Last night (March 22) at around 8 p.m. EDT, a meteoroid with a boulder size of ~1 yard in diameter entered the atmosphere above Pennsylvania and moved southeast, passing just south of New York City. It went dark over the Atlantic Ocean, and may have produced meteorites which dropped harmlessly into the water below. This trajectory plot, produced by Mike Hankey from the over 350 eyewitness accounts, is on the American Meteor Society’s website (http://www.amsmeteors.org/ and shows the meteor’s path.
Images were taken by Rob Suggs and Aaron Kingery in twilight through cirrus clouds around 00:36 UT on 17 Mar 2013 with a 14 inch Schmidt-Cassegrain telescope at Marshall Space Flight Center’s Automated Lunar and Meteor Observatoryin Huntsville, Ala. The detector was a low-light level B&W video camera with a focal reducer giving a 20 arcminute horizontal field of view. The view shows the over-exposed coma and a faint division in the 2 sides of the dust tail. The images were not flat-fielded or dark-subtracted.
The darker image is a stack of 60 video frames (2 seconds), enhanced to show the tail. The lighter image is produced by simply stacking 1600 video frames (53.3 seconds).
So how can we tell that the Russian meteor isn’t related to asteroid 2012 DA14?
One way is to look at meteor showers — the Orionids all have similar orbits to their parent comet, Halley. Similarly, the Geminids all move in orbits that closely resemble the asteroid 3200 Phaethon, which produced them. So if the Russian meteor was a fragment of 2012 DA14, it would have an orbit very similar to that of the asteroid.
It does not…
If you look at the image, the orbit of the Earth is the green circle. That of 2012 DA14 is the blue ellipse that is almost entirely within the orbit of the Earth; notice that it is close to circular. The other blue ellipse, stretching way beyond the orbit of Mars, is the first determination of the orbit of the Russian meteor. Notice that the two are nothing alike; in fact, they aren’t even close.
This is one reason — a big one — why NASA says the asteroid 2012 DA14 are not connected.
This is the question that keeps cropping up, and it deserves an answer. Images are being posted showing the fragments and they look like ordinary chondrites of asteroidal origin. This material is dark, and not very reflective, which makes it difficult to spot out in outer space, especially if the object is bus or house size.
Astronomers measure brightnesses in magnitudes — the larger, more positive the number, the fainter the object is. The Sun is magnitude -27, the planet Venus -4, the star Vega 0, and the faintest star you can see is about +6. The best asteroid survey telescopes have a magnitude limit of about +24, which is about 16 million times fainter than what you can see with the unaided eye.
We can now use the latest orbit determined by Dave Clark (and yes, the meteor came roughly from the East, not from the North as stated in the initial NASA reports) and combine it with the estimated size and reflectivity to figure out when we should have seen the meteoroid in the asteroid survey telescopes. The calculations can be displayed in a graph like this one. Note that, even with very large telescopes, the meteoroid would not have been visible until a mere 2 hours (135,000 km from Earth) before impact — very little time to sound a warning.
Even if we had been looking at the right spot and the right time, there is another problem — the meteoroid would be in the daylit sky, and telescopes cannot see faint objects in the daytime.
Simply put, the meteoroid was too small for the survey telescopes and came at us out of the Sun.
The bright blue line in the diagram above shows the orbit of the Russian meteor prior to the meteor breaking apart over the city of Chelyabinsk. The meteor hit the atmosphere at a speed of 18 km/s (11.2 miles per second or 40,300 mph). It was moving at a shallow entry angle (less than 20 degrees) and broke apart some 15-25 km above the Russian city. Most of the damage was caused by the shock wave produced when the meteor disrupted.
Several thousand meteors enter Earth’s atmosphere each day. The vast majority of these, however, occur over the oceans and uninhabited regions, and a good many are masked by daylight. Those that occur at night also are rarely noticed by people. Due to the combination of all of these factors, only a handful of witnessed meteorite falls occur each year. The Russia meteor was one of those rare instances.
According to NASA scientists, the trajectory of the Russian meteor was significantly different than the trajectory of the asteroid 2012 DA14, making it a completely unrelated object. Information is still being collected about the Russian meteor and analysis is preliminary at this point. In videos of the meteor, it is seen to pass from left to right in front of the rising sun, which means it was traveling from north to south. Asteroid DA14’s trajectory is in the opposite direction, from south to north.
This image shows asteroid 2012 DA14 and the Eta Carinae Nebula, with the white box highlighting the asteroid’s path. The image was taken using a 3″ refractor equipped with a color CCD camera. The telescope is located at the Siding Spring Observatory in Australia and is maintained and owned by iTelescope.net.
NASA experts will hold a teleconference for news media at 4 p.m. EST today to discuss a meteor that streaked through the skies over Russia’s Urals region this morning.
Scientists have determined the Russia meteor is not related to asteroid 2012 DA14 that will pass safely pass Earth today at a distance of more than 17,000 miles. Early assessments of the Russia meteor indicate it was about one-third the size of 2012 DA14 and traveling in a different direction.
Panelists for the teleconference are:
— Bill Cooke, lead for the Meteoroid Environments Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. — Paul Chodas, research scientist in the Near Earth Object Program Office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
The teleconference will be carried live online at:
This is the most common question we are asked, and the answer is “maybe.” It all depends on where you are located and what sort of equipment you have.
Closest approach will be around 19:25 UTC on February 15; this will be when the asteroid will be at its brightest. Even at this time, when 2012 DA14 is only about 17,000 miles above Earth’s surface, it will not be visible to the unaided eye due to its small size. Observers in Indonesia (which is favored to see close approach) will need binoculars to catch a glimpse of the asteroid as it moves rapidly through the sky.
The rest of us will need to use a telescope. In North America, 2012 DA14 will be no brighter than magnitude 11 when the Sun sets on the 15th. This is over 60 times fainter than the faintest star you can see with your eyes under perfect sky conditions. Also, it will still be moving quickly through the constellations — over 3 degrees (6 Moon diameters) per hour — and this speed, combined with its fading, will make it a challenging target, even for experienced amateurs. Algorithms in many of the software programs used to drive telescopes are not suited for fast movers like this one, and may point the telescope in the wrong locations (A test we conducted using a popular software package showed that it would point the telescope over a degree away from the actual position of DA14, well outside the one half degree field of view of most instruments). So seeing 2012 DA14 before it fades beyond the limit of most amateur telescopes will not be a simple task; it will require some thought and advanced planning. An invaluable tool in planning your observations is the JPL Horizons website (http://ssd.jpl.nasa.gov), which can calculate the precise positions of 2012 DA14 for your location.
So can I see 2012 DA 14? The answer is yes — if you have access to a decent telescope, if you take the time to figure out where you need to look in advance, and if your sky is clear. A lot of work, but the reward is a glimpse of a house-size visitor from another part of the Solar System as it whizzes by our planet at a distance closer than many of the communications satellites we depend upon in our daily lives. A rare event, to be sure.
Those without telescope access may also get a glimpse. NASA will be streaming the latter part of the asteroid flyby on Ustream at http://www.ustream.tv/channel/nasa-msfc – if the skies are clear in Alabama and the MSFC-based telescope can view DA14, you can use the Internet to get a peek at 2012 DA14 (which will look like a fast moving star) from the comfort of your home.
The Marshall Meteoroid Environment office put together the plot below showing the distribution of end heights of Geminids seen with our fireball camera network. 85% of Geminids burn up 40 to 55 miles above Earth’s surface and 15% get below 40 miles altitude.
Geminids penetrate deeper into the atmosphere than the Perseids because they are moving slower (78,000 mph for the Geminids compared to 130,000 mph for the Perseids) and are made up of denser material, owing to the fact that the Geminid parent body is rocky asteroid 3200 Phaethon and the Perseid parent is a comet yielding more fragile material.
This video shows meteors captured by a wide-field camera at the NASA Marshall Space Flight Center on the night of December 12. There are 141 events; at least 77 of these are Geminids, based on their angular speed and direction of travel. Near the end of the movie, a couple of satellites are visible crossing the field of view.
For those of us sky watching for meteors , this means we have a good chance of viewing a Geminid meteor. Tonight, December 13, into the early morning of December 14 is the peak. Happy meteor watching!