Venus

Venus is the second planet from the Sun. It is similar in size and mass to Earth, but it has no liquid water. Instead, Venus has a very thick and dense atmosphere made mostly of carbon dioxide, with thick clouds of sulfuric acid. The surface of Venus is extremely hot, reaching temperatures of about 464 °C (867 °F), and the pressure is 92 times greater than on Earth.

From Earth, Venus looks like a bright star in the sky, often called the "morning star" or "evening star" because it shines more brightly than any other natural object in the night sky. Venus orbits the Sun closer than Earth does, and it sometimes comes closer to Earth than any other planet. Because of this, Venus is often used as a helpful stopover point for spacecraft traveling to other parts of the solar system.

Venus rotates very slowly in the opposite direction compared to most planets, taking about 117 Earth days to complete one rotation. A year on Venus, the time it takes to orbit the Sun, is about 225 Earth days. Venus does not have any moons and has a weak magnetic field. Inside Venus, there is a core, mantle, and crust, and the planet has active volcanism instead of the moving plate tectonics found on Earth.

In the past, Venus might have had liquid water and a more comfortable environment before its thick atmosphere caused a runaway greenhouse effect. Today, scientists are interested in studying Venus because some conditions in its clouds might be similar to Earth and could possibly support life on Venus. Many spacecraft have visited Venus since the first flyby in 1961, and more missions are planned for the future.

Physical characteristics

Venus is one of the rocky planets in our Solar System, similar in size and mass to Earth. It is nearly round because it spins very slowly. Venus has a very thick atmosphere made mostly of carbon dioxide, which creates a strong greenhouse effect. This makes the surface of Venus extremely hot.

The surface of Venus was mysterious until probes visited in the 20th century. These probes showed a landscape covered in sediment and rocks. Scientists have mapped Venus and found it has volcanoes, mountains, and many unique features. Most of the surface is smooth volcanic plains, with two large highland areas. Venus also has special volcanic shapes not found on Earth, like pancake-like features called "farra" and spiderweb-like cracks called "arachnoids."

Atmosphere and climate

Main article: Atmosphere of Venus

Further information: Extraterrestrial sky § Venus

Venus has a very thick atmosphere made mostly of carbon dioxide, with some nitrogen and small amounts of other gases. This atmosphere is about 92 times heavier than Earth’s and creates very high pressure on the surface—similar to being deep underwater on Earth. Because of this thick atmosphere and lots of carbon dioxide, Venus has a strong greenhouse effect, making it extremely hot, even hotter than Mercury, which is closer to the Sun.

The clouds on Venus are made of sulphuric acid and cover the whole planet. These clouds reflect a lot of sunlight, making Venus very bright from space. The atmosphere moves very fast up there, with winds whipping around the planet much quicker than Venus itself rotates. Scientists study Venus to better understand how Earth’s climate might change in the future.

Orbit and rotation

Main article: Orbit of Venus

Venus orbits the Sun at an average distance of about 108 million kilometers, completing one orbit every 224.7 days. Its orbit is almost a perfect circle, much more so than the orbits of other planets.

Unlike most planets, Venus rotates in the opposite direction — clockwise — when viewed from above its north pole. This means that a day on Venus, which lasts 243 Earth days, is longer than a year on Venus. Because of this unique rotation, the Sun would appear to rise in the west and set in the east if we could see it through Venus's thick clouds. Venus does not have any natural moons.

Observability

Venus is very easy to spot in the night sky. To the naked eye, it looks like a bright white star, even brighter than any actual star. It is the brightest object in the sky after the Sun and the Moon. Venus can sometimes be seen during the day if you know where to look, though this is rare.

Venus changes its position relative to Earth and the Sun every 584 days. This causes it to switch between being visible after sunset, called the “Evening Star,” and before sunrise, called the “Morning Star.” Because it is so bright, Venus is often mistaken for an unidentified flying object.

Phases

Main article: Phases of Venus

When viewed through a telescope, Venus shows phases similar to the Moon. When it is far from the Sun, it appears as a thin crescent. When it is closer to Earth, it looks like a full disc. These phases can be seen clearly with even a small telescope.

Daylight apparitions

Venus can sometimes be seen in the daytime if the sky is clear and you know where to look. Famous people such as emperor Napoleon Bonaparte and president Abraham Lincoln reported seeing it during the day.

Transits

Main article: Transit of Venus

A transit happens when Venus passes directly between Earth and the Sun, appearing as a small black dot moving across the Sun’s face. These transits are rare, happening in pairs separated by over a century. The last transit was in 2012, and the next one will not happen until 2117.

Ashen light

Some people have reported seeing a faint glow on the dark side of Venus when it is a thin crescent. This glow, called “ashen light,” has never been proven to exist and might just be an optical illusion.

Observation and exploration history

Main article: Observations and explorations of Venus

Venus is bright enough to see without any special equipment, making it one of the objects humans have known about for a very long time. Ancient people saw Venus as both the "morning star" when it appeared in the sky before sunrise and the "evening star" when it appeared after sunset. They didn’t realize it was the same object until later.

In the 1600s, Galileo used a telescope and discovered that Venus changes shape, just like the Moon. This showed that Venus orbits the Sun, not the Earth. In the 1700s, scientists discovered Venus has an atmosphere. In the 1960s, space probes began visiting Venus. These probes learned a lot about Venus, including its very hot surface and thick atmosphere. Today, scientists are planning more missions to Venus to learn even more about this fascinating planet.

Possibility of life

Main article: Life on Venus

Some scientists wonder if tiny life might exist high in the clouds of Venus, about 50 kilometers above the surface. In these layers, the temperature and pressure are more like Earth’s, though the clouds are very acidic. These clouds contain water, carbon dioxide, and sunlight — ingredients needed for life as we know it.

In the past, some researchers thought they saw signs of tiny organisms in Venus’s clouds. More recently, scientists looked for a gas called phosphine, which could be a sign of life, but later studies suggested other explanations. Because Venus’s surface is too hot and harsh for life, the idea of life exists only in these upper cloud layers, though much more research is needed to know for sure.

In culture

Venus is one of the brightest objects in the night sky, and many cultures have given it special meaning in myths, stories, and art. In ancient times, people in places like Mesopotamia and Egypt saw Venus as a goddess. The planet’s appearance in the sky, sometimes as the "morning star" and sometimes as the "evening star," inspired many stories and poems.

Later, in cultures such as Greece and Rome, Venus was linked to the ideas of love and beauty. Today, Venus still appears in books, music, and even flags—like the flag of Chile, which shows a bright star that is actually Venus.