Monday October 22, 2012 (WS - Trans-Neptunian Regions of the Solar System)

The Launch Pad Monday, 10/22/12 Identify these objects. Pluto and Charon

The Launch Pad Monday, 10/22/12 Does our Solar System end at the orbit of Neptune? Explain.

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Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day Quiz 6S110/5 10/26 Quiz 7S210/12 10/26 WS – Comets and Meteoroids F210/1610/1810/22 WS – Dwarf Planets F310/1810/2210/24 Quiz 8S310/19 11/2

Recent Events in Science Keck Observations Bring Weather of Uranus Into Sharp Focus htm Read All About It! In 1986, when Voyager swept past Uranus, the probe's portraits of the planet were "notoriously bland," disappointing scientists, yielding few new details of the planet and its atmosphere, and giving it a reputation as a bore of the solar system. Now, however, thanks to a new technique applied at the Keck Observatory, Uranus is coming into sharp focus through high- resolution infrared images, revealing in incredible detail the bizarre weather of the seventh planet from the sun. The images were released in Reno, Nev. today (Oct. 17, 2012) at a meeting of the American Astronomical Society's Division of Planetary Sciences and provide the best look to date of Uranus's complex and enigmatic weather.

Trans-Neptunian Regions of the Solar System There are four basic regions of our Solar System. Remember that the Solar system is defines as the area of space under the influence of the Sun’s gravitational field, and the objects contained therein. The four regions of our Solar System are: the Planetary Region the Kuiper Belt the Oort Cloud the Scattered Disk

The Kuiper Belt We have already discussed the planetary region of our Solar System, so let’s move on to the region known as the Kuiper Belt. The Kuiper Belt is a region of the Solar System beyond the planetary region, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun.

The Kuiper Belt The Kuiper Belt is similar to the asteroid belt, although it is far larger (20 times as wide and 20 to 200 times as massive.). Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System's formation. While most asteroids are composed primarily of rock and metal, Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water.

The Kuiper Belt The classical belt is home to at least three dwarf planets: Pluto, Haumea, and Makemake. Some of the planetary region’s moons, such as Neptune's Triton and Saturn‘s, are also believed to have originated in the region.

The Kuiper Belt Thousands of icy objects orbit the Sun beyond Neptune in a region commonly called the Kuiper Belt. Credit: NASA/Johns Hopkins University Applied Physics Laboratory Pluto OrbitNeptune Orbit

Credit: NASA, ESA, and A. Field (STScI)

Comparison of the Sizes of Some Kuiper Belt Objects to Earth Figure 22.31

The Oort Cloud The Oort Cloud is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light- year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper Belt and the Scattered Disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth of the Oort Cloud's distance..

The Oort Cloud The outer limit of the Oort Cloud defines the cosmographical boundary of the Solar System and the region of the Sun's gravitational dominance. The Oort Cloud is thought to comprise two separate regions: a spherical outer Oort Cloud and a disc-shaped inner Oort Cloud, or Hills cloud. Objects in the Oort Cloud are largely composed of ices, such as water, ammonia, and methane.

The Oort Cloud

Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System and many of the Centaurs and Jupiter-family comets as well. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way Galaxy itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud.

The Oort Cloud Although the Kuiper belt and the farther scattered disc have been observed and mapped, only four currently known trans- Neptunian objects (90377 Sedna, 2000 CR105, 2006 SQ372 and 2008 KV42 ) are considered possible members of the inner Oort cloud.

A View From The Oort Cloud

The Oort Cloud

The Scattered Disk The scattered disc is a distant region of the Solar System that is sparsely populated by icy dwarf planets, a subset of the broader family of trans-Neptunian objects. The scattered disc objects (SDOs) have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater than 30 astronomical units.

The Scattered Disk These extreme orbits are believed to be the result of gravitational "scattering" by the gas giants, and the objects continue to be subject to perturbation by the planet Neptune. While the nearest distance to the Sun approached by scattered objects is about 30–35 AU, their orbits can extend well beyond 100 AU This illustration shows two planets orbiting about a common star. The outer planet takes more time to complete an orbit than the inner planet, so once per orbit the inner planet overtakes the outer planet. When the planets are at a, the outer planet exerts a gravitational perturbation that accelerates the inner planet, advancing the body ahead of its normal path. When the planets reach b, the reverse is true and the inner planet is decelerated. This perturbing influence is what led to the discovery of the planet Neptune.

The Scattered Disk This makes scattered objects among the most distant and cold objects in the Solar System. The innermost portion of the scattered disc overlaps with a torus-shaped region of orbiting objects known as the Kuiper belt, but its outer limits reach much farther away from the Sun and farther above and below the ecliptic than the belt proper.

Worksheet Trans-Neptunian Regions of the Solar System