Sounds from the Arizona Fireball

Last Tuesday’s fireball over southern Arizona was accompanied by many reports of sounds. These sounds ranged from bangs and rumbles to a crackling sound. The map below is an updated version of one posted last week. Though the path of the fireball has not changed and is still considered uncertain, many sounds reports have been added.

The majority of sound reports are of the distant thunder, low rumble variety. These sounds were heard 1-3 minutes after the fireball was seen and were strong enough to rattle houses in some cases. Some observers likened it to a sonic boom. In fact, that is exactly what they heard, a series of sonic booms. As the fireball descended through Earth’s atmosphere, its broke into numerous pieces. As these pieces decelerated from supersonic to subsonic speeds, they created a sonic boom. There could easily have been dozens to hundreds of small sonic booms though they probably all merged into one.

It is interesting that the sonic boom reports (circles with a heartbeat symbol on the map below) are mainly located to the north and west of the fireball’s path.  Except for reports from the Sierra Vista area immediately to the east of the path, there are no other reports from the East (Benson, Bisbee, Tombstone, Douglas, Willcox, etc.). It is unknown if this is due to something intrinsic to the fireball or just a population density bias (fewer people living out there, hence fewer eyewitnesses reports).

Tucson_Fireball_sounds

Map of sounds heard from the June 23 fireball. Circles with a "heartbeat" pattern denote delayed sonic booms while purple triangles denote sounds heard at the same time the fireball was seen.

The purple triangles denote a different kind of sound phenomenon. These are sounds heard by the observer while the fireball was visible. Most sounds are created at the fireball and then take time to travel to the observer since the speed of sound is many times slower than the speed of light. Hearing sounds at the same time as seeing the fireball suggests that the sound traveled as fast as light. Well, not quite. The shock wave produced by a fireball is so hot that it radiates across most of the EM spectrum. Sometimes structures near an observer (houses, trees, etc) act as antenna and pick up these waves and vibrate. As a result, a buzzing or crackling sound can be heard at the same time as the fireball is seen.

More info on the so. AZ fireball

Here are a few news items regarding Tuesday’s fireball.

A  story from The Herald of Sierra Vista where the fireball passed nearly overhead.

The MMT sky cam caught the first few seconds of the fireball which was used to estimate the trajectory of the fireball. The folks at the MMT (Multiple Mirror Telescope) posted a movie and some more images on their blog. The images show the inside of the MMT dome a minute before the fireball and during the fireball when the dome was illuminated by it. Also they posted a movie made from the sky cam. The movie spans a few minutes centered on the time of the fireball which is only visible on 2 frames.

From KOLD, Tucson’s local CBS affiliate, a video of the fireball taken by a security camera in Marana (just north of Tucson). The video shows what appears to be 2 fainter pieces below and to the right of the main fireball. I believe those 2 fainter objects are just reflections caused by the optics of the camera and are not actually real. What is real is the main fireball appearing in 3 or more pieces right before it faded from view. [Note, if anyone else has picture or videos of the fireball, or even just of the ground being lit up by the fireball, we’d like to see them. This is not just for their cool factor, but they are also very useful for mapping where this fireball originally came from and where it finally came down.]

Comparing the so. AZ fireball to the 1992 Peekskill fireball

For those who didn’t see the fireball or want to (sort of) relive it, here is a video of a similar event. Note, this is NOT a video of last Tuesday’s fireball but a video of the Peekskill meteorite fall from October 9, 1992.

That fireball was observed up and down the east coast and was one of the best documented fireballs in history. The reason, it was a Friday evening during High School football season and there were lots of folks with camcorders taping games. Eventually the small meteorite that remained landed in the trunk of a car in Peekskill, NY. For more on that fireball and what we learned see this nice summary.

The so. AZ fireball looked very similar to the Peekskill one. The colors are a close match with the head of the main fireball and pieces a brilliant blue-green while the long tails appeared reddish. Both fireballs also produced many fragments which broke off the main body and quickly fell behind.

Based on my own recollection, Tuesday’s fireball didn’t last as long as Peekskill or move as far across the sky but it had many more fragments.

So for those who missed it, here’s what a similar event looked like. And for those who saw it, I hope it brings back some good memories.

Update on the so. Arizona fireball – June 23

Reports continue to come in from all over southern and central Arizona of Tuesday evening’s fireball. The most interesting reports involve a series of loud sonic booms heard from Tucson southward. Most of the sonic boom reports are from the Sierra Vista to Green Valley area.

I would like to thanks everyone who has submitted reports. It is greatly appreciated and will help us understand this event better. Also remember to file a report with the American Meteor Society at http://www.amsmeteors.org/fireball/report.html .

I was hoping to find more video of the fireball especially from amateur all-sky fireball cameras. There are 3 such cameras in the area but all were down for maintenance and testing during the time. And yes that is partially my fault. Oh, well, next time… An additional camera near El Paso would have seen it but was clouded out.

Luckily, there is an all-sky camera that runs all day and night on Mount Hopkins, where the 6.5-m MMT telescope resides. This camera is used by the astronomers to check sky conditions during their observing runs. It is usually used to watch for clouds and fog. But it is also great at picking up other things such as meteors and satellites. [Note: all of the movies taken by this camera are archived on line and can be seen by the public at http://skycam.mmto.arizona.edu/ .

The camera takes a series of ~10 second exposures. Tuesday’s fireball was picked up on 2 consecutive images. The 1st image below shows the early stages of the fireball. At this point the fireball is bright but probably not much brighter than Venus. Note the time is 9:21 pm.

MMT_fireball1

Single frame from MMT skycam. Thanks to Tim Pickering for giving permission to post this image and Rich Kowalski for making the snapshot.

The 2nd frame is completely washed out. During the 2nd half of the fireball’s flight, its brightness rivaled the Full Moon. This easily overwhelmed the camera since its len iris was wide open for night-time observing.

MMT_fireball2

Single frame from MMT skycam. Thanks to Tim Pickering for giving permission to post this image and Rich Kowalski for making the snapshot.

The single MMT sky cam image does provide some great information on where the fireball came from and its path. Combing this image with my own naked eye observations, I was able to map out a preliminary path over southern Arizona. The map below (made with Google Earth) combines the MMT sky cam observations of the 1st few seconds of the fireball with my observations of the last few seconds.

Note: This is my first time doing this so the path could be completely wrong. For all of you meteorite hunters out there, don’t completely trust this path. Then again, if it helps you find some pieces, I want one. :)

The first detection (by the sky cam) occurs over the border to the east of Nogales at an altitude of 70-80 km. The sky cam is limited to bright objects, so naked eye observers may have been able to see it even earlier. My last observation occurs between Benson and Huachuca City at an altitude of ~20-30 km. The “heartbeat” symbols are reports of sonic booms. These reports cluster nicely near the middle to end of the path when the fireball was breaking up and should have produced sonic booms.

Tucson_traj_Jun23

Possible path of the June 23 fireball over so. Arizona. "Heartbeat" symbols denote sonic boom reports. Made with Google Earth.

So what was this? It was most likely a small asteroid hitting the atmosphere at ~20 km per seconds (12 miles per second). Originally the asteroid was probably not much bigger than a basketball. Again by combining the data from above, the fireball originated from the direction of the constellation of Corvus (that would be its radiant). There is a very poorly observed meteor shower called the Corvids that may be active right now. It is possible that this fireball is a member of this shower but it is more likely that it was just a Sporadic (meaning it was not associated with any shower).

So the fireball was caused by a small lonely asteroid that just happened to be at the wrong place at the wrong time. Or the right place and time for those lucky enough to have seen it.

Southern Arizona Fireball – June 23

Earlier this evening, I was outside in my driveway trying to find Comet Garradd with my 10×50 binoculars. Suddenly I was distracted by a flickering light out of the corner of my eye. At first I thought it was the neighbor’s light. In fact, it was probably the most beautiful fireball I’ve ever seen (or at least have seen in 10+ years).

From my home in central Tucson, the fireball was located to the southeast and traveled further to the east and slightly downward. It was a brilliant blue-green and was trailed by dozens of smaller fragments. Though the head, or front, of each fragment was blue-green, the end of the trails were more purplish or reddish (I’m not completely sure). The whole event lasted for greater than ~2 seconds (it could easily have been longer since I didn’t notice it right away).

I estimated that the fireball was a little fainter than the Full Moon (maybe magnitude -11). It was obvious that it was bright enough to cast shadows. One report I received (from Rick) mentioned a rumble heard a minute or so after the event. This is most likely due to a series of sonic booms created as small pieces of the original asteroid slow down and start to travel sub-sonically. The fact that the sound took a minute or more to reach Rick gives you an idea of how far away the explosion was (over 10 miles).

Unfortunately my meteor cameras don’t cover the whole sky, and due to some trees, don’t point to the south so nothing was seen. Plus (embarrassingly) I hadn’t turned them on yet. I do know of an all-sky camera that might have been up and running. If so, I’ll try to post the video.

I wasn’t the only one who saw it and reports have come in from Phoenix and Tucson. The following comments have already been posted to this blog.

From Anna: “I saw something fall form the sky tonight that looked almost the size of a grapefruit, on fire and falling. It had a blue light with yellow behind it. t looked so big that it seemed like it landed only a few miles away. I have been watching the news, but nothing. It just scared me a little! I am in Phoenix.”

From Loretta: “I saw a giant meteor june 23 about 915 or 920. It was in the southern sky and went from west to east.”

From Teryn: “I saw that too south of Tucson. It lit the ground up like the sun.”

From Ed: “We were on our back patio in Green Valley and watched as it flashed across the sky. At first we thought it was a firework, as we had not seen one that appeared this close ever.”

From Rick: “Also, there was a low rumble about 1 minute or so after seeing the flash, in south Tucson… impact or shockwaves? The “rumble” was heard coming from the east, right on the reported trajectory.”

From CJS: “Was driving south in Queen Creek and saw it off to the southwest. Looked so close and was such a vivid green with gold sparks behind it, also wondered if it was a firework. But it moved like a meteor, so decided to check the internet after getting home to confirm what it was. What a wonderful sight. Had never seen one that close or that colorful before.”

From Julie: “I was sitting in my yard talking to a friend on the phone. My whole yard lit up like a spot light was on it. I turned around and looked up and saw the bright trail of green blue and kinda silver. .very vivid zoom through the sky. It moved like a shooting star. I was thrilled by it. It lasted about 10 seconds and then just went out.”

From Shannon: “I was driving south on La Canada when I saw it come in from the southern sky, diagonally down towards the mountains. It . . . was . . . incredible! I lost my breath. In fact, I’m embarrassed to say, I was on my cell phone at the time and stopped talking mid-sentence. I lost my breath and had to pull over. I started crying it was so beautiful! It was huge and you could definitely see tons of fragments breaking off the back, blue and yellow flames, and a red glow around the head rock. It seemed to be right above tree line when it extinguished/burned up, but from the size in the sky it looked for sure like it was going to hit somewhere. I saw the entire thing. The event seemed to last for like 5 seconds, but I know it just seemed that long because I was caught up in the moment. It was closer to earth than fireworks and much more beautiful. I feel extremely lucky to have seen it :)

From Frank: “I was sitting outside in Patagonia, AZ, USA facing south under a covered patio. I do not know exact time somewhere between 9 &10 pm. A bright greenish bkue flash lit the sky enough to cause shadows. I figures it might have been a fireball but unfortunately did not witness it directly. Several minutes later a loud sonic boom hit. Searching internet confirms that it was a fireball. WOW! I am envious of those who saw it directly.”

From RacerX: “I was driving east on River near Swan and saw the entire sky light up this bright blue color. I asked my son if he saw something and he told me that a bright blue fireball was coming down from the southwest. I looked over just in time to see the sparkling remnants of the debris. It was my sons first meteor sighting, special indeed.”

From Amanda: “I was standing joking around with some friends and then the ground got brighter and we looked up and saw it, it was so beautiful. I thought it was a firework for a second but hell no lol!!!! We heard it hit about 3 minutes later, it was loud. I feel really lucky to have witnessed that. :)

From Ben: “I was driving home from phoenix heading south on I-10 a few miles from Picacho Peak at approximately 9:30pm when the night sky turned slowly from an olive green to a brightness as the meteor slashed across and down breaking up in a brilliant white sparkling fireball! My wife saw more of it as she was sitting back in the passenger side. I thought it may have been a trick of my eyes the the sky glowed green until I read the comments this morning. Incredible. I considered it to possibly have prices landing either in tucson or maybe Mexico as I am unsure of how close it actually was. A spectacular show, may be a once in a lifetime to have seen this. We heard no ‘booms’ as we were driving. Breathtaking and exciting!”

From Nancy: “I was driving when I saw it and did a doubletake — thought it was a helicopter with a searchlight at first, and then looked again and it was sparking and moving so quickly, and clearly was not an aircraft. I was headed due south at the time, and it seemed to come in from the southwest, heading east, but still definitely south of my position in Gilbert (Phoenix’s east valley).

It was an absolutely incredible thing to see! I have always lived near metro areas — meaning a lot of smog — so have not witnessed anything too amazing in the night sky before. Have watched some predicted meteor showers (Perseids), but in comparison, this was 100 times bigger and brighter. If you were outside and oriented even remotely in the right direction, you couldn’t have missed it.

Fantastic!”

From Michael: “We were playing a softball game last night in Mesa, Arizona. Just as I released a pitch, we saw this huge fireball in the southern sky. It was the largest I have ever seen. It distracted our players big time and the batter ended up with an “in-the park” home run. Oh well…. also, we didn’t hear any sound but lots of noise in the park. Very cool.”

From Amadon: “A group of 12 of us were gathered around a bonfire at Avalon Organic Gardens Farm and Ranch (Tumacacori, AZ) last night laying and looking at the stars. We all saw the meteor as described above and all heard the loud boom/rumble a minute or so afterward. Very exciting, easily the biggest meteor I have ever seen. Truly awesome! We all jumped up and ran around and got excited, just when we were chillin back down, we heard the BOOM! We thought that it either hit the earth, or struck the atmosphere and created some type of sonic boom. Another 6 different people on our ranch saw it as well!”

If you saw it as well, please comment to this post. Also if it isn’t too much trouble, please submit a formal report to the American Meteor Society’s fireball page at http://www.amsmeteors.org/fireball/report.html. I already submitted mine.

I’ll try to add more info tomorrow.

June 22/23 Meteors

After a quick trip to Radio Shack I was able to get both cameras up and running again. Clouds were a problem for most of the night. Luckily it cleared up for the last hour or two of the night which is also when the most meteors can be seen.

May and June are historically very dry and clear months in Tucson. They are usually very hot as well. This year has been out of the ordinary since we have experienced lots of clouds, bouts of rain, and temperatures “only” in the 90s F. The persistent clouds have really hampered meteor observing the past few months.

Now we have to contend with the monsoon. Though it usually starts in early July, the monsoon can start as early as mid-June. The forecast is for the monsoon to ramp up this week with rain coming as soon as Wed or Thurs. As a result, meteor reports will be even more hit or miss depending on the weather for the next few months. On the positive side, July and August are very interesting months for meteor watchers with lots of active showers (including some major ones) and much higher rates.

Obs  Date (UT)   TotTime TOT SPO ANT JBO
TUS  2009-06-23  01h 49m  8   7   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
SPOSporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions
JBO – June Bootids

June 20/21/22 Meteors

After a few weeks of no active meteor showers, the June Bootids should now be active. Last night was the 1st night of their predicted activity though none were observed. This shower is usually weak though it has produced nice displays on 4-5 times during the past 100 years.

The numbers from the past 2 nights are down a bit because only 1 camera was operational. I had some hardware issues which have now been resolved so the system will be back at 100% for tonight.

Obs  Date (UT)   TotTime TOT SPO ANT JBO
TUS  2009-06-22  07h 40m  5   4   1   0
TUS  2009-06-21  06h 51m  8   7   1

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
SPOSporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions
JBO – June Bootids

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