Small objects
Discovery & follow-up 17-23 May

This past week, discoveries were announced for three small objects — asteroids with absolute magnitude H greater than 22.0, thus estimated at under roughly 135 meters/yards wide. During this period nine more were followed, and observations were also reported for another from back in early April.

Thirty-one observing facilities participated in the week's work. Two discoveries were from LINEAR in New Mexico and the other with the Spacewatch 0.9m telescope in Arizona. These three were among the five smallest tracked, probably under 65 meters wide.

Last Sunday's report noted that 2004 JO20 and 2004 JP1 would fly past Earth at just beyond three lunar distances (LD) on Monday and Tuesday. 2004 KG1 also flew past on Tuesday, at 6.7 LD the day before it was discovered. No small object close flybys are predicted for this coming week or any time soon.

<< previous report | skip table | Small objects table >>

Notes: Diameters in the following observation summary table are rough best estimates from a standard but 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 planetary MOIDs are from Lowell Observatory. Current Minor Planet Center H is also given, along with the original H from each object's discovery MPEC. Priorities, visibilities, and campaigns are from the European Spaceguard Central Node (SCN). Flyby distances and times are from the JPL Close Approach Table.

Craters USA:  The Earth Impact Database currently lists 25 craters in the continental U.S. and one in Alaska. How many can you name without using a locator map? What probably comes to mind first is "Meteor Crater" in Arizona, more properly known as Barringer Crater. You might be surprised to learn that Illinois, Tennessee, and North Dakota each have two impact sites, and Texas three. Hidden in plain sight is Chesapeake Bay, which a Baltimore Sun article today describes as "largest of the 30 impact craters discovered in the United States and the sixth-largest [and maybe best-preserved] of 170 in the world." See more links about this in May 7th A/CC news.

A hiking story posted May 20th, "Rainy day in the desert," is a reminder of the less recognized but spectacular Upheaval Dome in Utah. About 250 miles (400 km.) due north of the much smaller Barringer Crater, it is located inside Canyonlands National Park (311Kb PDF trail map). See John Louie's pages to learn about the scientific research on this crater.

Risk monitoring 23 May

The Sunday Daily Orbit Update MPEC has observation of 2004 JA27 from LINEAR yesterday morning in New Mexico and from Great Shefford Observatory in England very early today UT. It is interesting to note that, during the 7.7 days from discovery May 15th until Great Shefford reported it this morning, the only observations of 2004 JA27 had come from LINEAR. Today NEODyS and JPL both removed all impact solutions for this object, which is roughly estimated at 835 meters/yards wide.