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

Today's issue status: done

• Small objects – report for 13-19 September 2004
  Observation summary
• Precovery, recovery & comet news
• Risk monitoring

Cover: The imagery at left, a stack of 45 eight-second exposures, is from Peter Birtwhistle's confirmation small object 2004 RN251 at Great Shefford Observatory in England last Wednesday evening. He writes: “The set of images was the first I took, centered on the nominal ephemeris position. The object was at the time unconfirmed and moving at 24"/min with an uncertainty area 90'x50' in size. I was already exposing adjacent areas expecting to have a bit of a search to do by the time I managed to spot the 19th mag object towards the edge of frame on the first run! ” See below for more about 2004 RN251, which flew past Earth yesterday at 4.2 lunar distances.

Small objects
Discovery & follow-up for 13-19 September 2004

It was a week with a new Moon, great for discovering small asteroids (“small” is defined at right). Of 22 near-Earth discoveries announced in the last seven days, 12 were small — the most since March (13 in one week). Ten were found by LINEAR in New Mexico, one by the Siding Spring Survey in New South Wales, and one by a Vermont FMO Project volunteer reviewing images online from Spacewatch in Arizona. Another five small asteroids were tracked, one was reported from 1-5 September, and 29 observing facilities participated in the week's work.

A discovery from last week, 2004 RU109, made the closest known passage this week, at 0.957 LD on Monday. 2004 RN251 was at 4.2 lunar distances (LD) yesterday and 2004 SA1 at 9.8 LD on Thursday. Many of this week's discovery announcements were for objects caught after passing their closest point to Earth, including 2004 RG164, which was at 8 LD on September 9th. Nothing close is predicted for the coming week.

Last week's small objects report originally mis-attributed 2004 RC11 observations by Jim Bedient. At least five people have now independently submitted astrometry from New Mexico Skies MPC code H06, all of them so far using Rent-A-Scope remote-controlled instruments. So, unless or until it is known who did certain work, H06 observations in A/CC news will have to be reported as simply coming from “New Mexico Skies.”

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MPEC 2004-S17, issued with a 1638 UT time stamp yesterday, showed that an asteroidal object, which LINEAR in New Mexico found in July wandering around the Main Belt and was observed up through yesterday, had been caught exhibiting cometary activity. Not quite two and a half hours later, MPEC 2004-S18 reported precovery positions for this comet, now designated P/2004 NL21 (LINEAR). These were found by Maik Meyer in 8 and 15 September 1996 images from NEAT's telescope on Haleakala in Hawaii.

The next MPEC issued yesterday, 2004-S19, carried archive precovery work from “R. Haver, A. Pelloni, G. Forti, M. Read,” who had located 2004 DA62 in scans of plates from 12 March and 17 April 1983 from the U.K. Schmidt 1.2m telescope at Siding Spring in Australia. Discovered by LINEAR on February 25th and observed up through July 21st, this object travels a highly inclined (i=52.2°) path that takes it through the ecliptic inside Jupiter's orbit and outside Saturn's. From its brightness, it is estimated to be on the order of 9.3 km. (5.8 miles) wide, and maybe larger.

Three MPECs, and less than six hours, later, MPEC 2004-S22 early today reported the recovery and precovery of Edgeworth-Kuiper Belt object 2003 UZ117. It was caught

early yesterday by Erich Meyer at Linz Observatory in Austria and last night on both sides of midnight at KLENOT in the Czech Republic. And Reiner Stoss is reported to have found it in 13 November 2002 NEAT images from its Mt. Palomar telescope. This object, which was discovered 24 October 2003 with the Spacewatch 0.9m telescope in Arizona, had been last reported seen on 22 November, and is estimated very roughly from its brightness to be about 385 km. (240 miles) wide.

And the large PHO 2003 QO104, which hadn't been reported since 22 December 2003, was in Friday's Daily Orbit Update MPEC (DOU) as having been picked up Thursday morning with the Spacewatch 1.8m telescope. Estimated at 2.3 km. (1.4 miles) wide, this object gave NEO observers quite a chase after its 31 August 2003 discovery with NEAT's telescope on Haleakala and announcement on September 2nd. It was listed at Torino Scale 1 for much of the time until its last impact solutions were removed on October 13th. Later that month, in the DOU of the 31st, a set of archival positions were reported from 20 December 2001 from NEAT/Palomar.

Risk monitoring 19 Sept.

The Sunday Daily Orbit Update MPEC has observation of 2004 RQ252 from yesterday from its discoverer, the Siding Spring Survey (SSS) in Australia. Today NEODyS cut its risk assessment to just one low-rated impact solution in 2012, and JPL solidly lowered its its overall risk ratings for this small object.