What’s Out Tonight?

A general ASTRONOMY site to get you started exploring the night sky


Facts about Venus 

• Second planet from the Sun 
• It’s a Terrestrial Planet & the hottest planet. Terrestrail means that its surface is rock like and can be walked on. 

Diameter: 7,521 miles 
Mass: 0.82 Earth’s mass 
Density: 5.25 where water = 1 
Gravity: 0.9 times that of Earth 
Albedo (% of Sunlight reflected): 65% 
Rotation on Axis: 243 days 
Inclination of Axis to Orbit: 177.4° 

Distance from Sun: 67,230,000 miles 
Revolution about Sun: 224.7 days 
Inclination of Orbit to Earth’s Orbit: 3.4° 

Atmosphere: 96% Carbon dioxide, 2.7% Nitrogen plus traces of Argon and Oxygen 
Surface Temperature: 900° F 
Atmosphere Pressure: 90 times that of Earth 

Moons: Venus has no moons. 

Most interesting features in a small telescope: With any small telescope at just 50x, you can observe Venus in one of its phases. Since it it totally covered in clouds, no surface features are ever visible and it is not possible to see subtleties in the clouds as in the picture to the right. Venus is a crescent when it is the brightest in the sky and this is a pretty sight!

The surface of Venus beneath the ever present white clouds is cratered from extreme volcanic activity. This type of image was obtained using radar from spacecraft that have been placed into orbit around the planet.

The Planet Venus

One cold, moonless, winter night in Milwaukee, I went outside to look at the stars. Snow covered the back yard and Venus was high and bright. Something that night seemed different. I noticed the shadows of the lilac branches, plainly visible on the snow. Venus was casting shadows! Venus has the distinction of being the brightest Planet in our sky, reaching magnitude –4.6. 

Venus is often referred to as the morning or evening star because it hugs close to the Sun’s rising and setting. Since Venus orbits inside Earth’s orbit, it also cycles through phases. 

In the past, Venus was referred to as Earth’s sister Planet because the diameters of the two Planets are almost the same. This connotation vanished when we discovered that Venus is totally inhospitable to life; so much so, that even scientific probes can last only several minutes on its surface. Its atmosphere is 96% carbon dioxide with temperatures soaring over 900° F. This temperature is more than hot enough to melt lead, zinc or tin. Its atmospheric pressure is 90 times Earth’s, equivalent to water pressure at 3,000 feet below sea level. 

Venus’ day is longer than its year, and in comparison to all the other Planets, it rotates on its axis almost upside down. 

Locating and Observing 
Venus Venus is very easy to find in the sky because of its brightness and close proximity to the rising or setting Sun. Reaching magnitude –4.6, Venus easily outshines all the other stars and Planets. If you see a very bright star lower in the sky during the early morning or night, it will almost always be Venus. When Venus is shining it brightest, it can seem eerily bright. With a small telescope and moderate magnifications of 50x to 100x, Venus appears brilliantly white and featureless because of its thick cloud cover. Since this Planet is inside Earth’s orbit, it cycles through phases just like the Moon. However, unlike the Moon, it varies in size. Venus is at its largest and brightest when a crescent. The crescent phase of Venus can be seen in well-focused binoculars.

Slightly enhanced photo of Venus showing the structure of its clouds. Through a telescope, the clouds are brilliantly white and do not show details like in this image,

Venus cycles through phases because it orbits inside Earth’s orbit. It is a crescent when it is at its brightest.

An image of Venus’ surface from the USSRs’ spacecraft Venera 9 in 1975. Transmission lasted only 53 minutes from the surface because of Venus’ extreme temperature and pressure. You can see some of and parts of the spacecraft. A wide angle lens was used for the image.