April 2002 Asteroid/Comet News
Updated: 22 July 2003, links corrected 18 June 2012 & 5 Dec. 2012
<<March 2002 News ^UP^ May 2002 News>>
The Southwest Research Institute and NASA Dryden Flight Research Center put out news releases about the 2002 Spring equinox high-flying search for hypothetical Vulcanoids (go to that link for the April and subsequent news releases).
The Spaceguard Central Node (SCN) observing campaign for 2002 EX12 was successfully retired, removed also this day from NEODyS Risk page, and from the JPL list where it had been the second highest concern before being pulled. The SCN campaign for 2002 FU5 was also retired, two days after FU5 was dropped from both risks pages.
JPL and the University of Arizona in multiple news releases announced the publication of two related scientific papers in the 5 April 2002 edition of Science magazine. One of these reports that the orbit for 29075 1950 DA can be calculated to the point of being able to predict a 1-in-300 chance of Earth impact on 16 March 2880, making it the most dangerous known NEO. The other paper explains the Yarkovsky effect, which complicates the calculations but also provides solutions if it's decided in the next 35 generations of scientists that a deflection effort is needed.
A European Space Agency (ESA) news release reports a conclusion, from space-based infrared observations which sampled the Main Belt population, that the belt's count may be twice what was previously estimated--perhaps as many as 1.9 million asteroids between Jupiter and Mars. These results are reported in the April 2002 Astronomical Journal by Edward F. Tedesco and Francois-Xavier Desert from 1996-97 observations made with ESA's Infrared Space Observatory (ISO).
A fireball known as the Bavarian bolide flew over central Europe on the night of 6 April 2002. From infrasound, radiometric, and all-sky camera data, Ondrejov Observatory reports that the object was probably a stony chondrite meteoroid of about 500 kg. (1,100 pounds) mass, and some fragments probably survived. The orbit has been calculated and comes up the same as the Pribram fall almost exactly 43 years earlier, on 7 April 1959 in what is now the Czech Republic.
In a news release, the European Space Agency commented that its coming Gaia mission will be well suited to spot potentially hazardous asteroids inside Earth's orbit--a major blind spot for ground-based observers (see 2002 EM7 for a recent surprise flyby). Gaia's mission is to take a positional census of the "the billion brightest objects in the sky" from Earth's L2 Lagrangian point beginning at the end of this decade. ESA anticipates that this will include discovering about one hundred asteroids a day over a five-year period, mainly larger Main Belt and Kuiper Belt objects.
XingMing Zhou of China was the first on 12 April 2002 to announce on the SOHO chat page (current chat) the appearance of SOHO-422 (C/2002 G3). It put on a good show and was thought might be one of the rare sungrazers to go on to become telescopic objects, but faded considerably before leaving the LASCO view eight days later.
The NEODyS Risk page was reorganized to regroup most of its listings as "lost objects."
In the 22 April updating of Discovery Circumstances by the IAU Minor Planet Center, there were no new numberings but quite a variety of new namings. For instance, 31122 1997 SD was named Brooktaylor, 32569 2001 QW71 became Deming, and 34854 2001 TP17 from now on will be referred to as the asteroid, Paquifrutos.
The European Spaceguard Central Node successfully retired an intense effort to determine the orbit of 2002 EZ11. It was dropped from the JPL Risks page on 16 April and from the NEODyS Risk page the next day. Until 2 April, EZ11 had been listed in the second-highest position on JPL's page, at Torino Scale 1 ("merits special monitoring"). See SCN's 26 April report for credits to many observing sites.
2002 CU11 was pulled from the NEODyS and JPL risks pages. Until that point it had been the only listing on the JPL Risks page at Torino Scale 1. The next day the SCN observing campaigns page posted this update to its CU11 listing: With the observations reported from Powell Observatory, KS, USA, on April 25 all the collision solutions seem to have disappeared, according to both NEODyS and SENTRY. But the alarm has not ceased: we need additional observations over the next few months to make the current orbital solution of 2002 CU11 and its risk assessment much stronger.
Minor objects with companions, both near-Earth and far away in the Edgeworth-Kuiper Belt, were in the news during mid-April. The near-Earth asteroid 2000 DP107 was in the spotlight on 11 April, followed by trans-Neptunian object 1998 WW31 a week later. See binary minor objects for more about binaries as a general topic
Comet 19P/Borrelly in April continued to make news following the Deep Space 1 flyby the previous September. Science Express published a paper by L. A. Soderblom et al. on 4 April 2002, and JPL put out a news release on 5 April about how hot Borrelly's surface was found to be. This was reported by BBC 5 April and Sky & Telescope 22 April. See also an Astronomy 16 March 2002 report.
NEAT Centaur discoveries
While scouring the skies for threatening asteroids NEAT also discovered a couple of objects with orbits that never get so close as Saturn. 2002 GB10, found on 8 April, is a Centaur with an estimated diameter of 140 km. (80 miles) and an orbit between the orbits of Saturn and Neptune. Found on April 12th, 2002 GO9 has an orbit that was originally calculated (and reported here) to run from near Saturn out to 100 AU, which would have put it into the scattered disk object (SDO) classification. But its orbit was updated in June 2002 from additional observations as running between Saturn and Neptune. GO9's diameter is estimated at 85 km. (50 miles).
Risk concerns removed in April
Potentially hazardous asteroids removed from the NEODyS and/or JPL risk pages during March 2002 include: 2002 EY2, 2002 GM2, 2002 GO5, and 2002 GT, as well as 2002 CU11, 2002 EX12, and 2002 FU5, as already mentioned above.