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

Today's issue status: done, updated 2x

• News briefs – meteor news, bits & pieces
  panel 2 – unusual object
• Risk monitoring – JPL has posted 2004 NL8

Cover: Do you remember where you were? Ten years ago today comet C/Shoemaker-Levy 9 (1993e) began its six-day assault on Jupiter with 20 or so pieces, “the largest of which,” one report said ,“were probably a few kilometers across.” The Hubble Space Telescope large color image shows impact features strung along latitude -44°, as detailed here. Also from Hubble, the images at bottom left show the fragment G large impact feature through green (left) and methane color filters. The inside of the thin ring around the dark spot in the left image is about the size of Earth. The animation shows at one-third speed the impact flash of the last fragment to hit, as caught by the approaching Galileo spacecraft. Credits: NASA and STScI or JPL.

Meteor news:  From information Marco Langbroek has gathered, it appears that the 12-13 July Finnish event (see “Meteor news” Wednesday) was a single fireball rather than a meteor shower.

ETH Zurich has a news release from July 14th about the July 15th Nature article on how meteorites from Main Belt asteroid collisions can fall to Earth in short time spans (hundreds of thousands rather than many millions of years, see July 14th meteor news). A Space.com report yesterday notes that the relatively recent half-billion-year-old collision talked about in this news was not the most recent known. That distinction goes to a six-million-year old collision reported in February 2002.

Revised: The Oregonian told yesterday that the Cascadia Meteorite Laboratory (CML) at Portland State University, with the help of a NASA educational grant, is opening a meteorite exhibit at the Rice Northwest Museum of Rocks and Minerals.

Jim Gamble and Sandia Labs' all-sky cameras each caught a bright meteor overnight 13-14 July over Albuquerque, New Mexico (9:53pm, JPEG) and El Paso, Texas (2:59am), and Sandia had another at 3:40am today (JPEG).

WESH-TV in Winter Park, Florida has a report today, “Did Meteorite Strike Central Florida?” about July 4th when witnesses “heard a large boom and saw bright flashes of light across the evening holiday skies.” There was a severe storm in the area, but this is claimed to have been like no storm.

Bits & pieces:  The Planetary Society has a July 14th news release citing the tenth anniversary of the Jupiter impacts by pieces of comet Shoemaker-Levy 9 to issue a call for proposals “from amateur and under-funded professional observers anywhere in the world” for 2004 Shoemaker NEO Grants, deadline October 1st. See reports from previous grant recipients for some very interesting reading about the work of amateur astronomers in hazardous NEO monitoring.

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The University of Chicago Chronicle has an article from yesterday about the university's Dust Flux Monitor Instrument (DFMI) on the Stardust comet mission, noting that, in the January encounter with 81P/Wild 2 (Index), the first dust impact was recorded at “1,010 miles from the cometary nucleus [and the last] at a distance of 3,500 miles as the spacecraft sped away” [1,625 and 5,635 km.].

Sky & Telescope has an article from yesterday, “Hubble Panel Endorses Servicing Mission,” and Space.com has another report from July 14th (see news links).

Disaster News Network has an item from July 14th about a sociologist's viewpoint on disaster probabilities, perceptions, and preparedness. Lee Clarke of Rutgers University notes that, statistically, you are safer in an airliner than traveling by car, but, if you are in an airplane that goes down, the situation is likely to be worse than if you were in a car crash. Similarly, “Asteroid and comet impact . . . risk is low [but] you're all at very high risk if [one] hits.”

Unusual object:  MPEC 2004-O09 with a time stamp of 0200 UT July 17th (10pm EDT at the Minor Planet Center) announced an asteroidal object for which “observations with large-aperture instruments to clarify [its] physical nature” are needed. It has a retrograde orbit (currently calculated at i=165.3°), not unusual for a comet but few non-cometary objects travel around the Sun counter to the rest of the Solar System. The MPEC cites two, 1999 LE31 and 20461 Dioretsa [link|alt] (1999 LD31), in making assumptions for calculating a highly preliminary orbit.

From Gareth Williams' MPEC commentary, 2004 NN8's path could be one-way through the inner Solar System, or could average a distance much closer to the Sun than currently calculated (a=4 vs. 15 AU). Size is necessarily a very rough estimate, perhaps on the order of 3 km. (1.9 miles) wide or more, based on the first calculation of absolute magnitude (H=15.3).

2004 NN8 was discovered July 13th by the Siding Spring Survey (SSS) in Australia and confirmed through Friday by five other southern hemisphere observing facilities plus McDonald Observatory in Texas.

Risk monitoring 16 July

The Friday Daily Orbit Update MPEC (DOU), which was posted late due to a network outage at the Minor Planet Center (see status page), carries no observations of objects with impact solutions. Yesterday, the DOU carried July 13th observations of 2004 MP7 from Reedy Creek Observatory in southeastern Queensland, Australia, and JPL very slightly raised its low risk assessment for this object.

Late update: Still Friday evening in Pasadena but early Saturday UTC, JPL has posted 2004 NL8, which was announced just before midnight in MPEC 2004-O07 as discovered early July 15th by LINEAR in New Mexico, linked to LINEAR observations four days earlier, and confirmed Friday by LINEAR and from six other observing facilities. JPL estimates the object's diameter at roughly 1.55 km. (0.96 mile) and, in its very preliminary risk assessment, has a low rated impact solution less than three years away.