Transcript Jupiter

Astronomy 101
The Solar System
Tuesday, Thursday
2:30-3:45 pm
Hasbrouck 20
Tom Burbine
[email protected]
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
Office Hours
• Mine
• Tuesday, Thursday - 1:15-2:15pm
• Lederle Graduate Research Tower C 632
• Neil
• Tuesday, Thursday - 11 am-noon
• Lederle Graduate Research Tower B 619-O
Homework
• We will use Spark
• https://spark.oit.umass.edu/webct/logonDisplay.d
owebct
• Homework will be due approximately twice a
week
Class Averages
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For people who took all 4 tests:
Class average is 81
Grades range from a 98.5 to a 55.4
Scores will go up when the lowest exam grade is
dropped after the final
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A (92.50 – 100)
A- (89.50 – 92.49)
B+ (87.50 – 89.49)
B (82.50 – 87.49)
B- (79.50 – 82.49)
C+ (77.50 – 79.49)
C (72.50 – 77.49)
C- (69.50 – 72.49)
D (59.50 – 69.49)
F (below 59.49)
Final
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Cumulative
Monday - 12/14
4:00 pm
Hasbrouck 20
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Review Session
Sunday -12/13
3:00 pm
Hasbrouck 134
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Formulas
you
may
need
to
know
2
3
p =a
F = GMm/r2
F = ma
a = GM/r2
Escape velocity = sqrt(2GM/r)
T (K) = T (oC) + 273.15
c = f*
E = h*f
KE = 1/2mv2
E = mc2
• Density = mass/volume
• Volume = 4/3r3
More Formulas
• Power emitted per unit surface area = σT4
• λmax (nm) = (2,900,000 nm*K)/T
• Apparent brightness = Luminosity
4 x (distance)2
Intelligent Life
• Intelligent life that we can detect is usually
defined as life that can build a radio telescope
Radio
• Transmitting information over radio waves is very
cheap
• uses equipment that is easy to build
• has the information-carrying capacity necessary
for the task
• The information also travels at the speed of light.
Fermi’s Paradox
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Where are they?
Fermi’s Paradox
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Why have we not observed alien civilizations
even though simple arguments would suggest
that some of these civilizations ought to have
spread throughout the galaxy by now?
Reason for question
• Straightforward calculations show that a
technological race capable of interstellar travel at
(a modest) one tenth the speed of light ought to be
able to colonize the entire Galaxy within a period
of one to 10 million years.
Explanation
• Interested in us but do not want us (yet) to be
aware of their presence (sentinel hypothesis or
zoo hypothesis)
Explanation
• Not interested in us because they are by nature
xenophobic or not curious
Explanation
• Not interested in us because they are so much
further ahead of us
Explanation
• Prone to annihilation before they achieve a significant
level of interstellar colonization, because:
(a) they self-destruct
(b) are destroyed by external effects, such as:
(i) the collision of an asteroid or comet with their
home world
(ii) a galaxy-wide sterilization phenomenon (e.g. a
gamma-ray burster
(iii) cultural or technological stagnation
Explanation
• Capable of only interplanetary or limited
interstellar travel because of fundamental
physical, biological, or economic restraints
Fermi’s paradox
• The Fermi paradox is the apparent contradiction
between high estimates of the probability of the
existence of extraterrestrial civilizations and the
lack of evidence for, or contact with, such
civilizations.
• http://en.wikipedia.org/wiki/Fermi_paradox
Jupiter
• Largest planet
– Mass - 1.899×1027 kg (317.8 Earths)
– Jupiter is 2.5 times more massive than all the other
planets combined
• Mean density - 1.326 g/cm3
• Equatorial diameter - 142,984 km (11.209 Earths)
Probes to Jupiter
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Pioneer 10 – 1973
Pioneer 11 - 1974
Voyager 1 – 1979
Voyager 2 - 1979
Ulysses - 1992
Galileo – 1995 - Orbiter
Cassini - 2000
Jupiter
• Jupiter's atmosphere is composed of
~81% hydrogen and ~18% helium.
• Jupiter probably has a core of rocky material amounting
to something like 10 to 15 Earth-masses.
• Above the core lies the main bulk of the planet in the
form of liquid metallic hydrogen. This exotic form of
the most common of elements is possible only at
pressures exceeding 4 million bars
– 1 bar ≈ standard atmospheric pressure at sea level on Earth.
• Jupiter is composed
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relatively small rocky core
surrounded by metallic hydrogen
surrounded by liquid hydrogen
surrounded by gaseous hydrogen.
Clouds
• clouds of ammonia (NH3), methane (CH4),
ammonia hydrosulfide (NH4HS)
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zone for the light stripes
belt for the dark stripes
http://en.wikipedia.org/wiki/Cloud_pattern_on_Jupiter
The differences in colors are caused by slight
differences in chemical composition and temperature
• http://zebu.uoregon.edu/~imamura/121/lecture13/vjupitr2.mov
Galileo Probe
Great Red Spot
• A particularly violent
storm, about three times
Earth's diameter, is
known as the Great Red
Spot, and has persisted
through more than three
centuries of human
observation.
• The spot rotates
counterclockwise, once
every 7 days.
Jupiter’s Rings
• Jupiter has a faint planetary ring system
composed of smoke-like dust particles knocked
from its moons by meteor impacts.
Jupiter has four rings
Voyager 1 and 2
• Voyager 2 launched first (1977)
• Then Voyager 1 (1977)
Grand Tour
• Planetary Grand Tour was an ambitious plan to
send unmanned probes to the outermost planets of
the solar system. Conceived by Gary Flandro of
the Jet Propulsion Laboratory, the Grand Tour
would have exploited the alignment of Jupiter,
Saturn, Uranus, Neptune and Pluto
Voyager 2
• Went to Jupiter, Saturn, Uranus, and Neptune
Voyager 1
• Went to Jupiter and Saturn
Voyager Golden Record
Pioneer 10 and 11 Plaques (1972)
Saturn
Saturn
• Known since prehistoric times
• Galileo was the first to observe it with a telescope
in 1610
• In 1659, Christian Huygens correctly inferred the
geometry of the rings
• Saturn is the least dense of the planets; its density
(0.7 g/cc) is less than that of water.
Rings
• Very thin
• 250,000 km or more in diameter they are less than
one kilometer thick
• The ring particles seem to be composed primarily
of water ice, but they may also include rocky
particles with icy coatings.
Roche Limit
• Rings are either a satellite torn apart by tidal
forces or material that was never allowed to
condense into moons because of the tidal forces
• http://csep10.phys.utk.edu/astr161/lect/saturn/rings.html
Cassini-Huygens
• Visited Saturn and Titan
Uranus
Uranus
• Discovered by William Herschel in 1781
• In 1977, the first nine rings of Uranus were
discovered
Atmosphere
• The atmosphere of Uranus is composed of 83%
hydrogen, 15% helium, 2% methane and small
amounts of acetylene and other hydrocarbons.
• Methane in the upper atmosphere absorbs red
light, giving Uranus its blue-green color.
Unusual
• Tipped on its side
• Why?
Probably
• Due to a collision
Uranus’ Satellites
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Cordelia
Ophelia
Bianca
Cressida
Desdemona
Juliet
Portia
Rosalind
2003U2
Belinda
1986U10
Puck
2003U1
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Miranda
Ariel
Umbriel
Titania
Oberon
2001U3
Caliban
Stephano
Trinculo
Sycorax
2003U3
Prospero
Setebos
2002U2
• Instead of being named after people from classical
mythology, Uranus' moons take their names from
the writings of William Shakespeare and
Alexander Pope.
Neptune
Neptune
• After the discovery of Uranus, it was noticed that its orbit
was not as it should be in accordance with Newton's
laws.
• It was therefore predicted that another more distant
planet must be perturbing Uranus' orbit.
• Neptune was first observed by Johan Galle and Heinrich
d'Arrest on 1846 Sept 23 very near to the locations
predicted from theoretical calculations based on the
observed positions of Jupiter, Saturn, and Uranus.
Galileo
• Galileo's astronomical drawings show that he had
first observed Neptune on December 27, 1612,
and again on January 27, 1613;
• on both occasions Galileo had mistaken Neptune
for a fixed star
• Neptune's blue color is largely the result of
absorption of red light by methane in the
atmosphere
Great Dark Spot
• Thought to be a hole
Scooter
Small dark spot
Great Dark Spot has disappeared
Neptune’s Rings
Shoemaker-Levy 9
• Comet that hit Jupiter
• Discovered in 1993
• Hit Jupiter in 1994
Roche Limit
• The smallest distance at which a natural satellite can orbit
a celestial body without being torn apart by the larger
body's gravitational force. The distance depends on the
densities of the two bodies and the orbit of the satellite.
• If a planet and a satellite have identical densities, then the
Roche limit is 2.446 times the radius of the planet.
• Jupiter's moon Metis and Saturn's moon Pan are
examples of natural satellites that survive despite being
within their Roche limits
Why is the Roche Limit important?
• Comet Shoemaker-Levy 9's decaying orbit around
Jupiter passed within its Roche limit in July,
1992, causing it to break into a number of smaller
pieces.
• All known planetary rings are located within the
Roche limit
• The first impact occurred at 20:15 UTC on July 16, 1994
• Fragment A of the nucleus slammed into Jupiter's
southern hemisphere at a speed of about 60 km/s.
• Instruments on Galileo detected a fireball which reached
a peak temperature of about 24,000 K, compared to the
typical Jovian cloudtop temperature of about 130 K,
before expanding and cooling rapidly to about 1500 K
after 40 s.
Has this happened before?
Ganymede
Ganymede-Europa
Satellites
• Jupiter has 63 known satellites
• The four large Galilean moons plus many more
small ones some of which have not yet been
named:
Simon Marius (1573-1624)
• In 1614, Marius published his work Mundus Iovialis
describing how he had discovered Jupiter’s Moons some
days before Galileo did
• The names by which these satellites are known today (Io,
Europa, Ganymede and Callisto) are those given them by
Marius.
• But untile the middle of the 20th century, these satellited
were known as "Jupiter I," "Jupiter II," "Jupiter
III," and "Jupiter IV"
• Gan De, a Chinese astronomer, may have discovered the
moons in 362 BC
Galileo
Galileo spacecraft
• Launched in 1989
• It arrived at Jupiter on December 7, 1995
• On September 21, 2003, Galileo's mission ended
by crashing into Jupiter's atmosphere to avoid any
chance of it contaminating the Galilean moons
with bacteria from Earth.
Sagan’s Criteria for Life
(From measurements of Earth by Galileo)
• Strong absorption of light at the red end of the visible
spectrum, caused by absorption by chlorophyll in
photosynthesizing plants
• Absorption bands due to molecular oxygen (O2), which is
also a result of plant activity (O2 in our atmosphere is
many orders of magnitude greater than is found on any
other planet in the Solar System)
• Infrared absorption bands caused by methane (CH4)
(about 1 part per million in Earth's atmosphere), a gas
which must be replenished by either volcanic or
biological activity)
• Modulated narrowband radio wave transmissions
uncharacteristic of any known natural source.
Densities
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Io - 3.53 g/cm3
Europa - 3.01 g/cm3
Ganymede – 1.94 g/cm3
Callisto (JIV) – 1.83 g/cm3
Io
Io
• Io has almost no craters as first seen by Voyager I
(1979)
• What does that mean?
• It is geologically active
• Voyager I saw 9 active volcanos
• The energy for this
activity probably derives
from tidal interactions
among Io, Jupiter, and
two other moons of
Jupiter, Europa, and
Ganymede.
Europa
Europa
• Very smooth surface
• Its albedo is one of the highest of all moons
• Lack of craters indicates a young and active
surface
• Symmetric ridges in the
dark bands suggest that
the surface crust was
separated and filled with
darker material,
somewhat analogous to
spreading centers in the
ocean basins of Earth.
• Spectroscopy suggests that the dark reddish
streaks and features on Europa's surface may be
rich in salts such as magnesium sulfate (Epsom
salt), deposited by evaporating water that emerged
from within.
Europa
• It is thought that under the surface there is a layer
of liquid water kept warm by tidally generated
heat.
Ganymede
Ganymede
• Largest Moon of Jupiter
• Largest Moon in the solar system
• Surface is a mix of two
types of terrain:
– very old, highly cratered
dark regions
– somewhat younger (but
still ancient) lighter regions
marked with an extensive
array of grooves and
ridges.
Galileo Regio
Callisto
Callisto
• One of the most heavily cratered objects in the
solar system
• No large mountains
Any Questions?