The Leonid meteors over the weekend have produced some spectacular fireballs, though as expected rates were fairly low and there was no ‘meteor storm’.
A spectacular Leonid, photographed at 02:30 UT on 19 November 2017 among the stars of Coma Berenices. The constellation of Leo itself is to the right. Photo: Paul Sutherland
These displays are caused by a swarm of dust particles along the track of Comet Tempelâ€“Tuttle, which orbits the Sun once every 33Â¼ years. But this year, the comet is just about as far as it can get from Earth, beyond the orbit of Uranus. Because the comet is at the other end of its orbit, the particles that have spread along its orbit were not very plentiful. Peak time was on the early morning of Saturday, 18 November, though a few Leonids are likely to occur for a few
The orbit of Comet Tempelâ€“Tuttle. Graphics from JPL
The bright meteor shown at the top of the page was photographed by Paul Sutherland from Walmer. Kent, looking over the Channel towards Belgium and Holland. He used an automated Fuji X-M1 camera with 12 mm f/2 Samyang lens to take continuous 20-second exposures at ISO1600. Out of some 1000 exposures, a bright Leonid appeared on only one. However, this one was a cracker and left a train which persisted for over 10 minutes. It was also photographed from Belgium. Click on the image below to see an enlarged version of the sequence.
Here’s a GIF animation of the same event, which runs in a continuous loop. The object coming in from the top is an aircraft trail.
For more pictures and updates on the 2017 Leonids, check our Meteor Section Leonid page.
Q & A
Will Comet Tempel-Tuttle hit Earth in future?
Although its orbit intersects that of Earth, the comet is always well clear of this point in November when the Earth crosses its path. The closest it gets to Earth for the next few centuries will be in December 2163, but it will be well above the plane of the Earthâ€™s orbit. Even then, the comet will be some 20 million km from Earth.
What causes a shooting star?
This happens when a tiny grain of dust from a comet hits Earthâ€™s upper atmosphere. The speed of impact from the Leonids is about 71 km/sec so in no time they heat up and vaporise, leaving a trail of ionised air that is visible from the ground. This all happens at altitudes of around 100 km above Earthâ€™s surface. Itâ€™s amazing that such a tiny particle can be visible at such a distance.
Why are the Leonids so fast?
Comet Tempel-Tuttle orbits the Sun in the opposite direction to Earth, so the closing velocity of the dust particles is greatly increased. Some other meteor showers, such as the Taurids, which are active at the same time as the Leonids, are much slower because the bodies orbit in the same direction around the Sun as the Earth.
Is there any danger from the Leonids?
Yes â€“ you might catch a chill if you donâ€™t dress up warmly! But thereâ€™s no risk of the shooting stars reaching the ground â€“ they all disintegrate high in the atmosphere.
How can I photograph the meteors?
They happen so quickly that as soon as you spot one, itâ€™s gone â€“ so thereâ€™s no time to swing the camera round and press the shutter. The only way is to keep the shutter open for as long as you can and hope that one dashes through the field of view during the exposure.
|A Leonid meteor photographed by David Entwistle|
- Put the camera on a tripod or fix it viewing the sky
- Use a high ISO setting â€“- 1600 or higher
- Make sure the camera is focused on infinity. Switch off auto-focus, as the camera will have nothing to focus on
- Give the longest exposure you can without the image being overexposed due to light pollution. Compact cameras may not allow more than a few secondsâ€™ exposure, but aim for at least 30 seconds if possible, with the lens at full aperture
- Check for dewing up every so often
- Aim at about 45Âº altitude (halfway up the sky) and a similar distance from the radiant.