I
URANUS
Serena Yang
Physics 1040
Sec 10
Name and Discovery
Uranus was the first planet ever to be discovered by scientists in the Modern Day with the
aid of technology. On March 13, 1871, William Herschel spotted the planet through a handmade
telescope. It’s often mistaken as a star or a comet; even Hershel himself was deceived by the
planet. It was first sighted by John Flamsteed in 1690, who recorded and catalogued the planet as
34 Tauri. [1-2]
William Herschel originally named the planet,“the Georgium Sidus”, after King George
III. This was later altered, and instead was named after the Greek God of the Sky, Ouranus.
Other proposed names were: “Hypercronius” (above Saturn), “Minerva” (Roman Goddess of
Wisdom), and “Herschel”. [3]
8.6810 x 1025 kg
Rotation Period
17.24 hours
Diameter:
Density:
51,488 km (32,000 miles)
1,270 kg/m^3
Revolution:
Tilt of Axis:
84 years
98 degrees or 82
degrees
Orbital
Semimajor
Axis:
Minimum
Distance
from Sun:
Maximum
Distance
from Sun:
Minimum
Distance
from Earth:
19.19 AU
Surface Gravity:
8.69 m/s^2 (0.89 x
Earth’s)
2.7 billion km (1.7 billion miles)
Temperature at Cloud
Tops:
-200 degree Celsius
(-328 F)
3 billion km (1.87 billion miles)
Average Cloud Top
Temperature (K)
73 K
2.57 billion km (1.6 billion miles)
Planetary Symbol:
Mass:
Chart : [Source 1]
Physical Characteristics
Uranus is mostly covered in a hydrogen-helium atmosphere, which produces methane
that results in the blue-green color of the planet. Uranus’s disk is streaked by white clouds. It is
an ice giant since most of its mass is made up of a mix of water, methane, and ammonia ice. One
of its amazing features is the tilt of its rotational axis, which is so far tilted that its North and
South Pole are almost turned perpendicular towards the sun, resulting in retrograde. The tilt of
Uranus has the scientists puzzled and still cannot be explained. [3-4]
The rings of Uranus, from the innermost rings to the outer rings, are approximately
37,000 to 39,500 km radius. Up to 14,160 km totals the width of Uranus’s ring system. The rings
were first seen from the Kuiper Airborne Observatory. The discovery of Uranus’s rings helped
the scientists understand that the rings are a common feature of planets, not just a unique feature
of Saturn. There are 13 identified rings of Uranus (1986U2R, 6, 5, 4, Alpha, Beta, Eta, Gamma,
Delta, Lambda, Epsilon, Nu and Mu), there are certainly many other rings, they’re just difficult
to spot, because their either thin or very dark. The rings have low albedo (low reflectivity),
which makes them hard to see since they don’t reflect much sunlight. Uranus’s ring system has a
complex structure, only three zones can be distinguished: the outermost (brightest), then
followed by a darker zone of rings, and then inner zone, brighter than the dark zone. The tenth
ring were discovered by Voyager 2 in 1986, and two others were seen by the Hubble Telescope.
[4]
Atmosphere and Climate
Uranus possesses an atmosphere that mainly consists of hydrogen and helium, and a
small percentage of methane. Its aquamarine color tells us that Uranus is covered with clouds.
The methane gas traps the red light in the atmosphere and doesn’t allow the color to escape.
Uranus gets very extreme seasons, because of its far tilt. The extreme seasons can last to 20 years
long. The poles receive more quantity of sunlight than the planet’s equator, which also causes
half of the planet to experience extreme summer, and leaving the other half of the planet to
experience a long, harsh winter. [4-5]
Composition and Internal Structure
The planet, Uranus, is mostly composed of ice and rock. Being that about 60-70 percent
of ice, 25 percent rock, and 5-10 percent hydrogen and helium. [3] Uranus has a gassy internal
structure. The core has a radius of about 7,500 km, surrounded by a mantle composed of
molecular hydrogen, helium methane, and ammonia in a liquid state. The mantle, then, is
surrounded by a surface layer of hydrogen and helium. [4] The core composed of iron and
silicate is still a hypothesis.
Magnetic Field
The mission of Voyager 2 was a big contributor to find out magnetic field of Uranus. The
scientists did suspect some type of magnetic field, because the IUE (International Ultraviolet
Explorer) had measure ultraviolet radiation coming from Uranus. Uranus’s magnetic pole is
tilted at about 55 degrees. The magnetosphere of Uranus has a strange twisted structure, which is
a possible outcome of the whole tilt of Uranus along with the tilt of the magnetic poles. [4,5]
Satellites
Uranus has 27 known moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet,
Portia, Rosalind, Mab, Belinda, Perdita, Puck, Cupid, Miranda, Francisco, Ariel Umbriel,
Titania, Oberon, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, and
Ferdinand. All of the satellites are outside of the rings, except for Cordelia, which acts like a
shepherd satellite. The five major and largest satellites are Oberon, Titania, Umbriel, Ariel, and
Miranda. Oberon and Titania, the two largest moons was discovered by William Herschel in
1787. Ariel and Umbriel was discovered by William Lassel. Then, Miranda was discovered by
Gerard Kuiper in 1948. It wasn’t till 1986 that Voyager 2 spacecraft discovered and tripled the
number of known moons Uranus has. Astronomers have also raised the number of known moons
to 27 using the Hubble Space Telescope. [2,4] The geology of the satellites seems to be that the
closer they are to the planet, the more activity there are on the satellite. Oberon and Titania, the
most distant and largest satellites, don’t show any internal activity. Umbriel and Ariel, smaller
and less distant, shows signs of internal activity. Finally, Miranda, the smallest of the five and
being nearest to the planet, shows huge evidence of internal activity.
Oberon
Oberon is the largest satellite of Uranus. Voyager 2 got a good look at Oberon’s surface.
Oberon’s surface seems to look dark and flat with some craters surrounded by lighter zones.
There is a very large crater that’s being observed as well as a mountain about four miles high. [4]
Titania
The second largest satellite has larger area of pale surfaces on a dark background and
many craters. A visible trench or fracture between a bright hemisphere and a dark hemisphere is
Titania’s main feature, which would be evidence of tectonic activity. There is also valleys
visible, about 50-100 km wide and several hundred kilometers long. [4]
Umbriel
This satellite has a much darker surface than Titania, and less uneven than any other
satellites. One unique feature of Umbriel is its large pale, ring shaped feature, which is seen near
the equator, and about one-tenth of Umbriel. [4]
Ariel
The next closest to Uranus, Ariel’s surface seems to be decorated with lots of craters with
super wide valleys, which would mean that there are lots of internal activates. The craters,
obviously, was caused by impacts. The valleys and their deep floors may have been eroded by
liquid. [4]
Miranda
Smallest of the five major satellites and nearest to the planet. The photographs shows an
entire hemisphere, and on the center of it, there’s a large, dark spot, below it there is a shape of
the letter ‘’v’’. Miranda is full of craters and numerous numbers of grooves. There also seems to
be a great deal of ancient terrain visible, with lots of craters. This structure dates back at least
three and a half million years ago. [4]
Missions
Voyager 2 spacecraft was the first and only probe to observe Uranus on January 24,
1986. The probe made a fly-by visit of the planet at a distance of only 81,500 km. The probe
traveled at a speed of 9.3 miles per second. The probe send back photos that showed evidence of
a boiling hot ocean on planet Uranus just below the clouds. It discovered ten new moons and two
new rings. Voyager 2 was able to send back photos of Uranus’s satellites’ surface features. It
showed the geological features of Mirada to be part ancient and part newly formed. The probe
also confirmed the existence of a magnetosphere, which the magnetic field is said to be stronger
than that of Saturn’s. Voyager 2 send back thousands of photographs showing us what Uranus
really looked like. We discovered the reason behind the aquamarine color of Uranus, which was
the atmosphere of helium and hydrogen with small amounts of acetylene and methane that
caused it. [4]
What I wish we knew about the subject
Some topics we should know about Uranus is how Uranus spin on its axis. Why does
Uranus retrograde? What caused the tilt of its rotation axis? Why is its interior cold? Why
doesn’t Uranus radiate more heat than other gas planets do?
The only possibility of learning more about Uranus is advancement of our technology. If
we could send another probe to observe Uranus, we could possibility learn more about Uranus.
We need the time and money to do it.
Bibliography
1. "Uranus." Nineplanets.org. Nine Planets, 14 Aug. 2014. Web.
<http://nineplanets.org/uranus.html>.
2. "Uranus." Solar System Exploration: Planets. National Aeronautics and Space
Administration, 9 Oct. 2014. Web.
<http://solarsystem.nasa.gov/planets/profile.cfm?Object=Uranus>.
3. Choi, Charles. "Uranus, Seventh Planet in Earth’s Solar System Was First Discovered
Planet." Space.com. Purch, 9 Nov. 2010. Web. <http://www.space.com/45-uranusseventh-planet-in-earths-solar-system-was-first-discovered-planet.html>.
4. Caprara, Giovanni. The Solar System. Firefly, 2003. Print.
5. "Uranus." Windows to the Universe. National Earth Science Teachers Association, 1 Jan.
2012. Web. <http://www.windows2universe.org/uranus/uranus.html>.