Wednesday, February 29, 2012

Mysterious solar system object 2012 DR30: period ~50,000 years, inclination 75°, perihelion 14 AU

You know that something important has been discovered in the solar system when Mike Brown is tweeting every few minutes about it - which yesterday was the case with 2012 DR30: the originally pubished orbit from Feb. 26 (at first revised slightly only) had a semimajor axis of 160 AU, corresponding to a period of ~2000 years, but Brown has heard that the semimajor axis could be 1400 AU which would mean a periode of roughly 50,000 years. This is based on an arc from Jan. 3 til Feb. 28: If true, the eccentricity would be 0.99 (instead of 0.91), since the perihelion distance is only 14 AU - 2012 DR is about as close as it gets to Sun & Earth now. But why wasn't it found earlier? The body - with an absolute magnitude of 7.2 roughly 200 km in diameter shines at 18th magnitude now, easily caught by several amateur astronomers who found it to be star-like without a coma. Yet the high-inclination orbit with i~75° (diagram), the huge eccentricity and perhaps a sudden turn-on would surely speak for a cometary nature. Observations with big telescopes are now called for to find out. Incidentally there is another asteroid on a comet-like orbit, but the elements of 2011 YU75 are not nearly as extreme.

In other small bodies news comet Lovejoy on Feb. 22/23 was a tail without a comet while on Feb. 21 it had looked pretty normal - most observers have lost it now because of the low surface brightness. • Comet Holmes - the one with the big outburst in 2007 - has been imaged at 21 mag. on Feb. 24. • Comet Garradd still sports three tails as seen in pictures from Feb. 28, Feb. 27, Feb. 26 (more), Feb. 22, Feb. 21 (with a disconnection event), Feb. 20 (more) and Feb. 19 (more); also a collage spanning many months showing the changing tail geometry - which some don't get (see comment 8!) what others then copy ...

Among the planets Mars is approaching opposition on March 3rd - and despite it being about as far away from Earth as possible, some nice pictures have been obtained, e.g. on Feb. 26, Feb. 25, Feb. 20, Feb. 19 and other dates. • There was a nice constellation of the Moon, Venus & Jupiter on Feb. 24-26 (also on Feb. 27; more and more pics - and the Moon only 18 hours old on Feb. 22 and Jupiter on Feb. 10/11). • A NEO of radar interest in 2013 is 2012 DA14, of which more observations are needed - dito for 2011 AG5 which has a small impact probability of 1:625 in 2040 (causing unnecessarily alarmist headlines here, here and hier - bored of Apophis, eh?). • And why were there so many fireballs in February, all unrelated?

The Sun was partially eclipsed by the Moon but only for the SDO on Feb. 21 - also an animation of the May ASE. • There were 5 eruptions on the Sun in rapid sequence but no low-latitude auroral comsequences. • The temporary loss on an amateur dish receiving STEREO quick data (see also here and here) was mildly worrying, this blog has confirmed. • Feb. 19 aurora over Ireland, a rocket launch during an aurora, the Jan. 22 aurora from the Shetlands (from this site), ISS aurora video also featuring a nightly impactcrater and an astronaut-endorsed older ISS aurora video with 3D-like effect. • A timelapse video from Paranal and how it was made, a crazy sunrise (also discussed here) and universal scales interactively animated. • The highlights of March include the Mars opposition, the evening apparition of Mercury and the close approach of Venus & Jupiter on March 13.

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