But, once again, things are complicated by the fact that Venus has an unusual rotation period. In fact, Venus takes Earth days to rotate once on its axis — the slowest rotation of any planet — and its rotation is retrograde to its orbital path. Combined with its orbital period, this means that a single solar day on Venus the time between one sunup to the next is Earth days. So basically, a single year on Venus is lasts 1. Cytherean days. Again, this would make for some confusing time-cycles for any humans trying to make a go of it on Venus!
Add to that its unusual day-night cycle, variations are very slight. Comparatively speaking, a year on Earth is pretty predictable, which is probably one of the reasons why life is able to thrive here.
In short, our planet takes But because our axis is tilted, there is considerable variation in the seasons during the course of a year. As a result, between the summer and winter, the length of days and nights, temperatures, and seasons will go through significant changes.
In the southern hemisphere the situation is exactly reversed, with the South Pole experiencing a midnight sun, a day of 24 hours, again reversing with the South Pole. Every six months, the order of this is reversed. Mars has one of the highest eccentricities of any planet in the Solar System, ranging from ,, km at perihelion and ,, km at aphelion. Jupiter took most of the mass left over after the formation of the Sun, ending up with more than twice the combined material of the other bodies in the solar system.
In fact, Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite. About 4 billion years ago, Jupiter settled into its current position in the outer solar system, where it is the fifth planet from the Sun. The composition of Jupiter is similar to that of the Sun — mostly hydrogen and helium.
Deep in the atmosphere, pressure and temperature increase, compressing the hydrogen gas into a liquid. This gives Jupiter the largest ocean in the solar system — an ocean made of hydrogen instead of water. Scientists think that, at depths perhaps halfway to the planet's center, the pressure becomes so great that electrons are squeezed off the hydrogen atoms, making the liquid electrically conducting like metal.
Jupiter's fast rotation is thought to drive electrical currents in this region, generating the planet's powerful magnetic field. It is still unclear if deeper down, Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. It could be up to 90, degrees Fahrenheit 50, degrees Celsius down there, made mostly of iron and silicate minerals similar to quartz. The planet is mostly swirling gases and liquids.
The extreme pressures and temperatures deep inside the planet crush, melt, and vaporize spacecraft trying to fly into the planet. Jupiter's appearance is a tapestry of colorful cloud bands and spots. The gas planet likely has three distinct cloud layers in its "skies" that, taken together, span about 44 miles 71 kilometers. The top cloud is probably made of ammonia ice, while the middle layer is likely made of ammonium hydrosulfide crystals.
The innermost layer may be made of water ice and vapor. The vivid colors you see in thick bands across Jupiter may be plumes of sulfur and phosphorus-containing gases rising from the planet's warmer interior. Jupiter's fast rotation — spinning once every 10 hours — creates strong jet streams, separating its clouds into dark belts and bright zones across long stretches. With no solid surface to slow them down, Jupiter's spots can persist for many years.
Stormy Jupiter is swept by over a dozen prevailing winds, some reaching up to miles per hour kilometers per hour at the equator. The Great Red Spot, a swirling oval of clouds twice as wide as Earth, has been observed on the giant planet for more than years.
More recently, three smaller ovals merged to form the Little Red Spot, about half the size of its larger cousin. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom. From this collapse, pockets of dust and gas began to collect into denser regions.
As the denser regions pulled in more and more matter, conservation of momentum caused them to begin rotating, while increasing pressure caused them to heat up. Since temperatures across this protoplanetary disk were not uniform, this caused different materials to condense at different temperatures, leading to different types of planets forming. As a result, planets like Jupiter, which are located beyond the Frost Line, condensed out of denser materials first like silicate rock and minerals , then were able to accumulate gases in a liquid state.
We have written many articles about Jupiter here at Universe Today. We have also recorded an episode of Astronomy Cast about Jupiter. You can listen here, Episode Jupiter. All of the Jovian planets offer examples of pretty extreme physics that exist below the level of stellar physics.
Second, the earth revolves around the sun, like a tetherball at the end of a string going around the center pole. The top-like rotation of the earth on its axis is how we define the day.
The time it takes the earth to rotate from noon until the next noon we define as one day. We further divide this period of time into 24 hours, each of which is divided into 60 minutes, each of which is broken into 60 seconds. There are no rules that govern the rotation rates of the planets, it all depends on how much "spin" was in the original material that went into forming each one.
Giant Jupiter has lots of spin, turning once on its axis every 10 hours, while Venus takes days to spin once. The revolution of the earth around the sun is how we define the year. A year is the time it takes the earth to make one revolution - a little over days. We all learn in grade school that the planets move at differing rates around the sun. While earth takes days to make one circuit, the closest planet, Mercury, takes only 88 days.
Poor, ponderous, and distant Pluto takes a whopping years for one revolution. Below is a table with the rotation rates and revolution rates of all the planets. We need to go back to the time of Galileo, except that we're not going to look at his work, but rather at the work of one of his contemporaries, Johannes Kepler Kepler briefly worked with the great Danish observational astronomer, Tycho Brahe.
Tycho was a great and extremely accurate observer, but he did't have the mathematical capacity to analyze all of the data he collected.
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