WISE, a mission that will find ALL the neighbours |
WISE, a mission that will find ALL the neighbours |
Guest_PhilCo126_* |
Nov 27 2009, 08:42 AM
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#16
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Guests |
Greg, the onboard frozen Hydrogen is expected to last 10 months, allowing WISE to map most of the sky a second time in order to see what has changed. So only a partial 2nd survey should be possible...
Launch is now set to 9th December |
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Nov 27 2009, 06:48 PM
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#17
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
I guess I'm counting on even that number having some safety factor in it. :-)
Something else I've thought about recently is that two observations six months apart aren't enough to characterize an orbit. Even if it finds thousands of new asteroids, the fact that we can't observe them from the ground seems to limit the immediate usefulness of the data. Or perhaps it's hoped it could justify a followup mission a few years later? Or maybe just offer good initial targets for Pan-STARRS. My personal hope is still that it finds a brown-dwarf companion to the sun that offers some explanation for things like the orbit of Sedna and the abrupt edge of the Kuiper belt -- not to mention a REALLY great flagship mission target. And even if not, WISE ought to be able to absolutely rule out the possibility of such a thing. We're probably still a good year away from any results, I guess. Unless they really DO find that brown dwarf. --Greg |
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Nov 27 2009, 10:22 PM
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#18
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
When is a brown dwarf a black dwarf? When it no longer emits any visible light at all? If they find any of those nearby I think Herschel will be on the case.
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Nov 27 2009, 10:39 PM
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#19
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
I always thought that a black dwarf was a completely burned-out star, normally a former white dwarf...considerably more massive than a brown dwarf.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Nov 27 2009, 10:56 PM
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#20
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Probably right. I just wanted to make the point that WISE could discover objects close to room temperature. Would it really be appropriate to call them brown dwarfs? If the term 'black dwarf' is to be confined to cooled white dwarfs then we need a new name for cooled brown dwarfs and other objects that were never even hot enough to be brown for any length of time but could still turn up in IR surveys.
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Nov 28 2009, 12:14 AM
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#21
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Junior Member Group: Members Posts: 87 Joined: 17-May 08 Member No.: 4114 |
Something else I've thought about recently is that two observations six months apart aren't enough to characterize an orbit. Existing and future narrow angle instruments should be able to follow up on them. You'd never get Herschel, Keck or VLT time for a large area survey, but they are definitely candidates for followup. |
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Guest_PhilCo126_* |
Nov 28 2009, 10:34 AM
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#22
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Guests |
It isn't just two obsevations six months apart;
There’ll be sufficient overlap, so that each position in the sky gets eight or more independent exposures on successive orbits. |
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Nov 28 2009, 10:48 AM
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#23
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Thing is, what if we have a companion brown dwarf about a 0.5 LY out with an orbital period of 100,000 years or so? Finding such a thing should be easy with WISE, but it may take a decade or more to confirm that it's probably in orbit around the Sun, even longer to derive a decent ephemeris. The problem isn't frequency of observation, it's very low orbital velocities for distant objects.
New Horizons is still trying to work out ephemeris uncertainties for Pluto because it hasn't been observed for even half an orbit since its discovery. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Nov 28 2009, 06:52 PM
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#24
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
Proxima Centauri is 0.21 ly from the Alpha A/B barycenter, and even after 100 years, we're still not QUITE sure it's actually orbiting the other two.
http://en.wikipedia.org/wiki/Proxima_Centauri I'd hope we'd do a BIT better with an object nominally orbiting our own sun, but it'd still take a while. Even with the overlapping observations, I think the trouble with the WISE data will be that it spans just one year. Of course, something that barely moves after one year (like a remote brown dwarf) probably won't get lost easily, but an Earth-crossing asteroid might well be hard to find again. As for black dwarfs, the Universe probably isn't old enough for any to exist yet: http://en.wikipedia.org/wiki/Black_dwarf There are already known brown dwarfs with estimated temperatures as low as 500K: http://en.wikipedia.org/wiki/Brown_dwarf#D...gh_mass_planets It seems plausible that smaller, cooler ones exist and even might be more plentiful than regular stars, given the mass/frequency curve we seem to see everywhere else in the universe. WISE could well find LOTS of brown dwarfs closer to the sun than (say) 4 light years. I guess we'll know in eighteen months or so! --Greg |
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Nov 29 2009, 04:03 AM
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#25
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Junior Member Group: Members Posts: 87 Joined: 9-November 07 Member No.: 3958 |
If the IR broadband signature for brown dwarfs really is distinctive enough, candidates can be followed up with large ground-based telescopes once WISE points them out. That would give much higher angular resolution as well as time baseline. One of the bumper-sticker descriptions of WISE (back when it was NGSS, which someone thought would be too confusing compared to NGST which is now JWST) was that it should discover both the most luminous galaxies and our nearest stellar neighbors; practically something for everybody.
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Nov 30 2009, 06:24 PM
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#26
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Member Group: Members Posts: 166 Joined: 20-September 05 From: North Texas Member No.: 503 |
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Guest_PhilCo126_* |
Dec 10 2009, 10:31 AM
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#27
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Guests |
Launch postponed: The WISE launch is currently scheduled for no earlier than Saturday, December 12th, at 6:09:33 am pacific, from Vandenberg Air Force Base in CA...
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Dec 10 2009, 03:36 PM
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#28
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
...and even that doesn't look likely at this point.
-------------------- If Occam had heard my theory, things would be very different now.
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Dec 10 2009, 11:32 PM
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#29
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
We might want to lower our expectations just a bit for finding brown dwarfs closer than Proxima. There is a distinct possibility for finding none at all.
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Dec 11 2009, 01:05 AM
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#30
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
At least not until after it launches anyway. Which is now set for Sunday the 13th. I'll miss that one, but if it gets bumped over to Monday or Tuesday I might be able to make it again.
-------------------- If Occam had heard my theory, things would be very different now.
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