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#40
by
hop
on 11 Dec, 2015 18:12
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A not all the quotes are anonymous.
B You preclude the fact that some of the comments may also be by experts.
C Because of course Twitter is such an effective forum to debate scientific papers in the first place.
You can quibble with how Brown worded it, but his basic point is obviously correct: These things being real requires that the ALMA observations got stupendously lucky, or an implausible population, or both.
The fact that the ALMA people claim to have seen
two of these things (with at least one author common between the two papers) should really ring alarm bells. If you read the papers, you also find that additional unlikely coincidences are required to explain the apparent motion of these things and why these things weren't seen before.
Brown is far from the only outer solar system expert calling this out as implausible, pretty much everyone in the field I've seen comment has been similarly skeptical.
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#41
by
Star One
on 11 Dec, 2015 19:27
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A not all the quotes are anonymous.
B You preclude the fact that some of the comments may also be by experts.
C Because of course Twitter is such an effective forum to debate scientific papers in the first place.
You can quibble with how Brown worded it, but his basic point is obviously correct: These things being real requires that the ALMA observations got stupendously lucky, or an implausible population, or both.
The fact that the ALMA people claim to have seen two of these things (with at least one author common between the two papers) should really ring alarm bells. If you read the papers, you also find that additional unlikely coincidences are required to explain the apparent motion of these things and why these things weren't seen before.
Brown is far from the only outer solar system expert calling this out as implausible, pretty much everyone in the field I've seen comment has been similarly skeptical.
It's not necessarily disagreeing with the basic point but rather with how it was delivered.
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#42
by
Moe Grills
on 11 Dec, 2015 19:32
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I remember when Sedna was discovered, and 10 years later we've found this new object that orbits even further out.
If this leads to a "super-Earth" it could be our first glimpse of this kind of planet, there have been so many found orbiting other stars but not ours.
A super-Earth way out there would likely have a dense atmosphere because of its strong gravity and brutal cold temperatures (example: Titan). A 22'd Century parachute probe anyone?
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#43
by
notsorandom
on 11 Dec, 2015 20:41
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I remember when Sedna was discovered, and 10 years later we've found this new object that orbits even further out.
If this leads to a "super-Earth" it could be our first glimpse of this kind of planet, there have been so many found orbiting other stars but not ours.
A super-Earth way out there would likely have a dense atmosphere because of its strong gravity and brutal cold temperatures (example: Titan). A 22'd Century parachute probe anyone?
It is so cold out that far that any atmosphere has likely frozen out long ago.
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#44
by
Bob Shaw
on 11 Dec, 2015 21:23
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Also, it is really important to examine the effects of a close flyby of a brown dwarf or similar small object. What happens to distant orbits if a 100-Jupiter mass object passed 1 lightyear from the Sun a billion years ago?
A close pass by something reasonably massive has often been proposed as the cause of the Late Heavy Bombardment, but so far as I recall most such claims were made before the more recent descriptions of the presumed orbital migration of the outer planets and their consequent effects on smaller bodies - and these migrations don't seem to be caused by passing brown dwarfs. If there's a single thing to have come out of extrasolar planet discoveries it is the fact that not all star systems have the same distribution of bodies as our own, so things certainly are varied out there - star systems are no longer neat.
Having said that, the Sun orbits the Milky Way once every 250 million years, which opens up all sorts of opportunities for interactions with other stars and free-floating 'planets' and bigger 'things'. There's generally a logarithmic distribution of objects out there, as shown by crater sizes, so we should expect many, many times more small objects to be out there than big ones. If I was looking for non-radiating massive bodies then I'd start looking in areas like molecular clouds, where a transiting body might leave a turbulent trail.
One interesting question regarding Super Earths is the matter of internally generated heat; unlike gas giants and ice giants, radioactive decay should play a big part in keeping such bodies 'warm' internally. I doubt, however, if greenhouse gas effects will be very effective without an external radiant heat source and with an infinite cold trap sucking heat away, so the surface should still be generally cold. Nevertheless, a Super Earth might have volcanic activity, impact basins, and the rest - and perhaps even be an abode of life.
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#45
by
jgoldader
on 12 Dec, 2015 11:00
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An historical fact in astronomy is that when you open up a new bit of observational phase space, through, say, great increases in sensitivity, resolution, or new wavelengths, you find new things. *If* those detections are real, perhaps it's some new phenomenon entirely, and not in the solar system at all.
This could also be an astronomical analog of the irreproducible medical studies. With enough samples, eventually you'll get false hits. Nobody necessarily screwed up.
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#46
by
Star One
on 12 Dec, 2015 12:15
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Is there any plans for another instrument similar to ALMA, then at least you might be able to get some independent secondary validation?
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#47
by
as58
on 12 Dec, 2015 12:49
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Is there any plans for another instrument similar to ALMA, then at least you might be able to get some independent secondary validation?
ALMA is by far the most expensive astronomical instrument on Earth (I think it has cost about $1.2B), so you won't be seeing a copy soon. The problem with these observations is that there's currently really nothing except ALMA that has the sensitivity and resolution to confirm (or disprove) this. Not sure if even JWST would help, if the objects are very cold.
All astrophysical explanations (extreme TNOs, rapidly varying background sources etc.) seem unlikely, so of course the possibility of some sort of artefact with ALMA or processing of observations must be considered (and that is also mentioned in the papers). On the other hand, the detections are fairly strong, so it'd be strange and disconcerting if ALMA produces such spurious sources.
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#48
by
Star One
on 12 Dec, 2015 18:34
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Is there any plans for another instrument similar to ALMA, then at least you might be able to get some independent secondary validation?
ALMA is by far the most expensive astronomical instrument on Earth (I think it has cost about $1.2B), so you won't be seeing a copy soon. The problem with these observations is that there's currently really nothing except ALMA that has the sensitivity and resolution to confirm (or disprove) this. Not sure if even JWST would help, if the objects are very cold.
All astrophysical explanations (extreme TNOs, rapidly varying background sources etc.) seem unlikely, so of course the possibility of some sort of artefact with ALMA or processing of observations must be considered (and that is also mentioned in the papers). On the other hand, the detections are fairly strong, so it'd be strange and disconcerting if ALMA produces such spurious sources.
I didn't realise it was so costly. Just must hope that technology might drive the cost down in future & someone may instigate another facility otherwise you're going to keep getting the issues associated with single source detections.
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#49
by
JamesG123
on 12 Dec, 2015 23:30
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Also blogs. Comments on blogs are usually reliable and accurate and unbiased.
And Web discussion forums?
This (the extent of the outer solar system/ort cloud) reminds me of that scene from "Finding Nemo" (yes, I have little kids) when they are going down into the abyss and Dory says, "It just keeps going doesn't it?"
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#50
by
AegeanBlue
on 13 Dec, 2015 03:02
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ALMA is by far the most expensive astronomical instrument on Earth (I think it has cost about $1.2B), so you won't be seeing a copy soon. The problem with these observations is that there's currently really nothing except ALMA that has the sensitivity and resolution to confirm (or disprove) this. Not sure if even JWST would help, if the objects are very cold.
I was wondering if the Event Horizon Telescope would help. I know it is still in the making, getting all the telescopes all over the globe to actually work at the same time but perhaps it could help. The other telescope I am thinking would be the Allen Telescope Array after phase 4. I know that they have been having trouble fundraising to keep it running on phase one, let alone expand but perhaps it could rival ALMA when completed
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#51
by
Bubbinski
on 13 Dec, 2015 03:20
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How could ALMA do a good follow up on this, if there's no other telescope like it that can be used? If a different team of scientists runs an observing program on ALMA and finds this same object a few months from now, in a slightly different location near where it was last observed, would that increase the confidence level?
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#52
by
hop
on 13 Dec, 2015 04:06
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The problem with these observations is that there's currently really nothing except ALMA that has the sensitivity and resolution to confirm (or disprove) this. Not sure if even JWST would help, if the objects are very cold.
Should be noted this depends which on which of the scenarios you are looking at. Nothing can replicate the ALMA observations, but if "Gna" really is a ~200-800km centaur, it should be easily observable with existing ground based telescopes. In fact it would be bright enough to argue against this model, but it's possible something big slipped through the cracks.
The other problem for follow up is that the possible orbits are very poorly constrained. Even if JWST could detect say, a super earth in the inner Oort cloud, it would be very tough to argue for the time to do a large scale survey with it.
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#53
by
as58
on 13 Dec, 2015 08:25
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The problem with these observations is that there's currently really nothing except ALMA that has the sensitivity and resolution to confirm (or disprove) this. Not sure if even JWST would help, if the objects are very cold.
Should be noted this depends which on which of the scenarios you are looking at. Nothing can replicate the ALMA observations, but if "Gna" really is a ~200-800km centaur, it should be easily observable with existing ground based telescopes. In fact it would be bright enough to argue against this model, but it's possible something big slipped through the cracks.
The other problem for follow up is that the possible orbits are very poorly constrained. Even if JWST could detect say, a super earth in the inner Oort cloud, it would be very tough to argue for the time to do a large scale survey with it.
Yeah, a large centaur should indeed be easy to detect and as you say, some strange coincidences would be needed to explain why it hasn't been seen before. I don't think anyone will (or should) get time for blind surveys for super-Earths in the Oort cloud with JWST (or ALMA for that matter), the small field of view makes such searches very inefficient.
As for what's next for these two possible objects, I guess if "Gna" is a super-centaur, it'll be seen in some large scale optical survey sooner or later. At least by LSST, if not before. If it's some other kind of Solar System object farther out, I think it's pretty much ALMA or nothing, but it's hard to argue for ALMA time without knowing where to look. The Alpha Centauri object is moving slower so maybe it could still be within ALMA field of view targeting Alpha Cen (I haven't checked the details though), so maybe a repeat observation in the nearish future could be useful. I guess people are also looking closely at the data to see if they could somehow explain the detection(s) as artefact(s).
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#54
by
as58
on 13 Dec, 2015 08:44
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I was wondering if the Event Horizon Telescope would help. I know it is still in the making, getting all the telescopes all over the globe to actually work at the same time but perhaps it could help. The other telescope I am thinking would be the Allen Telescope Array after phase 4. I know that they have been having trouble fundraising to keep it running on phase one, let alone expand but perhaps it could rival ALMA when completed
The two arrays you mentioned are working at much longer (radio) wavelengths. I don't think a cold outer Solar System object would emit much radiowaves. ATA is also too far north at least for Alpha Centauri observations.
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#55
by
jgoldader
on 13 Dec, 2015 12:08
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How could ALMA do a good follow up on this, if there's no other telescope like it that can be used? If a different team of scientists runs an observing program on ALMA and finds this same object a few months from now, in a slightly different location near where it was last observed, would that increase the confidence level?
That's a reasonable suggestion. In one of the two papers linked early on, the authors talked about funding the candidate in subsets of the data, which is about all they could be expected to do. (The other paper just accepted the detections as real.)
I'd hope they have a little director's discretionary time that could be used. I'd do two runs at different times of day, with slightly different pointings, and see if there's a detection at the same RA/DEC.
I'm wondering if this might be some kind of weird sidelobe issue, a "ghost" of a source outside the intended field of view. I never did array work, so have no direct experience with the issues you get with telescope arrays. One would suspect there'd have been work on characterizing that sort of thing during the commissioning phase.
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#56
by
Mongo62
on 17 Dec, 2015 00:48
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Tentative planetary orbital constraints of some scenarios for the possible new Solar System object recently discovered with ALMASome of the scenarios envisaged for the possible new Solar System object, whose discovery with the ALMA facility has been recently claimed in the literature, are preliminarily put to the test by means of the orbital motions of some planets of the Solar System. It turns out that the current ranges of admissible values for any anomalous secular precession of the perihelion of Saturn, determined in the recent past with either the EPM2011 and the INPOP10a planetary ephemerides without modeling the action of such a potential new member of the Solar System, do not rule out the existence of a putative Neptune-like pointlike perturber at about 2500 au. Instead, both a super-Earth at some hundreds of au and a Jovian-type planet up to 4000 au are strongly disfavored. An Earth-sized body at 100 au would have a density as little as ∼0.1−0.01 g cm−3, while an unusually large Centaur or (Extreme) Trans Neptunian Object with linear size of 220−880 km at 12−25 au would have density much larger than ∼1 g cm−3.
So a Neptune-size body at around 2500 AU is not ruled out -- at least not by Saturn's orbital motions.
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#57
by
Star One
on 17 Dec, 2015 06:44
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Tentative planetary orbital constraints of some scenarios for the possible new Solar System object recently discovered with ALMA
Some of the scenarios envisaged for the possible new Solar System object, whose discovery with the ALMA facility has been recently claimed in the literature, are preliminarily put to the test by means of the orbital motions of some planets of the Solar System. It turns out that the current ranges of admissible values for any anomalous secular precession of the perihelion of Saturn, determined in the recent past with either the EPM2011 and the INPOP10a planetary ephemerides without modeling the action of such a potential new member of the Solar System, do not rule out the existence of a putative Neptune-like pointlike perturber at about 2500 au. Instead, both a super-Earth at some hundreds of au and a Jovian-type planet up to 4000 au are strongly disfavored. An Earth-sized body at 100 au would have a density as little as ∼0.1−0.01 g cm−3, while an unusually large Centaur or (Extreme) Trans Neptunian Object with linear size of 220−880 km at 12−25 au would have density much larger than ∼1 g cm−3.
So a Neptune-size body at around 2500 AU is not ruled out -- at least not by Saturn's orbital motions.
Perhaps that's the missing gas giant that some believe was expelled from the Solar System.
http://blogs.discovermagazine.com/badastronomy/2011/11/16/did-jupiter-toss-a-giant-planet-out-of-the-solar-system/
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#58
by
redliox
on 17 Dec, 2015 07:13
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So a Neptune-size body at around 2500 AU is not ruled out -- at least not by Saturn's orbital motions.
Perhaps that's the missing gas giant that some believe was expelled from the Solar System.
http://blogs.discovermagazine.com/badastronomy/2011/11/16/did-jupiter-toss-a-giant-planet-out-of-the-solar-system/
I'd call it a fair possibility. Whatever the object is, they might be able to compute its orbital history in the same way we learned that the gas giants migrated...with this would-be-planet being one of the casualties. If it's the size of Earth or greater odds are it more likely originated within the Solar System instead of the Oort cloud where it would have gained mass more swiftly.
Too early to say yet. It could still be a bright Kuiper-like body or even Alpha Centauri's planet.
Hopefully Hubble can swing into action to help as it did for New Horizons.
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#59
by
notsorandom
on 17 Dec, 2015 15:05
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So a Neptune-size body at around 2500 AU is not ruled out -- at least not by Saturn's orbital motions.
Perhaps that's the missing gas giant that some believe was expelled from the Solar System.
http://blogs.discovermagazine.com/badastronomy/2011/11/16/did-jupiter-toss-a-giant-planet-out-of-the-solar-system/
I'd call it a fair possibility. Whatever the object is, they might be able to compute its orbital history in the same way we learned that the gas giants migrated...with this would-be-planet being one of the casualties. If it's the size of Earth or greater odds are it more likely originated within the Solar System instead of the Oort cloud where it would have gained mass more swiftly.
Too early to say yet. It could still be a bright Kuiper-like body or even Alpha Centauri's planet.
Hopefully Hubble can swing into action to help as it did for New Horizons.
According to WISE data (and Phil Plat) there can't be a Jupiter sized object closer than 20,000 AU or a Saturn sized object closer than 10,000 AU. Any object that big would be too warm to have escaped notice by WISE. These proposed objects discovered by ALMA if closer need to be smaller and cooler than a gas giant. A Neptune sized object would be smaller and cooler than Saturn but I am unsure if it could be as close at 2,500 AU and not be seen by WISE.
