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calendar   Tuesday - February 28, 2012

Close Call Next Year

“Brand New” Asteroid Will Just Miss Hitting Earth Next February

2012 DA14
Discovered 2012-02-23 by J75 OAM Observatory, La Sagra
Object is flagged as a Virtual Impactor by SENTRY (JPL)
NEODyS has posted 2012 DA14 as an impact risk.
... Classification: Apollo [NEO]
Earth Close-Approach 2013-Feb-15 19:25UT Nominal Distance (AU) 0.000217508367454278 AU =~ 0.085 Lunar Distance = * * close passer * *
absolute magnitude H = 24.243 roughly 45 meter diameter





I saw the edge of this story yesterday when posting about the visible planets being ... visible. I looked into it a bit more today, then was sidetracked for some time trying to make it fit the end of the Mayan calendar. Now them old Mayans didn’t seem to have watches, or even much in the way of horology, but they kept a pretty accurate calendar. The thing is rather like the odometer in your car, and it’s set to roll over during the 3rd week of December this year. End of the world? Well, maybe not. As far as I can tell, no Mayan legend foretells that; it’s just that the earth was destroyed by the gods the last 3 times their calendar flipped over, so go figure for this one. Anyway, the Mayan calendar dates back to the middle of August, 3114BC, though nobody knows when they actually built the thing; the crest of the Mayan civilization was 2000BC to 900AD. So trying to figure out if a minor error on their part - about 2.5 seconds per day, in a civilization without clocks - would push the “end of the world” forward 56 days to February 15/16 when this asteroid comes by. Those calculations turned out to be moot, since I have no idea when they actually started using thing. Furthermore, it seems they used both a 365 day solar year and a 260 regular year calendar at the same time, it’s numbering system being described in both Base 20 and Base 18 numbers simultaneously. And then it gets complicated.

But it struck me, as we stand here on the verge of yet another Leap Year’s Leap Day, that such a culture with a grand reputation for naked eye astronomy would have to use a solar dating far more accurate than just 365 days. We have Leap Year now, because we’ve figured out that a year is actually 365 and a quarter days ... for a nation of stargazers, their predictions would be off a full day every 4 years if they didn’t have something similar. And since they had writing, and watched the skies for several thousand years, they’d have to have had a higher level of accuracy even than that: the solar year is 365.256363 days long; that extra 0.006363 part adds up to more than 15 hours every century, which will throw your priestly prediction of eclipses and stuff off by quite a bit. It turns out we’ve been adding leap seconds here and there to our calendar, one or two or none per year, for the past 40 years. So our day keeping system isn’t exactly perfect either.

It’s not like I wanted to be able to bend things so I could play Nostradamus Junior and foretell the end of the world. It’s just that the calculated orbit of this new chunk of rock is accurate to within half an hour, and the minimum distance calculation shows it missing Earth ... by about 15 minutes. Oops. And the size calculation seems to be 45-90 meters, when the Tunguska Impact of 1908 - the one that leveled a good chunk of Siberia - appears to have been made by a 50-100 meter ice ball, delivering the kinetic energy of an H-bomb. Double oops. Even 1/8 of that would totally suck.

But back to the asteroid. 2012 DA14 - such a name, I guess Cassandra was taken? - is an unusual beastie. While many asteroids have highly elliptical orbits that take them out to the far corners of the solar system, or at least in and out of the Oort Cloud, DA14 seems to live pretty much on Earth’s orbital path. It’s an inner asteroid, with an orbit very much like our planet’s, except that it’s a bit off the solar plane.

image

And the good news ... or at least they’re telling us it’s good news ... is that the closest approach, the minimum edge of the envelope, of this space potato will be about 26,900 kilometers, which is about 2.12 planetary diameters. This is actually well inside the orbital radius of all the geosynchronous satellites, which are out there at about 36,000 kilometers. So it’s going to be close. Razor burn close. But the smart boys and girls at JPL, NASA’s good buddies, where Rocket Science and Complex Mathematics truly are a matter of life and death, are giving the calculated Min/Max distances as 0.000180613845633866 AU and 0.00200199212143104 AU. 18 digit precision, thank you very much. Probably calculated in FORTRAN too! Too bad they define 1 AU as “approximately 150 million km”, which is not exactly confidence inspiring although it is scientifically honest, because the Earth’s orbit is slightly elliptical. Thank goodness they give us an Earth MOID of .000221174 AU (Minimum Object Intersection Distance), which means we’re safe by a whole 0.000040561AU, which is around 6084 kilometers, which is a bit LESS THAN HALF THE DIAMETER OF OUR PLANET.

Phew, for a second there, I was worried. Good thing NASA and JPL are on it, having made dozens of observations and calculations ever since this chunk of rock, which closely follows Earth’s orbit, years after year, century after century, was discovered all of last week. While they still have a 100% variation on the size of it, they’ve got it’s orbit figured out to the 18th decimal place, so sleep soundly.

According to scientists, asteroid 2012 DA14 has a length of 100 meters and in the case of hitting the Earth, can be released the energy, which equivalent to the explosion of the hydrogen bomb. On February 15, 2013 will be the first recorded case in which an asteroid can fly at a small distance from the Earth, we note, that the asteroid 2005 YU55, which caused the attention of scientists in November 2011, flew at a distance of 325 000 kilometers from Earth, more than 10 times higher, than the distance of the asteroid 2012 DA14, so some scientists do not rule out a collision the Earth with asteroid, because 27,000 kilometers - the distance, that may be in the range of errors of astronomical calculations, and this short distance is actually evidence of real probability of a collision, so other planets of the Solar system can change the trajectory of this asteroid.

obviously a Russian web page, and everybody knows you can’t trust those!

See More Below The Fold

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Posted by Drew458   United States  on 02/28/2012 at 07:51 PM   
Filed Under: • Space •  
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