Sky and Telescope magazine is reporting that Peter Brown (University of Western Ontario) has made a preliminary identification of the impact site of 2014 AA, the New Year’s Earth impacting asteroid. Or more exactly, Dr. Brown has found the point where 2014 AA disintegrated in the Earth’s atmosphere.
Brown and his group used data from infrasound arrays to detect the ‘noise’ of the explosion. The location of the fireball was triangulated by measuring the time of arrival of the infrasound signal at a number of infrasound arrays around the world. This technique has been used to pinpoint the location of other large fireball events as well as the detonation of nuclear weapons. As reported by S&T, the preliminary location is at 40° west, 12° north or about 1,900 miles (3,000 km) east of Caracas, Venezuela.
This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight “streaking” of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona
2014 has started off with fireworks! The first designated asteroid of the year, discovered only half an hour before midnight on New Year’s Eve (Tucson local time) but 6.5 hours into 2014 in Universal (or Greenwich Mean) time by Richard Kowalski of the Mount Lemmon Survey, was an Earth impactor.
Based on 7 astrometric measurements taken over the course of 70 minutes, the Minor Planet Center’s orbit has determined that 2014 AA impacted the Earth around Jan. 2.2 +/- 0.4 UT somewhere along an arc stretching from the eastern Pacific Ocean, southern Nicaragua, Costa Rica, very northern Columbia and Venezuela, a long stretch of the Atlantic Ocean and the African countries of Senegal, Gambia, Mali, Burkina Faso, Niger, Chad and Sudan. Maps of the possible impact points have been produced by Bill Gray and can be found here and here. The most likely impact point is in the Atlantic Ocean off the coast of western Africa.
With an absolute magnitude of ~30.9, 2014 AA was likely a very small asteroid with a diameter on the order of 1-5 meters. Such an object would have posed no danger to the ground though small meteorites may have survived passage through the atmosphere. If it fell in the ocean there is a good chance that no one directly witnessed it though the signature of its resulting fireball may be found in weather satellite images.
This marks the second time that an asteroid was detected in space prior to impact. The first impactor, 2008 TC3, was also found by Rich Kowalski and the Mount Lemmon 1.5-m reflector. That body was observed to fall over northern Sudan and led to the recovery of many meteorites (named Almahata Sitta). More on the fall of 2008 TC3 and Almahata Sitta can be found at this blog (here, here, here, and here), the Meteoritical Bulletin and Wikipedia.
Note, that for every small asteroid discovered before hitting the Earth (of which we’ve seen only two) there are many thousands of similar sized objects (and countless smaller ones) that go undetected until seen as brilliant fireballs or meteors. Hopefully planned upgrades to current asteroid surveys such as the Catalina Sky Survey/Mount Lemmon Survey and future surveys like ATLAS will result in more warning time for incoming asteroids.
2012 DA14 may not be on a collision course with Earth later today but a smaller asteroid was. A major fireball (and most likely also a meteorite dropping event) occurred over the city of Chelyabinsk, Russia. Chelyabinsk is a city of 1+ million people located just to the East of the Ural Mountains and just north of the Russia-Kazakhstan border.
The fireball that occurred there this morning appeared brighter than the Sun and produced a sonic boom that shattered windows causing flying glass-induced injuries to hundreds of people. A large building in town also seems to have been damaged. Though it is still uncertain if this was due to a large meteorite or the sonic boom.
An event like this happening only hours before the close flyby of the ~45-meter in diameter asteroid 2012 DA14, begs the question of whether the two are linked. It is probably unlikely that the Chelyabinsk fireball and 2012 DA14 are related. Luckily there are so many great videos of the fireball that an accurate orbit for the asteroid that caused the fireball should be easily determined.
[Update: 2012 DA14 and the Russian fireball can not be related. The radiant (the region of the sky that a DA14 or a piece of DA14 would appear to come from) of DA14 is at the very far southern declination of -81 degrees. This is the reason why DA14 is only visible from the southern hemisphere as it approaches Earth. A radiant that far south could not produce a fireball over Russia which is in the northern hemisphere. Any pieces of DA14 would only be able to impact Earth over the southern hemisphere or a few degrees north of the Equator. The fact that the Russian fireball and the 2012 DA14 close approach are happening on the same day is just a coincidence.]
Up-to-date information can be found at RT, here and here, and RMNB.
Many videos have been posted. The first 2 show the fireball itself. The last 2 are videos of the resulting contrail. What is very impressive about the last two is that the videos also caught the sonic boom. In one of the videos you can hear glass shattering in the background. Simply awesome…
A brilliant fireball was observed over southern California, Nevada, Arizona and Sonora on Wednesday evening, September 14. Hundreds of reports have been submitted to the American Meteor Society, and even a few to this blog. The best site for learning more about this event and other fireball events is at the American Meteor Society. Their page dedicated to this fireball (including a map of all reported eyewitnesses) can be found here.
An eyewitness in southern California was able to get a video of the event.
Down in Hermosillo, Sonora, Mexico, Salvador Aguirre picked up the fireball on his all-sky camera. In the image below, the fireball is seen low on the horizon to the NNW of Hermosillo.
So what caused the fireball? Most likely it was a small asteroid, no bigger than a basketball, hitting the upper atmosphere at 20-40 km per second. Based on the behavior of similar objects, it first became visible at an altitude of ~90 km and ceased to be visible at an altitude of ~20-30 km. Though some material may have survived to impact the ground as small meteorites, at least 90% or more of the asteroid burned up in flight.
A brilliant and well observed fireball was observed flying over the American Midwest Wednesday evening. The map below shows that sightings were made from Kansas in the south to Minnesota in the north and from Indiana in the east to South Dakota in the north. The yellow stars denote a sighting while the red stars denote reports of sonic booms (a tell tale sign that meteorites may have survived to hit the ground).
Zooming in on the area where most of the sonic booms were heard brings us to southwestern Wisconsin. We now know that meteorites were found in this area. Not only did the sonic booms and the large number of videos point meteorite hunters to this area but as many as 3 NWS Doppler radars picked up the meteorites as they were falling through the atmosphere. The blue square pinpoints were the radars place the most likely area of meteorite falls.
All of these observations have allowed researchers to quickly find meteorites from this fireball. Meteorite related stories can be found here and here.
The net is hopping with reports of a brilliant fireball seen from Wisconsin to Missouri. All reports are consistent with a meteor that rivaled the Full Moon in brilliance. Reports of sonic booms also suggest that shattered remains of the small asteroid (original size was probably no larger than a basketball, but that’s only a guess) may have survived to hit the ground as small meteorites (maybe fist sized, probably much smaller).
I’ll try to get more info and maybe even post a sighting/sonic boom map.
In the meantime, here are some comments posted to this blog.
From Jennifer in Spring Grove, IL:
I think I saw a meteor west of where I live in Spring Grove Il a bit after 10 pm today April 14th. It was very large and brite. It lit the whole sky as if a full moon just peeked out from a cloud. It looked very near to the ground before it fizzled out. So low I waited to hear an explosion.
From Amy near Wautoma, WS:
My husband and I were driving in Mt. Morris near Wautoma, Wisconsin. We were out away from the lights of the city and we both saw a large glowing green ball falling out of the sky! It was cool to my husband, but freaked me out. I was scared! I can never seen something like that before! There was no noise….it was just there, like a movie. I didn’t not see it all the way to the ground. It happened on Wednesday April 14, 2010 just before 10PM. Anyone else see this?
UPDATE: The Quad Cities IL/IA National Weather Service Office has a page devoted to the fireball. The site includes links to videos as well as a Doppler Radar image showing possible meteoric debris falling over Grant and Iowa counties.
Activity has been fairly consistent from night to night with anywhere from 10-16 meteors per night. Though a single minor shower, the Gamma Normids, is active none have been seen. This isn’t too surprising since this shower only produces a meteor or 2 per hour for observers who can see down to 6th magnitude. My cameras are much less sensitive than the human eye and can only see down to ~2nd magnitude. Also the radiant of the Gamma Normids is located in the far southern sky so it takes a rare one to be seen this far north.
The highlight of the past 3 nights was a bright short lived fireball seen on the evening of March 17 at 10.:51 pm (March 18 @ 5:51 UT). This fireball lasted for a little over 1 second but traversed only a small part of the sky. The whole event was caught by SALSA2, my small FOV zenith-pointing camera as well as the all-sky cam at the MMT on Mount Hopkins. For some reason my all-sky camera did not record the event. Makes me wonder how many other bright meteors are being missed.
The video below is from the SALSA2 camera.
The next image is a screen shot of the all-sky camera at the MMT. This image is a ~10-second exposure so unfortunately we can’t get any video.
We can learn a surprising amount of information about this fireball just from the above images. The shareware program Fireball writen by Albino Carbognani (www.fis.unipr.it/~albino/ITASN/documenti/fireball.html) can be used to determine the trajectory through the atmosphere as well as an initial orbit.
Start Height = 71.7 km
End Height = 67.7 km
Total Length of Travel = 15.7 km
Geocentric Velocity = 12.1 km/s
Semi-major axis = 0.82 AU
Eccentricity = 0.22
Inclination = 0.6°
Perihelion = 0.64 AU
Aphelion = 1.00 AU
The object that caused the fireball was an Aten. This means it had crossed the Earth’s orbit and had a semi-major axis (its average distance from the Sun) less than 1.0 AU. The very slow geocentric velocity of ~12.1 km/s is almost as slow as a meteor can get (the slowest is 11.2 km/s, the fastest is ~72 km/s). The slow velocity is a result of impacting the Earth near the objects aphelion point. Note of warning, there is still much uncertainty in the positions and timing of this fireball. The orbit below is probably not exactly correct. Still, it is hard for this object to have been on an orbit other than an Aten with an aphelion near 1 AU. That much is certain. The perihelion distance, on the other hand, can be a few tenths of an AU larger or smaller.
Obs Date(UT) Time TOT SPO ANT GNO
TUS 2010-03-20 10h 16m 14 12 2 0
TUS 2010-03-19 09h 35m 16 14 2 0
TUS 2010-03-18 10h 19m 10 9 1 0
TUS - Camera in Tucson operated by Carl Hergenrother
SDG - Camera in San Diego operated by Bob Lunsford
TotTime - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - AntihelionsGNO - Gamma Normids