'Once in lifetime' comet to be visible in coming weeks - how to see it

Stargazers have a once-in-a-lifetime opportunity to see a comet larger than Mount Everest whizzing through the sky this month. 

Officially known as Comet 12P/Pons–Brooks, the comet has been compared with the Millennium Falcon from Star Wars because of its pair of 'horns' seen in images. 

Amateur astronomers have already been snapping photos of the comet with specialist telescopes, but it should soon become visible to the naked eye.

To see Comet 12P/Pons-Brooks, look westwards in the night sky and find the Great Square of Pegasus – the four stars of nearly equal brightness.

Over the next few weeks, the comet is moving from Great Square of Pegasus towards Aries the Ram, which forms a loose V-shape.

12P/Pons-Brooks: Key facts 

Discovered: July 12, 1812

Orbital period: 71 years

Type of comet: Cryovolcanic

Last perihelion: May 22, 1954

Next perihelion: April 21, 2024

Nucleus diameter: 18.6 miles (30 km)

The comet completes an orbit around the sun every 71 years and is seen from Earth only once in that period, making it a once-in-a-lifetime experience. 

Pons-Brooks is set to come as close as 72.5 million miles (116.8 million km) to the sun on April 21. 

Following that, a close approach with Earth of 144 million miles (232 million km) will happen on June 2.

However, if you're in the northern hemisphere, the best time to see it will be late March, according to Jessica Lee, an astronomer at the Royal Observatory Greenwich.

Although it's difficult to predict what a comet looks like and how bright it will become, the public should look out for what looks like 'an irregularly shaped dirty snowball'. 

'It’s predicted that this comet will reach maximum brightness for viewers in the northern hemisphere in late March,' Lee told MailOnline. 

'In late March the comet will be in the constellation of Aries, which is in the western sky just after sunset. 

'Ideally you should go somewhere with a clear view of the horizon in the west, and pick a night with clear skies.' 

When this close approach occurs, 12P/Pons-Brooks is expected to be visible to the naked eye as a faint star-like blob with a hazy tail. 

READ MORE: Here's the astronomical events of 2024 that you won't want to miss

'Right now, one of the brightest known periodic comets is on its way in towards the sun,' said Professor Paul Strøm, an astrophysicist at the University of Warwick.

'It is a big comet too with a size comparable to that of Mount Everest. 

'The comet is expected to reach a magnitude of 4.5 which means it ought to be visible form a dark location in the UK.' 

After making its closest approach to us, the space rock will be gravitationally flung back to the outer solar system and will not return until 2095. 

Comets consist of a nucleus made up of ice, dust, and small rocky particles, surrounded by an outer 'coma' – a hazy cloud of gases. 

12P/Pons-Brooks is what is known as a cryovolcanic – or cold volcano – comet, which means it exhibits volcanic activity. 

But instead of spewing out molten rock and lava like a volcano on Earth, a cryovolcanic comet releases a mixture of gases and ice. 

When a cryovolcanic comet gets closer to the sun – like 12P/Pons-Brooks is doing now – it heats up and builds pressure in the nucleus.  

The pressure continues to build until nitrogen and carbon monoxide explodes and flings out icy debris through large cracks in the nucleus's shell. 

These gaseous streams can form distinctive shapes when viewed through a telescope, such as devil horns, also described as a horseshoe or the Millennium Falcon from Star Wars. 

According to an astronomer, the comet erupted on October 31 – the second time in the space of a calendar month and the third time since July. 

Arizona-based amateur astronomer Eliot Herman, who has been monitoring the comet, said it abruptly brightened almost 100-fold on October 31 and continued to get brighter in the following days. 

Just like planets, comets in our solar system orbit the sun because they are attracted to the sun's massive gravitational pull. 

It takes 12P/Pons-Brooks 71 years to complete an orbit of the sun, but this is relatively short compared with the orbital length of most orbits which take thousands of years.

Explained: The difference between an asteroid, meteorite and other space rocks

An asteroid is a large chunk of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the Main Belt.

A comet is a rock covered in ice, methane and other compounds. Their orbits take them much further out of the solar system.

A meteor is what astronomers call a flash of light in the atmosphere when debris burns up.

This debris itself is known as a meteoroid. Most are so small they are vapourised in the atmosphere.

If any of this meteoroid makes it to Earth, it is called a meteorite.

Meteors, meteoroids and meteorites normally originate from asteroids and comets.

For example, if Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.