[2007 OR10] New large dwarf planet candidate announced, spotted at 85AU on Eris-like orbit

h2ouniverse · Jan 8, 2009

2007 OR10 has been announced on Minor Planet Center by M. E. Schwamb, M. E. Brown, D. Rabinowitz.Its absolute magnitude of 2.5 would place it on par with Quaoar (if at same albedo). Its orbit is inclined (30&deg

and eccentric (perihelion 32.7 AU, aphelion 110AU). Period 605 years (potentially consistent with an 11:3 resonance with Neptune, given the low perihelion).Would become the third largest dwarf planet candidate by absolute magnitude [after Sedna H=1.6 and Orcus H=2.3, and before Quaoar H=2.6]. It lies currently at 85.8AU from Sun, and is the third furthest object known in the Solar System after Eris (96AU) and Sedna (87.9AU) with an apparent magnitude of 22. Its orbit may mean a high albedo when close to aphelion like for Eris: in that case its diameter would be close to 500km. But if the albedo is low, the diameter can exceed 1000km.http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007+OR10&orb=1Let's hope we get "images" from Hubble soon, to see whether there are satellite(s)!

h2ouniverse · Jan 11, 2009

The ten « largest » transneptunians by absolute magnitude now become: (after correction of magnitude see post below)1.       Eris (H=-1.2)2.       Pluto (H=-0.7)3.       Makemake (H=-0.3)4.       Haumea (H=+0.2)5.       Charon (H=+1)6.       Sedna (H=+1.6)7.       2007 OR10 (H=+1.9)8.       Orcus (H=+2.3)9.       Quaoar (H=+2.6)10.   2005 QU182 (H=+3.1)The ranking by actual size will vary as absolute magnitude depends on size AND albedo.

h2ouniverse · Jan 13, 2009

News, already!!!Absolute magnitude and orbital parameters have been updated on MPC site and JPL.Now H=+1.9 (variation of 0.6, and no change in assessment of distance to Sun => i.e. +70% on amplitude !!!)perihelion 33.6 AU instead of 32.7aphelion 101 AU instead of 110...=> Period 552 years instead of 605...Would place it close to Sedna's absolute magnitude (hence 88% the size of Sedna if at same albedo). I updated the ranking above, now the seventh TNO by absolute magnitude. Just 0.9 short of the H=1 threshold of the IAU, to be automatically declared a dwarf planet.Given that it had been spotted in July 2007 by Brown's team, studied and observed several times "secretly" during one year and a half before its announcement last week (according to the observation log provided to the MPC), it is beyond my understanding that they now come with new data that are so different (70% on signal amplitude, 10% on aphelion) just one week after their declaration at MPC! May be an independant observation with a more powerful/accurate telescope?This being said, this is rather good news since this means an additional large TNO.Btw, at 552 years, it would be at the same period as Eris (1:1 at better than 1%).

MeteorWayne · Jan 13, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>News, already!!!Absolute magnitude and orbital parameters have been updated on MPC site and JPL.Now H=+1.9 (variation of 0.6, and no change in assessment of distance to Sun => i.e. +70% on amplitude !!!)perihelion 33.6 AU instead of 32.7aphelion 101 AU instead of 110...=> Period 552 years instead of 605...Would place it close to Sedna's absolute magnitude (hence 88% the size of Sedna if at same albedo). I updated the ranking above, now the seventh TNO by absolute magnitude. Just 0.9 short of the H=1 threshold of the IAU, to be automatically declared a dwarf planet.Given that it had been spotted in July 2007 by Brown's team, studied and observed several times "secretly" during one year and a half before its announcement last week (according to the observation log provided to the MPC), it is beyond my understanding that they now come with new data that are so different (70% on signal amplitude, 10% on aphelion) just one week after their declaration at MPC! May be an independant observation with a more powerful/accurate telescope?This being said, this is rather good news since this means an additional large TNO.Btw, at 552 years, it would be at the same period as Eris (1:1 at better than 1%). Posted by h2ouniverse</DIV> I note the JPL Small Body datbase has listed first obs of 2001-??-?? (and also no sigma (+/-) is listed for the magnitude). Perhaps after the announcement a backwards search was done for earlier images that may exist. If it was detected on images from 6 years ago, it could cause a large shift in parameters. At that distance, the movement is quite slow, and there's a lot of uncertainty in both orbit and magnitude. WIth a 7 year long arc, the uncertainly would be greatly reduced.BTW, do you have a link to that observing log?Here's the JPL page:http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007+OR10;orb=1 <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

h2ouniverse · Jan 13, 2009

hi Wayne, Good remark indeed for the JPL mention of a "2001" measurement that would indicate a "pre-covery". Strange though that the date is not mentionned.The log is given by the MPC circular of last week (still at H2.5, so before the update):http://www.cfa.harvard.edu/mpec/K09/K09A42.htmlyou can see it spans from July'07 to Aug '08. The first observations were with a 1.2 telescope. So it's strange that the illumination has been underestimated by a 1.7 factor. Indeed, the assessment of the current distance to Sun has not varied from last week (about 85.8 AU). So the assessment of H should directly reflect the amplitude of the optical signal received. Hence my perplexity... May be it has been induced by difference between red magnitude (in the log) and the blue magnitude.The revision of aphelion is strange given the large number of observations prior to the update.regards...

MeteorWayne · Jan 13, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>hi Wayne, Good remark indeed for the JPL mention of a "2001" measurement that would indicate a "pre-covery". Strange though that the date is not mentionned.The log is given by the MPC circular of last week (still at H2.5, so before the update):http://www.cfa.harvard.edu/mpec/K09/K09A42.htmlyou can see it spans from July'07 to Aug '08. The first observations were with a 1.2 telescope. So it's strange that the illumination has been underestimated by a 1.7 factor. Indeed, the assessment of the current distance to Sun has not varied from last week (about 85.8 AU). So the assessment of H should directly reflect the amplitude of the optical signal received. Hence my perplexity...regards... Posted by h2ouniverse</DIV> Thanx for the link. I see the observed magnitude varies from 21.2 to 21.7. It would be interesting to see what prerecovery images might be included. Who knows, it could be one observation from 2001 with a mag of 21; at that distance it might change the estimated magnitude that much.I'll keep trying to find out more, as I'm sure you will!Wayne <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

h2ouniverse · Jan 21, 2009

Now wikipedia-ed. http://en.wikipedia.org/wiki/2007_OR10About time. Google "2007 OR10" and you will mainly get wacky articles from... astrologers! The astrology / astronomy ratio is still 4 to 1. Sigh. Note that even Space.com has not issued anything after more than two weeks. (Grumble)<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-undecided.gif" border="0" alt="Undecided" title="Undecided" />Given that very recent IR observations tend to confirm Quaoar's reduced size (about 900 +/- 100 instead of 1200-1300 as previously claimed), 2007 OR10 might well be seventh by size too.

h2ouniverse · Jan 30, 2009

At last some coverage in science media (Ciel et Espace is a French-speaking monthly magazine for amateur astronomers and people interested in Space). Still nothing else after 3 weeks! Not even 5 lines on Scientific American or New Scientist. Only astrologers babbling on internet. It's also a test case btw to see how such news propagate. I would bet that as soon as one science medium shows attention, all others will follow within a few days.http://www.cieletespace.fr/evenement/2805_decouverte-d-une-planete-naine-au-dela-de-neptune

h2ouniverse · Feb 10, 2009

At last Mike Brown communicates (a little) on 2007 OR10.http://arxiv.org/PS_cache/arxiv/pdf/0901/0901.4173v1.pdf2007 OR10 was one of the 25 TNOs discovered in his latest survey. The survey aimed at detecting Sedna-like objects (in the dynamic sense: i.e. large objects with perihelion beneath 100 AU and a very very high aphelion). Mike Brown and his team have scanned 30% of the vault with ability to detect objects beneath 1000AU but with apparent mag brighter than 21.3. Finally, 2007 OR10 was not a Sednoid as its aphelion is relatively low (101 AU) and Brown detected no other object than Sedna. His purpose was to constrain the number of Sednoids bigger than Sedna (see figure 3). Note that the most likely figure (statistically speaking) is 40 objects with a brighter H than Sedna (H<1.6). And this is only for objects with q<100AU and Q at about 1000AU. This does not preclude big objects with perihelion q>100AU. Note also that Sedna itself was not far from the limit (an H=1.6 object would have been missed if beyond 93AU, and Sedna is at currently 90...) About 2007 OR10 he writes:"Of the objects found in our survey, only two reside past 80 AU: Sedna and 2007 OR10 (discovered in this survey). "From the discovery observations alone 2007 OR10 cannot be identified as a Sedna-like body on a high-perihelion orbit. Many scattered KBOs have aphelia well outside the planetary region past 50 AU. Both families of orbits provide reasonable fits to the short discovery arc. The two orbital solutions diverge sufficiently within a year after discovery, and a secure dynamical identification can only be made after these additional observations. Follow-up observations from the Palomar 60-inch telescope and the 0.9-m SMARTS telescope at Cerro Tololo between July 2007 and August 2008 confirm that 2007 OR10 is a scattered disk KBO close to aphelia. The best fit orbit yields a semi-major axis of a=66.99 +/- 0.06 AU, an eccentricity of e=.503 +/- 0.001, and an inclination of i=30.804 +/- 0.001 degrees."

MeteorWayne · Feb 10, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>Posted by h2ouniverse</DIV> Thanx for the update.-MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

h2ouniverse · Mar 12, 2009

Re: [2007 OR10] New large dwarf planet candidate announced, spot

hi all,

Mike Brown finally gets out from his silence about this object. He officalises the nickname "Snow White".

http://www.mikebrownsplanets.com/2009/0 ... ilout.html

Apparently a prognosis for a quite bright albedo but no evidence in either direction though. Says he could not find anything special to this object in first approach. I wonder if he has commanded or incited specific observations (spectro).

Danzi · Mar 18, 2009

Re: [2007 OR10] New large dwarf planet candidate announced, spot

Interesting!

I personally doubt it will be classified as a dwarf planet until Sedna is, and i do believe that Sedna is bigger unless I've read something wrong...

Oh well, the family of Dwarf Planets is almost defiantly going to grow and grow!

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[2007 OR10] New large dwarf planet candidate announced, spotted at 85AU on Eris-like orbit

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