The sky this month: February's a great month to star gaze

By IAN GRIFFIN*

For people lucky enough to live south of the Earth's equator, February is a great month for star gazing: the nights are starting to shorten, yet they remain warm enough to allow comfortable night-sky viewing for even the least hardy of souls.

With Venus, Mars, Jupiter and Saturn on view, there is no excuse not to spend at least one night this month enjoying the heavens!

To many people, the sky can seem slow moving and unchanging. But this month, several things happen which enable you to see interesting changes in the sky over the course of a couple of nights.

For example, this month's full moon (which occurs at 5:12 pm this evening) is the closest of the year. On this night, it will look 14 per cent bigger and 30 per cent brighter than the most distant full moon.

The elliptical (or egg) shape of the moon's orbit causes its distance from us to change constantly through the year; at this full moon the distance will be 50,000 kilometres less than when it is furthest from us, on September 2.

Venus is most bright this month, and this will doubtless lead to a large number of UFO reports at local observatories.

Visible in the west for about 90 minutes after the sun sets, the planet, named for the goddess of love, will shine like a beacon as it slowly descends towards the horizon as the night darkens.

Venus is really bright owing to a combination of circumstances.

First, it's the most reflective planet in the solar system because it is completely covered by clouds which reflect threequarters of the sunlight striking it. Second, during the last week of this month, Venus reaches perihelion, its closest point to the sun, and hence it is suffused with intense sunlight.

Finally this month, Venus and Earth are extremely close to each other. Combining these three factors results in the wonderful display put on by Venus.

February is also a good time to hunt for Mars in the morning sky.

The moon can be used as a guide to locate Mars on the morning of February 16 since it lies just to the east of the planet. As the month passes, early-rising star gazers will be able to watch Mars approach and then sweep majestically past a bright star in the constellation of the Scorpion. The closest approach will be between February 20 and 22.

As the chart shows, the motion of Mars (whose distance from us is 194 million km or just under 11 light minutes) carries the planet past the more distant star (called Beta Sco, 525 light years away).

Four hundred years ago it was by analysing naked-eye observations of the motion of Mars against the background stars that the astronomer Johannes Kepler figured out that the planets move round the sun in ellipses.

* Ian Griffin, former director of the Auckland Observatory and Stardome Planetarium, now works at the Hubble Space Telescope Science Institute in Baltimore.