Category Science

          Neptune boasts one of the most violent weather systems known. When the Voyager 2 spacecraft flew by in 1989, it discovered that winds around the planet’s equator reached speeds of 2100km/h (1240mph) — faster than anywhere else in the Solar System. Heat from inside the planet means that Neptune’s atmosphere is turbulent and constantly changing.

          Neptune is the most distant planet from the Sun, with temperatures that plunge down to 55 Kelvin, or -218 degrees Celsius. You would think that a planet that cold would be frozen and locked down, with very little weather. But you’d be very wrong. In fact, the weather on Neptune is some of the most violent weather in the Solar System. Just like Jupiter and Saturn, Neptune has bands of storms that circle the planet. While the wind speeds on Jupiter can reach 550 km/hour – twice the speed of powerful hurricanes on Earth, that’s nothing compared to Neptune. Astronomers have clocked winds on Neptune traveling at 2,100 km/hour.

          So why can the winds on Neptune reach such huge speeds? Astronomers think that the cold temperatures on Neptune might have something to do with that after all. The cold temperatures might decrease the friction in the system, so that winds can get going fast on Neptune.

         During its 1989 flyby, NASA’s Voyager 2 spacecraft discovered the Great Dark Spot on Neptune. Similar to Jupiter’s Great Red Spot, this is an anti-cyclonic storm measuring 13,000 km x 6,600 km across. A few years later, however, the Hubble Space Telescope failed to see the Great Dark Spot, but it did see different storms. This might mean that storms on Neptune don’t last as long as they do on Jupiter or even Saturn.

          The more active weather on Neptune might be due, in part, to its higher internal heat. Although Neptune is much more distant than Uranus from the Sun, receiving 40% less sunlight, temperatures on the surface of the two planets are roughly similar. In fact, Neptune radiates 2.61 times as much energy as it receives from the Sun. This is enough heat to help drive the fastest winds in the Solar System.

          Neptune’s discovery was unusual in that it was found with calculations rather than with a telescope. Astronomers observing Uranus noticed that it was drifting off the expected path of its orbit. Two mathematicians, working independently of each other, thought that this was because the gravitational pull of an unknown planet was disturbing Uranus’ orbit. The calculations of both men led to the planet being discovered in 1846.

          Billions of stars may twinkle above our heads at night, but there still remain only eight planets in our solar system. Jupiter is massive; Venus is our closest neighbour; Saturn looks awesome; Mars has a chocolate named after it; and Pluto plays the role of the hipster’s favourite. But our favourite is the much under-appreciated, Neptune.

          On September 23, 1846, German astronomer Johann Gottfried Galle first glimpsed Neptune, 2.7 billion km from Earth, through his telescope, the achromatic refractor, invented by Joseph von Fraunhofer in 1829.

          It helped that he knew where to look. Previous astronomers had detected irregularities in Uranus’ orbit that could only be explained by the existence of a father planet’s gravity. This spurred Urbanin Le Verrier and John Couch Adams, who worked in Paris and Cambridge respectively, to begin their own separate calculations to determine the nature and position of such a planet. Galle would find it less than one degree from the location predicted by Verrier.

          Though initially referred to as Le Verrier’s planet, Galle suggested Janus, the Roman ‘God of beginnings’, but it was eventually named Neptune by Le Verrier himself – maintaining the trend of naming planets after deities in Greco-Roman mythology, in this case the Roman ‘God of the sea’.

          For 84 years Neptune remained the furthers point in our solar system, until the discovery of Pluto. However, with Pluto’s status as a planet having long been disputed the decision was finally taken in 2006 for the International Astronomical Union to fully defined the word ‘planet’ for the first time. This definition meant that Pluto would be reclassified as a dwarf planet, therefore officially reinstating Neptune once again as the outermost known planet in our solar system.

          Planets have the colors that they have because of what they are made of and how their surfaces or atmospheres reflect and absorb sunlight. Mercury has a dark gray, rocky surface which is covered with a thick layer of dust. The surface is thought to be made up of igneous silicate rocks and dust. Venus is entirely covered with a thick carbon dioxide atmosphere and sulphuric acid clouds which give it a light yellowish appearance. Earth shows its blue oceans and white clouds as well as its green and brownish land. Mars is covered with a fine dust which contains iron oxide (rust). This gives Mars its orange color. Jupiter is a giant gas planet with an outer atmosphere that is mostly hydrogen and helium with small amounts of water droplets, ice crystals, ammonia crystals, and other elements. Clouds of these elements create shades of white, orange, brown and red. Saturn is also a giant gas planet with an outer atmosphere that is mostly hydrogen and helium. Its atmosphere has traces of ammonia, phosphine, water vapor, and hydrocarbons giving it a yellowish-brown color. Uranus is a gas planet which has a lot of methane gas mixed in with its mainly hydrogen and helium atmosphere. This methane gas gives Uranus a greenish blue color Neptune also has some methane gas in it’s mainly hydrogen and helium atmosphere, giving it a bluish color.

          Uranus’ colour comes from the presence of methane clouds in the planet’s atmosphere. Methane absorbs red light, reflecting only blue and green. Neptune’s upper atmosphere contains more methane than Uranus’, which gives the planet’s clouds their striking blue colour.

          Because of this, its poles are sometimes pointed almost directly at the Sun. Uranus’ atmosphere is made up of hydrogen, helium, and methane. The temperature in the upper atmosphere is very cold. The cold methane gas is what gives Uranus its blue-green color.

          The planet Uranus tilts over so far on its axis that it rotates on its side. Because of this, its poles are sometimes pointed almost directly at the Sun. Uranus’ atmosphere is made up of hydrogen, helium, and methane. The temperature in the upper atmosphere is very cold. The cold methane gas is what gives Uranus its blue-green color. The rapid rotation of Uranus causes winds up to 600 kilometers per hour to blow in its atmosphere. Uranus has eleven known rings which contain dark, boulder-sized particles. Uranus has 27 named moons. Some of these moons are less than 100 kilometers wide and black as coal. (The others are Jupiter, Saturn, and Neptune.) Its atmosphere is composed primarily of hydrogen and helium, with a small amount of methane and traces of water and ammonia. Uranus gets its blue-green color from methane gas. Sunlight is reflected from Uranus’s cloud tops, which lie beneath a layer of methane gas.

          Neptune’s atmosphere is made up of hydrogen (80%), helium (19%) and methane (1%). Despite only being a small fraction of the overall atmospheric composition, methane in the upper atmosphere is responsible for Neptune’s blue colour. Methane absorbs the red part of the light from the sun and reflects the blue light. This makes Neptune look blue.

          Although Uranus is devoid of surface features, its many moons display a fascinating portrait of a violent history. The cracked and distorted surfaces of Uranus’ moons are believed to have been caused by water. As liquid water rose from the interior of the moons, it froze and expanded, causing the crust to buckle outward. Miranda, one of Uranus’ larger outer moons, has one of the most chaotic surface patterns of anybody in the Solar System. The moon, shown left, resembles a patchwork, with parts of its core now on the surface, and parts of the crust buried deep underground. Scientists believe that this is because the moon was at one time pulled apart, and has gradually reformed.

          Uranus, the seventh planet of the Solar System, has 27 known moons, most of which are named after characters that appear in, or are mentioned in, the works of William Shakespeare and Aloxander Pope. Uranus’s moons are divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The inner moons are small dark bodies that share common properties and origins with Uranus’s rings. The five major moons are ellipsoidal, indicating that they reached hydrostatic equilibrium at some point in their past (and may still be in equilibrium), and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, about one-twentieth the mass of the Earth’s Moon. The orbits of the regular moons are nearly coplanar with Uranus’s equator, which is tilted 97.77° to its orbit. Uranus’s irregular moons have elliptical and strongly inclined (mostly retrograde) orbits at large distances from the planet.

          William Herschel discovered the first two moons, Titania and Oberon, in 1787. The other three ellipsoidal moons were discovered in 1851 by William Lassell (Arial and Umbriel) and in 1948 by Gerard Kuiper (Miranda). These five have planetary mass, and so would be considered (dwarf) planets if they were in direct orbit about the Sun. The remaining moons were discovered after 1985, either during the Voyager 2 flyby mission or with the aid of advanced Earth-based telescopes.

          The surface of Uranus may look as motionless as that of a snooker ball, but in reality the planet is no less turbulent than Jupiter and Saturn. Like its larger neighbours, Uranus does have bands of clouds that blow around the planet at incredible speeds, but because of an overlying layer of methane in the upper atmosphere, they are very faint. Only enhanced infrared pictures, like those taken by the Voyager space probe (right), show the weather on Uranus.

          Uranus is one of two ice-giant planets in the solar system. Like Neptune, the other ice giant, it is sometimes also called a gas giant. Information about Uranus comes mostly from data gathered by NASA’s Voyager 2 spacecraft, which approached within 80,000 kilometers (50,000 miles) of the planet’s surface. Uranus does not display the type of geological activity associated with terrestrial planets such as Earth and Mars. The rings and moons of Uranus, however, do exhibit recognizable geological features.

          Scientists report that between 80 percent and 85 percent of Uranus consist if an ice and rock mass. The ices are mostly frozen water, ammonia and methane around a liquid core. An envelope of hydrogen and helium, with traces of methane and ammonia, forms the planets’ atmosphere. Extreme temperatures and pressures in the planet’s interior could convert the carbon content of methane into diamond. According to space researchers Mona Delitsky, from California Specialty Engineering and Kevin Baines from the University of Wisconsin, Madison, the temperature at Uranus’ core could be 5,727 degrees Celsius (10,340 degrees Fahrenheit). This temperature could produce diamonds the size of a hand that precipitate from the liquid.

          Thirteen rings have been identified around Uranus. These consist of a combination of ice and rock and are replenished with dust from meteor impacts — also called space weathering — on Mab, one of Uranus’ small outer moons. Some could be Centaurs, captured asteroids that orbit the sun together with Uranus, or comets. Uranus’ 27 identified moons appear to be made of ice and rock. The satellite system is chaotic and unstable. Astronomers predict that within a few million years, the moons could collide.

          All of Uranus’ moons consist of ice and rock. Miranda and Ariel, two of the planets smaller moons, have features that indicate ongoing geological activity. Miranda’s diameter is just 450 kilometers (281 miles), yet it has surface fault scarps 10 kilometers (6 miles) high. Ariel, which has an 1,160 kilometers (725 miles) diameter, has canyons that could be between 3 and 5 kilometers (1.9 to 3.1 miles) deep. Miranda has areas of concentric fractures with surface volcanism called coronae, while the Ariel surface has ridged and smooth plains with surface volcanism. The extruded material could be ammonia and water ices that were melted by tidal heating of the moons’ interiors.