Welcome to Starry Monday at Otterbein Astronomy Lecture Series -every first Monday of the month June 6, 2005 Dr. Uwe Trittmann

Today’s Topics • Saturn – the ringed Planet • The Night Sky in June

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(Obs.) – http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)

Saturn – the ringed Planet

Saturn is a Jovian Planet Saturn Jupiter Uranus Neptune

Comparison •

Terrestrial

– close to the Sun – closely spaced orbits – small radii – small masses – predominantly rocky – high density – solid surface – few moons – no rings •

Jovian

– far from the Sun – widely spaced orbits – large radii – large masses – predominantly gaseous – low density – no solid surface – many moons – many rings

Saturn’s Atmosphere • 92% Hydrogen 7% Helium; some methane, water, ammonia • Belt structure similar to Jupiter’s, but fainter • Storms are rarer • White spot seen, 1990 (Voyager)

Aurora Borealis and Australis on Saturn

Ring Systems Saturn Uranus Jupiter Neptune

Saturn’s Rings • Rings composed of small, icy fragments, orbiting in concentric circles – James Clerk Maxwell; confirmed by James Keeler (1895) using Doppler shift • Orbits obey Kepler’s laws (of course!) – Inner rings move faster than outer ones

Visibility of Saturn’s Rings

Changing Ring Opening 1998 1999 2000 1997 1996

How Do They Form?

• Miscellaneous debris • • Moons or other small bodies torn apart by tidal forces Roche limit – distance inside of which an object held together by gravity will be pulled apart

Rings and Shepherd Moons Shepherd moons

Ring Formation • Rings may be short lived (on the time scale of solar system) • Means that they must form fairly frequently • A moon may pass too close to a planet (within the Roche limit) and be destroyed by tidal forces – This will probably happen to Triton (a moon of Neptune) within 100 million years!

Saturn’s Moons

Two-faced Saturn’s Moons looks like Star Wars’ Death Star plus Titan rooftop We saw these three at

Weitkamp Observatory Picture •

Saturn

(March 9, 2004, 20:50 EST) (Photographed with the LX200 10”, and department’s Sony DSC F-717 Digital Camera )

Saturn’s Moons from the Roof

Titan • Titan is the only moon in the solar system known to have an

atmosphere

Infrared picture shows surface details

Double-faced Japetus • Extremely different surface reflectivity • Probably dust

Space Probes:Voyager & Pioneer • Pioneer 10 – launched in early 1970ies – Still alive • Voyagers : launched 1977 – Jupiter 1979 – Saturn 1981 – Uranus 1986 – Neptune 1989

The Grand Tour Small window of opportunity in 1977

Leaving the Solar System • Voyager 1 – 8.6 billion miles (95 AU) out – Speed: 3.6 AU/year

The Sounds of Earth – Message to the Aliens

• On the chance that someone is out there, NASA approved the placement of a phonograph record on each of the Voyager spacecraft. The recording, called "Sounds of Earth" fits on a 12-inch, copper disc containing greetings from Earth people in 60 languages, samples of music from different cultures and eras, and natural sounds of surf, wind and thunder, and birds, whales and other animals. The record also contains electronic information that an advanced technological civilization could convert into diagrams, pictures and printed words, including a message from President Carter.

(Courtesy NASA)

• Cassini: NASA space probe •Huygens: ESA lander

Cassini at Saturn: a Picture Harvest

Phoebe –Saturn’s Outpost

A Look through the Rings

Rhea’s Bright Splat • Rhea (949 mi) • Cassini photo from 1.3 million miles

• Visible here are: Mimas (397 kilometers, or 247 miles across) near lower right; Janus (181 kilometers, or 113 miles across) below the F ring; and Enceladus (505 kilometers, or 314 miles across) at lower left.

Hyugens at Titan •

STRANGE TITAN:

Get ready for two of the strangest hours in the history of space exploration. That's how long it will take the European Space Agency's Huygens probe to parachute to the surface of Saturn's largest moon Titan on January 14 th , 2005 . Huygens will sample Titan's atmosphere, photograph its bizarre terrain, listen for alien sounds and, possibly, splash down in a liquid methane sea.

Surface of Titan

Titan from 10 km

360° Panorama of Titan

Titan’s thick atmosphere • made up of nitrogen and methane • extremely cold -290 degrees Fahrenheit • Scientists believe Titan's atmosphere may be similar to that of the primordial Earth and studying it could provide clues to how life began .

Titan’s Atmosphere

The Night Sky in June • The sun is at its highest -> shortest nights!

• Summer constellations are coming up: Hercules, Scorpius, Ophiuchus (Snake Bearer), Snake  lots of globular star clusters! • Center of the Milky Way in Sagittarius • Jupiter is in the South at sunset

Moon Phases

•

Today

(Waning crescent, 0%) • 6 / 6 (New Moon) • 6 / 14 (First Quarter Moon) • 6 / 22 (Full Moon) • 6/ 28 (Last Quarter Moon)

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

10 PM Typical observing hour, early March • no Moon • Jupiter past meridian • Pluto (experts only) Saturn sets

South West Virgo and Coma with the Virgo Coma galaxy cluster

Virgo Coma Cluster • Lots of galaxies within a few degrees

M87, M88 and M91

Zenith • Big Dipper points to the north pole

South – Canes Venatici – Corona Borealis – Bootes – Serpens Globular Star Clusters: • M 3 • M 5 • M 13 Galaxies: • M 51 • M 101 • M 64 (Bl. Eye) M 5

South East – Hercules – Ophiuchus – Serpens Globular Star Clusters: • M 13 • M 92 • M 12 • M 10 … Summer is Globular Cluster time!

M 5

M13: Globular Cluster

South East – Ophiuchus – Serpens – Scorpius Globular Star Clusters: • M 4 • M 19 • M 62 • M 80 … Summer is Globular Cluster time!

M 5

Summer Break: Mark your Calendars for Fall! • Next Starry Monday at Otterbein: October 3, 2005, 7 pm (this is a Monday ) • Web pages: – – http://www.otterbein.edu/dept/PHYS/weitkamp.asp

http://www.otterbein.edu/dept/PHYS/ (Obs.) (Physics Dept.)

Mark your Calendars II • Physics Coffee is every Wednesday, 3:30 pm • Open to the public, everyone welcome!

• Location: across the hall, Science 256 • Free coffee, cookies, etc.

• Will also return in the Fall!