Sunday25 July 20044:03pm MDT2004-07-25 UTC 2203 back top next  

The Asteroid/Comet Connection's
daily news journal about
asteroids, comets, and meteors

Today's issue status: done

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Cover: Tiny Earth-buzzer 2004 OD4 is seen here in discovery confirmation imagery from Peter Birtwhistle very early last Monday in England. This is a composite of 35 30-second exposures stacked on the object's fast motion, so the background stars appear as streaks. For more info about this object, the only nearby NEO discovery announced this past week, see Great Shefford Observatory's 2004 OD4 page, Monday news, and a news update below.

Details: 2004 OD4 imaged when 5 LD (0.014 AU) from Earth at 2004 July 19 0009-0036 UT. 35x30s (total exposure 17m 30s. Binned 2x2 and enlarged x2. Field 10'x10', North up. Motion 5.1"/min. in p.a. 317°. 0.3m f/6.3 Schmidt-Cassegrain + CCD, P. Birtwhistle (J95).
Small objects – panel 1/2 Major News for 25 July 2004 back top next  

Small objects
Discovery & follow-up for 19-25 July

This past week began big for small asteroids (defined at right), with the announcement in Monday's wee hours that the newly discovered 2004 OD4 had flown by at about 0.4 lunar distance (LD) on Friday (the ninth closest Earth flyby on record), more than 27 hours before discovery. With the brightening Moon and other mid-Summer interferences, observation fell off during the week and the only other NEO discovery announced was a distant larger object. Even so, six known small asteroids were tracked, and eleven observing facilities participated in the week's work.

The Tuesday Daily Orbit Update MPEC reported positions for many asteroids observed earlier in July from La Palma, including two small ones. This is credited to the Nordic Near-Earth-Object Network of Spaceguard (NEON) using the 2.5m NOT on La Palma (not, as originally reported, another NEON, the Network of European Observatories in the North Archive Observing School).

Of some 590 cataloged small asteroids, only one is numbered, 54509 2000 PH5 [link|alt], and this morning at 1015 UTC (6:15am EDT) it made the only known close small object flyby this week, coming within five LD. This Earth co-orbital will be the target for radar observation from Arecibo beginning tomorrow.

<< previous report | skip table | Small objects table >>

What’s so big about “small objects”? If an asteroid’s orbit brings it to within 0.05 astronomical units (AU) of Earth's orbit, it is categorized as “potentially hazardous” unless it has an absolute magnitude H greater than 22.0, which corresponds to a diameter on the order of 135 meters/yards. Larger H means less bright, thus smaller size. And 0.05 AU is about 19.5 times the distance between Earth and Moon (0.00256 AU). To be discovered and tracked, such objects usually must come close (a few are Earth’s nearest neighbors, coming closer than the Moon). They are exposed pieces of distant asteroid populations, and they have within their own population tomorrow’s meteors. And their discovery and follow-up represents today’s best amateur and professional asteroid observing work. Diameter & Earth MOID: In the following observation summary table, the stated diameters are rough best estimates from a standard but very inexact H-to-size formula using H (absolute magnitude, or brightness) from the JPL NEO Orbital Elements page, source also for Earth MOID (minimum orbital intersection distance). Current Minor Planet Center H is also given, along with the original H from each object's discovery MPEC. Other sources: Planetary MOIDs are from Lowell Observatory. Priorities and visibilities are from the European Spaceguard Central Node (SCN). And flyby distances and times are from the JPL Close Approach Table. See also the Sormano Observatory SAEL(H>22.0 and Earth MOID<0.015 AU), and NEODyS listings have yet another H calculation.
Small objects – panel 2/2 (table) Major News for 25 July 2004 back top next  

Small object observation summary for 19-25 July

H = absolute magnitude (brightness), from which size is roughly estimated   —   m/yd = meters/yards   —   [cross index]
All objects had observations reported last week. Those on a light-blue background had observations from only before the week.


Object
Estimated
diameter
JPL
H
MPC
H
Discovery
H in MPEC
Earth
MOID
European Spaceguard Central Node
priority/visibility/campaign
2004 OD4
Apollo
14 m/yd26.9127.226.7 2004-O150.001025 AU
NEW: 2004 OD4 was discovered on 17 July by LINEAR and was confirmed by LINEAR July 18th by Great Shefford Obs. July 19th (see cover above), and was announced in MPEC 2004-O15 of 19 July. This object was also observed on 19 and 20 July by Great Shefford and KLENOT, on 19 and 21 July by Powell Obs., and on 20 July by the NEO override program with the 2.5m Isaac Newton Telescope on La Palma. 2004 OD4 came inside the Earth-Moon system, to within 0.4 lunar distance of Earth, making the ninth-closest flyby on record at 0509 UT on July 16th, 1.134 days (more than 27 hours) before discovery. The day it was announced, it was posted by both JPL and NEODyS with a few very low-rated impact solutions (see news), but both removed it the next day with the next reported observations.
2004 MO4
Amor
32 m/yd25.1324.924.6 2004-M450.023272 AUNecessary, visibility ends 3 Aug.
2004 MO4 was observed on 22 June by CINEOS, on 7 July by Marxuquera Obs., and on 24 July by Mt. John Obs. It has an MOID of 0.027 AU with Mars.
2004 NF3
Amor
45 m/yd24.4024.524.5 2004-N400.057783 AUUseful, visibility ends 31 Aug.
2004 NF3 was observed on 19 and 21 July by Powell Obs., and on 22 July by KLENOT. It has an MOID of 0.046 AU with Mars.
2004 NU7
Amor
58 m/yd23.8524.624.6 2004-O010.013849 AUNecessary, visibility ends 3 Sep.
2004 NU7 was observed on 15 July by Sormano Obs. and on 19 July by Powell Obs. It has an MOID of 0.027 AU with Mars.
2004 EU22
Apollo
62 m/yd23.6723.823.7 2004-F220.008005 AU
2004 EU22 was reported this past week as having been observed on 26 May by the Nordic Near-Earth-Object Network of Spaceguard (NEON) on La Palma. This added 41.607 days to what had been a 31.203-day observation arc.
2004 NK8
Apollo
74 m/yd23.3123.523.1 2004-O060.035967 AUNecessary, visibility ends 13 Aug.
2004 NK8 was observed on 18 July by Great Shefford Obs., on 20 July by Begues Obs., and on 21 July by Powell Obs. and Sormano Obs.
2004 FP4
Amor
89 m/yd22.8923.123.3 2004-F470.052863 AU
2004 FP4 was observed on 19 July with the Australian Natl. Univ. (ANU) Obs. 1m telescope, adding 49.87 days to what had been a 71.43-day observing arc. It has an MOID of 0.009 AU with Mars.
2004 LK
Amor
99 m/yd22.6722.722.7 2004-L220.068727 AUUseful, visibility ends 10 Oct.
2004 LK was observed on 15 and 20 July with the ANU 1m telescope.
2004 HB39
Amor
99 m/yd22.6722.722.5 2004-H740.093463 AUNecessary, visibility ends 17 Aug.
2004 HB39 was reported this past week as having been observed on 23 June by NEON. This added 29.827 days and three positions to an observing arc that had had only 39 observations from a period of only 28.986 days.

  Small object observation cross index   [table top]
ObjectObserved by MPC code
2004 EU22J50
2004 FP4413
2004 HB39J50
2004 LK413
2004 MO4474, 599 & 952
2004 NF3246 & 649
2004 NK8170, 587, 649 & J95
2004 NU7587 & 649
2004 OD4246, 649, 704, 950 & J95
CodeObservatoryObjects observed (days)
170Begues Obs.2004 NK8
246KLENOT2004 NF3 & 2004 OD4(2)
413Australian Natl. Univ. Obs.1m telescope2004 FP4 & 2004 LK(2)
474Mt. John Obs.2004 MO4
587Sormano Obs.2004 NK8 & 2004 NU7
599CINEOS2004 MO4
649Powell Obs.2004 NF3(2), 2004 NK8, 2004 NU7 & 2004 OD4(2)
704LINEAR2004 OD4(2)
950La Palma2004 OD4
952Marxuquera Obs.2004 MO4
J50Nordic Near-Earth-Object Network
(NEON) on La Palma
2004 EU22 & 2004 HB39
J95Great Shefford Obs.2004 NK8 & 2004 OD4(3)
Risk monitoring - panel 1/1 Major News for 25 July 2004 back top next  
Risk monitoring 25 July

The Sunday Daily Orbit Update MPEC has observation of 2004 NL8 from Francisquito Observatory in southern California yesterday morning and from Pla D'Arguines Observatory in Spain this morning. And today JPL further lowered its risk ratings for this kilometer-size object while, now down to two impact solutions, of which only one is within the NEODyS time horizon. NEODyS in its update, however, has three solutions and very slightly raised its low assessment.

Summary Risk Table - sources checked at 2159 UTC, 25 Jul

Object

Assessment

Years

VI
PS
cum
PS
max
T
S
Arc 
days
 2004 NL8 NEODyS 7/252057-20773-3.91-4.17013.771
JPL 7/252057-20862-4.41-4.54013.771
 2004 ME6JPL 6/282017-209943-5.64-6.3500.873
 NEODyS 6/272044-20637-7.29-7.7600.873
VI = count of "virtual impactors" (impact solutions)
See A/CC's Consolidated Risk Tables for more and maybe
  newer details, and check the monitors' links for latest info.
Note that only objects recently in view are shown here.
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