Really Rocket Science

Today’s APOD is amazing: Orbits of Potentially Hazardous Asteroids.  Reminds me of D.C. traffic on a Friday afternoon.

Explanation: Are asteroids dangerous? Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low. Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth. Pictured above are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs). These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth — about 20 times the distance to the Moon. Although none of them will strike the Earth in the next 100 years — not all PHAs have been discovered, and past 100 years, many orbits become hard to predict. Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example. Of course rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes creating memorable fireball andmeteor displays.

A 400-meter wide Near-Earth asteroid will be cutting it close tomorrow. Will you be able to see it? Yes, but it won’t be easy.

Astro Guyz explains…

Closest approach to Earth occurs at 11:29 UTC/06:29 EST at about 202,000 miles distant, placing it high to the south west for observers on the US Eastern Seaboard. (Don’t forget to “fall back” to Standard time on Sunday, November 6^th; you wouldn’t want to miss seeing the asteroid because of  an anachronistic convention, but I digress..)  At its closest approach, 2005 YU₅₅ will glide along at one degree every 7 minutes, easily noticeable after a few minutes of observation at low power. I plan to target selected areas with my GOTO mount, sketch the field, then watch for changes. I may also take some wide-field piggyback stills with the DSLR, but mostly, this one will just be fun to watch. The asteroid will pass through the constellations Aquila, Delphinus, and Pegasus as it heads westward. Interestingly, 2005 YU₅₅ passes within a degree of Altair centered on 6:07:30PM EST only 27 minutes after local sunset, and also makes a very close pass of the star Epsilon Delphini during closest approach. These both make good visual “anchors” to aim your scope at during the appointed time and watch. Keep in mind, the charts provided are rough and “Tampa Bay-centric…” on an approach as close as this one, two factors muddle the precise prediction coordinates of the asteroid; one is the fact the gravitational field of the Earth will change the orbit of 2005 YU55 slightly, and two is that the position will change due to the position of the observer on the Earth and the effect of parallactic shift. Many prediction programs assume the Earthly vantage as a mere point in space, fine for positioning deep sky objects but not so hot for ones passing near the planet. A good place to get updated coordinates is JPL Horizons website which lets you generate an accurate ephemeris for your exact longitude latitude and elevation.