Mar 17/18/19/20 Meteors

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.

March 18 fireball from all-sky cam on Mount Hopkins. Credit: MMTO/SAO/Univ. of Arizona.

We can learn a surprising amount of information about this fireball just from the above images. The shareware program Fireball writen by Albino Carbognani ( 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.

Orbit of the Tucson fireball seen on March 18. Created with C2A and Fireball. Credit: Carl Hergenrother.
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 - Antihelions
GNO - Gamma Normids

1 Comment

  1. Carl:
    Thanks for the fireball data derived from the 3/17 event that you just recently posted. My ‘almost’ allsky camera get pick this one up and yes, it was short, but sweet. For me, it came into the constellation of Perseus and by using several 2 minute exposure frames put together as a ‘movie’, I reconstructed a short .avi that lasts about 8 seconds and does include the fireball from this perspective SE of Tucson. I can email it if desired; the file size is only about 276 Kb. Incidently, I also recorded a similar short fireball here at a later time that same night at around 0440 MST (1140 UT); that one was seen near Hercules.
    Re your earlier post, yes, I am still comet hunting, but not nearly as much as just a couple of years ago. I think you’re right about visual discoveries, but it’s still an engrossing pasttime, right? Between meteors, fireballs, and comets, after all, what else is there? .

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