Nov 7/8 Meteors and Lots of Taurid Fireballs

The nights have been nice and clear here in the southwest US. My Tucson camera continues to detect over 2 dozen meteors a night while Bob’s camera in San Diego is routinely finding ~100 meteors a night, give or take 20 or so. The Orionids are officially over, at least according to the International Meteor Organization. Analysis of video data by Sirko Molau finds that the Orionids may continue till November 21. Even if they do their rates will be very low. Now we wait for the start of the Leonids in the next few days.

The Taurids continue to produce a number of bright fireballs (meteors brighter than Venus or magnitude -4) every night. The American Meteor Society (AMS) collects and documents fireball observations. If you would like to submit your observations for use by the scientific community, the reporting form can be found at

http://www.amsmeteors.org/fireball/report.html.

The form is very basic and no knowledge of astronomy is needed to fill it out. A listing of all of the fireballs that have been reported to the AMS in 2008 can also be found at their site. Many of the fireballs reported to this blog over the past 2 months are already included.

Obs  Date (UT)   TotTime TOT SPO NTA STA
TUS  2008-11-08  11h 36m  26  18  3   5
SDG  2008-11-08  11h 22m  84  65  6   13

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)
NTA – Northern Taurids
STA – Southern Taurids

Report on the Impact of 2008 TC3

The Near-Earth Object Program office at NASA-JPL has just released a report about the impact of 2008 TC3. TC3 was the small asteroid discovered less than a day before entering the Earth’s atmosphere over northern Sudan. The text of the report can be found at:

http://neo.jpl.nasa.gov/news/2008tc3.html

Some highlights from the report include …

  • Discovered on 2008 Oct 6 at 6:39 UT by Richard Kowalski at the Catalina Sky Survey using the Mount Lemmon 1.5-m telescope, north of Tucson, Arizona
  • 26 observatories reported 570 astrometric (positional) observations
  • 2008 TC3 entered the atmosphere on 2008 Oct 7 at 2:45:40 UT
  • It detonated (exploded) 5 seconds later due to the high pressure of rapidly moving through the Earth’s dense atmosphere
  • TC3 was moving at 12.4 km/s when it hit the atmosphere. That’s 7.4 miles/s or 26,640 miles per hour!
  • It was tumbling as it moved through space and rotated about two axes with periods of only 97 and 49 seconds. Those periods are how long a “day” (sunrise to sunrise) would have lasted on TC3. This is not uncommon for small asteroids.
  • It was the first natural body other than the Moon to be eclipsed by the Earth. It entered Earth’s shadow an hour before it hit the atmosphere.
  • TC3 detonated at a rather high altitude for a large fireball (37 km or 22 miles or 117,000 feet). This suggests that TC3 was rather weak when compared to most asteroids/meteorites.
  • The fireball and/or flash was observed by a European weather satellite, US Defense satellites, a KLM flight crew and a video security camera in southern Egypt.

Taurids, Fireballs and Comet Encke

Over the past few weeks, a number of bright meteors and fireballs have been reported. On this blog, there have been reports from Colorado, New Jersey, Illinois, Florida, Michigan and Arizona. Over at the Fireball Report page of the American Meteor Society (AMS), multiple fireballs are being reported every night. So what’s going on?

There is a good chance that many of these fireballs are from the Taurid meteor complex. Most meteor showers are only visible for a few weeks to maybe a month. Often most of their activity is concentrated in a few night window around the time of their peak. The Taurids are different, though. Those who have paid close attention to my daily postings will notice that the Taurids have been active since late September. They will continue to produce meteors until the end of November. Another difference between Taurids and most other showers, is when they they take place. Most showers can only be observed after midnight. The Taurids can be seen at all hours of the night, whether morning or evening. As a result, they are active at a reasonable hour when many people are still awake and outside.So for the average person who is out and about in the evening, the months of October and November provide a greater than usual chance of spotting a nice meteor or fireball.

How can you see the Taurids?

The Taurids are visible at any time of the night. There are two separate branches of the Taurids, the Northern and Southern Taurids. Both showers are located within a few degrees of each other. In November, the radiants of both showers are located in the constellation of Taurus. Video data compiled by Sirko Molau find that the Southern Taurids are active from September 8 to November 30 with a broad peak around October 11. The Northern Taurids are active from October 8 to December 13 with a broad peak around November 14. Right now, both showers are active though more of the activity will be from the Northern branch.

The rates for the Taurids is fairly low. These are not major showers and at their best produce 10-15 meteors per hour from a dark site around midnight. For evening observers under suburban skies, the rates will be much lower. The thing to watch out for are evening fireballs. It is predicted that this year will see more fireballs than usual from the Taurids.

Taurid meteors look rather different from most meteors. Unlike the Orionids which are fast and only last a split second, Taurids are much slower and longer lasting. I have seen many early evening Taurids that appear as small green orbs or spheres that can take up to 3 seconds to cross most of the sky. Quite often they will be followed by a thin, short-lasting white tail or trail. They are definitely impressive.

Where do Taurids come from?

Taurid meteors are produced by Comet Encke which is one of the best observed comets in history. The reason for this is that it circles the Sun once every 3.3 years which provide lots of opportunities to observe it when bright. The fact that the comet is rather large and does not get very far from the Earth and Sun means that it is always observable by professional (and even some of the largest amateur) telescopes. But even after centuries of observation, Encke remains an enigma and continues to give professional comet researchers fits.

Comet Encke was first observed by the prolific French comet hunter Pierre Mechain on 1786 January 17. The comet was relatively bright (5th magnitude) but located deep in the bright twilight sky. After a few days, the comet moved to close to the Sun and was no longer observable. As a result, it became lost. Fast forward to 1795 November 7, Caroline Herschel (the first female comet discoverer and brother of William Herschel, the discoverer of Uranus) of Slough, England found a “new” comet which was observed for only a few weeks. There were not enough observations to identify the comet as a short-period comet. The 3rd “discovery” of Comet Encke occurred on 1805 October 20 when Jean-Louis Pons of Marseilles, France (until the last 15 years, Pons was the leading comet discoverer with 26 comets to his credit) discovered a comet which was followed for a month. Pons was so prolific at finding comets that he unknowingly found the same comet again on 1818 November 26.

One may be wondering why this comet is named Comet Encke rather than Comet Mechain-Herschel-Pons. Johann Franz Encke was a German astronomer and mathematician. In 1819, Encke calculated an orbit for Pons’  1818 comet and noticed that it resembled the orbit of Pons’ 1805 find. Working the orbit, Encke quickly relaized that the two Pons comets were really the same comet returning every ~3 years. Further work identified Mechain’s 1786 comet and Herschel’s 1795 comet as previous apparitions of Pons’ comet. In honor of Encke’s work, the comet was named Comet Encke. It is rare for a comet to be named after the mathematician who computed its orbit rather than its discoverer but there are a few cases of this, especially centuries ago. The most famous example being Comet Halley. Edmund Halley did not discover Comet Halley but he was the first person to recognize that his namesake comet returned at regular intervals. Comets Lexell and Crommelin are other examples of comets being named after an orbit computer.

//neo.jpl.nasa.gov/orbits/

Orbit of Comet Encke from the JPL Orbit Diagrams page @ http://neo.jpl.nasa.gov/orbits/

Since 1818, Comet Encke has been observed at every perihelion (closest approach to the Sun) except for one in 1944 at the height of World War II. Nowadays, it is rare for Comet Encke not to be observed at least once a year. In fact, Encke was the 2nd comet, after Halley, to be observed at more than 1 return, hence its official name of Comet 2P/Encke. The comet is currently located on an orbit that takes 3.3 years to circle the Sun. The comet’s orbit ranges from a perihelion (closest to the Sun) of 0.34 AU to an aphelion of 4.10 AU (farthest from the Sun). Its last perihelion was on 2007 April 19 and the next one will be on 2010 August 6. There is a short window before or after every perihelion when Encke is visible in small telescopes. The comet never gets bright enough for naked eye observations.

This is an image of short-period comet Encke obtained by Jim Scotti on 1994 January 5 while using the 0.91-meter Spacewatch Telescope on Kitt Peak. The image is 9.18 arcminutes square with north on the right and east at top. The integration time is 150 seconds.

This is an image of short-period comet Encke obtained by Jim Scotti on 1994 January 5 while using the 0.91-meter Spacewatch Telescope on Kitt Peak. The image is 9.18 arcminutes square with north on the right and east at top. The integration time is 150 seconds.

Where does Comet Encke come from?

Until a few years ago, it was theorized that all comets formed in the outer solar system beyond the orbit of Jupiter. As the outer planets migrated towards their current orbits, some comets were ejected into the Oort cloud, located out to a quarter of the distance to the nearest star, the Kuiper Belt, a belt of comets located just beyond Neptune’s orbit, or the Scattered Disk, located between the Oort cloud and the Kuiper Belt. Short-period comets, with periods less than ~20 years or so, spent billions of years in the Kuiper Belt or Scattered Disk before being kicked back into the inner solar system by the gravity of the outer planets. As a result, all comets go out as far from the Sun as the orbit of Jupiter or much further out. Encke only goes out to 4.1 AU. Since Jupiter is located at ~5 AU, Encke is safe from most of Jupiter’s gravitational interactions.

The question is how did Encke get there? Computer models find that it is very difficult to get an object from the outer solar system onto a Encke-type orbit. Though not impossible, it would require a very long amount of time. So long, in fact, that Encke should have burned out (run out of ice and volatiles) many 100,000s of years ago and should either appear as an inactive asteroid or perhaps have broken up into nothing more than dust by now. So what happened? It is possible that Encke took a very long time to get to its current orbit but was inactive, or dormant, for most of that time. If true, it would not have run out of ice and its cometary activity is a recent phenomenon. As we saw with the recent re-discoveries of Comets Giacobini and Barnard 3, comets can be inactive or barely active for many orbits.

Another possibility is that Encke is not from the outer solar system but rather from the Asteroid Belt between the orbits of Mars and Jupiter. It was long thought that the asteroids in the Asteroid Belt were all dead, dry objects, but recently a number of asteroids have been found that display the same activity as comets. Perhaps Encke was an asteroid from the Asteroid Belt until a collision or break-up event exposed a large area of ice resulting in cometary activity. Unfortunately, we could know a lot more about Encke but a planned mission to study Encke, and other comets, failed leaving Earth orbit. NASA’s COmet Nucleus TOUR (CONTOUR) mission was to fly-by Encke in 2003.

Incoming Fireball Over Sudan!!! – 2008 TC3

For the first time in recorded history a very small asteroid has been discovered before burning up in Earth’s atmosphere as a brilliant fireball. During the night of Oct 5/6, Rich Kowalski of the Mount Lemmon Survey discovered a new Near-Earth asteroid named 2008 TC3. It now appears that this object will hit the atmosphere of the Earth tonight (Oct 7 UT) at 2:46 UT (10:46 EDT) over northern Sudan in northeast Africa.

Based on the brightness of this asteroid, it is very small and probably on the order of 2-meters or 7-feet in diameter. As big as this may seem, objects this small usually break up into much smaller pieces with little remaining to hit the ground. If pieces do survive to hit the ground they will probably be small, no bigger than a grapefruit. What this object will do is produce a spectacular fireball for a few tens of seconds over the Sudan. The Near-Earth Object Project Office at NASA-JPL estimates that an event of this size occurs once every few months somewhere in the world. The fireball will probably be more spectacular than the Sept 19 fireball observed over southern California but will only be visible within a few hundred miles of northern Sudan. It will not be visible from the rest of the world.

This is the first time a small fireball producing asteroid has been observed before entering the Earth’s asteroid. Why hasn’t this happened before? Object of this size are very faint. In fact, of the 360000+ known asteroids, we have only found 2 other asteroids that are this small. Also asteroids very close to Earth move very fast. Now moving fast isn’t the problem, the problem is that there is so much junk in orbit around the Earth from decades of satellite launches, that it is very hard to tell the difference between a small close asteroid and an old satellite. So the current asteroid hunting telescopes have to be lucky to pick one of these objects up. In the future, the next generation of asteroid survey telescopes will be able to discover these objects further out. There may come a time in the not too distant future, when a spectacular fireball will be predicted to occur over a major population center days in advance. When that day happens, you won’t have to be lucky to see a fireball, you can just go outside at the predicted time and enjoy the show.

Before it hit the Earth’s atmosphere, 2008 TC3 was on an orbit that took it as close to the Sun as 0.91 AU and as far from the Sun as 1.63 AU. It took 1.43 years to orbit the Sun.

If any photos of the fireball become available I will post link to them.

Links to a few publications about 2008 TC3…

The discovery announcement from the Minor Planet Center

Press release from the University of Arizona

Press release from the Near-Earth Object Project Office at NASA JPL

Re-Entry of Jules Verne

From time to time, pieces of old satellites and rockets re-enter and burn up in the Earth’s atmosphere. Usually the space hardware is long past it’s warranty and no longer working. Most of the hardware is small and completely burns up leaving nothing to hit the ground.

For very large spacecraft that can survive re-entry, spacecraft operators command the spacecraft to re-enter over a part of the world with no population. Most of the Pacific Ocean makes for a good large safe place for re-entries.

On Sept 29, a 13-ton spacecraft called “Jules Verne” was commanded to re-enter over the Pacific Ocean. “Jules Verne” is a European Space Agency (ESA) spacecraft and also goes by the name ATV-1, where ATV doesn’t stand for “all terrain vehicle” but for “automated transfer vehicle”. Launched on March 9, it delivered supplies and fuel to the International Space Station.

An international campaign which included NASA scientists from the SETI Institute the NASA Ames Research Center, flew two NASA aircraft near the point of re-entry. They have a nice website which includes photos of the re-entry.

Due to the location of the re-entry in the South Pacific, this was not one of the many fireballs that have been reported over the past week.

Fireballs From Around the World – Sept 25-26

The past few days have seen a number of fireball reports being left in the comment sections from all over the world.

There does not appear to be anything in common between these sighting. Though fireballs are uncommon, they are not rare. If you spend enough time staring at the sky at night, you’re bound to see a spectacular one. As the Taurid meteor shower builds in intensity over the next month or two, many more fireballs should be seen.

Below is a quick summary of what was seen. All of the fireballs were caused by “space debris”, whether rocks or man-made, burning up in the Earth’s atmosphere at heights of 80-100 kilometers (50-60 miles).

Sept 25 – West Virginia

An orange/yellow fireball was sighted near Wheeling, West Virginia at 2 am EDT on Sept 25. The report was submitted by Courtney.

Sept 25 – Illinois/Ohio

Later the same morning at ~6:20 am EDT, Linda reported a fireball seen in Wapakoneta and St. Marys, Ohio. The multi-colored (white/yellow/orange) fireball traveled from the northeast towards the northwest and burned out (or terminated) overhead.

A posting to the ‘meteorobs‘ mailing list reports a probable sighting of this same meteor at ~5:30 CDT from Chicago, Illinois. Al Degutis saw a bright, slow-moving meteor move from just north of overhead to the eastern horizon. The time, direction of travel, and distance between Chicago and Ohio sightings suggest that this is the same object. A map of the 3 sightings is included below. Due to the difference in 3 hours, this fireball is not the same as the Wheeling meteor mentioned above.

Sighting of the Sept 25 fireball over Illinois and Ohio. Sighting are denoted by the red stars.

Sighting of the Sept 25 fireball over Illinois and Ohio. Sighting are denoted by the red stars.

Sept 25 – France/ Isle of Wight

Two reports from France and the Isle of Wight may be sightings of the same fireball. Sally Isaacs saw a fireball from the Isle of Wight at 10:15 GMT on the evening of Sept 25. One hour into a flight from Birmingham, UK to Milan, Italy, Lucy sighted a fireball moving from north to south. No time was given for this sighting but the  circumstances are close enough that the same object may have been seen.

Sept 25 – Louisiana

M Davey of Baton Rogue and Lisa Marie from southern Louisiana both saw a fireball over Louisiana at 11 pm CDT on Sept 25. Lisa Marie reported that other sighting were made offshore in the Gulf of Mexico. It was described as green-blue and moving East to West. At least one bright flare was reported.

Sept 26 – near Heathrow, England

Tim Allen, an Airbus A320 pilot, saw a nice fireball trailing sparks as he was heading into Heathrow airport at 10:30 pm GMT on Sept 26. The fireball moved from the northwest to the southeast.

Sept 26 – Florida

Bryan Tippetts reported a fireball over Tampa, Florida at 8:10 pm EDT on Sept 26. The fireball was seen in the eastern sky moving from north to south.

Sept 26 – Australia

Though there are were no reports of this fireball submitted to this blog, a posting on the Seesat-L (satellite watchers) mailing list states that many people witnessed a spectacular fragmenting fireball over Adelaide in South Australia. The event happened at 00:17 local time on Sept 26.

In this case, it was the re-entry and breakup of a Russian rocket upper stage which had launched 3 Glonass satellites a few days earlier. Glonass is the Russian equivalent of the American Global Positioning System (GPS) system.

Thanks again for all of the reports and keep them coming.

Fireballs over the Scotland/Ireland/England on Sept 20/22

Another round of fireball reports was submitted to this blog last night. Three fireballs were observed over England, Scotland and Ireland during the evenings of Sept 20 & 22.

The first fireball was seen at 23:16 BST on Sept 20 from Marlow, Buckinghamshire, UK. Marlow is located ~50km or 30 miles west of London. A detailed description can be found at the Wycombe Astronomical Society. It was described as a white slow-moving meteor with a brightness of -3 magnitudes (between the brightness of Jupiter and Venus). This looks like a natural meteor caused by a meteoroid. It is possible that it a piece of a re-entering satellite. Thanks to Ed Davies for calling attention to this sighting.

The second fireball was reported by Lucy from East Mersea in southeast England. She reported a fireball with 4 components around 8:30 PM on Sept 22. The description seems to suggest a fireball which has broken up. It could be either a natural meteor or a re-entering piece of man-made space junk.

The third fireball also occurred during the evening of Sept 22 at 9:30-9:40 PM. Largo (Hamilton, just outside of Glasgow in southwest Scotland) and Debbie (Islandmagee, County Antrim, Northern Ireland) both described a fireball moving from East to West. It was multi-colored with a tail. The East to West motion probably rules out a re-entering satellite so this one looks to be a natural meteor caused by a meteoroid or small asteroid.

A third report of this fireball has been submitted by Chris Day of Accrington, England. He described a white/yellow fireball which latest for at least 6 seconds. It moved from the West to the East before setting behind trees and buildings.

With 3 fireball sightings from the British Isles and the Sept 19th fireball over southern California, I’m sure everyone is wondering what’s going on?

Though very bright fireballs, such as the southern CA one, are rare, they occur nightly somewhere in the world. We don’t read much about them because they are usually missed. Most of the world is covered by oceans, or cloudy, or uninhabited, so we only hear of bright fireballs occurring over major population centers. Secondly, meteors with brightnesses comparable to the brightest planets, such as the Marlow meteor, probably occur nightly for any observer willing to spend all night staring at the sky. Since we are only outside and looking up for a fraction of the night we miss most of these as well.

There are many rare sights in the sky. But the more time you spend looking up, the more likely you are to see some of them.

Thanks again to everyone who submitted reports of fireballs. Keep sending them in.