It’s neither. It’s evidence, an early pre-discovery stage of science. When you get evidence you then have to follow up with more observations, in the hope of finding something, but not all evidence leads to discovery. You get many false leads in science, just through confusing and inevitable coincidences.
They said there’s 1 chance in 15,000 of the orbits of the other minor planets getting into their current configuration by chance. That might seem like a sure thing - in ordinary life if someone said they thought there were 99.9933…% sure of something, you’d say it is surely true. But in science you need much higher levels of confidence than that to claim a discovery.
The reason is that there are thousands of astronomers out there, and every year they each trawl through vast amounts of data. So, from time to time they are bound to turn up a 1 in 15,000 chance as just a coincidence. Indeed you’d expect that to happen maybe several times a year even. And the most striking ones get published.
So, it’s not at all a proof. And if it is real, not just a coincidence, the planet idea is only “an explanation” - there may be many. For instance a more recent idea is that it could be due to several smaller planets in different orbits not just one large planet.
It’s “3.8 sigma”. In particle physics,where they collect vast amounts of data, they will get three sigma results all the time and aim for five sigma for discovery announcements. 5 sigma is also the threshold for announcing a discovery or observation in “Physics Review Letters”, while three sigma would be “evidence”. See Does 5-sigma = discovery?
“Others, like planetary scientist Dave Jewitt, who discovered the Kuiper belt, are more cautious. The 0.007% chance that the clustering of the six objects is coincidental gives the planet claim a statistical significance of 3.8 sigma—beyond the 3-sigma threshold typically required to be taken seriously, but short of the 5 sigma that is sometimes used in fields like particle physics. That worries Jewitt, who has seen plenty of 3-sigma results disappear before. By reducing the dozen objects examined by Sheppard and Trujillo to six for their analysis, Batygin and Brown weakened their claim, he says. “I worry that the finding of a single new object that is not in the group would destroy the whole edifice,” says Jewitt, who is at UC Los Angeles. “It’s a game of sticks with only six sticks.””
from: Astronomers say a Neptune-sized planet lurks beyond Pluto
The next stage is to search for it using the very sensitive Subaru telescope in Hawaii
The Subaru telescope, on Mount Kea in Hawaii, with a wide field of view and sensitive to faint sources, probably has best chance of spotting this new Planet X.
Any of the very large telescopes could spot it but most are in the Southern hemisphere. Subaru could spot it throughout most of its orbit unless it is very distant or at the lowest end of the size range. They would need fifty nights of observation to do the search - which may not seem a lot but fifty complete nights on a big telescope competing with all the other researchers is a huge amount. And you can’t just buy the time but have to put a research proposal and get it accepted.
They are hunting for it though, and as a part of other searches, also searching for other possible objects out there - if they found an object that is not perturbed in the way it should be, that could disprove this planet X as well. Or they could get more evidence for it.
To find out more:
- On the hunt for a mystery planet (Scientific American - the 50 nights figure comes from here)
- How Astronomers Could Actually See "Planet Nine"
- How Astronomers Could Actually See 'Planet Nine' (the ten nights figure is from here)
- Planet Nine - Direct Detection (wikipedia)
- Planet Nine - Alternative hypotheses (wikipedia)
- New clues in search for Planet Nine - possible evidence of synchronization between the dwarf planets which may help narrow down where it is, if it exists, especially if we find new objects also synchronized in the same way
- Researchers find evidence of a real ninth planet
If they get more evidence about where to look, they could use longer exposures. and so find it even if it is only the size of Earth and at the furthest point in its orbit.
For more about Planet X, see my
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