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Spotlight on Venus

As the Earth’s nearest neighbour, Venus is one of the easiest planets to spot in the night sky. Named after the Roman goddess of love, it shines resplendently, often just after sunset or before sunrise. This week, it will be particularly bright, as it reaches its greatest brightness in the dawn sky of the 8th. So, what makes Venus stand out?

Venus in History

As a planet visible with the naked eye, Venus has been known to humans since antiquity. It was not, however, always known to be a planet. Early on, the word ‘star’ was attributed to all points of light in the sky, regardless of their modern day classification. There was, however, different types of star. Planets such as Venus were given the name ‘wandering stars’. This was due to their movement. Planets often appear to move independently to the stars behind them.

The Ancient Egyptians thought that Venus was in fact two different objects: the ‘Morning Star’ and the ‘Evening Star’. Because Venus’ orbit is closer to the Sun than ours, we only ever see the planet in a similar direction to the Sun. Therefore, it appears shortly after sunset or just before sunrise, close to the Sun in the sky. This belief permeated other civilisations, like the Ancient Greeks, as well.

It wasn’t until a Greek mathematician, Pythagoras, took a closer look at the two stars that he realised they were in fact the same object: Venus. Many years later, the famous astronomer, Galileo Galilei, pointed his newly-built telescope towards the planet. He discovered that it had phases, similar to the Moon. This was an incredible discovery that indicated that Venus moved around the Sun, and not around the Earth as previously thought.

The first spacecraft to successfully land on Venus was the Venera 7 lander, launched by the Soviet Union in 1970. This also marked the first successful landing on another planet. When it reached the surface, the signal turned to noise. But by looking at it closer, the scientists managed to access information from a signal at 1% the strength it had before landing. Venera 7 managed to survive temperatures of 465°C and pressure of 90 atmospheres (that’s 90 times our own!) for 23 minutes before its batteries failed.

What is Venus like?

Venus has the densest atmosphere in the whole of the solar system. This means that it is constantly covered in a thick layer of cloud, making it all but impossible for instruments to see down to the surface. This mystery gave rise to all sorts of theories about what the surface of Venus was like – from scientists and science fiction writers alike! People liked to imagine that Venus was a tropical world, full of jungles and rainforests. Perhaps even somewhere you could go on holiday in the distant future!

Unfortunately, this is far from the case. Venus’ dense atmosphere contributes to what is essentially a runaway greenhouse effect. In the same way that climate change is heating up our own atmosphere, massive amounts of carbon dioxide trap heat beneath the clouds. This leads to incredibly high temperatures and pressures. Just being on the surface is enough to melt lead!

Other than the inhospitable conditions, Venus is the Earth’s twin in many ways. It has a similar size and density, and orbits the Earth at 0.7 AU (1 AU is the distance between the Earth and the Sun). One year, or the time it takes to orbit the Sun, is 225 Earth days long. However, this only amounts to just under 2 Venusian days. Venus is one of two planets in the solar system that rotates from east to west, the other being Uranus. This is the opposite direction to the direction that it is moving around the Sun. Coupled with its slow rotation speed, this means that one day-night cycle takes 117 Earth days.

How to see it

Venus is an easy object to see with the naked eye. Being our nearest neighbour, it is the brightest object in the sky, except the Sun and Moon. At the moment, you can see it in the morning sky just before sunrise, shining in the east. It appears in the constellation of Taurus the Bull.

On the morning of the 8th, Venus appears at its greatest brightness, of -4.5 magnitude (lower magnitudes are brighter). This is when it will be best viewed, and can even cast a shadow without interference from artificial lights or the Moon. Then, on the 10th, it will reach aphelion, its furthest point from the Sun. However, this will not impact on its visibility from Earth.

Keep an eye out for the Morning Star this week!

Sources: Universe Today, Science Museum, NASA