Contents  on 21 December '18

Asteroid/Comet Connection (A/CC) Resources:

The latest A/CC news is available via framed access, RSS news feed RSS news feed, or redirection.

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. To keep track of what's new each day, watch the Chronology section.

Traffic Report  on 21 December '18

Eight objects reported inside ten LD

Eight celestial objects are known to be less than ten lunar distances (LD) from our home world today. The nearest is within Earth's sphere of gravitational influence. 2018 XC4 comes its closest to us this time around, reaching 1.60 LD at 1533 UTC.

Neighborhood Traffic - sorted by Earth passage distance, grouped by 1.0, 2.41, 5.0 & 10.0 LD boundaries
Earth passage I D ~Size Distance today  Inside ten LD Notes
0.09 LD Dec. 2 2018 WV1 3 m  8.10 to 8.52 LD Nov. 8 - Dec. 25 intruder, NHATS target
1.60 LD today 2018 XC4 20 m  1.60 LD Dec. 15 - 27 NHATS target, Moon closest 1.72 LD at 0346
UTC, Earth closest at 1533 UTC - DOU
2.62 LD Dec. 15 2018 VO9 14 m  4.36 to 4.87 LD Nov. 29 - Dec. 31 NHATS target, risk
2.76 LD Dec. 16 2018 XS4 31 m  9.40 to 11.25 LD Dec. 11 - 21 exits ten LD - DOU
2.96 LD Dec. 24 2018 XN5 25 m  4.93 from 6.12 LD Dec. 18 - 31 NHATS target, risk
3.92 LD Dec. 2 2018 TG6 12 m  6.45 to 6.68 LD Oct. 30 - Jan. 5 NHATS target
5.32 LD Dec. 17 2018 XR4 15 m  9.45 to 11.67 LD Dec. 14 - 21 exits ten LD, risk
7.36 LD tomorrow 163899 2003 SD220 1.17 km  7.36 from 7.50 LD Dec. 17 - 26 radar/NHATS target - DOU

This report was generated at 2140 UTC with the discovery of already departed 2018 YA1 (MPEC), which slipped past at about 6.9 LD on December 9th, and with follow-up in today's DOU MPEC for inbound 163899 2003 SD220, passing 2018 XC4, outbound 2018 XS4, and three departed objects: 2018 WS and risk-listed objects 2018 XA and intruder 2018 WA3 (1.10 days added to 9.17-day observing arc), plus distant 2007 VD12.

Approaching - sorted by 10-LD bubble entry date
Earth passage I D ~Size Distance today  Inside ten LD Notes
5.3   LD Dec. 26* 2018 XE4 17 m  11.5 from 13.4 LD tomorrow - Dec. 30 EPU +/- 3.33 hours*
7.8   LD Jan. 6* 2018 XO4 29 m  16.0 from 16.7 LD Dec. 30 - Jan. 13 EPU +/- 3.18 hours*, NHATS target
7.3   LD Jan. 9* 2013 YM2 19 m  19.3 from 20.2 LD Jan. 2 - 16 EPU +/- 3.75 days*, NHATS target
* EPU = Earth passage uncertainty



Notes: Ten times the distance to the Moon (ten LD) has no astronomical importance but is a useful boundary for reporting about transient natural objects that approach our planet's gravitational sphere of influence (SOI), which has a radius of about 2.41 LD from Earth's center. This puts a focus on some of the most important and very best NEO observation work, representative of the much larger NEO discovery and tracking effort. "Distant" is used here to describe an object that has come within ten LD since A/CC began these traffic reports (2007) but is not presently so close. Object temporal distances are derived by A/CC from JPL Horizons data. See also current sky chart and object details (alt-details), ephemerides, and today's timeline.

NEOCP Activity  on 21 December '18

The MPC's NEO Confirmation Page has 35 listings

When last checked at 2358 UTC today, the Minor Planet Center's Near Earth Object discovery Confirmation Page (NEOCP) had 35 objects listed. Of these, nineteen were "one nighters." So far The Tracking News has counted a total of 39 listings on the NEOCP today.

To learn how observers use the NEOCP, see the Practical guide on how to observe NEOCP object at Suno Observatory by Birtwhistle et al.

New MPECs  on 21 December '18

Minor Planet Electronic Circulars

As of last check at 2358 UTC, there have been four MPECs posted today from the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts.


MPEC 2018-Y57 - "16:20 UT" - 2018 YA1


MPEC 2018-Y56 - "16:16 UT" - 2018 YY


MPEC 2018-Y55 - "16:07 UT" - 2018 YZ


<< DOU on 21 Dec. '18 >>  MPEC 2018-Y54 - "13:07 UT" - Daily Orbit Update

Observers  on 21 December '18

A total of 21 observers appear in today's MPECs.

CodeObserver / observatory
H21Astronomical Research Obs. Westfield in Illinois, 21 in MPEC 2018-Y54 -- 2018 XZ2, 2018 XY4, 2018 XY2, 2018 XR, 2018 XN, 2018 XD, 2018 XC4, 2018 XB2, 2018 XA, 2018 WS, 2018 WO2, 2018 VJ5, 2018 VC5, 2018 UQ2, 2018 TC3, 2018 RR7, 2018 OB1, 2018 DF2, 2012 BN11, 2009 CR5, 177016
T05ATLAS Haleakala in Hawaii, 4 in MPEC 2018-Y54 -- 2018 XR, 2012 MS4, 2010 AK, 2009 SV17
T08ATLAS Mauna Loa in Hawaii, 2 in MPEC 2018-Y54 -- 523811, 345722
160Castelmartini Obs. in Italy, 2 in MPEC 2018-Y54 -- 96315, 457260
703Catalina Sky Survey in Arizona, 1 in MPEC 2018-Y57 -- 2018 YA1
807|Robert Holmes in Illinois via Cerro Tololo Inter-American Obs. in Chile, 1 in MPEC 2018-Y56 -- 2018 YY
157Frasso Sabino Obs. in Italy, 1 in MPEC 2018-Y54 -- 2012 MM11
E89Geyserland Obs. in New Zealand, 1 in MPEC 2018-Y54 -- 140928
695^Spacewatch via Kitt Peak Natl. Obs. (KPNO) in Arizona, 6 in MPECs 2018-Y54 & 2018-Y55 -- 2018 YZ, 2018 XY3, 2018 XW5, 2018 XE5, 2018 VX8, 2018 LB1
W85LCO Cerro Tololo A in Chile, 1 in MPEC 2018-Y54 -- 2012 MM11
W87LCO Cerro Tololo C in Chile, 1 in MPEC 2018-Y54 -- 418849
C94MASTER-II Tunka in Russia, 1 in MPEC 2018-Y54 -- 18736
G96Mt. Lemmon Survey in Arizona, 1 in MPEC 2018-Y54 -- 2015 ET3
Z80Northolt Branch Obs. in England, 1 in MPEC 2018-Y54 -- 163899
F51Pan-STARRS 1 (PS1) in Hawaii, 9 in MPECs 2018-Y54, 2018-Y55 & 2018-Y56 -- 2018 YZ, 2018 YY, 2018 YJ, 2018 XS4, 2018 XH, 2015 ET3, 2005 YY36, 2000 AA6, 164120
C95SATINO-1 in France, 3 in MPECs 2018-Y54 & 2018-Y57 -- 2018 YA1, 2012 MM11, 2004 XP14
K96Savelli Obs., 1 in MPEC 2018-Y57 -- 2018 YA1
691Spacewatch 0.9m telescope in Arizona, 7 in MPECs 2018-Y54 & 2018-Y57 -- 2018 YA1, 2018 XZ2, 2018 XH, 2018 XD5, 2018 XB4, 2018 XA, 2007 VD12
I52Steward Obs. Mt. Lemmon Station in Arizona, 3 in MPECs 2018-Y54, 2018-Y55 & 2018-Y57 -- 2018 YZ, 2018 YA1, 2018 XH2
T12UH/Tholen NEO Follow-Up 2.24m Telescope in Hawaii, 2 in MPEC 2018-Y54 -- 2018 WA3, 2018 JE1
L01Visnjan Obs., 1 in MPEC 2018-Y56 -- 2018 YY
For a list of all participating observatories that have Web addresses, see A/CC's Observatory Links page.

Impact Risk Monitoring  on 21 December '18

Summary Risk Table for Risk Assessments Updated Today   (last checks: NEODyS at 2358 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 and NEODyS listings is 100 years, and both post impact solutions beyond that for some special objects.
For the latest official risk assessments, and for explanations of the terminology, see the NASA/JPL Sentry and NEODyS CLOMON2 risk pages.
0000NNN000

Object

Risk
Monitor
When
Noted
UTC
0000T0000
Year
Range

VI
#
000NN00
Prob
Cum
T0000
PS
Cum
T0000
PS
Max

T
S


Notes for Today's Latest Risk Assessments
2018 YJJPL Sentry17002029-2118656.759263e-07-3.05-3.920JPL: Computed at 08:01 today Pacific time based on 27 observations spanning 4.1190 days (2018-Dec-16.5351 to 2018-Dec-20.65407). Diameter approximately 0.635 km. from weighted mean H=18.65.
2018 XW5JPL Sentry1700R E M O V E DJPL: Risk listing removed at 1600 UTC today
NEODyS1700R E M O V E D-
2018 XE5JPL Sentry1700R E M O V E DJPL: Risk listing removed at 1602 UTC today
2018 XB4JPL Sentry17002051-2118972.9668187e-05-4.34-4.840JPL: Computed at 08:04 today Pacific time based on 23 observations spanning 7.8294 days (2018-Dec-13.34358 to 2018-Dec-21.173). Diameter approximately 0.054 km. from weighted mean H=23.99.
2018 XAJPL Sentry17002099-209922.9693e-08-7.02-7.190JPL: Computed at 07:43 today Pacific time based on 135 observations spanning 19.922 days (2018-Dec-01.34686 to 2018-Dec-21.26929). Diameter approximately 0.063 km. from weighted mean H=23.64.
2018 WA3JPL Sentry17002055-206026.4413e-07-7.29-7.300JPL: Computed at 07:43 today Pacific time based on 31 observations spanning 10.269 days (2018-Nov-29.26148 to 2018-Dec-09.530805). Diameter approximately 0.009 km. from weighted mean H=27.85.
2005 TM173JPL Sentry17002019-21161509.42972e-07-5.41-6.270JPL: Computed at 08:06 April 8th of 2017 Pacific time based on 6 observations spanning 1.9467 days (2005-Oct-09.20072 to 2005-Oct-11.14743). Diameter approximately 0.051 km. from weighted mean H=24.12.

Legend: VI# = VI count, Prob Cum = cumulative probability, PS Cum/Max = cumulative/maximum Palermo Scale, TS = Torino Scale (next 100 years)

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 21 December '18

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

2140Generated Traffic Report
1700Noted that JPL Sentry has updated its 2005 TM173 risk assessment - see above
Noted that JPL Sentry has updated its 2018 WA3 risk assessment - see above
Noted that JPL Sentry has updated its 2018 XA risk assessment - see above
Noted that JPL Sentry has updated its 2018 XB4 risk assessment - see above
Noted that JPL Sentry has removed 2018 XE5 as an impact risk - see above
Noted that JPL Sentry has removed 2018 XW5 as an impact risk - see above
Noted that NEODyS has removed 2018 XW5 as an impact risk - see above
Noted that JPL Sentry has updated its 2018 YJ risk assessment - see above
Grabbed MPEC 2018-Y54 - Daily Orbit Update - see above
Grabbed MPEC 2018-Y55 - 2018 YZ - see above
Grabbed MPEC 2018-Y56 - 2018 YY - see above
Grabbed MPEC 2018-Y57 - 2018 YA1 - see above