Announcements. Students with last names starting from A to K go to the Planetarium right now L to Z – Thursday (11:00 a.m.). 1- 3 March: Brooks Observatory tours 7:30-8:30 p.m. – extra credit Bring back your ticket with your name on the back. March 2-18.
Students with last names starting from A to K go to the Planetarium right now
L to Z – Thursday (11:00 a.m.)
1- 3 March: Brooks Observatory tours 7:30-8:30 p.m. – extra credit
Bring back your ticket with your name on the back
Instructor: Anatoly Miroshnichenko
The lecture notes are available from:
Seasons on Uranus
Density and size – Jovian planets have very low densities and similar radii
The smallest stars are even smaller in radius than Jupiter, but ~80 times more massive
Uranus and Neptune have higher densities and a different chemical composition (hydrogen compounds and rocks and less pure H and He)
No solid surfaces
Content: Almost entirely H and He + trace amounts of methane (CH4), ammonia (NH3), and H20.
Jupiter’s weather occurs in troposphere where clouds can be formed of ammonia crystals and other compounds
Wind is driven by the planet’s rotation.
Jupiter’s rotation is so fast that the atmosphere breaks up into many swirling bands.
The bands of rising air are called zones
The adjacent bands of falling air are called belts
Belts and Zones on Jupiter
Great Red Spot is the most dramatic weather pattern in the Solar system (size of 2 Earths)
Different colors are due to trace gases or colored compounds, produced by chemical reactions
Saturn has almost the same color as Jupiter
Uranus and Neptune are blue (due to methane which absorbs red light and transmits blue)
Saturn has belts and zones
Neptune has bands and a high-pressure storm Great Dark Spot
Uranus has slowly changing weather
Magnetosphere consists of planet’s magnetic field and particles trapped within them.
Jupiter’s magnetic field is 20,000 times stronger than Earth’s. It deflects solar wind at 40 Jupiter radii (3 million km).
The charged particles from Jupiter’s magnetosphere bombard surfaces of Jupiter’s moons which leads to release of their atmospheric gases
There are more than 100 known moons orbiting Jovian planets (J-52, S-30, U-21, N-11)
Three main groups of jovian moons:
Small moons - less than 300 km in diameter
Medium-size - 300-1500 km
Large - more than 1500 km
Medium and large moons have circular orbits that lie close to the equatorial planes of their parent planets
Pre-visit expectations: cold and geologically dead
Voyager missions: the moons are active!
Four Galilean moons: Io, Europa, Ganymede, Callisto
Io has many volcanoes and no impact craters
Europa – no craters, fractured surface, icebergs
Ganymede – grooves on surface, magnetic field
Callisto – a heavily cratered iceball
Eruptions erased all Io’s impact craters.
Io has an additional heating source – tidal heating
Tidal heating is due to the Io’s orbit ellipticity.
Io is continuously flexed by Jupiter.
Source of the orbit ellipticity – orbital resonances
Periodical lining up of the three closest satellites of Jupiter (Io – 4 orbits, Europa – 2 orbits, Ganymede – 1 orbit)
Visible icebergs suggest the presence of an ocean below the surface.
Latest news: the ocean may be made of acids
Two of Saturn’s rings can be seen from Earth
In fact, there are as high as 100,000 individual rings and gaps
Rings and gaps are caused by grouping of particles at some orbital distances which are being forced out at others.
Gaps can be created by gap moons located within rings. They clear up gaps around their orbits.
These rings are much fainter than that of Saturn and were discovered after 1977.
The rings of Uranus and Neptune were discovered during a stellar occultation.
Rings are similar to each other. They lie in their planet’s equatorial plane, particle orbits are almost circular, gaps are due to gap moons.
Saturn’s rings have larger size, higher reflectivity, and greater number of particles.
Ring particles may not last very long.
They are ground into dust in a few million years.
It should be a source of new ring particles.
The most likely one is collisions of small moons and impacts between meteorites and small moons.
In the beginning, there were many more moons around jovian planets. Gradual dismantling of the moons created the ring systems.
Jovian planets are dynamic worlds with rapid winds, huge storms, strong magnetic fields, and interiors where common materials strangely behave.
Jovian moons are geologically active because of their ice compositions.
Ring systems were formed from small moons.
Study of jovian planets brought new concepts of ice geology, tidal heating, and orbital resonances.