Astronomers Find New Object, Possible Super-Earth in Our Solar System | Hacker News Reader

Astronomers Find New Object, Possible Super-Earth in Our Solar System

forbes.com

57 pointsalistairSH17 comments

Take it with a grain of salt. The reaction of the astronomer community is much more skeptical than this article leads you to believe. The paper in question, for instance, has been "withdrawn until further data is available" from arxiv.

There are many who think it can be an issue of data reduction - i.e. the process that leads from the raw instrument data to a publication-grade result.

http://www.astronomy.com/news/2015/12/a-new-planet-in-the-ou...

> As Caltech astronomer Mike Brown pointed out via Twitter, "Fun fact: if it is true that ALMA accidentally discovered a massive outer solar system object in its tiny tiny tiny field of view, ... that would suggest that there are something like 200,000 earth sized planets in the outer solar system. Which, um, no."

> The far more likely possibility is that the astronomers captured one of the many icy objects floating beyond Pluto in the Kuiper Belt and the far-flung Oort Cloud. There are millions of such objects, ranging in size from less than a mile in diameter to almost 1,500 miles.

Mike Brown: Obvious attempt at snark is obvious.

No it wouldn't suggest there are 200,000 earth sized planets in the outer solar system. Don't be absurd. The situation does seem reminiscent of how Clyde Tombaugh discovered Pluto (accidentally discovered a massive (compared to other nearby objects) outer solar system object in the Lowell Observatory telescope's tiny tiny field of view, no computer help either), but while it is possible that thousands of Kuiper Belt objects on the scale of Pluto exist (we've only discovered three or four so far because they would be so difficult to detect), hundreds of thousands of earth sized planets would have already collapsed gravitationally. Don't be absurd.

Another possibility (unless they've already ruled it out) is that it's a rogue planet passing through the Oort cloud. I don't know if thousands of them are any more plausible than thousands of gravitationally bound planets, but supposedly rogues outnumber star-bound planets. They would be spread pretty thin depth-wise and hard to detect.

His argument seems sound; I guess you may debate only the numbers. I would assign an a priori distribution of celestial objects on near the solar system concentrated on the the planetary plane, so this effect may compensate a narrow f.o.v. to some extent. Still, for a narrow enough field of view, you can make the argument that the probability of observation will be too low regardless of the a priori distribution details -- leading to the (possibly absurd) conclusion that many more planets probably exist. I'm just an amateur, but I believe old telescopes had a fairly wide f.o.v.; this is in part because their resolution doesn't even allow too much magnification. I assume they also had very flexible directing so you could survey large patches of the sky if necessary (and in particular you could concentrate around the planetary plane if you're eager for solar system objects).

Mike Brown discovered those "three or four" Kuiper belt objects to which you refer (at least if you're thinking of Eris, Sedna, and Haumea) and has the credentials to snark all that he wants to.

His book, "How I Killed Pluto And Why It Had It Coming", is a great read, highly recommended.

ALMA images are about 2000x2000. Its resolution is 0.01 arcsec. It has a planar angle field of view of about 20 arcsec horizontally, and 20 arcsec vertically, for a solid angle field of view of 9.4e-9 steradian, or 7.5e-10 of the entire sky.

Mike Brown implies his napkin-math yields 200000 Earth-scale planets in the outer solar system. If they have uniform density, that would be 15915.5 per steradian. That would give a probability of 1.5e-4 for such a planet to be in the field of view of any given ALMA image.

So ALMA would have to take 20000 non-overlapping images to have a 95% chance of imaging one such planet. I was unable to find a public source for the total amount of sky ALMA has surveyed over the last 2.5 years, but a mean 22 non-overlapping images per 24 hours at maximum resolution doesn't seem impossible.

If we assume that ALMA had only a 1% chance of capturing an image of such an object in 20000 tries, that yields a probability of 5.0e-7 per image, 53 planets per sterad, or 672 planets total.

With only a 0.001% chance, it's 5.0e-10 per image, .053 per sterad, and 0.67 in the entire sky. That's more reasonable, but it also means that ALMA either did not actually see an Earth-sized planet, or that it got extraordinarily lucky this time, as the only planet-sized object out there crossed its field of view once during its 2.5 years in operation. It would be like a sasquatch photobombing just one of your 20000 vacation pictures.

In order to see distant objects better, you have to either narrow your field of view or build a bigger telescope. As such, we really have no idea how many discrete, dark, cold objects are out there from 50-1000 AU, because no one has surveyed the entire sky with enough detail to resolve those objects in the spectrum viewed by the telescope.

For reference, 200000 Earth-sized planets would be approximately equal to the mass of the sun. The entire Oort cloud is estimated at maybe 5 Earth masses total.

So if there are cold Earth-sized planets out there beyond the heliopause, the chances of us detecting any of them visually from Earth are vanishingly small. They are too cold for infrared imaging, have too little mass and too much distance to affect more visible objects via gravity, and too little volume to detectably occlude a brighter object in the background.

Not an expert here, but Forbes doesn't seem like the go-to site for astronomy news.

Makes you feel a little uneasy, finding something so large right in our neighborhood. Like finding a cold campfire by your back fence.

Yeah, if it ends up being large. The other explanations seem more likely. Either way, it does make me feel really small in the overall scheme of the universe.

> Like finding a cold campfire by your back fence.

Great simile!

There's some great discussion about whether or not this is a real discovery on the Unmanned Spaceflight forum: http://www.unmannedspaceflight.com/index.php?showtopic=8127&...

Consensus seems to be similar to the superliminal neutrino claim a few years back - probably not a real signal, but worth tracking down further on the extreme off chance that it is.

Wow. A Nemesis star or Nibiru planet possibly?

https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)

https://en.wikipedia.org/wiki/Nibiru_cataclysm

It would be exciting to have large bodies out further and further from our planet. Like stepping stones to the stars.

I wonder how they found something so small and far out. It's almost like something wanted us to discover it ;)

"Their main immediate abode is a still undiscovered and almost lightless planet at the very edge of our solar system—beyond Neptune, and the ninth in distance from the sun. It is, as we have inferred, the object mystically hinted at as “Yuggoth” in certain ancient and forbidden writings; and it will soon be the scene of a strange focussing of thought upon our world in an effort to facilitate mental rapport. "

Correct me if I'm wrong, but shouldn't objects in 'our solar system' orbit around our sun? Sounds like these objects are in the Alpha Centauri solar system, which is one of our closest neighbours in the Milky Way galaxy. It'll be an interesting find if it turns out to exist, but the distinction between solar system and galaxy is important, as it changes it from somewhere we could feasibly visit to an object we can only see through telescopes (bar some sort of revolution in space propulsion).

The object is merely in the direction of the Alpha Centauri system. If it's in that system, given its brightness, it would probably be a red dwarf, and we would have found it years ago. Assuming it's not just an imaging glitch, it must be either a larger object farther away (very unlikely given its motion), or a smaller and closer body. More observations would be needed to distinguish among the possibilities.

This might help

https://www.youtube.com/watch?v=wLKtG6sy13o

The solar system is bigger than pluto's orbit (a few light hours)... A lot bigger.

Theoretically, the diameter could be as big as one light year in diameter.

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