Physical Characteristics
Based upon the observed brightness, Apophis' diameter was initially estimated at 450 metres (1,480 ft); a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 metres (1,150 ft). NASA's impact risk page lists the diameter at 0.270 km, or 270 metres (890 ft) and lists a mass of 27 megatonnes based on an assumed density of 2.6 g/cm3. The mass estimate is somewhat more rough than the diameter estimate, but should be accurate to within a factor of three.
During the 2029 approach, Apophis’ brightness will peak at magnitude 3.3, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be ~2 arcseconds, so that it will be barely resolved by telescopes not equipped with adaptive optics.
Read more about this topic: 99942 Apophis
Famous quotes containing the word physical:
“[In early adolescence] she becomes acutely aware of herself as a being perceived by others, judged by others, though she herself is the harshest judge, quick to list her physical flaws, quick to undervalue and under-rate herself not only in terms of physical appearance but across a wide range of talents, capacities and even social status, whereas boys of the same age will cite their abilities, their talents and their social status pretty accurately.”
—Terri Apter (20th century)