Main Belt object 596 Scheila in outburst on 15 Dec. 2010. 
Credit: NASA/Swift and Dennis Bodewits.

Last December's discovery by the Catalina Sky Survey of Main Belter 596 Scheila's sudden comet-like appearance was followed up immediately by amateur observers (see links) and soon from the Swift mission using its Ultraviolet/Optical Telescope (UVOT), as seen here, and later from the Hubble Space Telescope, as reported yesterday in news items from NASA HQ, HubbleSite, and NASA/GSFC. "The absence of gas around Scheila led the Swift team to reject scenarios where exposed ice accounted for the activity," and the simplest explanation is impact by an unknown small asteroid. Image credit: NASA/Swift and Dennis Bodewits (UMD).

Contents  on 29 April '11


The latest A/CC news is available via framed access, RSS news feed RSS news feed, or redirection. - Note: A/CC has a main Web site and also a backup site with its own duplicate RSS news feed.

Navigation tips: Use the << and >> arrows on the menus for each regular section (Observers, Risks, etc.) to move to the previous and next day's news for that section. Use the Index menu item to access specific days through a calendar interface. And use the all-up news archive to access news from any time since A/CC began in early 2002. To keep track of what's new each day, watch the Chronology section.

NEOCP Activity  on 29 April '11

The Minor Planet Center's Near Earth Object discovery Confirmation Page (NEOCP) was not checked on this day.

New MPECs  on 29 April '11

Minor Planet Electronic Circulars

There were four MPECs posted this day from the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts.

MPEC 2011-H54 - "21:13 UT" - 2010 JU39

MPEC 2011-H53 - "21:01 UT" - 2011 HL7

MPEC 2011-H52 - "20:56 UT" - 2011 HJ7

<< DOU on 29 Apr. '11 >>  MPEC 2011-H51 - "07:07 UT" - Daily Orbit Update

Observers  on 29 April '11

A total of 20 observers appeared in this day's MPECs.

CodeObserver / observatory
H21Astronomical Research Obs. Westfield in Illinois, 1 in MPEC 2011-H54 -- 2010 JU39
160Castelmartini Obs. in Italy, 6 in MPEC 2011-H51 -- 2011 GL62, 2011 EZ78, 2011 AO52, 188174, 163250, 137170
703Catalina Sky Survey (CSS) in Arizona, 6 in MPECs 2011-H51 & 2011-H53 -- 2011 HL7, 2010 TV149, 37336, 256670, 256412, 248083
807|Robert Holmes via Cerro Tololo Inter-American Obs. (CTIO) in Chile, 10 in MPECs 2011-H51 & 2011-H53 -- 2011 HT, 2011 HS, 2011 HP, 2011 HO4, 2011 HL7, 2011 HJ, 2011 HH, 2011 GP65, 2011 GH62, 2011 GD62
A77Chante-Perdrix Obs. in France, 1 in MPEC 2011-H51 -- 2011 GL60
J18Churchstoke Obs. in Wales, 1 in MPEC 2011-H51 -- 2011 GD60
448Desert Moon Obs. in New Mexico, 2 in MPEC 2011-H51 -- 2011 HP, 271480
F657Paul Roche in Wales via Faulkes Telescope North in Hawaii, 1 in MPEC 2011-H54 -- 2010 JU39
E10Faulkes Telescope South in New South Wales, 1 in MPEC 2011-H51 -- 2011 GN44
704LINEAR in New Mexico, 1 in MPEC 2011-H53 -- 2011 HL7
B67Mirasteilas Obs. in Switzerland, 1 in MPEC 2011-H51 -- 274138
474Mt. John Obs. in New Zealand, 1 in MPEC 2011-H53 -- 2011 HL7
G96Mt. Lemmon Survey (MLS) in Arizona, 4 in MPECs 2011-H51, 2011-H52 & 2011-H53 -- 2011 HL7, 2011 HJ7, 2009 CA2, 159923
A24New Millennium Obs. in Italy, 10 in MPEC 2011-H51 -- 2011 DS9, 2011 CH71, 260141, 256412, 23183, 228368, 22771, 198856, 3554, 1864
F51Pan-STARRS 1 (PS1) in Hawaii, 5 in MPEC 2011-H51 -- 1998 SR49, 24445, 152941, 11311, 6037
H06%Ernesto Guido in Italy via RAS Obs. Mayhill in New Mexico, 1 in MPEC 2011-H53 -- 2011 HL7
H06|Hidetaka Sato in Japan via RAS Obs. Mayhill in New Mexico, 1 in MPEC 2011-H53 -- 2011 HL7
H36Sandlot Obs. in Kansas, 1 in MPEC 2011-H53 -- 2011 HL7
691Spacewatch 0.9m telescope in Arizona, 3 in MPEC 2011-H51 -- 2004 FU4, 1998 HK49, 1866
291Spacewatch 1.8m telescope in Arizona, 11 in MPECs 2011-H51 & 2011-H52 -- 2011 HT, 2011 HJ7, 2011 GO27, 2011 GN44, 2011 GJ62, 2011 GH44, 2011 GH3, 2011 GD3, 2011 GB, 2011 FS6, 2011 FR17
I93St. Pardon de Conques Obs. in France, 1 in MPEC 2011-H53 -- 2011 HL7
For a list of all participating observatories that have Web addresses, see A/CC's Observatory Links page.

Impact Risk Monitoring  on 29 April '11

Summary Risk Table for Risk Assessments Updated Today   (last checks: NEODyS and JPL at 2359 UTC)
See the CRT page for a list of all objects rated recently as risks and our ephemerides page for a list of risk-listed objects under current observation.
The time horizon for JPL is 100 years from today and for NEODyS is usually the year 2090. Both also post impact solutions beyond 100 years for a few special objects.
For the latest official risk assessments, and for explanations of the terminology, see the JPL NEO Program Sentry and NEODyS CLOMON (backup) risk pages.





Notes for Today's Latest Risk Assessments
2011 HJ7JPL Sentry23592018-208865.5e-09-6.13-6.420JPL: "Analysis based on 12 observations spanning 3.0608 days (2011-Apr-26.21907 to 2011-Apr-29.2799)." Diameter approximately 0.129 km. from mean, weighted H=22.2.
2011 HO5NEODyS14002024-208681.56e-06-5.14-5.590NEODyS: "Based on 15 optical observations (of which 0 are rejected as outliers) from 2011-04-27.400 to 2011-04-28.473."
2011 GN44JPL Sentry1400206811.1e-07-3.34-3.340JPL: "Analysis based on 47 observations spanning 25.774 days (2011-Apr-03.44279 to 2011-Apr-29.21699)." Diameter approximately 0.710 km. from mean, weighted H=18.4.
NEODyS14002068-206815.9e-08-3.57-3.570NEODyS: "Based on 47 optical observations (of which 0 are rejected as outliers) from 2011-04-03.444 to 2011-04-29.218."

Legend: VI# = VI count, Prob Cum = cumulative probability, PS Cum/Max = cumulative/maximum Palermo Scale, TS = Torino Scale

An impact solution, also known as a "virtual impactor" (VI), is not a prediction but rather a possibility derived from a variant orbit calculation that cannot be eliminated yet based on the existing data. Elimination can come quickly with just a little further observation or may take weeks or months, sometimes years. Once superceded or eliminated, a former impact solution has zero relevance to an object's risk. See Jon Giorgini's "Understanding Risk Pages" to learn more.

Chronology  on 29 April '11

Times are UTC for when items were noted or added by The Tracking News.

2359Noted that JPL Sentry has posted 2011 HJ7 as an impact risk - see above
Grabbed MPEC 2011-H52 - 2011 HJ7 - see above
Grabbed MPEC 2011-H53 - 2011 HL7 - see above
Grabbed MPEC 2011-H54 - 2010 JU39 - see above
1400Noted that JPL Sentry has updated its 2011 GN44 risk assessment - see above
Noted that NEODyS has updated its 2011 GN44 risk assessment - see above
Noted that NEODyS has posted 2011 HO5 as an impact risk - see above
Grabbed MPEC 2011-H51 - Daily Orbit Update - see above