Halley's Comet is about 15 kilometres wide.
When is the meteor shower?
Each year, as Earth crosses the orbital path of Halley's Comet, stargazers are treated to a fantastic meteor shower known as the Eta Aquarid.
The Eta Aquarid meteor shower is active each year between April 19 and May 28, with its peak centred around May 6. The other shower is the Orionoid. Observers can expect 30 to 60 meteors per hour. It's in the southern sky if you're in the northern hemisphere, and in the northern sky if you're in the southern hemisphere.
Luckily for those on the bottom half of the globe, the meteor shower will be best seen in the Southern Hemisphere due to our Autumn night hours, meaning the longer dark time will mean more time to catch a glimpse of the meteors.
The shower is named after the faint Eta Aquarii star in the Aquarius Constellation, which acts as its radiant point - the area of the night sky that the meteors appear to emanate from.
In a post on its website, Nasa said: 'The constellation of Aquarius - home to the radiant of the Eta Aquarids - is higher up in the sky in the Southern Hemisphere than it is in the Northern Hemisphere.
"So you'd think the shower would be about the same as seen from around the globe".
Across the Northern Hemisphere, the best viewing is just before dawn.
Meteor shower will be best seen on 5 and 6 may. "That's why the tropics and southern temperate latitudes tend to see more Eta Aquarid meteors than we do at mid-northern latitudes".
'Earthgrazers are long meteors that appear to skim the surface of the Earth at the horizon'. Under the most favorable conditions, a dozen or more meteors per hour can be seen from the Eta Aquarid swarm.
The radiant rises about 2am in New Zealand, making the best time for observation around 5am, the Royal Society says.
The Eta Aquarids have a most interesting lineage.