2014 AA – New Year’s Earth impactor

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.

2008 TC3 – Sudanese Fireball Meteorite Recovered

Last year on October 6, a tiny asteroid was discovered in space. Unlike all of the asteroids discovered before this one, this asteroid (named 2008 TC3) was on a collision course with Earth. Only 20 hours after discovery, the 2-meter in diameter asteroid entered the Earth’s atmosphere over northern Sudan in Africa.

The New Scientist magazine reports that researchers from the University of Khartoum (in Sudan) and NASA have found meteorites from the impact of 2008 TC3. This marks not only the first time that an object was observed in space before impacting the Earth or its atmosphere, but also the first time an object was studied in space as an asteroid and on the ground as a meteorite.

The New Scientist report can be found here.

A PDF presentation by Lindley Johnson, head of NASA’s Near-Earth Object Observation program, can be found here. This presentation also includes photos of one of the meteorite. It is also a nice summary of the current state of the surveys which search for Near-Earth asteroids and comets.

Past Transient Sky posts include:

Incoming Fireball Over Sudan!!! – 2008 TC3“, “More on the Sudanese Fireball – 2008 TC3“, “Report on the Impact of 2008 TC3

Report on the Impact of 2008 TC3

The Near-Earth Object Program office at NASA-JPL has just released a report about the impact of 2008 TC3. TC3 was the small asteroid discovered less than a day before entering the Earth’s atmosphere over northern Sudan. The text of the report can be found at:

http://neo.jpl.nasa.gov/news/2008tc3.html

Some highlights from the report include …

  • Discovered on 2008 Oct 6 at 6:39 UT by Richard Kowalski at the Catalina Sky Survey using the Mount Lemmon 1.5-m telescope, north of Tucson, Arizona
  • 26 observatories reported 570 astrometric (positional) observations
  • 2008 TC3 entered the atmosphere on 2008 Oct 7 at 2:45:40 UT
  • It detonated (exploded) 5 seconds later due to the high pressure of rapidly moving through the Earth’s dense atmosphere
  • TC3 was moving at 12.4 km/s when it hit the atmosphere. That’s 7.4 miles/s or 26,640 miles per hour!
  • It was tumbling as it moved through space and rotated about two axes with periods of only 97 and 49 seconds. Those periods are how long a “day” (sunrise to sunrise) would have lasted on TC3. This is not uncommon for small asteroids.
  • It was the first natural body other than the Moon to be eclipsed by the Earth. It entered Earth’s shadow an hour before it hit the atmosphere.
  • TC3 detonated at a rather high altitude for a large fireball (37 km or 22 miles or 117,000 feet). This suggests that TC3 was rather weak when compared to most asteroids/meteorites.
  • The fireball and/or flash was observed by a European weather satellite, US Defense satellites, a KLM flight crew and a video security camera in southern Egypt.

More on the Sudanese fireball – 2008 TC3

The fireball caused by the impact of 2008 TC3 has been confirmed. The NASA’s Near-Earth Object Project Office reports that the fireball was observed on October 7 at 02:45:45 UT. The energy released was estimated at 0.9 to 1.0 kilotons of TNT. They do not give the source of this information though they state that more information is forthcoming. My guess, is this sighting is from the US Department of Defense’s Defense Satellite Program (DSP) satellites. The DSP program consists of a constellation of missile early warning satellites which monitor most of the world for missile launches. These satellites are also very good at detecting bright fireballs. Hopefully more details will become available.

The NEO Project Office also reports that an infrasound station in the African nation of Kenya made a detection. Dr. Peter Brown of University of Western Ontario in Canada estimates the energy released at 1.1 to 2.1 kilotons of TNT. A third report comes from a pilot on a KLM flight over the nation of Chad who saw a flash at the time of the fireball. More info on this last two reports can be found at Spaceweather.com.

The fact that there are no videos of this fireball are disappointing but not surprising. The fireball occurred over northern Sudan which is sparsely populated and rather poor. Sudan is also not a country that you can just show up and drive around in. It would have been difficult to have traveled to the fireball site. It will be interesting to see if any meteorites are found on the ground from this fireball. Even with all of the difficulties of travel in Sudan, I’d be surprised if a few meteorite hunters don’t find their way to the predicted impact site.

[Exciting new news]

An image of the fireball taken from a European weather satellite has been posted by Jiri Borovicka of the Czech Academy of Sciences. The image can be found on the frontpage of Spaceweather.com. More info on the this sighting can be found at the webiste of the EUMETSAT.

Incoming Fireball Over Sudan!!! – 2008 TC3

For the first time in recorded history a very small asteroid has been discovered before burning up in Earth’s atmosphere as a brilliant fireball. During the night of Oct 5/6, Rich Kowalski of the Mount Lemmon Survey discovered a new Near-Earth asteroid named 2008 TC3. It now appears that this object will hit the atmosphere of the Earth tonight (Oct 7 UT) at 2:46 UT (10:46 EDT) over northern Sudan in northeast Africa.

Based on the brightness of this asteroid, it is very small and probably on the order of 2-meters or 7-feet in diameter. As big as this may seem, objects this small usually break up into much smaller pieces with little remaining to hit the ground. If pieces do survive to hit the ground they will probably be small, no bigger than a grapefruit. What this object will do is produce a spectacular fireball for a few tens of seconds over the Sudan. The Near-Earth Object Project Office at NASA-JPL estimates that an event of this size occurs once every few months somewhere in the world. The fireball will probably be more spectacular than the Sept 19 fireball observed over southern California but will only be visible within a few hundred miles of northern Sudan. It will not be visible from the rest of the world.

This is the first time a small fireball producing asteroid has been observed before entering the Earth’s asteroid. Why hasn’t this happened before? Object of this size are very faint. In fact, of the 360000+ known asteroids, we have only found 2 other asteroids that are this small. Also asteroids very close to Earth move very fast. Now moving fast isn’t the problem, the problem is that there is so much junk in orbit around the Earth from decades of satellite launches, that it is very hard to tell the difference between a small close asteroid and an old satellite. So the current asteroid hunting telescopes have to be lucky to pick one of these objects up. In the future, the next generation of asteroid survey telescopes will be able to discover these objects further out. There may come a time in the not too distant future, when a spectacular fireball will be predicted to occur over a major population center days in advance. When that day happens, you won’t have to be lucky to see a fireball, you can just go outside at the predicted time and enjoy the show.

Before it hit the Earth’s atmosphere, 2008 TC3 was on an orbit that took it as close to the Sun as 0.91 AU and as far from the Sun as 1.63 AU. It took 1.43 years to orbit the Sun.

If any photos of the fireball become available I will post link to them.

Links to a few publications about 2008 TC3…

The discovery announcement from the Minor Planet Center

Press release from the University of Arizona

Press release from the Near-Earth Object Project Office at NASA JPL

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