March 27, 2017

Astro-Challenge: Catching the Flyby of Asteroid 2012 DA14.

Passage of 2012 DA14 by the Earth.

(Credit: NASA/JPL).

By now, you’ve heard the news. On the night of February 15th, Near Earth Asteroid 2012 DA14 will make a close passage by our fair world. It happens sometimes; hey, it’s a shooting gallery out there, with rogue space rocks roaming the inner solar system at will, seemingly looking for the occasional planet to smash into. This isn’t the closest near miss (or near hit?) of an asteroid; excluding such atmospheric skippers as the great daytime fireball of 1972, that record goes to MD 2011 with a passage of 12,000 miles from the surface of the Earth on June 28th, 2011. What does make this passage so special is that we’ve known about 2012 DA14 for sometime in advance.

The 50 meter (150 foot) asteroid was discovered by the OAM Observatory based in La Sagra Spain on February 23rd, 2012 nearly a full year before its passage. This has given researchers a fair amount of time to plan for observations of its close approach, and yes, also more than a fair amount of time for hype and mis-information concerning this asteroid to make its cyber-rounds. Yes, 2012 DA14 will most likely hit the Earth… someday. But not in 2013, or for the century hence. Observation campaigns to ‘ping’ the asteroid with the Goldstone radar based out of the Mojave will give us more refined projections of the asteroid’s future orbit.

The orbital path of asteroid 2012 DA14. (Created using  NASA/JPL Small-Body Database Browser).

This week’s passage will cross only 17,200 miles (28,700 km) from the Earth’s surface above Southeast Asia at around 19:25 UT on February 15th, its closest passage for this century. 2012 DA14 made a farther passage of 0.008AU (about three times the distance from Earth to the Moon) years before discovery on August 19th, 2004 and will make another close pass of 0.006AU (2x Lunar distances) on February 16th, 2046. Despite initial excitement, a possible impact on 2046 has been safely ruled out; Bruce Willis can stay home… for now. 2012 DA14 “skulks” the Earth’s orbit with a period of 366.3 days, and this close passage through the Earth’s gravitational well will deflect that orbit slightly.

So, how do YOU, the seasoned asteroid chaser, see said space rock? Well, first the bad news; 2012 DA14 will have dipped below +10th magnitude for North American observers and have faded into the distance into the constellation Ursa Minor by the time the sun sets. Middle Eastern and eastern European longitudes will have the best shot at catching the asteroid at +8 to +9th magnitude as it glides northward through the constellations of Corvus, Crater, Virgo and Leo low to the east in the late evening. Far East and Australian longitudes will see the asteroid at its brightest high in the sky in the early pre-dawn hours of the 16th.  And as mentioned on numerous sites around ye’ ole web, 2012 DA14 does indeed cross into the realm of the geosynchronous satellites at 22,300 miles distant from ~19:00-20:00 UT (see accompanying chart). The handy finder chart accompanying this piece shows the course of the asteroid through the celestial sphere during its dip above and back down below +10th magnitude. Asteroid 2012 DA14 will be truckin’ at about 0.8° degrees per minute (that’s 48” per second, or about the width of a Full Moon every 45 seconds!) On closest approach; its movement against the starry background will be immediately discernible at low power.

But first, a few caveats are in order before you start the asteroid hunt. Our chart also reflects the fact that the asteroid will display a HUGE amount of parallax as seen from different vantage points on the Earth. In fact, the asteroid’s apparent position will vary by 20° across the girth of our fair planet on closest approach! You can manually input asteroids such as 2012 DA14 into a planetarium software program such as Starry Night, but these programs do not take into account the aforementioned deflection of the asteroid caused by its close passage by the Earth, so again, predictions will be off.

So, what can you do? Well, NASA’s JPL Horizons ephemeris utility is an excellent tool to generate accurate positions for a target body. (That’s what we used to generate positions for the accompanying chart).                                                                               The passage of 2012 DA14 from 17:40-22:10UT

February 15. (Created by author).

Heavens-Above has also provided a   link to calculate the position of 2012 DA14 from your given location.  We’ve successfully caught nearby passages of asteroids such as 2005 YU55 by treating them as satellites and using the same satellite-hunting tactics to ‘ambush’ them. Simply pick a declination line that the asteroid is set to cross at a given time and begin sweeping at the lowest power and widest field of view available until you “scoop up” the moving asteroid. For example, note that it makes a close passage through the Bowl of Virgo (& many galaxies within it) and by the bright +2.1 magnitude star Denebola (Beta Leonis) around 19:50UT.

The Earth’s shadow from 17:40-21:10UT February 15th,

plus the overhead position of 2012 DD14 at closest approach.

Binoculars can also assist with this endeavor.  Unlike 2005 YU55 and 4179 Toutatis, 2012 DA14 will be such a fast mover that its motion should be immediately apparent. This asteroid juuuuuust misses passing through the Earth’s shadow (the Earth’s shadow is ~20° in apparent diameter at geosynchronous orbit) sitting in the Sickle of Leo at ecliptic longitude 147°. The Moon will be at 31% waxing crescent phase in the constellation Aries on the night of the passage. Watching such a space rock “whiz-by” our planet in the eyepiece can be an unforgettable experience; it’s not often that we as astronomers get to see apparent motion in a celestial object, in real time. An impact by a body the size of 2012 DA14 would be a Tunguska-class event, releasing ~2.4 megatons of energy… but not this year or any year this century. Good luck, and be sure to let us know of your tales of triumph and tribulation as you chase down your asteroid prey!

The position of the Earth’s shadow in the constellation Leo during closest approach.

(Created by the author in Starry Night).


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