In a galaxy not far away, a heavenly body is making a once-in-a-lifetime fly-by

Holidaying star-gazers this week have the chance to observe a huge chunk of ice and gas hurtling through the night sky faster than a speeding bullet.

Comet Lovejoy - discovered last August - is zooming north within about 70 million kilometres of Earth; a mere hair's breadth in astronomical terms.

Dr Grant Christie, from Auckland's Stardome Observatory, said the comet, named after its Australian discoverer, Terry Lovejoy, should be visible to the naked eye over the next few days and easily spotted through household binoculars.

He said at 10pm today the comet would be 60 degrees above the horizon at due north. And it was a once-in-a-lifetime opportunity to see it from Earth. The comet is not expected back in our skies for several thousand years.


"It's going to get pretty close - around half the distance of the Earth to the sun at one stage," he said.

Comets are mostly ice. Like other comets, Lovejoy is believed to be about 5km in diameter.

Its "tail" is the result of space dust and evaporating ice reflecting the sun's rays.

Christie estimated Lovejoy would be moving at somewhere in the order of 20-30km per second and by mid-January would be difficult to see, before disappearing over the horizon late January.

But there's plenty else to keep star-gazers occupied this summer. Astronomer Alan Gilmore, formerly the University of Canterbury's Mt John Observatory resident superintendent, said one of the brightest objects in the sky would be Jupiter, which comes up in the northeast sky in January.

Star-gazers using binoculars could try to spot the planet's four moons, which were first observed by Galileo in 1610.

"The old rule that stars twinkle and planets don't doesn't always work, but it does for Jupiter. It has a disk you can see in binoculars that sort of blurs the twinkling so Jupiter shines with a very steady golden white colour."

Venus would also appear as a bright star in the southwestern sky.

Gilmore said one of his favourite sights was the Matariki/Pleiades star cluster, low in the northeastern evening sky this month.

"If you're away from city lights you can see it as half a dozen stars close together. In binoculars you can see a couple of dozen stars.

"That's a good one."

Another interesting sight for the casual astronomer was the Orion Nebular, a glowing gas cloud south of Orion's Belt.

"If you look into the handle of the pot with binoculars you can see a fuzzy smudge of light around the middle stars of the handle. That's called the Orion Nebular.

"It's a glowing gas cloud where stars are forming or have formed in a cloud of dust and gas and the very hottest stars are lighting up the gas and making it glow."

On a dark night, you did not need high-tech equipment to be able to see other galaxies up to 200,000 light years away, Gilmore said.

"High up in the southern sky, above the Southern Cross are two glowing patches called the Clouds of Magellan, which are two nearby galaxies.

"To the eye they appear as clouds but with binoculars you can see various brightenings in them.

"In a decent-sized telescope you can see whole spherical clouds of stars, which are very pretty," Gilmore said. "There's plenty to see this summer."

New-age star gazing

Science Media Centre manager Peter Griffin's five top space apps:

Star Walk: Point your phone or tablet at the sky to get an overlay view of where celestial objects should be. The app uses the compass and GPS chip in your smartphone to pinpoint where you are under the night sky. Cost: $3.80.

StarMap: Ideal for amateur telescope users. Identifies the most visible celestial objects on any given night from where you are standing, including planets, galaxies and asteroids. Cost: $6.50.

Pocket Universe: Another point and track app, ideal for beginners because of its superb tips and tutorials. Cost: $3.80.

Solar Walk: Interactive 3D models of the planets and stars in the galaxy. Looks great on the iPad. Plug in a date to see how the planets align in the past or the future. Cost: $3.80.

Nasa: A space agency app that updates you on major celestial events, space missions and videos and images from the Hubble Space Telescope. Free.