Category: Guide to Space

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Venus is the second planet from the Sun, orbiting at an average distance of 108.2 million km. Venus takes a total of 224.7 days to orbit the Sun.

The Sun and Venus are vastly different sizes, of course. The diameter of Venus is 12,103 km, while the diameter of the Sun is 1.4 million km. In other words, the Sun is 115 times larger than Venus. You could fit about 1.5 million planets the size of Venus inside the Sun.

Venus is a terrestrial planet. It has a metal core surrounded by a mantle of silica rock. This is surrounded by a thin crust of rock. The Sun, on the other hand, is a massive ball of hydrogen and helium gas. Temperatures at its core are hot enough to ignite nuclear fusion – more than 15 million Kelvin.

The Sun has an enormous impact on Venus. The radiation from the Sun is trapped by the thick atmosphere of Venus, raising average temperatures across the planet to around 460 °C. In fact, this makes Venus the hottest planet in the Solar System.

Both the Sun and Venus formed at the same time, 4.6 billion years ago, with the rest of the Solar System. They formed out of the solar nebula, a cloud of gas and dust that collapsed down to become the Sun and planets.

Because Venus orbits closer to the Sun than the Earth, we always see it close to the Sun in the sky. Venus is either trailing the Sun or leading it across the sky. The best times to see Venus are just before sunrise or just after sunset.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA ISTP: Venus
NASA StarChild: Facts on Venus
NASA Facts: Magellan Mission to Venus

A conjunction of Venus occurs when Earth, Venus and the Sun are all lined up together. Imagine looking down at the Solar System from above and being able to straight line that goes through Earth, Venus and the Sun. That’s a conjunction of Venus.

There are two kinds of conjunctions that can happen: superior conjunction and inferior conjunction. A superior conjunction of Venus happens when Earth and Venus are on opposite sides of the Sun. Seen from above, it goes, Earth – Sun – Venus. An inferior conjunction of Venus occurs when Venus and Earth are on the same side of the Sun. So, if you drew a line it would go Sun – Venus – Earth.

From here on Earth, it’s not possible to see either inferior or superior conjunctions of Venus. When Venus is in a superior conjunction, it’s on the opposite side of the Sun, and the glare of the Sun is too bright to see it. The same situation happens with an inferior conjunction. In this situation, Venus is in between Earth and the Sun, and lost in the glare.

Because of the orbits of Venus and Earth, Venus very rarely passes directly in front of the Sun from our vantage point. This is called a transit of Venus, and it does occur every hundred years or so in pairs. The last transit of Venus was in 2004, and the next one will happen in 2012.

When there’s an inferior conjunction of Venus, the planet is approximately 41 million km away. It’s possible for Venus and Earth to get as close as 38.2 million km, but that happens rarely.

When seen through a telescope, Venus goes through phases, just like the Moon. When Venus is approaching its inferior conjunction, it becomes a thin sliver – but very bright. When it’s approaching a superior conjunction, we see it starting to look fully illuminated. It’s impossible to see Venus either in full inferior or superior conjunction because it gets lost in the glare of the Sun either way.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Reference:
NASA: The Solar System

The period of rotation for Venus is 243 days. In other words, Venus takes 243 days to turn once on its axis so that the stars are in the same position in the sky.

That seems like a long time, and it is. Especially when you consider that a year on Venus only lasts 224.7 days. In other words, a day on Venus lasts longer than its year. Even stranger, Venus is rotating backwards from the rest of the planets. Seen from above its north pole, Venus is rotating clockwise, while the rest of the planets in the Solar System are turning counter-clockwise.

If you could actually stand on the surface of Venus, with the scorching heat and crushing atmospheric pressure, you would see the Sun rise in the West and then travel slowly across the sky, to set in the East. The total time from sunrise to sunrise is 116.75 days.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

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Venus is similar to Earth in size, mass, density to Earth. In many ways it’s Earth’s twin planets. Of course its climate is completely different, with its hellish temperature and crushing atmospheric pressure. Oh, and don’t forget about the clouds that rain sulfuric acid. But does Venus have seasons like Earth.

No.

Obviously, Venus doesn’t have nice warm summers and cooler winters like Earth; in fact, the surface of Venus experiences no temperature variations at all. Everywhere you go in the entire planet, the temperature is the same average 460 °C. It doesn’t matter if you’re near the equator or near the poles. Whether you’re on the day side or the night side, the temperatures don’t change much from the global average of 460 °C.

Part of the reason is the fact that the axial tilt of Venus is only 2.7°. That means that the planet has very little difference between the angle of its axis during “summer” and “winter”. Our axial tilt here on Earth is 23.4°, and that significant tilt means that the hemisphere pointed towards the Sun gets a lot more energy than the hemisphere pointed away.

And the other part of the reason why Venus doesn’t experience any temperature variations is because of the thick atmosphere – 93 times more surface atmospheric pressure than we experience here on Earth. This carbon dioxide atmosphere traps the heat and distributes it around the planet.

Even though the planet rotates very slowly, with spots on the planet experiencing more than 50 days of night, the temperatures just don’t fluctuate.

And so, this is why there are no seasons on Venus.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

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Where did the planet Venus come from? What’s the origin of Venus. Actually, Venus and the rest of the planets in the Solar System all formed at the same time, out of the same nebula, about 4.6 billion years ago.

Let’s go back then, 4.6 billion years ago, before there was a Sun or any planets. In this region of space was a large diffuse cloud of cold molecular hydrogen. And then some event, like a supernova explosion, or gravitational disturbance of a passing star caused the cloud to collapse. As it collapsed, it broke up into knots of gas; each of which would eventually go on to form a star.

As the material collapsed down, it began to spin because of the conservation of momentum from all the particles in the cloud. The center of the cloud became denser and denser, eventually becoming our Sun. This was surrounded by a flattened disk of material; and within this disk is where the planets, including Venus formed. It’s believed that all the planets formed together, at the same time within this disk.

Once the Sun had enough temperature and pressure in its core to ignite fusion, it generated powerful solar winds that blasted away all of the leftover material in the Solar System. All that remained were the planets and their moons.

Astronomers know that all of the planets formed at the same time because of meteorites discovered here on Earth. No matter where in the Solar System they originally came from, all of these meteorites were formed at the same time; about 4.6 billion years ago.

So the origin of Venus is the same origin for all the planets in the Solar System. They all formed out of the solar nebula, billions of years ago.

We have written many articles all about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast all about Venus the planet. Listen to it here, Episode 50: Venus.

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What planet gets closest to Venus? It actually depends on where the planets are in their orbits; but you might be surprised to know that Earth is the closest planet to Venus.

What, you were thinking Mercury gets closer to Venus? At their closest point, Mercury and Venus are separated by only 46 million km. Of course, that’s when the two planets are aligned on the same side of the Sun. When they’re on opposite sides of the Sun, Mercury and Venus are 178.7 million km away from each other.

When Earth and Venus are at their closest point, lined up on the same side of the Sun, they’re only separated by 39 million km. But when they’re on opposite sides of the Sun, Earth and Venus are separated by more than 250 million km. So for most of the time, Mercury and Venus are closer to one another.

But the planet that gets closest to Venus is Earth.

And that’s why Venus looks so large and bright from here on Earth. After the Sun and the Moon, Venus is the brightest object in the night sky. It can even shine so brightly that it casts shadows.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

The clouds of Venus are its defining characteristic. We can see the surface of Mars and Mercury, but the surface of Venus is shrouded by thick clouds. For most of history, astronomers had no idea what was beneath those clouds, and they imagined a tropical world with overgrown vegetation and constant rainfall. They couldn’t have been more wrong.

The climate of Venus isn’t tropical at all; it’s hellish. Temperatures on the surface of Venus approach 475 °C, and the atmospheric pressure is 93 times what you experience here on Earth. To experience that kind of pressure, you would need to swim down 1 km beneath the surface of the ocean. Venus’ atmosphere is made almost entirely of carbon dioxide, and not the oxygen/nitrogen mix we have here on Earth.

The clouds we see on Venus are made up of sulfur dioxide and drops of sulfuric acid. They reflect about 75% of the sunlight that falls on them, and are completely opaque. It’s these clouds that block our view to the surface of Venus. Beneath these clouds, only a fraction of sunlight reaches the surface. If you could stand on the surface of Venus, everything would look dimly lit, with a maximum visibility of about 3 km.

The upper cloud deck of Venus is between 60-70 km altitude. This is the part of Venus that we see in telescopes and visible light photographs of the planet.

The clouds on Venus rain sulfuric acid. This rain never reaches the ground, however. The high temperatures evaporate the sulfuric acid drops, causing them to rise up again into the clouds again.

Venus spacecraft have detected lightning on Venus, coming out of the clouds with a similar process to what we have on Earth. The first bursts of lightning were detected by the Soviet Venera probes and later confirmed by ESA’s Venus Express spacecraft.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

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Earth has the Moon, Jupiter has more than 50 moons, even Pluto has 3 moons. So what about Venus? What number of moons does Venus have? Ready for this?

Venus: number of moons: 0.

That’s right, Venus has no moons at all; not even captured asteroids like Mars. Why doesn’t Venus have any moons?

There appears to be evidence that Venus did have moons in the ancient past. That’s because Venus is rotating backwards from the rest of the planets. Seen from above, all of the planets rotate counter-clockwise. From the surface of the planets, the Sun seems to rise in the east, travel across the sky and then set in the west. But on Venus, it’s backwards; the planet is rotating clockwise, so the Sun rises in the west and sets in the east.

Even stranger, a day on Venus lasts 243 days, while a year on Venus is only 224.7 days. In other words, a day on Venus lasts longer than a year on Venus.

This strange rotation is evidence that Venus was probably whacked hard in the past by a planetesimal; a similar event is believed to have happened to the Earth billions of years ago, forming the Moon. It’s possible that this collision threw up material that coalesced into a moon, or even moons. But the material wasn’t high enough in orbit to remain stable around Venus. Instead of orbiting the planet for billions of years, it would have crashed back into the planet. Perhaps the tidal forces from the Sun made the orbit unstable.

Unfortunately the evidence of any past moons of Venus has been completely wiped away. At some point in the last 300-500 millions years ago, the outer crust of Venus was completely resurfaced, removing all trace of impact craters, and ancient volcanism.

So we’ll never truly know the number of moons that Venus had. But today, it has no moons.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.