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

Today's issue status: done

• Small objects – report for 12-18 April
  Observation summary
• News briefs – comet news & namings
• Risk monitoring – JPL has posted 2004 HM

Cover: As 2004 FY31 raced from its discovery location (discovered by LONEOS March 31.30, upper-right red dot), Peter Birtwhistle in England pursued it through Draco and into Cygnus and the Milky Way (images and orange dots), where the last optical observation came from Tenagra II Observatory on April 11.47 after passing Earth at 12.1 lunar distances on the 10th. Arecibo radar caught it on April 14.54 (lower-left red dot). See Great Shefford Observatory's 2004 FY31 page for further explanation, an animation, and a different star chart. At JPL's absolute magnitude H=21.89 calculation, FY31 is bright enough to squeak into the potentially hazardous category.

Small objects
Discovery & follow-up 12-18 April

It was another spectacular week for small objects, those with absolute magnitude calculated at greater than H=22.0, which converts to roughly smaller than 135 meters/yards wide. Nine discoveries were announced, and the smallest actually flew through the Earth-Moon system early today UT. That one, 2004 HE, was discovered by Michael Van Ness at LONEOS, while the other eight were found by LINEAR. Besides the discoveries, another eight small objects were tracked, and older observations were reported for seven more. All this work was done by some 38 professional, educational, and amateur observing facilities plus one archive sleuth, but, oddly enough, neither of the Spacewatch telescopes were involved.

Of special note this week is the work of amateur astronomer Krisztian Sarneczky of the Szeged University (SZTE) Asteroid program in Hungary. Among his new data reported last week from the NEAT archives were observations that extended the old observing arcs of four small objects and added

positions for two more (and also updated a larger object on April 14th that has impact solutions).

Early today UT, 2004 HE was at 0.72 lunar distance (LD). Checking the Sormano SAEL and JPL Close Approaches for other flybys, 2004 HM was at 5.1 LD last Tuesday, and 2004 HL was at 5.6 LD and 2004 GD2 at 9.6 LD on Wednesday. This coming week, 2004 GD will be at 6.0 LD on Tuesday and 2004 HB at 10.2 LD on Wednesday.

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Notes: Diameters in the following table are rough best estimates from a very inexact H-to-size formula using H (absolute magnitude) from the JPL NEO Orbital Elements page, source also for Earth MOID (minimum orbital intersection). Other MOIDs are from Lowell Observatory. Current MPC H is also given, along with discovery MPEC H. Priorities and visibilities are from the European Spaceguard Central Node (SCN).

Comet news:  After an interruption earlier today, SOHO images of C/2004 F4 (Bradfield)'s perihelion passage have resumed being posted from intervals that are almost hourly. You can watch the spectacular show from here or here.

MPEC 2004-H26 today announces the newest comet discovery, C/2004 H1 (LINEAR). From the first very preliminary calculation, it reached perihelion this last January 13th out past Mars on a retrograde path (i=141.2°) — "driving on the wrong side of the Solar System," one might say. The first LINEAR observation in the MPEC is from early Friday, and it and four other observing facilities confirmed the object yesterday and today.

Namings:  The Minor Planet Center updated its Discovery Circumstances page April 16th with 65 new names, all for asteroids discovered by the LINEAR program, and all named for high school student finalists and finalist mentors in the 2004 Intel Science Talent Search (STS). You can read about them at LINEAR's Ceres Connection Winners for 2004 page, and in the STS 2004 finalists list. They include Lisa Glukhovsky, whose project was "A Rapid, Accurate Method of Determining the Distance to Near-Earth Asteroids." And, nothing to do with astronomy or even gastronomy, but, rather, biochemistry, we have to also mention Jennifer D'Ascoli, whose project was blueberry pie.

The last MPC namings update was March 5th.

Risk monitoring 18 April

JPL has posted 2004 HM, which was announced today in MPEC 2004-H25 as discovered early Friday by LINEAR in New Mexico, which also caught it yesterday morning, followed by Tenagra II Observatory in Arizona and then Mt. John Observatory in New Zealand. The confirmation process was closed out this morning by Pla D'Arguines Observatory in Spain and the Observatorio Astronomico de Mallorca (OAM), followed by Sabino Canyon and Tenagra II observatories in Arizona. JPL puts 2004 HM's diameter at about 90 meters/yards.

The Sunday Daily Orbit Update MPEC has observation of 2004 GE2 from LINEAR in New Mexico yesterday morning. Today JPL cut its impact solution count from five to one (in the year 2100) and slightly lowered its overall risk ratings for this object.