Lecture 13 Dwarf Planets and Solar System Debris October 18, 2017

Lecture 13 Dwarf Planets and Solar System Debris October 18, 2017 1

2 Pluto -- Basic Information Discovered by Clyde Tombaugh in 1930 Period: P orb = 248 years Distance: a = 39.5 AU 3 moons (Charon, Nix, Hydra) Demoted to Dwarf Planet in 2006

3 General Characteristics Mass = 0.0025 times the Earth Determined by using General form of Kepler s 3 rd Law Radius = 0.2 Earth Determined from eclipses of Charon, then by New Horizons = 2300 kg/m 3 made primarily of ice and rock Little was known due to its large distance Pluto is tilted on its side.

4 Charon Pluto 1208 km diameter 2370 km diameter (Earth s Moon: 3474 km) A portrait from the final approach. Pluto and Charon display striking color and brightness contrast in this composite image from July 11, showing high-resolution black-and-white LORRI images colorized with Ralph data collected from the last rotation of Pluto. Color data being returned by the spacecraft now will update these images, bringing color contrast into sharper focus. Credits: NASA-JHUAPL-SWRI

5 Spin and Orbit Highly elliptical orbit (e = 0.25) Pluto is sometimes closer to the Sun than Neptune Orbit is tipped 17 from ecliptic Aphelion = 49.3 AU Perihelion = 29.7 AU Both Pluto and Charon are tidally locked in synchronous rotation. P spin = 6.4 days (Pluto and Charon) P orb = 6.4 days (Charon)

6 Surface Properties Predominantly water ice Frozen methane detected on surface May have thin methane atmosphere Has a surprisingly thick, layered nitrogen and methane atmosphere though it is likely seasonal Similar in some respects to Triton

7 Surface Features Hubble Space Telescope Pluto had never been visited by a spacecraft (until the New Horizons probe arrived in 2015) so there were no clear images of its surface. At left are Hubble Space Telescope global maps of Pluto (smaller insets are actual images) that show bright and dark areas visible as the dwarf planet rotates. At right is a composite image in true color that is derived from eclipses by Charon.

8 Pluto s surface Four images from New Horizons Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this sharper global view of Pluto. (The lower right edge of Pluto in this view currently lacks highresolution color coverage.) The images, taken when the spacecraft was 280,000 miles (450,000 kilometers) away from Pluto, show features as small as 1.4 miles (2.2 kilometers). That s twice the resolution of the single-image view captured on July 13 and revealed at the approximate time of New Horizons July 14 closest approach.

9 Pluto s surface This high-resolution image captured by NASA s New Horizons spacecraft combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). The bright expanse is the western lobe of the heart, informally called Sputnik Planum, which has been found to be rich in nitrogen, carbon monoxide and methane ices. Credits: NASA/JHUAPL/SwRI

10 Pluto s surface New close-up images of a region near Pluto s equator reveal a giant surprise: a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body. Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Instead, a stiffer material, most likely water-ice, created the peaks. The close-up image was taken about 1.5 hours before New Horizons closest approach to Pluto, when the craft was 47,800 miles (77,000 kilometers) from the surface of the planet. The image easily resolves structures smaller than a mile across. Image Credit: NASA-JHUAPL-SwRI

11 Pluto s surface In this extended color image of Pluto taken by NASA s New Horizons spacecraft, rounded and bizarrely textured mountains, informally named the Tartarus Dorsa, rise up along Pluto s day-night terminator and show intricate but puzzling patterns of blue-gray ridges and reddish material in between. This view, roughly 330 miles (530 kilometers) across, combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC) on July 14, 2015, and resolves details and colors on scales as small as 0.8 miles (1.3 km).

12 Pluto s surface This image from the heart of Pluto s heart feature shows the plains enigmatic cellular pattern (at left) as well as unusual clusters of small pits and troughs (from lower left to upper right). This image was taken by the Long Range Reconnaissance Imager (LORRI) on NASA's New Horizons spacecraft shortly before closest approach to Pluto on July 14, 2015; it resolves details as small as 270 yards (250 meters). The scene shown is about 130 miles (210 kilometers) across. The sun illuminates the scene from the left, and north is to the upper left. Credits: NASA/JHUAPL/SwRI

13 Pluto s atmosphere Pluto's haze layer shows its blue color in this picture taken by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC). The high-altitude haze is thought to be similar in nature to that seen at Saturn s moon Titan. The source of both hazes likely involves sunlight-initiated chemical reactions of nitrogen and methane, leading to relatively small, soot-like particles (called tholins) that grow as they settle toward the surface. This image was generated by software that combines information from blue, red and near-infrared images to replicate the color a human eye would perceive as closely as possible.

14 Charon s surface Charon in Enhanced Color NASA's New Horizons captured this high-resolution enhanced color view of Charon just before closest approach on July 14, 2015. The image combines blue, red and infrared images taken by the spacecraft s Ralph/Multispectral Visual Imaging Camera (MVIC); the colors are processed to best highlight the variation of surface properties across Charon. Charon s color palette is not as diverse as Pluto s; most striking is the reddish north (top) polar region, informally named Mordor Macula. Charon is 754 miles (1,214 kilometers) across; this image resolves details as small as 1.8 miles (2.9 kilometers). Credits: NASA/JHUAPL/SwRI

15 If Pluto is sometimes closer to the Sun than Neptune, why doesn t it ever collide with Neptune? A. They do collide every few thousand 74% years. B. Neptune is primarily made of gases, so Pluto would pass right through it. C. Pluto s orbit is steeply tilted with respect to Neptune s, so they never actually cross. 0% 0% 26% D. The synchronized timing of their orbit periods ensures a collision never occurs. A. B. C. D.

16 http://photojournal.jpl.nasa.gov/catalog/pia05567 Origins of Pluto Composition much more like a moon Other objects similar to Pluto (such as Sedna, below) are being found in the Kuiper Belt http://photojournal.jpl.nasa.gov/catalog/pia05568

17 Comparison of distant planets Object Year discovered Diameter (km) Perhelion (AU) Aphelion (AU) Pluto 1930 2380 29.7 49.3 Eris 2005 2326 37.9 97.7 Haumea 2004 1632 35.0 51.5 2007 OR 10 2007 1535 33.1 101 Makemake 2005 1430 38.6 52.8 Quaoar 2002 1110 41.9 44.9

18 Kuiper Belt Objects Updated art from Wikimedia 28 April 2017

19 If you were standing on Pluto, and Charon was on your meridian, how would it move in the sky over time? A. It would move slowly west. B. It would move slowly east. C. It would move slowly north along the meridian. D. It wouldn t move at all. 86% 0% 10% 4% A. B. C. D.

20 Solar System Debris After formation of the Solar System, some material was left over. Asteroids, comets, and meteoroids give clues to composition of early solar system. Have undergone little processing (heating, weathering).

21 Comets Made of ices and some rocky material Travel in very elliptical orbits about the Sun. Comet McNaught, January 2007. Click on image for more info.

22 Long period comets May orbit once every million years Origin in Oort Cloud -- spherical cloud up to 100,000 AU from Sun Short period comets Periods < 200 years Origin in Kuiper Belt -- disk shape 30-100 AU from Sun.

23 Nucleus Anatomy of a Comet few km in diameter ices and rocky material ( dirty ice ball ) Only part of a comet that exists away from the Sun. Coma -- Gases evaporated off of surface of nucleus as Sun heats it.

24 Tails -- Always point away from the Sun Dust tail -- small dust particles, slightly curved in direction of orbit. Ion tail -- ionized molecules pushed straight back by solar wind

25

26 Comet NEAT

27 Halley s Comet Nucleus almost completely dark Period: 76 years Next Visit: 2061

28 Halley s Comet

29 Comet Shoemaker-Levy 9 Comet struck Jupiter in July 1994 Original comet ~2-10 km in diameter Before impact it broke into many small pieces

30 Comet Tempel 1 Deep Impact http://www.nasa.gov/mission_pages/deepimpact/multimedia/hri-937.html

31 Comet Tempel 1 Deep Impact revealed the composition of the comet Tempel 1 Some of the expected constituents: silicates (sand), water ice and some surprises: Clay, and carbonates (how did these form without liquid water?) iron compounds aromatic hydrocarbons

32 Comet 67P/Churyumov Gerasimenko Short period comet (P = 6.45 y) discovered in 1969 4.3 km 4.1 km about the size of Stevens Point Rosetta spacecraft orbiting the comet since September 10, 2014 Philae landed on November 12, 2014, but it bounced and landed oddly, lost contact with Rosetta Mosaic of four images taken by Rosetta's navigation camera (NAVCAM) on 19 Sept 2014 at 28.6 km (17.8 mi) from the center of comet 67P/Churyumov Gerasimenko. This animation consists of 86 images acquired by Rosetta ' s NavCam as it approached 67P in August 2014.

33 Philae lander lost! The first image from the surface of Comet 67P, by the CIVA camera. One of the lander's three feet can be seen in the foreground. The image is a two-image mosaic. Credit: ESA/Rosetta/Philae/CIVA OSIRIS image of the Philae lander, as it descended toward, and then bounced off, the surface of Comet 67P during touchdown on 12 November 2014 Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA Philae's final landing site, estimated by CONSERT. Credits: ESA/Rosetta/Philae/CONSERT

34 Philae lander found! (Sept 2016)

35 Surface of Comet 67P Rosetta s lander Philae is safely on the surface of Comet 67P/Churyumov-Gerasimenko, as these first two CIVA images confirm. One of the lander s three feet can be seen in the foreground. The image is a two-image mosaic.

Astronomers think that most comets come from A. interstellar space. 20% 75% B. a region in the extreme outer parts of the Solar System. C. condensation of gas in the Sun s hot outer atmosphere. D. material ejected by volcanic eruptions on the moons of the outer planets. 3% 3% 36 A. B. C. D.

37 The ionized gas tail of a comet is always aligned with A. the ecliptic plane. B. the comet s direction of motion. C. the line between the comet and the Sun. D. the gravitational field of the nearest planet. 17% 12% 69% 3% A. B. C. D.

38 Asteroids Bodies of rock (some iron) Irregular shape Typically 0.1-600 km Total number of visible asteroids may be 100,000. Detected by movement with respect to stars. Average distance between asteroids ~1,000,000 km

39 Path of Asteroid

42 Orbits of Asteroids Most orbit Sun in Asteroid Belt between Mars and Jupiter Debris that was not able to form a planet due to pull from Jupiter. Apollo Asteroids high orbital eccentricities. Cross the orbit of the Earth

43 Apollo asteroids A diagram showing the Apollo asteroids, compared to the orbits of the terrestrial planets Mercury(H), Venus(V), Earth(E) and Mars (M). As of 2015, the Apollo asteroid group includes a total of 6,923 known objects of which 991 are numbered (JPL SBDB)

44 Gaspra -- Galileo Image Size: 19 x 12 x 11 km

45 243 Ida and Dactyl -- Galileo Image Size: 1.4 km Size: 58 x 23 km

46 Eros -- NEAR Image Size: 33 x 13 km

47 Hayabusa mission Asteroid 25143 Itokawa First ever successful landing on an asteroid Launched 2 May 2003 Landed on asteroid Itokawa 19 November 2005 Returned sample of asteroid dust 13 June 2010 Analysis of results published 26 August 2011 issue of Science Mission web site Hayabusa 2 was launched 3 Dec 2014 and will arrive at asteroid 162173 Ryugu in July 2018

48 The group of asteroids that cross the Earth s orbit are A. The Apollo asteroids B. The Trojan asteroids C. The trans-neptunian asteroids D. The Kirkwood asteroids 89% 8% 3% 1% A. B. C. D.

49 Meteoroids Meteoroids -- small debris in space, usually < 100 m in diameter Meteor -- meteoroid falling through Earth s atmosphere. Friction with air causes it to heat and burn up. Seen as shooting star Most burn completely, only largest make it to the Earth Meteorite -- meteoroid that makes it to the surface of the Earth.

50 Meteor Showers Some cometary orbits cross orbit of the Earth. When they break up they leave debris in orbit. Earth passes through debris, many meteors are seen.

51 Meteor Shower

52 Meteor Showers Shower Date of Maximum Typical intensity hourly rate Constellation Quadrantids January 3 40 Boötes Lyrids April 22 15 Lyra Eta Aquarids May 4 20 Aquarius Delta Aquarids July 30 20 Aquarius Perseids August 12 80 Perseus Orionids October 21 20 Orion Taurids November 4 15 Taurus Leonids November 16 15 Leo Major Geminids December 13 50 Gemini Ursids December 22 15 Ursa Major

53 Meteorites Iron Stony-Iron Stony

54 Earth Impacts Earth is continually being bombarded. Barringer Meteor Crater, Arizona Diameter: 1.2 km Age: ~50,000 years

55 Tunguska Event -- Siberia (1908) Asteroid destroyed in atmosphere. Leveled trees for over 20 km from explosion.

56 Chelyabinsk Meteor February 15, 2013 The impacting asteroid started to brighten up in the general direction of the Pegasus constellation, close to the East horizon where the Sun was starting to rise. The impactor belonged to the Apollo group of near-earth asteroids. The asteroid had an approximate size of 18 metres (59 ft) and a mass of about 9,100 tonnes (10,000 short tons) before it entered the denser parts of Earth's atmosphere and started to ablate. At an altitude of about 23.3 km (14.5 miles) the body exploded in anair burst. Meteorite fragments of the body landed on the ground.

57 Chicxulub Crater -- Yucatan Peninsula, Mexico Dinosaurs -- possibly destroyed by asteroid impact ~65 million years ago Alvarez & Alvarez found iridium rich layer of clay Chicxulub Diameter ~170 km

58 Risks of Impact Diameter 20m 200m 2km

59 The New Yorker Collection 1998 Frank Cotham from cartoonbank.com. All Rights Reserved