Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine [e-mail]

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Astronomy 101The Solar SystemTuesday,
Thursday230-345 pmHasbrouck 20Tom
Burbinetomburbine_at_astro.umass.edu
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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.

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Office Hours

• Mine
• Tuesday, Thursday - 115-215pm
• Lederle Graduate Research Tower C 632
• Neil
• Tuesday, Thursday - 11 am-noon
• Lederle Graduate Research Tower B 619-O

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Homework

• We will use Spark
• https//spark.oit.umass.edu/webct/logonDisplay.dow
  ebct
• Homework will be due approximately twice a week

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Class Averages

• 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)

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Final

• Cumulative
• Monday - 12/14
• 400 pm
• Hasbrouck 20
• Review Session
• Sunday -12/13
• 300 pm
• Hasbrouck 134

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Formulas you may need to know

• p2 a3
• F GMm/r2
• F ma
• a GM/r2
• Escape velocity sqrt(2GM/r)
• T (K) T (oC) 273.15
• c f?
• E hf
• KE 1/2mv2
• E mc2
• Density mass/volume
• Volume 4/3?r3

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More Formulas

• Power emitted per unit surface area sT4
• ?max (nm) (2,900,000 nmK)/T
• Apparent brightness Luminosity
• 4? x
  (distance)2

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Intelligent Life

• Intelligent life that we can detect is usually
  defined as life that can build a radio telescope

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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.

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Fermis Paradox

• Where are they?

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Fermis Paradox

• 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?

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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.

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Explanation

• Interested in us but do not want us (yet) to be
  aware of their presence (sentinel hypothesis or
  zoo hypothesis)

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Explanation

• Not interested in us because they are by nature
  xenophobic or not curious

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Explanation

• Not interested in us because they are so much
  further ahead of us

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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

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Explanation

• Capable of only interplanetary or limited
  interstellar travel because of fundamental
  physical, biological, or economic restraints

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Fermis 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

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Jupiter

• Largest planet
• Mass - 1.8991027 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)

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Probes to Jupiter

• Pioneer 10 1973
• Pioneer 11 - 1974
• Voyager 1 1979
• Voyager 2 - 1979
• Ulysses - 1992
• Galileo 1995 - Orbiter
• Cassini - 2000

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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.

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• Jupiter is composed
• relatively small rocky core
• surrounded by metallic hydrogen
• surrounded by liquid hydrogen
• surrounded by gaseous hydrogen.

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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_Jupi
  ter
• The differences in colors are caused by slight
  differences in chemical composition and
  temperature
• http//zebu.uoregon.edu/imamura/121/lecture-13/vj
  upitr2.mov

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Galileo Probe
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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.

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Jupiters Rings

• Jupiter has a faint planetary ring system
  composed of smoke-like dust particles knocked
  from its moons by meteor impacts.

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Jupiter has four rings
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Voyager 1 and 2

• Voyager 2 launched first (1977)
• Then Voyager 1 (1977)

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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

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Voyager 2

• Went to Jupiter, Saturn, Uranus, and Neptune

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Voyager 1

• Went to Jupiter and Saturn

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Voyager Golden Record
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Pioneer 10 and 11 Plaques (1972)

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Saturn
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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.

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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.

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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

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• http//csep10.phys.utk.edu/astr161/lect/saturn/rin
  gs.html

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Cassini-Huygens

• Visited Saturn and Titan

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Uranus
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Uranus

• Discovered by William Herschel in 1781
• In 1977, the first nine rings of Uranus were
  discovered

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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.

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Unusual

• Tipped on its side
• Why?

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Probably

• Due to a collision

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Uranus Satellites

• Miranda
• Ariel
• Umbriel
• Titania
• Oberon
• 2001U3
• Caliban
• Stephano
• Trinculo
• Sycorax
• 2003U3
• Prospero
• Setebos
• 2002U2

• Cordelia
• Ophelia
• Bianca
• Cressida
• Desdemona
• Juliet
• Portia
• Rosalind
• 2003U2
• Belinda
• 1986U10
• Puck
• 2003U1

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• Instead of being named after people from
  classical mythology, Uranus' moons take their
  names from the writings of William Shakespeare
  and Alexander Pope.

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Neptune
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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.

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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

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• Neptune's blue color is largely the result of
  absorption of red light by methane in the
  atmosphere

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Great Dark Spot

• Thought to be a hole

Scooter
Small dark spot
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Great Dark Spot has disappeared
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Neptunes Rings
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Shoemaker-Levy 9

• Comet that hit Jupiter
• Discovered in 1993
• Hit Jupiter in 1994

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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

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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

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• The first impact occurred at 2015 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.

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Has this happened before?Ganymede
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Ganymede-Europa
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Satellites

• Jupiter has 63 known satellites
• The four large Galilean moons plus many more
  small ones some of which have not yet been named

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Simon Marius (1573-1624)

• In 1614, Marius published his work Mundus
  Iovialis describing how he had discovered
  Jupiters 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

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Galileo
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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.

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Sagans 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.

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Densities

• Io - 3.53 g/cm3
• Europa - 3.01 g/cm3
• Ganymede 1.94 g/cm3
• Callisto (JIV) 1.83 g/cm3

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Io
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Io

• Io has almost no craters as first seen by Voyager
  I (1979)
• What does that mean?

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• It is geologically active
• Voyager I saw 9 active volcanos

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• The energy for this activity probably derives
  from tidal interactions among Io, Jupiter, and
  two other moons of Jupiter, Europa, and Ganymede.

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Europa
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Europa

• Very smooth surface
• Its albedo is one of the highest of all moons
• Lack of craters indicates a young and active
  surface

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• 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.

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• 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.

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Europa

• It is thought that under the surface there is a
  layer of liquid water kept warm by tidally
  generated heat.

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Ganymede
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Ganymede

• Largest Moon of Jupiter
• Largest Moon in the solar system

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• 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.

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Galileo Regio
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Callisto
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Callisto

• One of the most heavily cratered objects in the
  solar system
• No large mountains

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Any Questions?