2 Bright and Loud East Coast Fireballs

The past 10 days have seen 2 extremely bright fireballs over the East Coast of the US. Both fireballs also were accompanied by loud sonic booms.

The latest meteor occurred on Sunday night, March 29, at ~9:50 EDT. Observed from Pennsylvania to North Carolina, the fireball seems to have ended over the Norfolk/Virginia Beach area of southeast Virginia. A loud noise similar to an aircraft sonic boom or distant thunder was heard and felt ~2 minutes after the fireball last disrupted.

This event has been widely reported in the press. A Space.com article on the fireball can be found at Yahoo news. For a local take on the fireball see this story at WAVY-TV 10.

According to many press stories, the Naval Observatory is reporting that the fireball was caused by the reentry of part of a Russian Soyuz rocket booster. Last Thursday this rocket launched 1 American astronaut, 1 Russian Cosmonaut and an American paid passenger to the International Space Station. Reports from the Joint Space Operations Center at Vandenberg AFB and the US Strategic Command both state that the fireball was not caused by the Soyuz booster and was most likely due to a small asteroid (see here and here).

Below is a map showing the location of some of the fireball reports. Yellow circles denote fireball sightings but no sound. Red circles are locations that heard sonic booms or concurrent noises. It is obvious from the maps that the fireball detonated over southeast Virginia.

mar29_va_fireball1

Little over a week earlier on March 20 at ~2:30-3:00 am EDT, another bright and loud fireball was seen and heard. As the map below shows, the fireball was seen over a 4 state area from Virginia to Georgia. Similar to the map above, red circles show were the fireball was heard. The concentration of sound reports in the Augusta area on the border of Georgia and South Carolina pinpoints where this fireball detonated.

mar20_sc_ga_fireball

[NOTE: This paragraph has been edited since it was originally posted.] There are 2 different ways a fireball can produce sound. The sound heard over southeast Virginia and the GA/SC border was a sonic boom caused by the fireball’s shock wave. This shock wave is the natural result of a fast moving solid object moving through the atmosphere. Since this usually occurs at a height of 20 or more miles it can take the sound a few minutes to travel to the observer. This is why the sound was heard ~2 minutes after the fireball was no longer visible.

The second way fireballs create sound is via EMF radiation. In this case, the high temperature fireball produces radiation at all wavelengths. Sometimes objects such as a metal frame or even a tree can convert the EMF waves into audible sounds. Since the EMF waves travel at the speed of light, these sounds can be heard at the exact same time the fireball is visible. It is possible these EMF sounds were heard by the March 20th fireball observer in Traxton, Virginia.

Mar 26/27/28/29 Meteors

The weather continues to be good with the occasional batch of high cirrus. Though March is often a difficult month for meteor watchers, April promises higher rates.

From Bob’s notes: “On Friday morning I woke to clear skies so I had an abbreviated session on that morning. The sky was clear Friday night/Saturday morning and I actually obtained some decent rates this morning.”

Obs  Date (UT)   TotTime TOT SPO ANT
TUS  2009-03-29  08h 59m  10  9   1
TUS  2009-03-28  09h 40m  6   4   2
SDG  2009-03-28  08h 38m  23  20  3
TUS  2009-03-27  07h 58m  6   5   1
SDG  2009-03-27  05h 18m  15  13  2

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

Mar 23/24/25/26 Meteors

The doldrums of March continue, at least with regards to meteor activity. At least the weather has been good though San Diego experienced some fog last night. One plus from the past few weeks, a good fraction of the detected activity has been from the broad antihelion region in Virgo. The MetRec software is only assigning 1 or 2 meteors a night to this source. If we assume the antihelion region is a bit larger than 1/4 to 1/3 of the meteors detected at Tucson are from this source region. This means that a few more meteors than usual are visible before midnight.

Obs  Date (UT)   TotTime TOT SPO ANT
TUS  2009-03-26  10h 02m  10  9   1
SDG  2009-03-26  05h 47m  5   3   2
TUS  2009-03-25  06h 01m  9   9   0
SDG  2009-03-25  09h 52m  11  10  1
TUS  2009-03-24  09h 27m  14  13  1
SDG  2009-03-24  09h 56m  11  10  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
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions

Venus: -4 Days Till Inferior Conjunction

Venus is getting harder and harder to see as it approaches inferior conjunction with the Sun. Due to breezy conditions in Tucson and all of the dust it kicked up, I was unable to locate Venus Monday afternoon. Luckily Bob Lunsford had better luck. Below are 2 pictures he took with his Celestron 9.25″ SCT and a Canon PowerShot digital camera.

venus_lunsford_200903232

This afternoon I was successful in finding Venus. At the time of the last observation (Mar. 24.83 UT), Venus was only 9.7 degrees from the Sun. The disk of Venus is now 59″.1 arc seconds (almost a full arc minute) across but only 1.4% of it is illuminated by the Sun. The crescent of Venus appears thicker in my Mar. 24th images compared to some of the previous dates because the seeing (turbulence in the Earth’s atmosphere) was much worse today. I just could not get a clear shot.

venus_mar8_24

Mar 21/22/23 Meteors

The past month or so has been difficult for meteor observing from both San Diego and Tucson. Though it has rarely rained this winter, the past few months have been plagued by clouds.

Last night finally saw clear skies over both sites. Even with the clear skies, activity remains at its normal low March levels. Half of the meteors detected in Tucson appear to radiate from the antihelion region in Virgo. This continues a trend from the past week.

We also say goodbye to the Gamma Normids (GNO). This minor shower is best observed from the Southern Hemisphere and is difficult to observe from the US. Over the past 2 weeks, one possible GNO was seen over San Diego while none were picked up over Tucson.

Obs  Date (UT)   TotTime TOT SPO ANT GNO
TUS  2009-03-23  09h 40m  8   4   4   
SDG  2009-03-23  05h 01m  20  18  2   
TUS  2009-03-22  04h 55m  2   1   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

Venus… -6 Days Till Inferior Conjunction

We are now within a week of Venus‘ inferior conjunction. From my backyard there is no way to observe Venus at night any more (too many trees on the horizon). As a result, all observations are during the day, usually late in the morning or late in the afternoon. The hardest part after finding Venus (I don’t have a computerized telescope so I need to find Venus in binoculars first) is trying to see Venus on the screen on my laptop in broad daylight.

As Venus marches (or orbits) towards inferior conjunction, it is gradually appearing larger and thinner. This is obvious to telescope users. Even small binocular users can easily see Venus as a crescent. For those with great eyesight, it may even be possible to see Venus as a crescent with just your eyes.

venus_mar8thru21

Below is a direct comparison between Venus from today and 2 weeks ago. On Mar. 8.06 UT, Venus was 0.332 AU from Earth (30.8 million miles or 49.4 million km). It was 50″.2 arc seconds in diameter and 12.6 percent of its Earth-facing disk was illuminated by the Sun. At the time, it was also easy to observe being 28.7 degrees from the Sun.

Today at Mar. 21.73 UT, Venus was 0.286 AU from Earth (26.6 million miles or 42.6 million km). The closer distance means Venus is now 58″.3 arc seconds across (or 16% bigger). As can be seen below, much less of the disk is illuminated (2.4%). The observation is also much tougher now that Venus is only 12.7 degrees from the Sun.

venus_mar8_21

At its closest to the Earth on March 27, Venus will be 0.281 AU from Earth (26.1 million miles or 41.8 million km). Only 0.97% of its 59″.3 arc second Earth-facing disk will be illuminated by the Sun. Hopefully at that time Venus will appear as a ring when its atmosphere refracts sunlight around its edge.

Mar 20/21 Meteors

Last night saw a bit of cirrus right before dawn. Now that the Moon is long past Full, almost the entire night is dark. The last few clear nights have seen between 12 and 16 meteors per night.

Obs  Date (UT)   TotTime TOT SPO ANT GNO
TUS  2009-03-21  08h 52m  12  10  2   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

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