Uranus: Quick Facts
Planetary Properties of Uranus
Orbital Semimajor Axis: 19.19 Astronomical Units (2,871 Million Kilometers)
Orbital Eccentricity: 0.047
Perihelion: 18.29 Astronomical Units (2,736 Million Kilometers)
Aphelion: 20.10 Astronomical Units (3,006 Million Kilometers)
Mean/Average Orbital Speed: 6.80 Kilometers Per Second
Sidereal Orbital Period: 83.75 Years (Tropical)
Synodic Orbital Period: 369.66 Days (Solar)
Orbital Inclination to the Ecliptic: 0.77 Degrees
Greatest Angular Diameter (As Viewed From Earth): 4.1”
Overall Mass: 8.68 x 1025 Kilograms (14.54 of Earth’s Overall Mass, if Earth = 1)
Equatorial Radius: 25,559 Kilometers (4.01 of Earth’s Equatorial Radius, if Earth = 1)
Mean/Average Density: 1,271 Kilograms Per Meter Cubed (0.230 of Earth’s Average Density, if Earth = 1)
Surface Gravity: 8.87 Meters Per Second Squared (0.91 of Earth’s Surface Gravity, if Earth = 1)
Escape Speed/Velocity: 21.3 Kilometers Per Second
Sidereal Rotation Period: -0.72 Solar Days (Indicative of Retrograde Rotation)
Axial Tilt: 97.92 Degrees
Surface Magnetic Field: 0.74 of Earth’s Surface Magnetic Field, Assuming Earth = 1)
Magnetic Axis Tilt (Relative to Rotation Axis): 58.6 Degrees
Mean/Average Surface Temperature: 58 Kelvins (-355.27 Degrees Fahrenheit)
Overall Number of Moons: 27 in Total
Quick Facts About Uranus
Quick Fact #1: The planet, Uranus, was first discovered in 1781 by William Herschel. At first glance, Herschel believed that he had discovered a comet-like object. Upon later inspection, however, Herschel was able to confirm that the dim object was, indeed, a planet. Herschel proposed that the planet should be named “Georgian Sidus” after King George III. After some debate, however, the name “Uranus” was chosen instead by astronomer Johann Bode; a name that derived from the Greek god, Ouranos.
Quick Fact #2: Uranus maintains a relatively rapid rotation rate, and completes a full rotation on its axis every seventeen hours and fourteen minutes. Due to its tremendous distance from the Sun, however, it takes the planet nearly 84 Earth years to complete one full cycle around the Sun.
Quick Fact #3: In addition to spinning on its side, Uranus also rotates around the Sun in a retrograde direction (opposite the direction that Earth and most of the other planets orbit the Sun).
Quick Fact #4: Uranus possesses thirteen known rings. Most of these rings are extremely narrow (at only a few kilometers in width). Scientists believe that the ring-system is a relatively new feature of the planet, and may have resulted from meteor or comet impacts on Uranus’s moons.
Quick Fact #5: Scientists believe that Uranus maintains a strong hydrogen and helium-based upper atmosphere (similar to the other gas-giants). However, astronomers and scientists, alike, often refer to Uranus as an “ice giant” since it is believed that the planet’s iron core is surrounded by a mantle composed of ice.
Quick Fact #6: Uranus is the second least dense planet in our solar system; second only to the planet Saturn. With a mean density of only 1.27 kilograms per meter cubed, it is only slightly more dense than Saturn which maintains an overall mean density of 0.687 kilograms per meter cubed. As a result of this low density, an individual would experience only 89 percent of gravity’s force on Uranus.
Quick Fact #7: Although Uranus possesses twenty-seven moons, each of these natural satellites are extremely small. In fact, all of Uranus’s moons combined (in terms of mass) are less than half the mass of Triton (Neptune’s largest moon). The largest of Uranus’s moons are Miranda, Umbriel, Ariel, Oberon, and Titania. Scientists believe that most of these moons are composed primarily of rock and ice, as well as carbon dioxide and ammonia. Scientists also speculate that Titania and Oberon may possess oceans of liquid water between their cores and mantles.
Quick Fact #8: Shortly after discovering Uranus, scientists and astronomers began to notice that at certain points, Uranus appeared to be drifting further into space. Nineteenth Century astronomers believed that this was the result of gravitational pull from another planet or object. After running numerous mathematical calculations on Uranus’s orbital patterns, astronomers Adams and Le Verrier were able to pinpoint the source of this gravitational pull on Uranus. At nearly 10.9 astronomical units from the Sun, astronomers discovered Neptune in 1846.
Quick Fact #9: Weather patterns on Uranus are very similar to Jupiter and Saturn. Weather systems rotate around the planet in separate bands, and generate wind speeds of approximately 900 kilometers per hour. Various dark spots in Uranus’s clouds have also been recorded by scientists in recent years. These features are believed to be vortexes and are often large enough to engulf much of the United States.
Fun Facts About Uranus
Fun Fact #1: Due to its orbital patterns, each of Uranus’s poles receive 42 years of direct sunlight or darkness, depending on its location around the Sun.
Fun Fact #2: Only one spacecraft has approached Uranus (Voyager 2). The spacecraft swept past the planet at a distance of 81,500 kilometers, returning numerous up-close images of not only the planet, but also its moons and ring-system.
Fun Fact #3: The largest moon orbiting Uranus is known as Titania. It is the eighth largest moon in the solar system. So far, 27 moons have been discovered around Uranus with the majority being named after characters from William Shakespeare and Alexander Pope.
Fun Fact #4: Wind speeds on Uranus can reach up to 900 kilometers per hour (or approximately 560 miles per hour).
Fun Fact #5: Uranus gets is pale blue color from its upper atmosphere, which is composed primarily of water, ammonia, and methane-based ice crystals.
Fun Fact #6: The planet Uranus plays a key role in astrology, and is the ruling planet of Aquarius.
Fun Fact #7: Shortly after the discovery of Uranus, German chemist, Martin Heinrich Klaproth, discovered a new chemical element in 1789; an element he later named Uranium, in honor of the discovery of Uranus only a few years prior.
Fun Fact #8: Uranus is approximately four times wider than Earth, in terms of size. This concept can be illustrated with the difference between an apple and basketball.
Fun Fact #9: Currently, scientists do not believe that Uranus is capable of supporting any form of life on its surface, due to its extreme conditions.
“Although Uranus and Neptune are superficially twin planets, they are different enough to remind us – as do Venus and Earth – that we still have a lot to learn about the mix of natural laws and historical accidents that formed the planets and fashioned their destinies.”— Timothy Ferris
Quotes About Uranus
Quote #1: “Although Uranus and Neptune are superficially twin planets, they are different enough to remind us – as do Venus and Earth – that we still have a lot to learn about the mix of natural laws and historical accidents that formed the planets and fashioned their destinies.” – Timothy Ferris
Quote #2: “There are amateurs who have seen that one of Uranus’s poles is brighter than the other, or who have seen cloud formations on the planet. For all we know, interesting things are happening there all the time.” -- Heidi Hammel
Quote #3: “Even after years of observing, a new picture of Uranus from Keck Observatory can stop me in my tracks and make me say, ‘Wow!’” – Heidi Hammel
Internal Heat of Uranus
Unlike most of the other gas-giants, Uranus maintains an internal temperature that is remarkably low (also known as a low thermal flux). Scientists are uncertain why this is the case since Neptune (a planet roughly the same size and same composition of Uranus) produces nearly 2.61 times the thermal energy of Uranus. In fact, Uranus maintains the lowest recorded temperature in our solar system at a reading of -224.2 degrees Celsius (or -371.5 degrees Fahrenheit).
In more recent years, scientists have speculated that Uranus’s low internal temperature may have been caused by a supermassive impact in its distant past. In this hypothesis, scientists believe that an impact from a comet, meteor, or asteroid may have dislodged much of the planet’s primordial heat, leaving it with a depleted core temperature. This theory appears logical, given the planet axial tilt (indicative of a large impact as well). Other theories for the planet’s low temperature include the hypothesis that Uranus possesses a barrier that may prevent heat from its core from reaching the surface of the planet. This would, in turn, greatly inhibit the upward movement of heat across the planet.
Formation of Uranus
Scientists believe that Uranus formed out of the "presolar nebula" that contained both gas and dust in the early stages of our solar system's formation. The gases, which were primarily hydrogen and helium, are believed to have aided in the development of our Sun, while dust particles likely helped form the first protoplanets.
As these planets continued to grow in size, scientists hypothesize that some of the planets (such as Uranus) may have had enough gravitational pull (due to their size) to collect parts of the nebula's gases. Following the "Nice Model" of planetary migration, it is believed that planets such as Uranus formed relatively close to the Sun, but moved outwards shortly after their formation.
Future Missions to Uranus
To date, Voyager 2 remains the only spacecraft to have visited Uranus. Some scientists in 2009 were optimistic about sending the Cassini spacecraft to Uranus after its mission to Saturn. However, this option was scrubbed in favor of crashing the spacecraft on Saturn. Although no missions are currently in the works for a mission to Uranus, the Planetary Science Decadal Survey in 2011 hinted at the possibility of such a mission between 2020-2023. Using the Pioneer Venus Multiprobe, a probe could easily descend throughout the first layers of Uranus’s atmosphere. Support for these missions, however, have been difficult to muster in the scientific community due to the extensive time it would take for probes to reach Uranus (nearly twelve to thirteen years with current technology).
Were you surprised by any of these facts about Uranus?
In closing, the planet Uranus is a remarkable component of our solar system and offers many exciting opportunities for scientific expeditions in the near (and distant) future. Further exploration of the planet may offer important clues to the formation of both our solar system and universe, at large. Only time will tell what new facts and figures can be learned about this fascinating planet, its origins, and role that it plays in the functionality of our solar system.
Wikipedia contributors, "Uranus," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Uranus&oldid=884890223 (accessed March 12, 2019).
© 2019 Larry Slawson