Download Pluto and Solar System Debris

Lecture 13
Dwarf Planets and Solar
System Debris
October 19, 2015
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2
Pluto -- Basic
Information
• Discovered by Clyde
Tombaugh in 1930
• Period: Porb = 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 3rd Law
• Radius = 0.2 Earth
– Determined from eclipses of Charon, then by New Horizons
•  = 2300 kg/m3
 made primarily of ice and rock
• Little was known due to its large distance
• Pluto is tilted on its side.
4
Charon
1208 km diameter
Pluto
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.
– Pspin= 6.4 days (Pluto and Charon)
– Porb = 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
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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.
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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.
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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
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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
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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).
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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
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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.
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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
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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 76%
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.
23%
D. The synchronized timing of their orbit periods
ensures a collision never occurs.
0%
A.
1%
B.
C.
D.
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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
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Comparison of distant planets
Object
Year
discovered
Diameter
(km)
Perhelion
(AU)
Aphelion
(AU)
Pluto
1930
2370
29.7
49.4
Quaoar
2002
1250
41.9
44.9
Sedna
2003
1800
76.1
942
Eris
2005
2860
38.2
97.6
2005 FY9
2005
1400?
38.7
52.6
2003EL61
2005
1500?
35.2
51.5
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Kuiper Belt Objects
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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.
65%
18%
10%
8%
A.
B.
C.
D.
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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).
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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.
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• 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.
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Anatomy of a Comet
• Nucleus
– 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.
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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
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Comet NEAT
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Halley’s Comet
•Nucleus almost
completely dark
•Period: 76 years
•Next Visit: 2061
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Halley’s Comet
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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
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Comet Tempel 1 – Deep Impact
http://www.nasa.gov/mission_pages/deepimpact/multimedia/HRI-937.html
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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
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•
•
•
•
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
Mosaic of four images taken by Rosetta's
Philae landed on November 12, 2014, but
navigation camera (NAVCAM) on 19 Sept
it bounced and landed oddly, lost contact
2014 at 28.6 km (17.8 mi) from the center
of comet 67P/Churyumov–Gerasimenko.
with Rosetta
This animation consists of 86 images
acquired by Rosetta‍ ‍'​‍s NavCam as it
approached 67P in August 2014.
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Philae lander
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
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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.
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
14%
the moons of the outer planets. 5% 6%
A.
B.
C.
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D.
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The ionized gas tail of a comet is always aligned with
A. the ecliptic plane.
B. the comet’s direction of
86%
motion.
C. the line between the
comet and the Sun.
D. the gravitational field of
the nearest planet.
10%
3%
A.
2%
B.
C.
D.
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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
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Path of Asteroid
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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
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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)
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Gaspra -- Galileo Image
Size: 19 x
12 x 11 km
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Ida and Dactyl -- Galileo Image
Size: 58 x 23 km
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Eros -- NEAR Image
Size: 33 x 13 km
46
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
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The group of asteroids that cross the Earth’s orbit are
A. The Apollo asteroids
B. The Trojan asteroids 79%
C. The trans-neptunian
asteroids
D. The Kirkwood asteroids
17%
2%
A.
B.
C.
2%
D.
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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.
49
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.
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Meteor Shower
51
Meteor Showers
Quadrantids
Date of Maximum
intensity
January 3
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
Shower
Typical
Constellation
hourly rate
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Boötes
52
Meteorites
Iron
Stony-Iron
Stony
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Earth Impacts
• Earth is continually being bombarded.
Barringer Meteor Crater, Arizona
Diameter: 1.2 km
Age: ~50,000 years
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Tunguska Event -- Siberia (1908)
• Asteroid
destroyed in
atmosphere.
• Leveled trees
for over 20 km
from
explosion.
55
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.
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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
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Risks of Impact
20m
Diameter
200m
2km
58
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