|
Small objects
Discovery & follow-up for 24-30 May
This last week was a light one for observing asteroids of any size and especially the smallest, those with magnitude (brightness) of H greater than 22.0. In the northern hemisphere, where most asteroid observing is done, nights are becoming shorter. The Moon was brightening but was a week away from full. Weather interfered some in Europe and also across the southwestern U.S., where Arizona wildfire smoke hampered seeing. And many European NEO observers were at MACE 2004 from Thursday through today.
It was a week in which ground-based discoveries were announced for two comets and only seven near-Earth asteroids. Two of those five have H>22.0. 2004 KF17 was announced early today and will pass at 1.8 lunar distances (LD) at 2110 UT tomorrow. 2004 KG17, announced late today, was caught early Friday by the FMO Project (see news), and the preliminary calculation has its flyby at 5.1 LD just after 2000 UT that day. No other close flybys were known to have happened last week or are predicted for the coming
|
week or month. Thirteen observing facilities took part in the week's work, notably Tenagra II Observatory in Arizona (which closes July 1st until September).
Finally, a discovery from the previous week, 2004 KE1, had its magnitude recalculated to H>22.0 when its observing arc was expanded by 30 days.
<< previous report | skip table | Small objects table >>
Notes: If an asteroid's orbit brings it to within 0.05 AU of Earth's orbit, it is categorized as "potentially hazardous" unless it has an absolute magnitude H greater than 22.0, which corresponds to a diameter on the order of 135 meters/yards. Larger H is dimmer, thus smaller. And 0.05 astronomical units (AU) is about 19.5 times the distance between Earth and Moon (0.00256 AU). To be discovered and tracked, such objects must usually come close, and a few of them are Earth's nearest neighbors, coming closer than the Moon itself. They are exposed samplings of distant asteroid populations, and they have within their own population tomorrow's meteors.
Diameter & Earth MOID: In the following observation summary table, the stated diameters are rough best estimates from a standard but very inexact H-to-size
formula using H (absolute magnitude, or brightness) from the JPL NEO Orbital Elements page, source also for Earth MOID (minimum orbital intersection distance). Current Minor Planet Center H is also given, along with the original H from each object's discovery MPEC.
Other sources: Planetary MOIDs are from Lowell Observatory. Priorities and visibilities are from the European Spaceguard Central Node ( SCN). And flyby distances and times are from the JPL Close Approach Table.
|
