One of the best meteor showers in decades could strike the Earth around 18 November. Some experts say it could produce thousands of shooting stars each hour during its peak.
The Leonid meteor shower takes place every November when the Earth passes through the dusty remnants of Comet Tempel-Tuttle.
Tiny fragments, no bigger than sand grains, burn up in the atmosphere to produce fleeting streaks of light, or "shooting stars". And because this year the Earth will be passing through a particularly dense swarm of dust, astronomers are hoping for a memorable display.
America, the Pacific and Asia should be best placed to see this year's event.
Possible storm
Comet Tempel-Tuttle orbits the Sun every 33.25 years and leaves its trail of dusty debris in a slightly different path with every orbit. The debris the Earth encounters is normally sparse, producing about 10-15 meteors per hour at most.
What might make this year exceptional is that Comet Tempel-Tuttle last passed close to the Sun in 1998 and left behind a much higher concentration of material in the inner Solar System than in normal years.
The Earth will pass close to three separate debris paths, which were created by close solar approaches in 1699, 1767 and 1866.
When the Earth skims these paths there is the chance of increased meteor activity and possibly a meteor storm.
Europe poorly placed
The first encounter will occur when the Earth passes close to the path created in 1767, at about 1000 GMT on 18 November. Observers in north-western South America, Central and North America will be well placed to see this.
The next possible outburst will occur about seven hours later at 1730 GMT from the debris path created in 1699. Observers in eastern Australia and the western Pacific should get a good view of this one.
The last possible outburst may be the best as the Earth passes very close to the 1866 path of the comet. This will occur at 1815 GMT. Unfortunately, although most of Europe and Africa will be in darkness at this time, the debris will be hitting another part of the globe.
The shooting stars appear to come from the constellation of Leo, but experienced meteor watchers say observers should be able to see streaks of light all over the sky. The best advice is to just go out and look up.
It is a difficult business predicting meteor rates but analysts say as many as 100 shooting stars per minute might be seen at some stage on Sunday.