Occultation by (99942) Apophis on 2021 February 21-22 - New March 4
Apophis is small, but important as it will pass very close to the Earth in 2029 and 2036, with a very small chance of impact in 2068
This event occurred before Goldstone-Greenbank radar observations planned starting on March 3rd, so it was deemed that the chances for success were too small to organize a champaign to try to observe this event.
The first predictions of this Apophis occultations were by the Unistellar occultation team and Observatoire de Paris. The SETI Institute and Unistellar encouraged observers to try to observe the occultation, as did IOTA for observers who were close to the path. This was the brighter and earlier of two US events, of 7.0-mag. HD 89707 = HIP 50671 = SAO 155919, at J2000 RA 10h 20m 50.1s, Dec -15° 28' 50", spectral type G1V. But Apophis is only about 350m across and the path uncertainty was about 50 times it width. With the poor chances for an occultation, we did not recommend long-distance travel for it, which was expected to last only 0.1 second. One IOTA observer, Kai Getrost, travelled to the predicted central line north of Jacksboro, Texas, where he recorded no occultation (a miss). An observer at an observatory near Waco, over 100 km from the predicted line, also had no occultation. Ernie Iverson started to set up his telescope at his home in Lufkin, Texas, a few kilometers south of the path, although the sky was mostly cloudy. He stopped when he received a severe thunderstorm alert; he didn't want to have his equipment rained on. Prediction information about the event is given below. The path passed over s.w. Washington State, s. cen. Idaho, s.w. Colorado, n. Texas, Louisiana, and the Florida Keys, just east of Key West. In Texas, the path passed over Dallas- Ft. Worth, over the northern part of Ft. Worth, the s. part of Alington, and the far southern suburbs of Dallas; also in Texas, the path passed near Amarillo and Lufkin. In northern New Mexico, it passed a little south of Raton. Due to retro- grade motion, the path moved from southeast to northwest, crossing the Florida Keys at 5:42 UT and exiting the Pacific coast of Washington at 5:54 UT, Feb. 22, UT. To see the path in detail, you should download this file by John Irwin and use it with Google Earth. With this plot, the predicted central line is yellow, the limits are orange, and the limits, in case of a 1-sigma path shift, effectively marking the most likely wide region that will be crossed by the narrow path, are green. If you zoom in on the path, black circled dota appear, positioned at 10s intervals; if you click on them, the event Universal Time, and the star's altitude and azimuth at the time, will appear. The path interactively takes into account the topography, shifting south with higher elevations above sea level. This is not the case with Josselin Desmar's Google Earth file, which some of you may have, nor with the Google map on Derek Breit's Web site (not yet available), so you should use this one (John Irwin's) instead. Steve Preston's page for the occultation, including his usual finder charts of different scales, is here, and the path is now available via Occult Watcher and the IOTA feed. I have used Guide8 to create some finder charts for this occultation, with links to them below: Naked eye chart, to mag. 6.0 Finder scope chart, to mag. 9.5 Detailed chart, to mag. 12.5 They show the FOV for an 80mm f/6 refractor. There is also a 5-deg. diameter circle, a typical finder scope FOV, centered on the target. The target star is in the center of each view, with the local vertical direction up, as seen from n. New Mexico; the view will be rather similar for other locations along the path across N. America. The target is about 2 degrees northwest of 3rd-mag. mu Hydrae. A NWS cloud cover forecast map from a couple of before is here; the forecast has changed little since then. Note that the UT date for this event is Monday, Feb. 22, but in the Pacific, Mountain, and Central time zones, the event will occur late Sunday evening, Feb. 21, local time. _ _ _ We hope to have better results from another occultation, of 8.3-mag. NY Hydrae, that will occur over a roughly similar path on March 7 UT. Hopefully, we'll get a much improved orbit from radar observations by then. For more about it, click here. _ _ _ David Dunham, 2021 March 4 e-mail: dunham@starpower.net; cell phone: 301-526-5590