By Eddie Wrenn
PUBLISHED: 03:45 EST, 27 September 2012 | UPDATED: 08:28 EST, 27 September 2012
They are one of the most spectacular views a human could hope to see – and next year a comet which could outshine the moon is due to fly by the Earth.
Comet ISON is visiting the inner solar system and is set to put on spectacular views for the Northern Hemisphere across November and December as it heads towards the sun.
It may prove to be brighter than any comet of the last century – visible even in broad daylight – and this may end up being its one and only trip to the solar system, as its trajectory may see it plunge into the sun in a fiery death.
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How Hale-Bopp looked above Alaska: Next year’s comet is predicted to be even more spectacular, and remain in the skies for weeks
It is currently moving inwards from beyond Jupiter, and as it approaches the Earth, the ‘dirty snowball’ could produce a dazzling display, burning brighter than the moon and potentially being visible in broad daylight.
The comet, discovered by astronomers using the International Scientific Optical Network telescope in Russia, will pass within two million miles of the sun’s surface – making it s ‘sun-grazing’ comet.
It is on a ‘parabolic’ orbit, which means it probably originated from the outer skirts of the solar system, perhaps from the Oort cloud – a mass of icy debris which lies 50,000 times further from the sun than the Earth does.
If comet ISON survives the encounter, it could take thousands – potentially millions – of years before the comet passes back through the inner solar system.
COMETS: THE REGULAR VISITORS TO OUR PLANET
Comets are dusty balls of ice, which generally originate from the Kuipler belt – a region of icy small bodies beyond Neptune.
Occasionally, a comet gets dislodged from its orbit, and plunges in to the inner solar system.
They differ from asteroids, which are made of metal or rock, and are usually the left over remnants of planets or moons.
Comets are not really reflective – they only reflect 4% of the the Sun’s rays, about the same as coal. So although they look brilliantly white from Earth, they are black at the surface.
Halley’s comet is the most well-known, named after Edmond Halley who noted the regular 75-76-year appearance of a comet, and predicted it would return in 1758, although sadly the astronomer died 16 years before he was proved correct.
Halley’s comet has passed within a fraction of the Earth before – in 1910 the Earth even moved through the comet’s tail.
Sadly, the 1986 re-appearance was the worst for 2,000 years, as the Earth and the comet were on opposite sides of the sun.
The comet will begin brightening once it gets within Jupiter’s orbit, as the sun’s heat begins boiling the ice locked within the comet, converting it directly into gas.
It is likely to recall the excitement of Comet Hale-Bopp, which sailed past the Earth in 1997, appearing as a static-looking smear in the skies across the Northern Hemisphere.
It is also set to outshine ‘the greatest comet of the last century’ – Comet McNaught, which shone brighter than Venus as it passed above the southern hemisphere in 1965.
Comets are known as ‘dirty snowballs’, although technically a better definition would be ‘snowy dirtballs’, as comets are generally rocky at the surface, with chemical-laden ice within the interior.
As the ice and chemicals heat up, they erupt as brilliant jets which can form tails lasting hundreds of thousands of kilometres in length.
The comet is expected to be bright throughout late November and early December.
Robin Scagell, vice-president of the Society for Popular Astronomy, said: ‘This is a very exciting discovery.
‘The comet looks like it could become a very spectacular sight in the evening sky after sunset from the UK in late November and early December next year.
‘Our members will be eagerly following it as it makes its first trip around the Sun and hoping to see it shining brilliantly and displaying a magnificent tail as it releases powerful jets of gas and dust.’
VIDEO: Up close & personal; sounds of a comet encounter:
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