1. The Kuiper Belt Presents

2. In a previous session we learned about the Oort Cloud. Today we will discuss the Kuiper belt as an extension to our discussion about the Oort cloud and our solar system. The Kuiper Belt

3. Most people think the Solar System ends with Pluto. This is not the case. The asteroids - leftover material from the formation of the solar system - between Mars and Jupiter are not all that remains from that violent time. Beyond the orbits of Neptune and Pluto lie a large number of small, icy bodies, making up what is known as the Kuiper Belt (pronounced Ki-per). PlutoasteroidsMarsJupiterNeptunePluto asteroidsMarsJupiterNeptunePluto The Kuiper Belt

4. From 1992 onwards, astronomers began to discover large numbers of these bodies orbiting beyond Neptune, between 30-50 AU. At least 70,000 are known with diameters above 100 km. The vast majority, however, are between 10-50 km across, and so are very dim indeed. NeptuneAU

5. Due to their vast distance from the Sun, they take hundreds of years to complete an orbit, and move very slowly. For all these reasons, detection is very difficult.Sun The Kuiper Belt

6. The Kuiper Belt is named after the famous Dutch astronomer, Gerald Kuiper [1905-73], who was a pioneer in solar system research using spacecraft. He put forward a new theory of how the solar system was formed, and it is generally accepted today. People had believed that the planets had formed from material hurled off from the Sun. Kuiper argued that a gas and dust cloud collapsed under gravity, forming the Sun and planets separately.Sun The Kuiper Belt

7. In 1951 he suggested that short-period comets (those coming from just beyond Pluto) originate from a collection of material left over from the formation. When the first KBOs were discovered, after Kuiper's death, the belt was named in his honour. comets Pluto The Kuiper Belt

8. Occasionally the orbit of a Kuiper Belt object will be disturbed by the interactions of the giant planets in such a way as to cause the object to cross the orbit of Neptune. It will then very likely have a close encounter with Neptune sending it out of the solar system or into an orbit crossing those of the other giant planets or even into the inner solar system. The Kuiper Belt

9. There are presently nine known objects orbiting between Jupiter and Neptune (including 2060 Chiron (aka 95 P/Chiron) and 5145 Pholus; see the MPC's list). The IAU has designated this class of objects as Centaurs. These orbits are not stable. These objects are almost certainly "refugees" from the Kuiper Belt. Their future fate is not known. Some of these show some cometary activity (ie, their images are a little fuzzy indicating the presence of a diffuse coma). The largest of these is Chiron which is about 170 km in diameter, 20 times larger than Halley. If it ever is perturbed into an orbit that approaches the Sun it will be a truly spectacular comet.listcomaHalley The Kuiper Belt

10. Curiously, it seems that the Oort Cloud objects were formed closer to the Sun than the Kuiper Belt objects. Small objects formed near the giant planets would have been ejected from the solar system by gravitational encounters. Those that didn't escape entirely formed the distant Oort Cloud. Small objects formed farther out had no such interactions and remained as the Kuiper Belt objects. The Kuiper Belt

11. Several Kuiper Belt objects have been discovered recently including 1992 QB1 and 1993 SC. They appear to be small icy bodies similar to Pluto and Triton (but smaller). There are more than 800 known trans- Neptunian objects (as of early 2004) Many orbit in 3:2 resonance with Neptune (as does Pluto). Color measurements of some of the brightest have shown that they are unusually red. In late 2002, a Kuiper Belt object over 1000 km in diameter was discovered and provisionally designated 2002 LM60 "Quaoar". In early 2004 an even larger one, 2004 DW, was found (its size isn't well known yet, but it's almost certainly smaller than Pluto).PlutoTriton2004 DW The Kuiper Belt

12. It is estimated that there are at least 35,000 Kuiper Belt objects greater than 100 km in diameter, which is several hundred times the number (and mass) of similar sized objects in the main asteroid belt.asteroid The Kuiper Belt

13. Breaking News On March 15, 2004, a team of astronomers (including Mike Brown, Chad Trujillo, and David Rabinowitz) announced the NASA-sponsored discovery of a very large planetary body (originally designated 2003 VB12) in one of the most distant planetary orbits yet discovered within the Solar System. Confirmed by the Spitzer (infrared) Space Telescope and tentatively named Sedna after the Inuit Goddess of the Sea (from which all creatures of the very cold Arctic sea were created), it is currently located around 90 AUs from our Sun, Sol -- an orbital distance that is roughly three times farther out than that of Pluto or Neptune -- but will eventually move as much as 10 times farther away (around 990 AUs) in a 12,260-year orbit around Sol; it's orbital semi-major axis is around 532 AUs with an extremely high eccentricity of 0.857. Based on its current distance, brightness, and presumed albedo or ability to reflect light, Sedna has been estimated to have more than half the diameter of Pluto and may be larger than any other planetary body found since Pluto -- at 730 to 1,470 miles or 1,180 to 2,360 kilometers (km) across, compared to Pluto's diameter of around 1,440 miles or 2,320 km.Mike BrownChad TrujilloSedna after the Inuit Goddess of the Sea The Kuiper Belt

14. Although inclined by only around 11.9 degrees from the ecliptic where the eight major planets orbit, Sedna's distant orbit is extremely elliptical indicating that its formation and orbit may have been influenced by by a passing nearby star during the early years of the Solar System, when Sol formed out of a molecular cloud with many other closeby stars around 4.6 billion years ago. Like 2000 CR105, Sedna may have been perturbed by a Solar-mass star at around 800 AUs from Sol more than 100 million years after its birth, given today's observed numbers of Oort Cloud comets. Hence, 2000 CR105 and Sedna are less likely to be members of the scattered disk that had their perihelion distances "increased by chaotic diffusion" or the result of other hypotheses (Morbidelli and Levison, submitted 2004).Morbidelli and Levison, submitted 2004 The Kuiper Belt

15. Sedna is the second most reddish planetary body in the Solar System, after Mars. Although an apparently slow rotation (40 days) indicated that Sedna might have its own moon, astronomers were unable to find such an object with the Hubble Space Telescope (more information and images from NASA). The icy object will move closer to the Sun over the next 72 years -- to 76 AUs of Sol -- before receding back towards the inner Oort Cloud (more information and images can be found from the NASA press release, Spitzer press release, astronomer Mike Brown's Sedna Page, Astronomy Picture of the Day, and the Kuiper Belt Page). information and imagespress release Sedna PageAstronomy Picture of the DayKuiper Belt Page The Kuiper Belt

16. On February 17, 2004, astronomers at the California Institute of Technology and (Caltech) Yale University announced that they may have found the largest Edgeworth-Kuiper Belt object, designated 2004 DW, since the discovery of Pluto on February 18, 1930. Based on its current distance of around 48 AUs from Sol, brightness, and presumed albedo or ability to reflect light, 2004 DW has been estimated to be around 870 to 990 miles (1,400 to 1,600 kilometers) across, or more than half the size of Pluto. Preliminary orbital characteristics have been determined using images of the object traced back to a First Palomar Sky Survey photograph of November 23, 1954 and to a November 8, 1951 photograph by Australia's Siding Spring Observatory. Suggesting a striking similarity to Pluto and membership to a class of objects called Plutinos, 2004 DW's orbital distance from the Sol varies between 30.9 and 48.1 AUs with an orbital inclination of about 20.6°, which is larger even than that of Pluto -- which is itself far larger than that any other planet in the Solar System. 2004 DW takes 248 years to complete its orbit. It reached its farthest point from the Sun in 1989 and so is now moving inbound towards Sol, reaching perihelion in 2113. The Kuiper Belt