ASTR-1010 Planetary Astronomy Day - 31

Size As Viewed From Earth

Course Announcements Homework Chapter 9: Due Wednesday April 13. Exam 3: Will be returned on Friday. The last 1 st Quarter moon observing nights are: Tuesday (April 20) & Thursday (April 22) 8:00 pm both nights. Exam 4 question

Looking for something different? ASTR-3005/3006 Observational Astronomy 1 hr lecture + 1 hr lab Dr. Buckner Prereq: Astr 1010 or 1020 ===================== Constellations and stars of the night sky; setup, align and use various types of telescopes. Hands-on use of APSU observatory. ASTR-3030/3031 Methods & Instrumentation 2 hr lecture + 1 hr lab Dr. Smith Prereq: Phys 2020 or 2120 ===================== Instruction on the techniques of modern astronomy and use of instrumentation. Hands-on experience at the APSU observatory.

Chapter 9 Lecture Outline Worlds of Gas and Liquid – The Giant Planets

The Giant Planets Jupiter and Saturn: mainly hydrogen and helium. Uranus and Neptune: have much more water. All these planets probably have a core of dense materials.

Jupiter & Saturn  Jupiter: NASA/JPL/University of Arizona  Saturn: NASA and E. Karkoschka (University of Arizona)

Uranus & Neptune  Uranus  Neptune: both images NASA Jet Propulsion Laboratory (NASA-JPL)

Characteristics of the Giant Planets Called giant planets because of their mass: from 15 Earth masses (Uranus/Neptune) to 300 (Jupiter). No solid surfaces: we just see the cloud layers in the atmospheres. Rapid rotation. Strong magnetic fields.

Cloud Patterns – Jupiter and Saturn Jupiter Strong dark and light bands. A long-lasting giant storm (Great Red Spot). Many smaller storms. Colors indicate complex chemistry. Saturn Similar to Jupiter, but less pronounced.

Cloud Patterns – Uranus and Neptune Uranus/Neptune Almost featureless as viewed from Earth. More detail seen from spacecraft or infrared observations from the Hubble Space Telescope. Weak banding. Small, scattered bright or dark clouds. Transient large storms (Great Dark Spot on Neptune).

Composition Mainly light elements (hydrogen/helium). Jupiter’s composition like that of the Sun (71% H, 27% He). Biggest difference is the amount of massive elements. Saturn has somewhat more than Jupiter. Uranus/Neptune have larger fraction of massive elements.

Probing the Atmospheres Density, composition, and circulation patterns vary with height. Temperature, pressure increases downward. Different appearance of planets from different heights of cloud layers. Example: Clouds on Jupiter. –Ammonia (NH 3 ) at T = 133 K. –Ammonium hydrosulfide (NH 4 SH) at T = 193 K. Strong winds, storms, and jet streams.

Cloud Layers

Winds and Storms Rapid planetary rotation results in strong Coriolis forces. This imparts a rotation to storms. Most extreme winds are in Saturn’s atmosphere (1650 km/hr). Alternating east/west winds make banded clouds on Jupiter. Circulation pattern differs from planet to planet in ways not understood.

Wind Speeds

Internal Heat All but Uranus have significant internal heat. Jupiter is hotter than it would be just from sunlight. Jupiter radiates about 65% more energy than it receives from the Sun. Heat flows from the hot interior outward. Heat has a big effect on the global circulation patterns.

The Zones and Belts are convection regions

Jupiter rotates faster at the equator than at the poles Polar Rotation Period 9 hr 55 min 41 sec Equatorial Rotation Period 9 hr 50 min 28 sec