ASTR-1010ASTR-1010Planetary AstronomyPlanetary Astronomy

Day - 31

Size As Viewed From EarthSize As Viewed From Earth

Course AnnouncementsCourse AnnouncementsHomework Chapter 9: Due Wednesday April 13.

Exam 3: Will be returned on Friday.

The last 1st Quarter moon observing nights are:

Tuesday (April 20) & Thursday (April 22)

8:00 pm both nights.

Exam 4 question

Looking for something different?Looking for something different?• ASTR-3005/3006• Observational Astronomy• 1 hr lecture + 1 hr lab• Dr. Buckner• Prereq: Astr 1010 or 1020

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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

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Instruction on the techniques of modern astronomy and use of instrumentation. Hands-on experience at the APSU observatory.

Chapter 9Chapter 9Lecture OutlineLecture Outline

Worlds of Gas and Liquid – Worlds of Gas and Liquid – The Giant PlanetsThe Giant Planets

The Giant PlanetsThe 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 & SaturnJupiter & Saturn

Jupiter: NASA/JPL/University of Arizona

Saturn: NASA and E. Karkoschka (University of Arizona)

Uranus & NeptuneUranus & Neptune

Uranus

Neptune: both images NASA Jet Propulsion Laboratory (NASA-JPL)

Characteristics of the Giant Characteristics of the Giant PlanetsPlanets

• 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 – Cloud Patterns – Jupiter and SaturnJupiter 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 – Cloud Patterns – Uranus and NeptuneUranus 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).

CompositionComposition

• 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 AtmospheresProbing 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 (NH3) at T = 133 K.– Ammonium hydrosulfide (NH4SH) at T = 193 K.

• Strong winds, storms, and jet streams.

Cloud LayersCloud Layers

Winds and StormsWinds 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 SpeedsWind Speeds

Internal HeatInternal 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 The Zones and Belts are convection regionsconvection regions

Jupiter rotates faster at Jupiter rotates faster at the equator than at the the equator than at the

polespolesPolar Rotation Period 9 hr 55 min 41 sec

Equatorial Rotation Period 9 hr 50 min 28 sec