Fireball Over Southern California – Sept 19

I have received a number of comments on this blog regarding an impressive fireball observed over southern California. The original comments can be found by going to the Sept 18/19 Meteors posting. Additional reports are published on the ScienceDude’s blog. Other than this blog and the ScienceDude’s, I have not been able to find any other reports.

The fireball was observed on Friday night, Sept 19, at approximately 11:10 PDT (6:10 UT). It was described as being yellow-orange and left a long trail in its path. Multiple observers noted that it broke into at least three pieces. One observer in Los Angeles reported hearing a sound similar to an explosion. Interestingly another meteor was observed within a minute or two of the fireball. This second meteor was not as bright and moved perpendicular to the path of the first.

A map showing the location of sightings is posted below.

Map of southern California with Sept 19 fireball sightings denoted by red stars. Updated on 9/26.

Map of southern California with Sept 19 fireball sightings denoted by red stars. Updated on 9/26.

So what was it? It was either one of two things, a small rock from the Asteroid Belt or a piece of an old satellite or rocket. Based on the reports, it is hard to rule out either of these possibilities.

So here’s what we know.

* The fireball was located just north of Los Angeles and traveled from West to East. Meteors can travel in any direction. At the latitude of LA, many satellites are moving from West to East so the direction of motion makes me wonder if this isn’t a re-entering piece of a satellite. If it was a meteor, it was not associated with any known meteor shower.

* It was a bright yellow-orange and broke up into multiple pieces. Most meteors are blue or green but can be any color. The same is true of re-entering spacecraft.

* The fireball was long lasting and disappeared behind the horizon for some observers. This is consistent with both rocks and satellites.

So based on the evidence, it is hard to say if it was a rock or a satellite.

If you are wondering why my camera didn’t see it. Meteors occur at a height of ~50-80 miles above the ground. As a result, any one particular meteor can only be seen over a distance of a couple of hundred miles. Tucson is just too far away from LA to have seen it.

I’d like to thank everyone who contributed comments. If there are any other reports, please post them in the comment section. And for those who did witness this event, count yourself lucky. A bright disintegrating fireball is one of the most awesome sights in the night sky.

I will continue to look for other reports and hopefully a video as well.

September 19/20/21st Meteors

The last two nights produced another 28 meteors. The Moon is still bright and high in the sky right before dawn. Since the number of observable meteors peaks right before dawn, the Moon is undoubtedly keeping rates down a bit. This should become less of an issue over the next few days as the Moon approaches its New phase.

Date                     TotalTime      TOT    SPO     ANT     DAU

2008-09-20 UT    10h 10m       12      12        0         0
2008-09-21 UT      6h 39m       16      13        1         2

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
DAU – δ-Aurigids (Delta Aurigids)

Sept 18/19th Meteors

Observing conditions were fairly good last night, though some clouds moved through during the hours right before dawn.

Last night saw my first detection of a possible Delta Aurigid. I say possible because there is evidence that this shower should not even be active till next month. So what was this particular meteor? Data from decades of naked eye observers suggest that both the September Perseids and the Delta Aurigids are active, though at very low levels. Since both showers radiate from the same part of the sky, my camera cannot differentiate between them. To do that requires calculating the orbit of the meteor which needs observations from at least 2 cameras separated by 50-100 miles.

The other possibility is that the meteor is not related to either shower and is just a background Sporadic. Video data over the past few years suggest that neither shower should have been active last night. One of the reasons why a large number of amateurs and I are operating cameras every night is find answers to questions like these.

Date                     TotalTime      TOT    SPO     ANT     DAU

2008-09-19 UT     9h 34m        16      12        3         1

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
DAU – δ-Aurigids (Delta Aurigids)

Sept 17/18th Meteors

Clear skies returned though the Moon is still hampering observing during the morning hours. Last night we bid farewell to the 2008 September Perseids and welcomed the Delta Aurigids. An overview of the Delta Aurigids is given in the September “In the Sky This Month“.

Date                     TotalTime      TOT    SPO     ANT     DAU

2008-09-18 UT    10h 07m       12       9         3         0

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
DAU – δ-Aurigids (Delta Aurigids)

Sept 16/17th Meteors

Clouds Clouds Clouds… With little over an hour of clear skies last night, the number of meteors was much lower than usual.

Date                     TotalTime      TOT    SPO     ANT     SPE

2008-09-17 UT     1h 17m         5        5         0         0

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
SPE – September Perseids

In The Sky This Month – Rest of September 2008

This feature highlights a number of meteor showers, comets and asteroids which are visible during the current month.

Meteors

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are sporadics. This is especially true for meteors observed during the evening. During September, ten (10) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

There are no major meteor showers visible during the month of September.

Minor Meteor Showers

Minor showers produce so few meteors that they are barely noticable above the background of regular meteors.

September Perseids (SPE)

The September Perseids which experienced a surprise outburst of activity on Sept 9 are winding down. By Sept 17 they should no longer be active.

Delta Aurigids (DAU)

Until a few years ago, the September Perseids and the Delta Aurigids were considered part of the same shower. Analysis of the orbits of their meteors suggested that there are in fact two overlapping showers each originating from a different unknown long-period comet. Like the SPEs, this minor shower usually produces no more than ~3 meteors per hour at its maximum. There is some disagreement as to when this shower is active. Naked eye observations over the past few decades suggest a period of activity from Sept 18 through Oct 10 with a broad peak between Sept 23 and Oct 3. Recent video data finds a later period of activity between Oct 6 and 12 with no obvious peak. The DAUs radiate from the northern part of the constellation of Auriga just to the north of the bright star Capella.

Additional information on these showers and other minor showers not included here can be found at the following sites: Robert Lunsford’s Meteor Activity Outlook, Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2008 Meteor Shower Calendar.

Comets

Naked Eye Comets

There are no comets bright enough to be seen without binoculars or a telescope.

Binocular Comets

Comet C/2008 A1 (McNaught)

Comet McNaught is a long-period comet that will pass closest to the Sun on Sept 29 at a distance of 1.07 AU (100 million miles or 160 million km). It was the first comet discovered in 2008 having been found by  Robert McNaught of the Siding Spring Survey back on Jan 10. It was McNaught’s 43rd comet discovery.

Currently the comet can only be seen from the Southern Hemisphere. Next month the comet will be visible for observers in the Northern Hemisphere as an early evening object. As of Sept 16, the comet is located in the constellation of Centaurus. By months end it will clip the southeast corner of Hydra and enter Libra. The comet is as bright as it is going to get at magnitude 6.5. A comet of this brightness can be seen in binoculars or a small telescope.

A finder chart for Comet McNaught can be found at Comet Chasing.

Small Telescope Comets

Comet 6P/d’Arrest

Comet d’Arrest was one of the first short-period comets to be observed. First seen by the Frenchman Philippe de la Hire in 1678, the comet was definitively discovered by Heinrich Louis d’Arrest of Germany on 1851 June 28.

Comet d’Arrest is in a short-period orbit with a period of 6.5 years. It passed closest to the Sun back on Aug 14 at a distance of 1.35 AU (125 million miles or 200 million km). Currently located in the southern constellation of Grus, the comet is a very difficult object for observers in the Northern Hemisphere. With a brightness of magnitude 8.5 it will require a telescope to be seen though observers at very dark sites may be able to see it in binoculars.

A finder chart for Comet d’Arrest can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below the surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres is located in Cancer at magnitude 8.8.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(2) Pallas

Pallas is also a carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is large with dimensions of 350x334x301 miles or 582x556x501 km. This month it is located in the southern constellation of Lepus at magnitude 8.7-8.8.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(4) Vesta

Though not as large as Ceres, Vesta is more reflective making it the brightest asteroid in the Main Belt. Vesta is peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta is similar in size to Pallas with dimensions of 347x336x275 miles or 578×560×458 km. Vesta will also be visited by NASA’s Dawn spacecraft which will arrive in 2010. This month it is located in Cetus at magnitude 7.0.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

Sept 15/16th Meteors

In contrast to the previous 2 nights, last night was a return to normal with 22 meteors detected in 10 hours of observing. The Moon is just past Full so the sky conditions should improve over the next week.

Date                     TotalTime      TOT    SPO     ANT     SPE

2008-09-16 UT    10h 01m        22      19        2          1

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
SPE – September Perseids

Sept 14/15th Meteors

The bright moon and a dusty atmosphere combined to keep meteor detections low last night. In fact, I picked up more birds and bugs illuminated by the moonlight then meteors last night. This will continue to be the case until the Moon is a few days past Full. So hopefully by the end of this week, rates will start ramping up again.

We are nearing the end of the window of visibility for the September Perseids (the shower that surprised us with an unpredicted outburst on Sept. 8/9). Luckily, another minor shower will become active in the next few days, the Delta Aurigids. Looking even further ahead, two of the better annual showers of the year will become active in late September and early October, the Taurids from Comet Encke and the Orionids from Comet Halley. I’ll post more on the specifics for all three upcoming showers over the next few weeks.

Date                     TotalTime      TOT    SPO     ANT     SPE

2008-09-15 UT     9h 51m         10       9          1         0

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
SPE – September Perseids

Sept 13/14th Meteors

It was another good night weather-wise. Compared to the rest of the month when my camera was detecting ~20 meteors a night, only 14 were seen last night. Perhaps the bright sky (the Moon is only 2 days from Full) is washing out the fainter meteors. So far this September, the camera has picked up 229 meteors.

Date                     TotalTime      TOT    SPO     ANT     SPE

2008-09-14 UT     9h 55m         14      12        2         0

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
SPE – September Perseids

Sept 12/13th and Antihelion meteors

I’d like to thank all of you who have visited this page over the past few days. If you have any questions pertaining to comets, asteroids or meteors, please send them to me in the comments section and I’ll try to answer them ASAP. Your comments will also allow me to focus some future posts on topics that people are interested in.

The sky was clear last night although the Moon is a few days from full which is limiting the number of meteors which can be seen. When the Moon is in the sky it makes it hard to see anything faint whether stars or meteors. Even with the Moon, 19 meteors were detected last night. This is close to the my nightly average for September.

Date                     TotalTime      TOT    SPO     ANT     SPE

2008-09-13 UT     9h 13m         19      13        6         0

TOT – total # of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions (meteors coming from the opposition region, opposite the direction of the Sun)
SPE – September Perseids

The best meteor was seen at 10:51 pm. It was slow and bright while leaving a short-lived trail behind it. A movie of the meteor can be seen below. Now that I’ve figured out how to convert avi files to gif, I will be posting more movies rather than just still frames.

XX on Sept 12.

Almost a third of last night’s meteors were Antihelions. They appear to come from the part of the sky opposite the Sun and usually do not originate from any one specific comet. Over the millennia many comets have been releasing dust that are visible as meteors when they enter the Earth’s atmosphere. Over time this dust will move away from the orbit of their parent comet. The Antihelions can be thought of as orphan dust particles from 1000s of years worth of short-period comets whose perihelion (closest distance to the Sun) is within the Earth’s orbit (less than 1 AU or Earth-Sun distance). They are inbound particles headed towards their perihelion. Outbound particles are called Helions and since they appear to originate from the part of the sky near the Sun can only be observed during the day. We know of their existence because radio and radar telescopes, which can observe all day and night, have detected them.

Over the past few weeks, their have been an average of ~1 Antihelion observed per night. Last night 6 were observed. Interestingly, four may have come from the same radiant (point of origin on the sky). The plot below shows the path of a number of meteors extrapolated backwards. The circle with an X marks the center of the Antihelion region which covers tens of degrees (about halfway from the center to the right and left edges of the plot). You can see that the backward drawn path of four meteors crosses in the constellation of Pisces just east of the Antihelion point. Could these meteors be related, perhaps originating from a common comet? It’s possible, though with only four meteors in the group it could easily be a chance alignment. Observations from other observers and from other nights are required to confirm if this is a real meteor shower or just statistical noise. IMHO, it’s probably statistical noise.

Plot of meteor paths traced backed to origin. Plot shows the antihelion region on 2008 Sept. 13 UT.

Plot of meteor paths traced backed to their origin. Plot shows the antihelion region on 2008 Sept. 13 UT.

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