2003 WT153 from Great Shefford Observatory last night. Multiple images are centered on the faint fast-moving object, thus each background star looks like a string of beads.

Earth-Moon flyby

2003 WT153 was first spotted at 0733 UT (12:33am local) yesterday by Robert McMillan with the Spacewatch 1.8m telescope on Kitt Peak south of Tucson, Arizona, and was followed over a period of two hours and 42 minutes. First to confirm the discovery was Great Shefford Observatory last night in England (see imagery at right), and it was caught this morning by Sandlot and Sabino Canyon observatories in Kansas and Arizona, as well as with the Spacewatch 1.8m.

Converting this object's brightness (absolute magnitude H=28.4) by standard formula gets a rough size estimate of six to twelve meters/yards wide, with seven as best guess. And, going by the MPC's Closest Approaches page and the preliminary orbit calculation, this will be the 24th or 25th closest approach on record, eighth closest this year, and third smallest of those eight objects.

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2003 WT153 spends most of its time between Earth and Venus, and crosses Earth's orbit at an inclination of less than half a degree. It will soon disappear as it drops behind Earth and moves back inside our orbit, out of view from ground-based optical telescopes.

Updates:  JPL this morning posted 2003 WT153 to its Current Impact Risks page with 44 highly preliminary and low-rated impact solutions in the years 2044 to 2101. Later, late on a Sunday night in Pisa, Italy, NEODyS posted WT153 to its Risk page. See more about this below. When objects this small enter Earth's atmosphere, they usually self-destruct spectacularly but harmlessly at high altitude.

Tony Beresford wondered aloud to the Minor Planet Mailing List (MPML) today about whether 2003 WT153 might be spacecraft garbage. Dr. Allan Harris responded that "The orbit does look like a good prospect for something left over from a launch toward Venus from the Earth."

The 2003 WT153 discovery MPEC credits both R.S. McMillan and A.S. Descour for observations made with the Spacewatch 1.8m telescope. A/CC has received clarification that Robert Macmillan made the discovery and did the first follow-up, while Anne Descour did the next morning's follow-up.

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2003 WT153's interaction with the Earth-Moon system based on preliminary orbital elements, shown in an animation by Pasquale Tricarico using his ORSA Linux software.

Lunar flyby:  When an object comes within less than two lunar distances (LD) of Earth like 2003 WT153 is doing today, an immediate question is, where is the Moon in all of this? Pasquale Tricarico studies the orbital stability of Trojan swarms as a doctoral student in physics at Padova University, and has written the beta ORSA (Orbit Reconstruction, Simulation and Analysis) software for Linux. He provided the animation at right that shows how 2003 WT153 is moving through the Earth-Moon system, passing Earth today at 1.76 LD and passing the Moon at 0.87 LD at around 0715 UT (2:15am EST) tomorrow.

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Risk monitoring 30 Nov.

JPL posted 2003 WT153 to its Current Impact Risks page early Sunday with 44 highly preliminary and low-rated impact solutions, and NEODyS late Sunday night posted 2003 WT153 to its Risk page with 26 low-rated impact solutions. See above for more about this tiny object.

The Sunday Daily Orbit Update MPEC doesn't carry observations of 2003 WG, but for 2003 WW26 it reports one position from last night from Linz Observatory in Austria and a triplet from Jornada Observatory this morning in New Mexico. Today both JPL and NEODyS have again slightly raised their overall low risk ratings for this small object.

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Late update:  JPL has posted 2003 WY153 with one very low-rated impact solution. Announced today in MPEC 2003-W78, this is yet another Tunguska-class object, with width estimated at roughly 50 meters/yards. It was discovered early yesterday by LINEAR and confirmed overnight by Great Shefford, Sabino Canyon, Desert Moon, and Tenagra II observatories.