The brightest comet for several years should become visible in the Northern Hemisphere night sky over the next few days.
Sky-watchers should be able to spot comet Pan-STARRS, or C/2012 L4, with the naked eye; certainly with binoculars or with a small telescope. It's actually heading away from Earth right now - it reached its closest point earlier this week - but is expected to become very bright at its closest approach to the sun on Sunday.
"Although we have discovered many comets with the telescope, so far this is the only one likely to be seen by eye," says Professor Alan Fitzsimmons of Queen’s University Belfast, and one of the Pan-STARRS project leaders. "Comets can be quite beautiful and for that reason alone it’s worth making the effort to see them."
Discovered by and named after the Pan-STARRS telescope in Hawaii, the comet was first detected in June 2011, when it was an extremely faint object 1.2 billion km from the sun.
Like many other comets - including one that's due to make a close fly-by of Mars next year - Pan-STARRS appears to have come from the Oort Cloud, a vast region containing millions of comets a little over two light years from the sun.
It's already been spotted in the southern hemisphere, where it was visible to the naked eye - although this doesn't guarantee the same will be true in the North. The best views should be on 12 and 13 March. Pan-STARRS should appear after sunset low down in the west, looking like a misty patch not far from the crescent moon. The tail should point up from the horizon. Over the following days it will become fainter, but be visible higher in the sky.
"Bright comets are fairly rare and we usually don’t know when the next one is on the way," says Fitzsimmons. "Whether you’re an experienced amateur astronomer or just have an interest, Pan-STARRS is well worth a look."