Out to Jupiter we can spot objects as small as a few kilometers in diameter. out to Pluto - tens of kilometers through to hundreds of kilometers. But further out we could miss even rather large planets. Far enough out and we could miss even a planet as large as Jupiter.

“The four zones of the solar system include a staggering amount of unexplored space–almost everything beyond Pluto is barely known. (Credit: M. Brown/Caltech/R.Hurt/C.Powell)” (figure from this article)

There could be not just one big planet - there could be many - planets the size of Mars, the Earth, this ‘Planet 9’ the size of Neptune - and maybe even larger ones. We could miss Jupiter if you go out far enough from the sun. The Oort cloud stretches out much of the way towards the nearby stars. There could be objects orbiting a light year away or more.

Am object as large as Jupiter a light year away would not form in the manner of the other planets from the same blob of gas that collapsed to form our solar system. But it could form as a sub-brown dwarf - a planet that condenses out of a separate blob of material, in similar fashion to a binary star.

We do know that there is no companion second stars. The WISE infrared space telescope disproved that. No brown dwarfs either unless they are really really cold (unlikely) as they would be easy to spot by the heat radiation - can be seen up to ten light years away.

MIKE BROWN PREDICTION OF A FUTURE DISCOVERY OF A MARS SIZED DWARF PLANET NON PLANET BEYOND NEPTUNE

You may remember that the IAU declared that Pluto was not a planet some time back, because, they said, a planet has to “clear its orbit” of most other objects. Mike Brown who discovered Sedna, although he is strongly in favour of demoting Pluto as a planet, is also one of those who has speculated that perhaps the IAU defijnitionhas a "sell by date", at least with the general public. If we discover Earth sized objects out there, the general public are bound to call them planets, not "dwarf planets". Many planetary scientists like Alan Stern want to use the geophysical definition according to which any object large enough to be rounded under gravity counts as a planet, with different sub categories according to size and properties.

Here is Mike Brown'svideo where he predicts using a statistical argument from the orbit of Sedna, that we are likely to find planets beyond Neptune that are Mercury, Mars or even Earth sized. He then goes on to say.

"What is strange about this one, we happened to find this one almost at the closest point it ever gets to the sun. Not by coincidence. Because there is only about a 200 period shown in red here when we could have seen it. ... So 200 years out of 12,000 years means 1 in 60 chance of finding it. So either we are very lucky, which astronomers don't like to think of themselves as lucky, or scientists in general, but instead what we like to think is that if we found something and we only had a 1 in 60 chance of finding it, probably there are 60 of them and we just found the one that happens to be close. ... Now maybe it's not 60. Maybe it's 30 and we got a little bit lucky. Maybe it's 90 and we got a little bit unlucky. But there are a lot of objects in this very distant region where we never knew of anything before. This is the first time we found anything in this region out here."

""Now the fun thing to think about is, if there are 60 of these, and Sedna is about 3/4 times the size of Pluto, if there are 60 objects 3/4 the size of Pluto there are probably, oh, 30 objects the size of Pluto, that's a lot of objects the size of Pluto. There are probably 10 objects that are twice the size of Pluto and there are probably two or three objects that are three and four and maybe even five times the size of Pluto. in this region here. It's a little bit vague, since we have only found one object, to be able to extrapolate to these things, but it is not that vague. There must be some of these very large objects out there. And our big goal now, and one of my current grad students PhD thesis is to find these objects, if there are some big objects out there two or three or four times the size of Pluto, these things are the size of Mercury, these things are the size of Mars, these things are the size of the Earth. If you take that final thought and you look at the kuiper belt and you put this object on there, that's the size of Mars,"

"I am willing to go out on a limb there and say, we will find something like that, the size of Mars, in this region of space. And scientifically, this will be fantastic because we will get to learn about an entirely new class of objects, and try to understand how they got there. But just as much fun, of course, is that this will cause the astronomers to go into a tizzy again. Because, if you find it, what do you call it? Well by the current definition - and I forgot to tell you of course, the current definition is, you have the eight planets, and if you are not a planet but you are still one of those round things, you are a dwarf planet. " "It's a weird word because there are very few cases in the English language where you have adjective, noun, combination "dwarf planet" is not a "planet". Dwarf planets are not planets. They are dwarf planets. But by the official definition this object the size of Mars would be a dwarf planet. I actually believe that that's the right classification. Because I still think that this population deserves to be put together and the planets are actually special. But I don't think most people are going to buy that. I think if you find something the size of Mars, something the size ofthe Earth, I think most people are going to want to call it a planet, and I think astronomers are going to get in an uproar again. Maybe they will have as much fun as they did in Prague...."

and goes on to speculate about the future IAU meeting after astronomers find a Mars sized Dwarf Planet Non Planet according to the IAU definition.
The video is here

‘Planet 9’ if it exists would just sneak in as orbit clearing

The vertical axis shows its mass in Earth masses.

At the distance of ‘Planet 9’ none of the terrestrial planets, not even Earth would count as orbit clearing. If there was a planet as big as Earth with a semi-major axis as large as Sedna, or ‘the Goblin’, it would not count as a ‘planet’ according to the IAU.

You can also see from this diagram that both Pluto and Eris would count as planets if they were in the same orbit that Mercury is in now, and that Mercury would be right on the boundary at the distance of Pluto and well below it at the distance of Eris. Meanwhile, a sub-brown dwarf the size of Jupiter would not count as orbit clearing if it formed more than a light year away from our sun.

And - we continue to find many more of these objects, that we'd only notice because they are close to the sun when we find them. So far Sedna is the largest. But surely we can't, just by chance, have found the largest one in the population of these objects. There must with a near certainty be larger ones. So how large do they get? As large as Mike Brown's speculation of objects the size of Mercury, Mars and even Earth?

THESE NEW PLANETS, IF FOUND, CAN'T COME INTO THE INNER SOLAR SYSTEM

Planet X is a general term for any hypothesis for a planet that hasn't been found yet. Pluto was the first "planet X" before they found it. There have been many since then, most of which were disproved, for instance Robert Harrington proposed a planet to explain anomalies in the orbit of Neptune. The need for it went away when Myles Standish recalculated the mass of Neptune after the Uranus flyby, and the anomalies vanished, and since then all the planets in the solar system are behaving exactly as predicted.

Neptune would have been called 'Planet X' before it was discovered if they had had that terminology then. I think it was Lowell who started the search for Pluto who first came up with this. X stands for "unknown". And 'Planet 9' is not the only one at present either. There are usually several on the go at once and this is another current contender though the evidence for it isn't that strong: see UA Scientists and the Curious Case of the Warped Kuiper Belt

This shows its possible orbit.

As you can see,llike 'Planet 9;, it would orbit way beyond Neptune. Neptune is not the slightest risk to Earth and neither is this planet, if it exists.

The evidence for it isn’t that strong. We have now found many objects way beyond Neptune in the “Kuiper belt” between Neptune and the distant Oort cloud of comets - and more of them are one side than the other of the plane of the solar system. There’s a 1% chance of this happening by chance - which you might think means there is a 99% chance of this planet existing. But no, it doesn’t work like that. Astronomers have to sift through a lot of data and look at it in many different ways, so 1 in 100 chances turn up quite often, just through chance.

If it does exist, the Large Synoptic Survey Telescope should find it when it comes online in the early 2020s. This is a large telescope dedicated to finding faint objects including asteroids that may be hazardous for Earth.

It’s such a huge telescope and it’s such a major step forward that it’s expected to make many new discoveries of asteroids in the first few days of operation. It should then continue to find more discoveries over the next decade. It’s got a huge 8.4 meter diameter mirror and a very wide field of view, 3.5 degrees, seven times the visual diameter of the Moon in the sky, and extremely sensitive camera, a 3.2-gigapixel CCD imaging camera, the largest digital camera ever constructed.. The camera is optimized for taking photographs quickly too. It should survey the entire sky every few nights. .

It has a good chance of finding some of the new planets out in our outer solar system, if they exist.

If you search for news about 'Planet X' then google fills your search page with search results about 'Nibiru', a mythical planet that cannot exist. Here is planet x -bikes - Google Search (to exclude the 'Planet X' bike company from the searches).

Two out of the top three search results claim that ‘The Goblin’ could prove that ‘Nibiru’ exists. If you are an amateur or professional astronomer you may never have heard of ‘Nibiru’. It is an absurd conspiracy theory that there is an extra planet in our solar system that is about to hit Earth or flyby Earth. They have been claiming it will do this ever since 2003 since a lady Nancy Lieder claimed that extra terrestrials from the Zeta Reticuli - Wikipedia star system 39 light years away told her about ‘Nibiru’ through an organic implant in her brain. Of course nothing happened.

This is because Google is rubbish at filtering out fake science news about planets. The same is true about Apple News and Facebook trending. The problem is that all three treat the UK "red top tabloids" as high quality news sources when they are not. They often just make things up for thrills. And will run stories based sometimes on no more than a YouTube video uploaded by an anonymous uploaoder or a couple of Facebook comments by undisclosed people, or out and out fake news made up by their own reporters. Their stories are often scary, thrilling, viral and widely shared and so it's no surprise they go to the top in Google.

The conspiracy theorists claim that all these disproved planets were the same planet 'Nibiru' - including Robert Harrington’s ‘Planet X’. They claim he was murdered to hide the news (actually his theory was disproved six months before he died of throat cancer). They ignore such differences such as the hypothetical planets since Pluto orbit permanently way beyond Neptune.

In principle a planet could cross Neptune's orbit - Pluto does - by being in a resonance, a 3:2 resonance. There are many others known now, in resonances of 1:2. 1:3, 1:4, 1:5, 2:3, 3:5, 2:5, 4:7 and various other ratios, collectively called the resonant trans Neptunian objects.

An object can't be in resonance with both Neptune and Uranus though because those two planets are not in resonance with each other. That’s why any planet or dwarf planet that comes as close as Uranus won't last long.

One that crosses all the gas giants and reaches Earth's orbit couldn't last a million years. If it is a brown dwarf it is even worse, all the other planets would be gone within a million years, indeed very quickly, even just one flyby of the inner solar system would disturb it so much that the planets would be in bizarre elongated orbits, probably swap orbits and so on. They would soon hit the Sun, ‘Nibiru’, or be ejected altogether.

So it is impossible our solar system has such a brown dwarf. And a planet smaller than Jupiter would have had very obvious effects on Earth's orbit and we'd have probably have lost our Moon too if it had buzzed Earth 3600 years ago. The idea is just absurd, LOL silly to astronomers and has been since Newton first figured out the mathematics of gravity, that planets follow the inverse square law of attraction..

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