Solar System Survey – Uranus, Neptune and the Kuiper Belt (Part VI)
By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the sixth article in a seven-part series reviewing the extraterrestrial planets and other bodies of the solar system, as well as exploratory missions to study them.
The farthest planets from the Sun in our solar system also happen to be some of the most interesting. Uranus is often called the “ice giant” planet because it experiences the coldest temperatures of all of the planets. Although it is visible to the naked eye, it is so dim and slow-moving (it takes Uranus 84 Earth years to orbit the Sun) that it wasn’t recognized as a planet until it was observed by telescope in the late 1700s. Perhaps the most peculiar thing about Uranus is that its rotational axis is tilted 98° from the ecliptic plane, so it spins in a top-down (rather than side-to-side) fashion. Uranus has several moons and two distinct sets of dark rings.
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Neptune is the only planet not visible to the naked eye; it was discovered by telescope in the mid-19th century. Although Uranus experiences the coldest extremes, the average temperatures on Neptune are colder due to its further distance from the Sun. Neptune’s primary claim to fame is its active weather. Its atmosphere is comprised of hydrogen, helium, and methane. Wind speeds on the planet have been measured in excess of 900 mph, making storms on Neptune the most violent in the entire solar system. This is largely attributable to the fact that Neptune spins on its axis very quickly, taking only 18 Earth hours to complete a rotation. Neptune has 14 moons and some very thin rings.
The Kuiper Belt is a body of smaller icy bodies that extends from the orbit of Neptune more than 20 astronomical units (AU) out to the inner Oort Cloud. The belt contains hundreds of thousands of satellite objects ranging from small chunks of ice to dwarf planets, including Pluto. The Kuiper Belt dates back to the earliest days of our solar system, and many short-period comets are traceable to origins in this region.
In 1981, NASA launched Voyager 2 toward the outer solar system. On January 24, 1986, Voyager 2 made the flyby of Uranus to date. Voyager 2 came within about 82,000 km (50,952 miles) of the planet and took over 8,000 images, including photos of Uranus’s rings and moons.
However, because of the orientation and timing of the flyby, the space probe was only able to see the southern hemispheres of the planet and moons. As a result of the Voyager 2 visit, 10 new moons were discovered in the system.
Three and a half years later, on August 25, 1989, Voyager 2 passed by Neptune, which was also the only visit to the outermost planet so far. Because Neptune was Voyager 2’s last mission target, the operators decided to take the probe extremely close to the planet — within 5,000 km (3106 miles) of the atmosphere. Voyager took about 10,000 photos of the Neptunian system. The probe discovered six new moons and many new details about the rings of Neptune.
In 2006, NASA launched the New Horizons space probe on a mission to the Kuiper Belt. New Horizons leveraged a gravity assist from Jupiter in 2007, and after a nine-year trip it finally arrived at Pluto in 2015. New Horizons traveled within 10,000 km (6,214 miles) of Pluto and took countless photographs of the former planet and its moon Charon.
New Horizons is still an active mission and is currently on its way to its second target in the Kuiper Belt, 2014 MU69, which is another billion miles past Pluto. New Horizons made the rendezvous on . Provided that the spacecraft remains healthy, New Horizons is slated to visit another two dozen objects in the Kuiper Belt. In addition to photography, the probe is also measuring the plasma, dust, and gas densities along its path of travel.
Several follow-up missions to visit Uranus and Neptune have been proposed over the past few decades, but none so far has been approved for development. This includes the NASA OCEANUS orbiter concept. Additionally, the ESA has put forth the Pathfinder, ODINUS, and MUSE mission concepts. Pathfinder and ODINUS have been abandoned, but MUSE is still under consideration for execution.
Uranus, Neptune, and the Kuiper Belt of icy bodies are some of the most fascinating features of our solar system. This dark and frozen region has preserved a lot of evidence about the formation of our solar system. So further study would undoubtedly improve our understanding of how our neighborhood of planets and moons came to be.
Unfortunately, missions to these outer bodies take considerable time and must be carefully timed to maximize the efficiencies of the journeys. However, these circumstances are not so infrequent that they would dramatically hinder our ability to conduct these exploratory missions. All we need are the funding and support for them. Hopefully, the future will bring with it more opportunities of this kind.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.