Leonid Meteor Shower Peaks

Earth pays its annual visit to the Leonid meteor shower Thursday night and Friday morning; this view is at 1 a.m. looking east.

CREDIT: Starry Night Software

As the Earth moves around the sun in its annual orbit, it passes through patches of space debris left behind by comets and asteroids.

As it moves through these clouds of dust and sand-sized particles, it sweeps them up, and they are heated to incandescence by friction with the Earth's atmosphere, causing bright streaks of light in the night sky known to scientists as meteors, and to skygazers as shooting stars.

Meteors can be seen every night; these are known as sporadic meteors but when the Earth passes through a cloud of debris, it sometimes produces displays known as meteor showers.

A famous annual shower known as the Leonids is set to peak Thursday night (Nov. 17).

Unlike rain showers, meteor showers are not concentrated. Usually they mean seeing 10 or 20 meteors an hour, as opposed to the typical average of one or two.

Most of the time the Leonids are a fairly quiet shower, but every 33 years they put on a major display, known as a meteor storm.

This last happened in 1999, when more than a thousand meteors per hour were observed.

Leonid Meteor Shower adds to Space Debris Hazards

Meteor showers produce gorgeous light shows. But the space debris responsible for them – usually dust cast off from comets – can seriously damage spacecraft, since it travels at relative speeds of up to 260,000 kilometres per hour.

This year, the Leonid shower peaks on 17 November and could produce a spectacular 300 meteors per hour during its peak.

This image of the 1999 Leonid shower was taken from an aircraft.

(Image: NASA-ARC/Shinsuke Abe and Hajime Yano/ISAS)


Satellites are not totally defenceless, however. When especially intense meteor showers are expected, they can orient their solar panels edge-on to the stream of impactors to minimise the chance of damage.

That was not possible for the European Space Agency's Olympus 1 satellite during the 1993 Perseid shower. An earlier meteoroid impact had disabled the pointing system on one of its solar arrays, leaving it exposed to the meteors, according to NASA's Bill Cooke.

Unfortunately for Olympus 1, the shower was especially intense that year because the comet responsible for the shower, Swift-Tuttle, had passed by Earth just the year before, leaving a fresh trail of debris.

During the shower, a Perseid impact seems to have led Olympus 1 to spin out of control. Efforts to regain control used up most of the spacecraft's fuel, leaving just enough to send it into a "graveyard" orbit, where it would not hit other satellites.

(Image: ESA)

New Moon Sets Stage for Brilliant Leonids Meteor Shower11.13.09

A Leonids meteor explodes in Earth's upper atmosphere on Nov. 23, 1998.

Image credit: Robotic Optical Transient Search Experiment (ROTSE) team. Watch the meteor explode


This year's Leonids meteor shower peaks on Tuesday, Nov. 17. If forecasters are correct, the shower should produce a mild but pretty sprinkling of meteors over North America followed by a more intense outburst over Asia. The phase of the moon will be new -- setting the stage for what could be one of the best Leonid showers in years.

"We're predicting 20 to 30 meteors per hour over the Americas, and as many as 200 to 300 per hour over Asia," says Bill Cooke of the Meteoroid Environment Office at NASA's Marshall Space Flight Center. "Our forecast is in good accord with independent theoretical work by other astronomers."

Leonids are bits of debris from Comet Tempel-Tuttle. Every 33 years the comet visits the inner solar system and leaves a stream of dusty debris in its wake. Many of these streams have drifted across the November portion of Earth's orbit. Whenever our planet hits one, meteors appear to be flying out of the constellation Leo.

"We can predict when Earth will cross a debris stream with pretty good accuracy," says Cooke. "The intensity of the display is less certain, though, because we don't know how much debris is in each stream." Caveat observer!