Starry Monday at Otterbein Astronomy Lecture Series -every first Monday of the month- October 5, 2010 Dr. Uwe Trittmann Welcome to

Today’s Topics Close Encounter with Jupiter The Night Sky in October

Observing Planets Inner Planets: closer to sun than Earth –Mercury & Venus –Always close to sun in the sky Outer Planets: further from sun than Earth –Mars, Jupiter, Saturn, Uranus, Neptune, Pluto –Best viewing when opposite of sun in the sky

Inner Planets Inner planet Earth superior conjunction inferior conjunction western elongation eastern elongation

Outer Planets Outer planet Earth conjunction opposition quadrature

Close Outer Planet (Mars) Outer planet Earth Size of planet varies a lot as Earth moves

Far-Out Planet (e.g. Jupiter) Outer planet Earth Size of planet varies little as Earth moves

Jupiter Color: yellowish-white Brightness: up to –2.9m Size: up to 50” When to observe: most of the year, except for some months around conjunction Difficulty: easy, moons visible in binoculars

Jupiter & Moons

General Features of Jupiter Largest planet Low density –Primarily ball of light gases compressed by gravity Fastest rotation No seasons Has Rings 63 Moons 1/1000 mass of sun, 320x Earth

Jupiter’s Orbit Average distance from Sun: 779 mill. km = 5.2 A.U. Eccentricity: Closest to Sun: 741 mill. km Farthest from Sun: 817 mill. km Jupiter Year = Earth years

Kepler’s First Law The orbits of the planets are ellipses, with the Sun at one focus

Ellipses a = “semimajor axis”; e = “eccentricity”

Kepler’s Second Law An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal times

Kepler’s Third Law The square of a planet’s orbital period is proportional to the cube of its orbital semi-major axis: P 2  a 3 a P Planet Orbital Semi-Major AxisOrbital Period Eccentricity P 2 /a 3 Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto (A.U.)(Earth years)

Jupiter Opposition 2010 Best since 1951, until 2022 Distance: AU unexpected disappearance of Jupiter's South Equatorial Belt (SEB) earlier this year SEB’s return is often impressive, with dramatic storms erupting suddenly. Days or years before Jupiter looks normal again

Jupiter’s Atmosphere Cloud bands parallel to equator Great Red Spot –First observed in 1664 by Robert Hooke

Jupiter’s Atmosphere 86% Hydrogen, 14% Helium; some methane, water, ammonia Several layers of clouds: ammonia, ammonium hydrosulfide, water Colors mostly due to compounds of sulfur and phosphorus

Great Red Spot About twice the diameter of the Earth A hurricane that is hundreds of years old!

GRS As seen by Voyager 1, 1979

Jupiters’ Bands: Zones and Belts Belts: cool, dark, sinking Zones: warm, bright, rising Jovian weather mostly circles the planet due to high rotation rate Bands exhibit east–west flow  Great Red Spot lies between regions of opposite wind flow

Naming of Belts & Zones Tropical, equatorial, temperate Zone/Belt

Jupiter Changes

Missing Belt!

Rotation About 9 hours for Jupiter and Saturn Differential rotation: rotation speed varies from point to point on the “surfaces” –Gaseous bodies with no solid surfaces! –On Jupiter, the equatorial regions rotate 6 minutes slower than polar regions Flattening of planet! Tilt of rotation axis: –almost none – no seasons!

4 Galilean Moons + 59 others

4 Moons are Planet Size

Jupiter’s Galilean Moons

Io Jupiter’s innermost moon Size and mass similar to our moon Zips around Jupiter in just 2 days

Io The most volcanically active object in the solar system –Heated by tidal friction Eruptions as high as 200 miles, may last for months

Europa Europa might have liquid water oceans under the surface  Life?

Ganymede Largest Moon in the solar system: 5260km diameter Icy surface, dark parts are oldest

View through the Telescope

Comet Shoemaker-Levy 9 HST image (1994); Earth added to show scale

Comet Shoemaker-Levy 9 Headed for Jupiter…

Impact on Jupiter

Space Probes Pioneer –Jupiter and Saturn; early 70's –First man-made object to leave solar system Voyager –“Grand Tour” of Jupiter, Saturn, Uranus and Neptune –Launched 1977; arrived 1979 Galileo –Launched in 1989 on space shuttle –Boosted by gravitational assists from Earth and Venus –Two-part spacecraft arrived late 1995 Atmospheric probe entered Jupiter's atmosphere 12/7/95 Orbiter the first permanent orbiter of outer planets Cassini - arrived at Saturn 2004, Huygens probes Titan right now

Internal Structure Gas of increasing density and pressure On Jupiter and Saturn, conditions are such that hydrogen becomes metallic; dense cores Uranus and Neptune probably have conducting slushy layers

Magnetospheres Very strong – Jupiter's extends past the orbit of Saturn! Indicate the presence of conducting cores

The Night Sky in October The sun is past autumn equinox -> longer nights! Autumn constellations are coming up: Cassiopeia, Pegasus, Perseus, Andromeda, Pisces  lots of open star clusters! Jupiter is visible most of the night

Moon Phases Today (Waning Crescent) 10 / 7 (New Moon) 10/ 14 (First Quarter Moon) 10 / 22 (Full Moon) 10/ 30 (Last Quarter)

Today at Noon Sun at meridian, i.e. exactly south

10 PM Typical observing hour, early October Uranus Neptune Jupiter

South- West High in the sky: The summer triangle

Due North Big Dipper points to the north pole

High up – the Autumn Constellations W of Cassiopeia Big Square of Pegasus Andromeda Galaxy

“PR” Foto Actual look

East Perseus and Auriga with Plejades and the Double Cluster

Greek Mytho- logy in the Sky

South Planets –Uranus –Neptune Zodiac: –Capricorn –Aquarius

South – 2007 Planets –Uranus –Neptune Zodiac: –Capricorn –Aquarius

South – 2008 Planets –Uranus –Neptune Zodiac: –Capricorn –Aquarius

South – 2009 Planets –Uranus –Neptune Zodiac: –Capricorn –Aquarius

South – 2010 Planets –Uranus –Neptune Zodiac: –Capricorn –Aquarius

Mark your Calendars! Next Starry Monday: November 1, 2010, 7 pm (this is a Monday ) Web pages: – (Obs.) – (Physics Dept.)