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Discovery of 'Goblin' Solar System Object Bolsters the Case For Planet Nine (gizmodo.com)
Astronomers have discovered a dwarf planet, dubbed "the Goblin," in the outer reaches of the Solar System that never gets any closer to the Sun than 6 billion miles. Some experts say its orbital configuration points to the existence of Planet Nine, a hypothetical planet in our Solar System that is estimated to be about 10 times the mass of Earth. Gizmodo reports: The Goblin, or 2015 TG38 as it's more formally called, is what's known as an extreme trans-Neptunian object, or ETNO. As the moniker implies, these objects, of which there are potentially thousands, are located well beyond the orbit of Neptune. The researchers who discovered the object, a team led by Scott Sheppard from the Carnegie Institution for Science and Chadwick Trujillo from Northern Arizona University, estimate that the Goblin is around 185 miles (300 kilometers) in diameter. At this size, it could very well be sphere-like in shape. Its mean distance from the Sun is about 80 astronomical units (AU), where 1 AU is the average distance from the Earth to the Sun. That's 7.45 billion miles, or 12 billion kilometers.
The Goblin's extreme orbital path means it never comes close enough to impose gravitational influence on the Solar System's giant planets, like Neptune or Jupiter. And at the astounding distance of 2,300 AU, it gets slotted into an emerging astronomical category known as Inner Oort Cloud objects (IOCs), of which 2012 VP113 and Sedna are the only other two known members. [...] The discovery of 2015 TG38 is bolstering the case for Planet Nine -- a hypothetical planet, sometimes referred to as Planet X, that's allegedly several times larger than Earth and located hundreds of AU away. As noted in the new study, published today in The Astronomical Journal, the location of Goblin's perihelion is similar to what's observed with Sedna and 2012 VP113, along with other ETNOs. This is a clue to astronomers that something potentially big, i.e. a super-Earth, is pushing these objects into similar types of orbits.
The Goblin's extreme orbital path means it never comes close enough to impose gravitational influence on the Solar System's giant planets, like Neptune or Jupiter. And at the astounding distance of 2,300 AU, it gets slotted into an emerging astronomical category known as Inner Oort Cloud objects (IOCs), of which 2012 VP113 and Sedna are the only other two known members. [...] The discovery of 2015 TG38 is bolstering the case for Planet Nine -- a hypothetical planet, sometimes referred to as Planet X, that's allegedly several times larger than Earth and located hundreds of AU away. As noted in the new study, published today in The Astronomical Journal, the location of Goblin's perihelion is similar to what's observed with Sedna and 2012 VP113, along with other ETNOs. This is a clue to astronomers that something potentially big, i.e. a super-Earth, is pushing these objects into similar types of orbits.
If you count everything as a planet, Pluto is not the ninth, there is a lot more. Wikipedia's list of minor plants has 523584 entries today.
Pluto isn't even the only thing once considered a planet that got "downgraded" to dwarf-plant. It happened to Ceres in the 1850s before. Ceres was discovered on the 1st of January 1801, far earlier than Pluto. Its orbit between those of Mars and Jupiter and it is far bigger than Goblin.
Assuming it does exist, then based on the IAU's current position on what constitutes a planet and where it's orbiting, the most likely current classification would seem to be either a Kuiper Belt Object or a Plutoid. Alternatively, they could go back to the drawing board again and revamp the classification system to try and make arbitrarily pigeon-holing lumps of rock and gas going around stars into types at least a little less confusing and contentious.
UNIX? They're not even circumcised! Savages!
To be able to so wildly disturb the orbits of the multiple ETNO's we have discovered so far, the suspected mystery planet is not going to be a minuscule speck like Pluto but a gas giant along the lines of Uranus or Neptune. Rest assured that should we discover something that big orbiting the Sun, it will be a designated a planet.
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Fascinating bit of research; kudos to the authors.
Just one bit of pedantry (sorry!). When the OP writes, "This is a clue to astronomers that something potentially big, i.e. a super-Earth, is pushing these objects into similar types of orbits.", the use of the term "super-Earth" prompted a non-technical friend of mine [who was reading the article over my shoulder] to ask, "So there's, like, an amazing Earth, way out in space, right on the edge of our solar system?"
Obviously I explained that in this context the phrase simply meant, "physically bigger than the Earth in size and/or mass" and that in reality, any planet orbiting beyond Pluto would be a barren world of rock and/or ice, to which the response was, "Well, why doesn't the article say that, then?"
Given the way that lots of content covered by slashdot gets picked up by the mainstream media, maybe we should try and avoid terms liable to confuse or be misunderstood by less technical readership?
You've misread. Goblin's not the one that's several times larger than Earth -- Goblin is the 300km one. The fact that Goblin's orbit is where it is, is more evidence pointing to an as-yet unobserved hypothetical planet further out, Planet Nine, that is several times larger than Earth.
You're probably right on that, but there are still a lot of assumptions here - including that the thing even exists and is a single entity; it could turn out to be a collection of gravitationally bound objects in a common orbit similar to Pluto and Charon, for instance. In that case, even if the combined mass is similar to Uranus/Neptune and the individual mass of the larger objects is larger than (say) Earth, would that still a planet, singular, or even an ETNO? What about the individual larger masses - planets or ETNOs?
Personally, I don't really care whether Pluto is officially a planet or not; because it was when I was first learning about space that's still how I think of it, but on a practical level given the range of other objects we now know are out there it probably does make more sense to have it in some other category. Alternatively, if you're going to officially classify Pluto as a planet, then what about Eris, which has more mass but with a much greater orbital eccentricity? With a little luck, this new object will turn out to be something that doesn't fit the current classification schema, force the IAU back to the drawing board on definitions, and they'll then figure out a way to include Pluto as a planet again (based on mass and orbital inclination/circularity, perhaps?) to stop at least some of the bickering.
UNIX? They're not even circumcised! Savages!
80 AU's is mentioned as the mean distance. NOT the minimum distance. If 80 AU's is the mean distance, and 2300 AU were aphelion (which is NOT what they said), the Goblin would have to have an orbit that pretty much brushed the Sun, took a few tens of thousands of loops around the Sun down near Mercury, followed by a close pass of Mercury that tossed it out toward Jupiter, then a close pass of Jupiter tossed it into the outer system to reach that 2300 AU level, then fall back to the Sun, close pass by Jupiter, another close pass by Mercury to keep it low for a few thousand years, lather, rinse, repeat.
Now, it's quite possible that they meant to write (and didn't, because they were idiots who didn't know what the words meant) that perihelion was 80 AU, and aphelion was 2300 AU.
Or someone cut & pasted from two articles to make this article. And one of the articles referred to one object, but the other referred to another....
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Although a planet, by definition of the *word*, is every body orbiting a star!
By that definition, even your momma is a planet.
Come to think about it, she too is by some other definitions, but that's beside the point.
CLI paste? paste.pr0.tips!
With a perihelion of 80, and an aphelion of 2300, Goblin is not a planet, its a comet.
I suggest that we call planet 9 "Pluto". There is another object called "Pluto" but since it isn't a planet, it should be no problem, right?
While all true, the distinction is generally only in how to choose to word our definitions.
I'd say Pluto is closer in "sameness" to Mars than Mars is to Jupiter, yet both Mars and Jupiter have been classified as planets while Pluto has not.
I don't have strong feelings about it either way, and to me anyone with strong feelings I view with suspicion. Arguing the definition had nothing to do with science and everything to do with language. And in general it seems that the primary reason for declassifying Pluto was that if Pluto was a planet then we'd have "too many" planets.
I find it comical though that the primary theory for Earth's moon formation was that there was a second "planet" orbiting in the same vicinity as Earth 1.0, the two collided, and the combined mass of the two formed current Earth with the debris scattered into orbit forming the moon. That means that by the current definition, neither of those bodies were planets prior to them colliding, since until that point neither had cleared out their orbit.
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