Caoimhín's Content

Today we are looking at Venus. We won’t just look at Venus, just like some previous videos about the gas giants, we’re going to take a look a the view from Venus as well. The video above does begin with a quick look at how the sky appears at the moment, showing Saturn disappearing soon after sunset, with Jupiter visible higher in the evening sky. As we push towards morning time, Jupiter doesn’t disappear until around midnight, when we are joined by constellations such as Leo and Virgo. As we approach sunrise, the red star Antares in Scorpius pops up just a little before Venus. The Moon passes very close to Antares early in February this year, the small crescent moon will be just below Antares. Venus is still visible just above the Sun as a bright dot early in the month, but it will sink lower and grow fainter as we come up to the middle of the month, leaving our sky by the end of the month.

Due to the current position of Venus so close to the sunrise, it isn’t the best time to observe it with a telescope. The extra light of the Sun will effect your view and could damage you’re telescope or eyes. Besides that, all we get to see when we look at Venus is it’s atmosphere, no matter how powerful your telescope is. In good viewing conditions, the swirls and banks of cloud may be visible, but this time of the year doesn’t provide those conditions from Ireland at least. Even without considereing the possible danger, the orange-yellow glow of the sky at sunrise will effect the apparent colour of Venus.

A lot of the atmosphere of Venus is carbon dioxide, and this contributes greatly to the amounnt of heat trapped by the planet. There is also a lot of sulphur dioxide and water vapour, which can combine to form sulfuric acid. In true darkness it is meant to appear as a light yellowy orange, which I describe in the video as butterscotch. The pinkness may be down more to the red-orange glow of sunrise. As I also mention in the video, I am colourblind, so seeing it for yourself is the best way to decide. The planet is named after the Roman goddess of love and beauty Venus and the Greek goddess of love, beauty and sometimes war Aphrodite. As the brightest night time object besides the Moon, other names were also given to the planet based on this brightness. Phosphoros was used to refer to Venus in the morning, and Hesphoros in the evening in Ancient Greek. Lucifer was also used in Latin to refer to Venus, when it simply meant “light-bringer”. Both Lucifer and illuminate are related words, as well as the terms lux and lumen, all coming into Latin from the Proto-Indo-European root *lewks, which probably meant light.

Of course those names are a little bit old fashioned and not English. Many people today would call it the Morning Star or the Evening Star, but of course it isn’t a star at all. However, thanks to its thick light reflecting atmosphere, it outshines every star except our own Sun. Despite reflecting so much light, it still absorbs a lot of infrared, which is then carried down towards the surface and trapped by the Greenhouse Effect. Carbon is a greenhouse gas, able to re-reflect heat, keeping it on the inside of the atmosphere. With close to 95% of it’s atmosphere being carbon dioxide, Venus gives a very extreme example of this.

Unfortunately, this all prevents us from seeing the surface of Venus from the Earth. A couple of images have been taken of the surface, but no probe sent to Venus survives the surface for very long. Detailed maps have been made, mostly using radar, which can penetrate the clouds. The surface of Venus appears covered in volcanic structures and craters. We commonly see craters on planets with little to no atmosphere, such as Mercury and Mars, or objects like the Moon and asteroids. Titan doesn’t seem to have many craters, nor does the Earth. Even though there is a lot of thick atmosphere on Venus, there doesn’t seem to be a lot of erosion, besides volcanic activity, but the surface of Venus is older than the surface of the Earth. Thanks to subduction zones swallowing up the Earths crust and volcanoes and divergent plate boundaries making new crust, the surface of the Earth gets recycled a lot faster than Venus. Venus certainly had a lot of volcanic activity, but there is no plate tectonics today. There does still seem to be volcanism, but less than there seems to have been in the past. Another factor may be the type of rain and the high temperature that Venus has. Although the rain is composed of sulfuric acid, which would erode the surface heavily, this rain doesn’t hit the surface, instead evaporating as it walls into lower, warmer, parts of the atmosphere and floating back up to condense as clouds again.

If we were to fly to the surface of Venus, the thick clouds would obscure the sky, and the brightest it would get would be the same as a very overcast day here on Earth. For the above video, the atmosphere is ignored, similarly to the videos about the gas giants. This view would really only be possible if you were floating at the edge of the atmosphere. One of the main things I want to show is how things move across the sky from Venus, so we need to be able to see the stars and planets. Venus orbits the Sun in a very normal way, it is between the Earth and Mercury and so orbits the in between their speeds as well, faster than the Earth but slower than Mercury. It’s orbit is close to circular, only a little elliptical, not as eccentric as the Earth’s or other planets’ orbits. Venus isn’t as tilted as the Earth and so it doesn’t really have seasons. It becomes clear quickly in the above video that Venus rotates very slowly, as the Sun sluggishly moves across the sky. The strangest thing about Venus’ rotation is that is rotates backwards.

From the perspective of an observer on Venus, the run Sun moves from West to East, along with the planets, the reverse of what we would see on Earth. Here, everything moves across our sky from East to West because of the way that we rotate. Venus rotates in retrograde, and this backwards rotation makes everything appear to rise in the West and set in the East. I’ve talked about retrograde motion here before, regarding apparent motion of the planets in the sky. In the above video, I use Mercury as an example, because it’s the only planet closer to the Sun than Venus. This means it is the only one that appears to move backwards as it orbits around the Sun, at least in the way I’m discussing here, the way both Venus Mercury appear to turn around after they reach their greatest elongation from our point of view here on Earth. Of course, no planet actually orbits the Sun backwards, but Venus does rotate backwards, Venus is turning in what we would regard the wrong way compared to its orbit around the Sun, which is what really defines prograde and retrograde. It’s turning clockwise as it goes around the Sun anticlockwise, if you’re looking down on it from the North, rather than turning anticlockwise as well, like every other planet.

This firstly means that the Sun moves backwards, but can also mean that the day is very long depending on how you measure it. If you measure the time from one midday to the next, using the point when the Sun is at its highest in the middle of the sky, it’s about 116 Earth days. This is a shorter day than Mercury, and much longer than the Earth. The Earth turns around at over 1500km per hour, where as Venus turns at a speed of just 6.5km per hour. However, if you pick a distant star and wait for it to come back to the same place in the sky, it’s much longer, 243 days, longer than the year on Venus which is about 225 Earth days. Using the Sun, the rotation of Venus is the reason for the long day, but if you use the stars, the reversed direction of rotation is the reason. Here on Earth, the difference between those measurements is only about 4 minutes, because we are rotating the “correct” way. The Earth turns around at over 1500km per hour, where as Venus turns at a speed of just 6.5km per hour.

There are still many familiar things in the sky from Venus. We still see the same constellations and all of the planets along the ecliptic. The ecliptic is still where you would see eclipses from Venus, but Venus doesn’t have a moon so unfortunately there is eclipses to see. It isn’t known exactly why Venus is turning the wrong way compared to every other planet, but the thick atmosphere might be part of it. The atmosphere of Venus might be slowing it down at least, even though these winds can be very fast themselves. What is Venus’s North Pole today may once have been its South Pole, it may have originally rotated the right way but got knocked over.

Watching the Sun pass from the West to the East is one Venusian day, according to the “opposite of night” definition of the word. Venusian is the adjective for something from or to do with Venus, like Venetian is if something is from Venice. Venusian is commonly used, and Cytherean has also been used, but less commonly Venerean and related Venereal. The same that Mars, the god of war, gives us Martian and martial, Venus gives us Venerean and venereal. It is the connection between the Ancient Greek and Roman goddess and love, particularly physical love and lust, that contributes to the (almost) modern day usage of the word venereal for diseases, though that too is getting old fashioned.

One detail left out of the video is the air pressure. As well as the heat, gloom, volcanism and evaporating acid rain, the tick atmosphere of Venus is incredibly heavy, as heavy as 92 Earth atmospheres. A human might be able to survive that pressure if they are breathing a special mix of gasses, or in a pressure protected suit, as even oxygen at that pressure can be toxic. Of course, all of these factors together mean that we probably aren’t going to Venus anytime soon. Then again, we almost certainly will return to the topic of Venus in the future, possibly to observe its orbit from above. I hoped you enjoyed reading about one of the stranger planets in the solar system, and I hope you’ll come back to read more in the future.