Australasian Science: Australia's authority on science since 1938

Star Chart for March 2012

By Dave Reneke

Read about some special features in the night sky from February 23, and download the Sydney Observatory's star chart for March 2012.

Attention all budding sky watchers, grab your telescopes. What you’re about to read might give you an uncontrollable urge to dash outside. The brightest planets in the solar system are lining up in the evening sky, and you can see the formation, some of it at least from 23 February.

Go out at sunset and look west. Venus and Jupiter pop out of the twilight even before the sky fades completely black. The two brilliant planets surrounded by evening blue is a spellbinding sight. Hey, grab your smartphone, hold it steady and see what a pic looks like.

If you go out at the same time tomorrow, the view improves because Venus and Jupiter are converging. In mid February they are about 20 degrees apart. Astronomers measure angular separation of objects in degrees. There are 360 degrees in a circle. 20 degrees equals the width of two closed fists held at arms length.

By the end of the month, the angle narrows to only 10 degrees – so close that you can hide them together behind your outstretched palm. Their combined beauty grows each night as the distance between them shrinks.

Friday 24 February is a special night, and Saturday night too when the crescent Moon moves in to form a slender heavenly triangle with Venus, Jupiter and the Moon. One night later it happens again and this arrangement will be visible all around the world, from city and countryside alike.

The Moon, Venus and Jupiter are the brightest objects in the night sky and together they can shine through urban lights, fog, and even some clouds. They’ll probably defeat the glare from your outside streetlights so carelessly left unshrouded by most councils.

After hopping from Venus to Jupiter in late February, the Moon exits stage left, but the show is far from over. In March, Venus and Jupiter continue their relentless convergence until, on March 12th and 13th, the duo lie only three degrees apart, a spectacular double beacon in the sunset sky. Now you’ll be able to hide them together behind a pair of outstretched fingertips!

There’s something mesmerizing about stars and planets bunched together in this way—and, no, you’re not imagining things when it happens to you. The phenomenon is based on the anatomy of the human eye. Your eye is a bit like a digital camera, there's a lens in front to focus the light, and a photo array behind the lens to capture the image. The photo-array in your eye is called the retina. There’s a tiny patch of tissue near the centre called ‘the fovea.’

Whatever you see with the fovea, you see in high definition. The field of view of the fovea is only about five degrees wide. Most nights in March, Venus and Jupiter will fit within that narrow cone. And when they do – presto! It’s spellbinding astronomy.

Are you a meteor freak like I am? Good news fellow sky watchers, the delta- Leonids meteor shower is still happening and the best view will be over this weekend. Gotta get up around midnight though so I’ll meet you in the backyard with a cuppa!

While you’re waiting check out that bright red ‘star’ high overhead. You’re looking at Mars, the “Red Planet,” so called by the Romans as the God of War because of its similarity to the colour of blood.

Standing outdoors, mesmerized by planets aligned in a late summer sunset, you might just forget all about Julia, Kev and Tony for awhile. At least the stars make sense.

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