Venus..

the column submitted to Namoi Independent

Venus – the brightest of all the Planets.

As discussed last time, over the next few weeks we are going to consider the planets the Galileo could see and look at how we can find them in the sky.

Last week, we discussed Mercury, in its role of morning star. Don’t forget if you are out early next Monday (Feb 23) at around 6am before the sun comes up – you will be able to see Jupiter, Mercury and Mars very close to the crescent moon.

This month finds Venusin the constellation of Pisces and at its brightest. Even in small telescopes, Venus can be seen to dramatically increase in size and go from being a "half Moon" shape to a distinct crescent, however as Venus gets closer to the horizon it will be harder to see. Towards the end of the month Venus's crescent shape may be seen in powerful binoculars.

Venus, named after the goddess of love, is the brightest of all the "stars" in the sky. Even though it is always covered with thick cloud, so we can't see its surface, we know more about the surface of Venus than the surface of any other planet. More than 20 spacecraft have visited Venus which is more than have visited any other planet in the solar system.

Almost an identical twin to Earth in mass and size it is the hottest and flattest of all of the planets in the inner solar system. On Earth, we generally find that there are few clouds higher than 15 km above sea level and on average; only about 50% of the Earth’s surface is covered by cloud at any given time. On Venus, however, clouds cover 100% of the surface constantly. The clouds don’t start until about 50 km above the surface, and then extend for another 25 km. They are made up of droplets of sulphuric acid, which are about 50 times smaller than the thickness of a human hair. On Venus it takes 225 earth-days to make a complete orbit of the Sun and we don’t understand why, but the planet rotates in an opposite direction to all the other planets in the Solar System (except Uranus). A day on Venus lasts the equivalent of 243 Earth Days, hence on Venus a day is longer than a year.

Lightning also seems to be as common on Venus as it is on Earth with most of the lightning happens within the thick high cloud deck. The clouds on Venus though race around the planet nearly 60 times faster than the surface rotates and just like on Earth, the thunderstorms and lightning on Venus seem to happen mostly in the afternoon and at dusk.


On February 28, you will see the crescent moon close to Venus, which by that the end of the month is just a hand span above the western horizon half an hour after sunset.

If you have any questions about what you see in the sky or want more information on what is on in this International year of Astronomy, please feel free to contact me – Donna Burton, Australian National University, Siding Spring Observatory, Coonabarabran 2357, phone 6842 6255 or via email donna@mso.anu.edu.au. Remember – The Universe – it is Yours to Discover!