So – you’re still interested in astronomy?
If you remember, last time we took a look at 10 things you wanted to know about the Asteroid Belt. This time, I thought it would be a great idea to consider 10 facts you might find interesting about one of the most mysterious places in our Solar System – Venus. (I mean, what happens behind all those clouds?)
1. Is Venus special?
She certainly is. Venus is named after the Roman Goddess of love and beauty, and in a way, that’s quite fitting because people love to look at her. You might have heard of something called, The Morning Star or The Evening Star? Well, that’s Venus. As the brightest object in the night sky besides the Moon, she is often the first thing you notice.
Fact: Did you know, Venus is so bright, she can actually cast shadows?
2. Where is Venus?
Venus is the second planet from the sun, and orbits our star at a distance of 108,000,000(eg million) KM / 47 million 000,000 miles., once every 225 Earth days. She is classed as an inferior planet, because like Mercury, she is closer to the sun than Earth.
3. Don’t some people call Venus, Earth’s sister?
Yes they do. Why?
Because she is very similar in size, gravity, and bulk composition. Venus is both the closest neighbor to Earth, and the closest in size. With a diameter of 12,100 km (7521 miles) she is, in fact, only 650 km (404 miles) smaller than Earth. (Look at the comparison in the picture, where we see all 4 of the inner planets. Mercury; Venus; Earth; Mars)
4. So, Venus really is a twin of Earth then?
Actually, NO! She’s not.
Despite the apparent similarities, conditions are very, very different.
Of the four terrestrial planets, Venus has the densest atmosphere. It is comprised of over 95% Carbon Dioxide. On the planet’s surface, atmospheric pressure is 92 times that of Earth. Because of a runaway greenhouse effect, her surface temperature is 735K. (462 C / 863 F).
5. Could Life exist on Venus?
That is highly doubtful. Venus is shrouded in by an opaque layer of highly reflective clouds of sulfuric acid. YES – acid! 190 mph winds add to the hostile conditions. Her lack of magnetic field means she is subjected to harsh exposure to solar winds, and the pressure we mentioned earlier would squash us.
Fact: Did you know, Venus is the hottest planet in the solar system? So hot, those temperatures are higher than those used to achieve sterilization.
6. Did you know, a day on Venus lasts longer than a year?
Yes – it’s true. Remember, I mentioned earlier that Venus orbits the sun once every 225 Earth Days. But, Venus rotates on her axis once every 243 Earth days. (Called a sidereal day). And, she does so in the opposite direction to most of the other planets. (Called retrograde rotation).
All the planets in the solar system orbit in an anti-clockwise direction. Most rotate in that direction too. Venus doesn’t. Scientists think this anomaly came about during the planets formation. Chaotic spin changes caused by a conflict between the Sun’s gravitation and the tidal effects of her very thick atmosphere caused her to slow down as billions of years passed.
FACT: Not only is Venus’s day the longest day in the entire solar system, but, she’s still slowing down! (6.5 seconds every sidereal day)
7. Does Venus have any more surprises?
Well, yes she does. It’s difficult to explain simply – but I’ll have a go…
If you remember, in the last paragraph I mentioned a term called Sidereal day.
Sidereal days are a time scale based on Earth’s rate of rotation measured relative to fixed stars. The simplest way to think of this is to think of a model globe on a table.
On Earth, a sidereal day is 23 hours 56 minutes and 4.1 seconds long. (Eg, one fixed rotation of the globe on a stationary table).
However, there’s also something called a solar day.
That is the time that actually passes from sunrise to sunrise if you were stood at one point on the surface of the planet. On Earth, that takes 24 hours.
Why is there a four minute difference?
Look at the little diagram with a point of reference (the arrow) pointing through it.
Simply put, the difference occurs because the Earth doesn’t just spin on her axis in a fixed position (like a globe on a stationary table). Don’t forget, she also moves through space in orbit around the sun. (It’s like rotating the globe, AND having someone pick up the table and move it around a fire located in the center of the room at the same time).
So, the distance Earth travels through space around our star every day adds that extra bit of time on. You have to travel a little bit further for the arrow to point at the sun again.
Because the difference is so small for us, we merely compensate for it by tiny adjustments in our clocks and calendars.
Now, let’s get back to Venus.
Her globe on a table – sidereal spin – takes place once every 243 Earth days.
BUT – if you had to stand of the surface of Venus and wanted to experience the joy of watching a sunrise to sunrise, you’d be in for a shock.
Remember, her globe spins the other way. To all intent and purpose, she spins backward, but the table still orbits the sun forward. So, your solar, “sunrise to sunrise day” would be hugely different. In fact, just under 117 Earth days long, significantly less than the length of her sidereal day.
Fact: So, one Venusian year is about 1.92 Venusian solar days long
I hope you were sitting down for that one
8. Does Venus have any Moons?
Sherlock Holmes would love Venus. There’s so much to investigate.
Simply put – No – Venus does not have any moons that we know of.
In the 17th century, Italian/French mathematician & astronomer Giovanni Cassini thought he’d spotted a moon orbiting the planet, but this later turned out to be a genuine mistake.
At the moment, there is an asteroid, called 2002VE68 that maintains a quasi-orbital relationship with Venus. But this object actually orbits the Sun, not Venus.
(Quasi-orbital refers to two or more celestial objects that orbit at the same – or very similar path – from their parent object).
And you can appreciate why early astronomers were fooled. 2002VE68 has been calculated as having been a ‘companion’ to Venus for the last 7,000 years, and is due to be ejected from this arrangement about 500 years from now.
But – an interesting thing is… A study of models of the Solar System, at the Californian Institute of Technology shows that billions of years ago, it is highly likely that Venus did have a moon, created following a huge impact event. However, about 10 million years later, another similar event reversed the planet’s spin direction, causing the Venusian moon to gradually spiral inward until it collided and merged with Venus itself.
Whatever the case, the effects of strong solar tides generated by Venus will prevent any future moon from becoming a permanent feature around this mysterious planet.
9. Are there any Continents and Seas?
Surface conditions make it impossible for seas to exist. Venus’s crust is older than that of Earth, and much less flexible. She has 3 times as many volcanoes, and 167 of them are more than 100 km (60 miles) across. Take a look of her surface in this picture.
Because of constant volcanism, 80% of the surface is covered by smooth volcanic plains. However, there are 2 highland ‘continental’ areas. The northern continent is about the size of Australia. The second one, Aphrodite Terra, lies just south of the equator and is similar in size to South America.
Fact: Venus is littered by hundreds of pristine impact craters. But, because of a combination of very dense atmosphere and ancient surface crust, none under 3 km (about 1.8 miles) in diameter exist.
10. So, there’s a lot about Venus we still don’t know?
There certainly is. A long standing mystery surrounding Venus relates to a phenomenon called Ashen Light – an apparent weak illumination seen on the dark side of the planet when she is in her crescent phase.
The first claimed observation was made in 1643, and many astronomers and scientists since then have also stated they have observed this condition. (Sir William Herschel, Sir Patrick Moore, Dale P. Cruickshank and William K. Hartmann, to name a few). But do you know; the existence of this illumination has NEVER been reliably confirmed, even when special equipment has been used.
Some observers have speculated Ashen Light may be caused by electrical activity in the unique environs of Venus’s upper atmosphere. Others say it is merely an illusionary effect, caused by a combination of contrasts between the solar background and the reflection of intense sunlight on the rest of the highly reflective atmosphere.
Whatever the case, our closest neighbor is certainly a place to capture the imagination. And I’m sure she will continue to do so for many years to come.
So, there you go. I hoped you enjoyed this brief look at Venus. Next time, we’ll look at 10 interesting things about something else we mentioned in this article. Mercury, the closest planet to the Sun itself.
See you then, and remember to bring sunglasses.