Hot on the trail of the morning star
ANY of you looking up to the skies in the evening this month will undoubtedly see a very bright object – the planet Venus.
The orbit of Venus can bring it within about 26million miles of the Earth, closer to us than any other planet.
Venus is also the hottest planet in the Solar System, closer to the Sun than Earth and covered with a thick atmosphere that traps heat from the Sun.
Venus is traditionally known as the “morning star” or “evening star”, since it appears quite bright at dawn or dusk.
These are the only times that it is visible, as it is closer to the Sun than the Earth, so the Sun’s light mostly obscures our view of it.
Like the Moon, Venus’s appearance changes from our point of view as it orbits around the Sun. It goes through phases, from full to gibbous and crescent and back again. Telescope viewers can easily observe this phase of Venus. Venus is a planet which, in some respects, closely resembles Earth. Both its size and mass are similar to Earth and it was at one time considered a sister planet.
A day on Venus, however, is very different. It takes 243 Earth days for Venus to turn once on its axis.
Its atmosphere is much denser than ours, with a pressure equivalent to that of being half a mile underwater on Earth. Composed of carbon dioxide and sulphur dioxide, layered with clouds of sulphuric acid, it is a much more poisonous atmosphere.
This atmosphere has also contributed to a runaway greenhouse effect on Venus.
Heat from the Sun passes down toward the surface of the planet, but then cannot escape.
The trapped heat energy builds and builds, making the planet’s surface hotter and hotter, to the point where surface temperatures on Venus are now approximately 400C.
So in short, a visitor to Venus would have to struggle against the dense atmosphere while being baked to oven-like temperatures and rained down on by acid rain. Not exactly a tropical paradise.
For a long time, our views of Venus were blocked by the total shrouding of cloud cover. Spacecraft have since travelled to Venus, with NASA’s Magellan probe peering through the clouds using radar and the Soviet Venera probes landing on the surface.
The planet Venus will continue to improve throughout January and is very easily visible under clear skies.
It is already a brilliant object in the south-western evening sky and visible until after 7.30pm.