THE 8 PLANETS
LAST STOP: NEPTUNE!
The last planet Neptune, is quite a spectacle, essentially a blue marble. As with Uranus, methane (trace amount) gives Neptune its blue coloration. Named after the Roman god of the seas Neptune was noted by Galileo in 1612, but discovered as a planet by Urbain Le Vernier, John Couch Adams and Johann Galle on September 23, 1846. Neptune has a very elliptical orbit, and was further than Pluto between 1979 and 1999. Uranus and Neptune are usually paired together as “ice giants.” Uranus is light blue, named after the god of the sky, while Neptune is dark blue, named after the god of the seas. Unlike Uranus’s bland surfaces, Neptune’s ephemeral storms make up the planet’s active atmosphere. The Great Dark Spot is comparable to Jupiter’s Great Red Spot, but the Great Dark Spot comes and goes. With the strongest gales in the solar system, winds (rotates opposite of the planet’s rotation direction) on Neptune have speeds up to 2,100 kph— almost reaching supersonic flow! Winds called the scooter that speed across Neptune reach up to 3000 kph! Although Neptune’s atmosphere is one of the coldest places of the solar system, Neptune has a faint, fragmented ring system called arcs discovered during the 1960s and confirmed during the 1989. The rings give off a faint red hue, comprising mainly of ice and carbon-based materials. Like that of Uranus, Neptune’s magnetosphere is also relatively tilted (47º). The pressure on Neptune is so great that it rains diamonds there! On Neptune, that pole facing the Sun is 10ºC hotter than the other pole, so when the seasons change, frozen methane warm up and leak out into space.
Neptune has 13 known moons, the largest are Triton and Nereid. In mythology, Triton and Nereid are Neptune’s sons. Interestingly, Triton has a retrograde orbit (spins east to west), which suggests the Neptune gravitationally pulled Triton into its orbit. In fact, in 3.6 million years, Neptune will pull Triton past the Roche Limit (past this limit, all moons are doomed to crash into the planet), and the moon will crash into Neptune! Neptune’s second largest natural satellite, Nereid, an irregular moon, has one of the most eccentric (elliptical) orbits in the solar system.
MISSIONS: Voyager 2
- Order in Solar System: #8
- Number of Moons: 13
- Orbital Period: 164.8 years
- Rotational Period: 16.11 hours
- Mass: 1.0243 x 10^26 kg ( 17.147 Earths)
- Volume: 6.254 x 10 ^13 km³ (57.74 Earths)
- Radius: 24,764 km (3.883 Earths)
- Surface Area: 7.6183 x 10^9 km² (14.98 Earths)
- Density: 1.638 g/cm³
- Eccentricity of Orbit: 0.0112
- Surface Temperature (Average): 72 K
- Escape Velocity: 23.5 km/s
- Apparent Magnitude: 8.02 to 7.78
NEXT STOP: URANUS!
Unlike any other planet in the solar, Uranus (Ur-uh-nus)’s name derives from Greek mythology, namely the Greek god of the sky. Uranus preceded Jupiter and Saturn in mythology as he and Gaia created the sky and earth. Named planets long after the ancient planets (Mercury, Venus, Mars, Jupiter, and Saturn), Uranus (Sir William Herschel, 1781) and Neptune are sometimes in a separate category called the “ice giants.” The two planets’ icy blue coloration comes from a primary composition of more heavier elements, “ices” such as water, ammonia, and methane. Like Venus, Uranus spins in a retrograde motion with a tilt of 97.77°! So, while other planets spin like spinning tops, Uranus spins like a rolling ball. A large object may have knocked Uranus on its side! Uranus’ rings spin parallel to its axis of rotation. Because of its unusual axial tilt, Uranus has unusually long seasons— each pole gets 42 years of sunlight followed by 42 years of darkness. Near the time of equinoxes, however, Uranus’ day-night cycle reaches that of those on other planets. Even Uranus’ magnetic field, with a tilt of 59º, is abnormal and does not line up to Uranus’ axis, with the north side strong and the south side comparatively weak. The second least dense planet, Uranus comprises of a rocky core, icy mantle, and an outer hydrogen and helium envelope. Because Uranus’ atmosphere is mainly methane, the planet is very smelly, like cow pastures. Uranus’ faint rings were mainly formed from scattered moons. Unlike the other gas giants, Uranus radiates hardly any heat; the planet’s core may have been depleted in an high-mass impact. Though Uranus is bland, dark spots like those usually found on Neptune, have recently been found on Uranus.
Uranus has 27 known moons named after characters from Shakespeare’s and Alexander Pope’s masterpieces. Uranus’ five main moons are Miranda, Ariel, Umbriel, Titania, and Oberon. These moons are comparatively and dull (brightness), comprising of 50% rock and 50% ice. Of the satellites, Ariel is the youngest with few impact craters and Umbriel is the oldest. Miranda has canyons, layers, and many variations in surface features caused by tidal heating (push and pull of the moon’s interior caused by gravitational pull) within the moon.
MISSIONS: Voyager 2
- Order in Solar System: #7
- Number of Moons: 27
- Orbital Period: 84 years
- Rotational Period: 17 hours
- Mass: 8.6810 x 10^25 kg (14.536 Earths)
- Volume: 6.833 x 10 ^13 km³ (63.086 Earths)
- Radius: 25,559 km (4.007 Earths)
- Surface Area: 8.1556 x 10^9 km² (15.91 Earths)
- Density: 1.27 g/cm³
- Eccentricity of Orbit: 0.044405586
- Surface Temperature (Average): 76 K
- Escape Velocity: 21.3 km/s
- Apparent Magnitude: 5.9 to 5.32