Observing the Planets: Venus

By Peter Forrester | December 26, 2018

If you have gotten out to look at the sky one or two hours before sunrise, and seen a really bright star to the east or slightly southeast, that is actually not a star, but the planet Venus.

The second planet from the Sun is the third brightest object in the sky, after the Sun and Moon. It outshines even the brightest stars, with its apparent magnitude reaching as high as -4.6 (for historical reasons, the brightness index is inverted, with the lowest numbers being the brightest).

This neighboring planet is a twin of the Earth – they are very similar in size, though Venus’s thick atmosphere of mostly carbon dioxide would be poisonous to breathe. That atmosphere, however, is a boon for stargazers, as it reflects sunlight very well.

Venus is often called the “morning and evening star” because it appears just before sunrise or just after sunset. Since it is closer to the Sun than our Earth, which in astronomers’ language makes it an “inferior planet”, it is always fairly close to the Sun in the sky, within about 47 degrees. Because it is closer to the Sun, Venus also goes through phases, like the Moon, which can be seen through a strong pair of binoculars, or a telescope. It is at its brightest when in crescent phase, ironically enough, because that is when it is closest to us.

The best time to see Venus is either in the early morning, 1-2 hours before sunrise, or 1-2 hours after sunset, though it can also be seen sometimes during full daylight. Right now it is in its “morning” part of its cycle. The full cycle of morning star and evening star (including times when it can not be seen at all) takes 584 days, although Venus only takes 224 days to orbit the Sun.

Occasionally Venus crosses in front of, or “transits” the Sun. The last time this happened was in 2012. I would caution you to take extreme care when watching this, using undamaged eclipse glasses (anything not so dark, such as ordinary sunglasses, exposes your eyes to damage from the Sun). But it seems pointless – the next transit of Venus will be in 99 years, in the year 2117. However, the smaller planet of Mercury transits much more often; more on this later.

Being a bright planet, Venus has been known ever since man stood and looked up at the stars, though apparently it took the ancients a while to discover that the “morning star” and the “evening star” were the same object. The oldest records show the ancient Sumerians recognized it as one object, connecting it with their goddess Inanna; however the Chinese had separate names for the morning and evening appearances. The Babylonians also had detailed observations and called it “the bright queen of the sky”. The Romans called the two aspects Lucifer, the “Light-bringer”, and Vesper, the name of the evening star (Hesperus was the Greek equivalent, and considered to be a god), though the Greeks had discovered that they were one object (this rediscovery was credited to both Pythagoras and Parmenides). Of course, famously, the Romans also named the planet after their goddess of love.

The Pawnee in North America and the Mayans also observed Venus. In fact, measuring the movement of the planet was one of the main reasons the Mayans built their observatory at Chichen Itza, and some parts of their calendar system are based on the movements of Venus.

As late as 1960, writers were hoping its thick atmosphere would make the planet conducive to life, but these hopes were shattered by the various space probe missions to the planet, the first of which was sent in 1961. NASA’s Mariner 2 was the first successful flyby in 1962, later followed by several successful missions from the Soviet Union. These Russian probes became the first to accomplish several things in space exploration.

  • The first to enter the atmosphere of another planet: Venera 4, 1967
  • The first to make a soft landing on another planet: Venera 7, 1970
  • The first to return photographs from the surface of another planet: Venera 9, 1975
  • The first to perform high-resolution radar mapping of Venus: Venera 15, 1983

These observations, as well as improved technology of Earth-based telescopes, helped clinch the death of the idea of life on Venus. In addition to the high CO2 content, it also has a very high atmospheric pressure, 100 times that of Earth, and the surface temperature of 860 – 900 degrees Fahrenheit is hot enough to melt lead. Apparently there is still hope of doing missions to the upper atmosphere, however, where the temperature and pressure are much lower.

For more on the history and observation of this sister of our Earth, see the sources below. In particular, the Cosmic Pursuits article has an excellent explanation and diagram of the phases of Venus.

Happy stargazing!

See also:

Skies Over Milton, December Edition and What Is the Zodiac, Anyway?


Cosmic Pursuits. (2016, November 24). A Brief Guide to Observing the Planet Venus. By Brian Ventrudo. Retrieved from https://cosmicpursuits.com/1366/guide-to-observing-planet-venus/

Wikipedia. (2018, December 26). Transit of Venus. Retrieved from https://en.wikipedia.org/wiki/Transit_of_Venus.

Wikipedia. (2018, December 26). Venera. Retrieved from https://en.wikipedia.org/wiki/Venera.

Wikipedia. (2018, December 26). Venus. Retrieved from https://en.wikipedia.org/wiki/Venus



Author: Peter Forrester

I have been interested in astronomy and stargazing for many years, and now delight to offer some of my learning to others through my weekly blog posts.

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