Category Archives: Meteor Showers

The Geminid meteor shower, which peaks this year on Dec. 13th and 14th, is the most intense meteor shower of the year. It lasts for days, is rich in fireballs, and can be seen from almost any point on Earth.

The Geminid meteor shower, which peaks this year on Dec. 13th and 14th, is the most intense meteor shower of the year. It lasts for days, is rich in fireballs, and can be seen from almost any point on Earth.halebopp6_aac_big

A Geminid fireball explodes over the Mojave Desert in 2009. Credit: Wally Pacholka / AstroPics.com / TWAN.

It’s also NASA astronomer Bill Cooke’s favorite meteor shower—but not for any of the reasons listed above.

“The Geminids are my favorite,” he explains, “because they defy explanation.”

Most meteor showers come from comets, which spew ample meteoroids for a night of ‘shooting stars.’ The Geminids are different. The parent is not a comet but a weird rocky object named 3200 Phaethon that sheds very little dusty debris—not nearly enough to explain the Geminids.

“Of all the debris streams Earth passes through every year, the Geminids’ is by far the most massive,” says Cooke. “When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of 5 to 500.”

This makes the Geminids the 900-lb gorilla of meteor showers. Yet 3200 Phaethon is more of a 98-lb weakling.

3200 Phaethon was discovered in 1983 by NASA’s IRAS satellite and promptly classified as an asteroid. What else could it be? It did not have a tail; its orbit intersected the main asteroid belt; and its colors strongly resembled that of other asteroids. Indeed, 3200 Phaethon resembles main belt asteroid Pallas so much, it might be a 5-kilometer chip off that 544 km block.

Geminids 2010 (impact, 550px)

An artist’s concept of an impact event on Pallas. Credit: B. E. Schmidt and S. C. Radcliffe of UCLA. [larger image]

“If 3200 Phaethon broke apart from asteroid Pallas, as some researchers believe, then Geminid meteoroids might be debris from the breakup,” speculates Cooke. “But that doesn’t agree with other things we know.”

Researchers have looked carefully at the orbits of Geminid meteoroids and concluded that they were ejected from 3200 Phaethon when Phaethon was close to the sun—not when it was out in the asteroid belt breaking up with Pallas. The eccentric orbit of 3200 Phaethon brings it well inside the orbit of Mercury every 1.4 years. The rocky body thus receives a regular blast of solar heating that might boil jets of dust into the Geminid stream.

Could this be the answer?

Geminids 2010 (coronagraph, 200px)

The path of 3200 Phaethon through STEREO’s HI-1A coronagraph camera. False-color green and blue streamers come from the sun. [more]

To test the hypothesis, researchers turned to NASA’s twin STEREO spacecraft, which are designed to study solar activity. Coronagraphs onboard STEREO can detect sungrazing asteroids and comets, and in June 2009 they detected 3200 Phaethon only 15 solar diameters from the sun’s surface.

What happened next surprised UCLA planetary scientists David Jewitt and Jing Li, who analyzed the data. “3200 Phaethon unexpectedly brightened by a factor of two,” they wrote. “The most likely explanation is that Phaethon ejected dust, perhaps in response to a break-down of surface rocks (through thermal fracture and decomposition cracking of hydrated minerals) in the intense heat of the Sun.”

Jewett and Li’s “rock comet” hypothesis is compelling, but they point out a problem: The amount of dust 3200 Phaethon ejected during its 2009 sun-encounter added a mere 0.01% to the mass of the Geminid debris stream—not nearly enough to keep the stream replenished over time. Perhaps the rock comet was more active in the past …?

“We just don’t know,” says Cooke. “Every new thing we learn about the Geminids seems to deepen the mystery.”

This month Earth will pass through the Geminid debris stream, producing as many as 120 meteors per hour over dark-sky sites. The best time to look is probably between local midnight and sunrise on Tuesday, Dec. 14th, when the Moon is low and the constellation Gemini is high overhead, spitting bright Geminids across a sparkling starry sky.

Bundle up, go outside, and savor the mystery.

Large Meteor Explodes Over 8 States, EM Interference/Sonic Booms Reported

NASA has confirmed with satellite radar that a meteor has struck the earth, although no exact location has been given yet.

A very large fireball – or series of them – was seen this evening across several states and is apparently causing strange interference with23554347_BG1-300x225 cellular, internet, and even satellite communications throughout the Ohio Valley.

The American Meteor Society quickly received almost 200 online reports of the event, with 131 reports coming from Ohio, Kentucky, and Indiana, and 46 more from Illinois, Michigan, Pennsylvania, and West Virginia as of shortly after midnight Eastern Daylight Time.

Radio show “Ground Zero with Clyde Lewis” received dozens of calls from frightened witnesses, one of whom also put the phone up to the Satellite-connected TV service during the call, which was making a very odd and very persistent noise consistent with EM interference.

Witnesses also turned to Twitter to express their shock and awe at the event:  Watched fireball over north-central WV. Brightest explosion / fastest movement I’ve ever seen or imagined. Fully expected a shockwave. None

September Epsilon Perseids Meteor Showers

New data for the September Epsilon Perseids (SPE) shows that this radiant is active from September 1st through the 28th with perseid_map2maximum activity occurring on the 9th. The radiant position is currently located at 02:52 (043) +41. This position lies in southwestern Perseus, only three degrees west of the famous eclipsing variable star known as Algol (Beta Persei). The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Rates are currently less than one per hour but will increase to near 3 per hour at maximum. Commencing on September 5th, this radiant will become the strongest source of activity in the sky and will remain so throughout most of the month. This shower experienced an outburst in 2008 with ZHR’s near 25 for a short time. Many bright meteors were produced during this outburst with the brightest estimated at magnitude -8. With an entry velocity of 66 km/sec., most activity from this radiant would be swift. This activity is visible from the tropical regions of the southern hemisphere, but further south the radiant becomes too low in the sky to produce much activity.