Aug 10/11/12 Meteors

If everything goes according to schedule, tonight will mark the peak of the Perseids meteor shower. Over at the IMO, observers from around the world have reported over 4000 Perseids with rates reaching as high as ~46 per hour (assuming dark skies and perfect conditions). Hopefully those rates will double tonight.

Two nights ago (Aug 10/11) were clear here in Tucson. The SALSA3 video system detected 43 meteors of which 18 were Perseids. This number may seem low for a camera system that was running all night. It is when comparing against the number of meteors that a visual observer would see. For starters the camera can only detect brighter meteors (down to 2nd/3rd magnitude) and it only covers a small part of the sky (~50×60 degs).

That night I also spent an hour watching the shower with my own eyes. During that hour I saw 14 meteors of which 9 were Perseids. That isn’t bad for 2 days before the peak and with thick cirrus affecting half of my view.

Yesterday was a wet one in Tucson with major thunderstorms hitting the house around 7 am and 7 pm. Though I woke up a few times during the night to see if it was clear to observe, I ultimately didn’t go out since the sky was always covered in patchy clouds. To my surprise, the video camera picked up 41 meteors between the clouds. It probably would have seen many more if it were clearer.

Obs Date(UT)     Time    TOT SPO ANT PER SDA ERI KCG Oth
SAL 2015-08-12  04h 21m   41  10  1   22  3   2   0   3
SAL 2015-08-11  08h 42m   43  12  4   18  1   1   0   7
VIS 2015-08-11  01h 00m   14  5   -   9   -   -   -   -
SAL 2015-08-10  00h 43m   3   2   0   1   0   0   0   0

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
VIS - Visual observations from Tucson (Carl Hergenrother)
Time - 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
PER - Perseids
SDA - Southern Delta Aquariids
COM - Southern Iota Aquariids
ERI - Eridanids
KCG - Kappa Cygnids
Oth - other minor showers

August 9/10 Meteors

The plan was to get myself outside last night and start my 2015 Perseids visual observing campaign. Unfortunately, there were other showers going on in Tucson with rain occurring off and on all night long. My SALSA3 camera system was running and did manage to pick up 3 meteors between the clouds. In short, I can’t personally add much to what the Perseids were up to last night.

Luckily it can’t be cloudy everywhere and others were able to observe the Perseids. Observers from around the world reported observations to the International Meteor Organization. These reports show a shower that is already producing ~25 Perseids per hour. This number comes with the caveat that it is valid for those observing from very dark skies, with no obstructions to their vision and the Perseids radiant overhead. Most observers will be observing under lesser conditions and will see fewer meteors.

In addition to visual observers, automated electronic surveys have also been watching the sky. Up in Canada, the Canadian Meteor Orbit Radar (CMOR) detects small meteors. In many cases, these meteors are smaller and fainter than those visible to the average backyard meteor watcher. A map of the sky from ~17 UT on 2015 August 10 shows a number of active showers. At least for very small particles, the Perseids are not the most active shower. The Southern Delta Aquariids (SDA) appear more active than the Perseids (PER) and the Northern Delta Aquariids (NDA) are a little less active than the Perseids. This will change over the next 2 nights.


Map of meteor radiant locations for 2015 August 10 at ~17 UT from Western Ontario, Canada. Meteors were detected by the Canadian Meteor Orbit Radar (CMOS). Credit: The University of Western Ontario Meteor Physics Group.


While radar was good at picking up very small meteors, all-sky fireball cameras are excellent at seeing the very largest meteors. What we call fireballs. NASA has a number of cameras set up to “triangulate” the observation of fireballs and determine their original orbits around the Sun. There are 4 groups of cameras in NASA’s All Sky Fireball Network including 3 in the Tucson area that I was somewhat involved in setting up. Even thought the Tucson cameras were hampered by the same rain and clouds that I was at home, the other camera groups detected a number of fireballs. Of the 21 fireballs, 14 of them were Perseids. At least at the large end of the meteor ‘spectrum’ the Perseids are dominating the night sky.

Orbits of fireballs detected on the night of 2015 August 10 UT by NASA’s All Sky Fireball Network. Most of the orbits are similar because most of the fireballs are Perseids. Credit: NASA All Sky Fireball Network/NASA Marshall.