A composite image of 13 Eta Aquarid meteors from the NASA All Sky Fireball Network station in Mayhill, New Mexico the morning of May 6, 2013. Clouds seriously hampered our view of the ETAs this year. Observations reported to the International Meteor Organization indicate an outburst in the early hours of May 6th UTC.
(Credit: All Sky Camera Network)
Despite interference from the moon and clouds (and rising sun!), this morning we snagged our first observations of the 2013 Eta Aquarids. Here’s an image of one from the all sky camera in Tullahoma, Tennessee. The Eta Aquarids peak in the pre-dawn hours on May 6 and are material from Halley’s comet. They zoom around the solar system at speeds near 148,000 mph. The one seen here burned up completely in our atmosphere over Nunnelly, Tennessee at a height of 58.7 miles above the ground.
(Credit: All Sky Camera Network)
(Credit: MSFC Meteoroid Environment Office)
A Lyrid meteor streaks though the dawn sky over North Georgia College and State University. Moving at 105,800 mph, this inch-diameter piece of Comet Thatcher lasted less than one and a half seconds, burning up 46 miles above Earth’s surface. The second image shows the same meteor seen from the Tellus Science Museum located in Cartersville, GA, some 50 miles distant. By measuring the change in the meteor’s position (triangulation), we can determine its trajectory and speed.
Lyrids are pieces of debris from the periodic Comet C/1861 G1 Thatcher and have been observed for more than 2,600 years. In mid-April of each year, Earth runs into the stream of debris from the comet, which causes the Lyrid meteor shower. You can tell if a meteor belongs to a particular shower by tracing back its path to see if it originates near a specific point in the sky, called the radiant. The constellation in which the radiant is located gives the shower its name, and in this case, Lyrids appear to come from a point in the constellation Lyra.
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.
(Credit: American Meteor Society)
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.Text/image credit: NASA/MSFC/Meteroid Environment Office
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.
Image credit: NASA/MSFC/Aaron Kingery