Download A Look at Our Solar System: The Sun, the planets and more

A Look at Our Solar System: The
Sun, the planets and more
by Firdevs Duru
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Uranus and Neptune
Uranus discovered by William Hershel in 1781.
Deviations of the Uranus’ orbit from the simple elliptical orbit lead
to the discovery of Neptune.
John Adams (1845) and Urbain Leverrier (1846) determined the
mass and the orbit of the new planet.
Johanne Galle found the new planet within a few degrees of the
predicted position.
Uranus’ tilt
It’s spin axis is nearly in its orbital plane. Each pole: 42 years
darkness, 42 years sunlight.
Not dramatic temperature differences, due to dense
atmosphere, very far away from the Sun.
Atmospheres
84 % H, 14 % He, 3 % methane on Neptune
84 % H, 14 % He, 2 % methane on Uranus
Ammonia not seen.
Blue color: due to methane
Weather
Few clouds in Uranus’ cold upper
atmosphere
Winds with speeds between 200 to 500
km/s
More atmospheric features are visible
in Neptune than in Uranus.
Due to extra warmth, Neptune’s
stratospheric haze is thinner and cloud
layers are less dense.
Numerous methane clouds
Largest storm: The Great Dark Spot
Interior
Uranus and Neptune have Earth-size cores.
Rocky cores.
85 % of the mass of these two planets is contained in a thick layer
of rock and ice.
Outer envelope is made of H, He, water, methane, ammonia.
Internal energy
Neptune has excess energy as Jupiter.
Uranus does not have the heat flowing out.
Magnetic fields and Magnetospheres
Populated largely by electrons and protons.
Magnetic fields are not aligned with the planets’ rotational axes
and are significantly offset from the planets’ centers.
Could be due to the fact that the fields are generated by currents
within icy fluids far from the centers of the planets.
Rings - Uranus
Ring system of Uranus is
discovered in 1977.
They are dark, narrow, and
widely spaced.
A few tens of meters thick.
Made of carbon mostly.
Large particles.
Rings - Neptune
Neptune surrounded by four dark
rings.
Extremely dark and faint.
First three are narrow, fourth one is
broad and more diffused.
Space between them are filled with
dust.
Made mostly of microscopic
particles.
Triton
4.5 billion km from
the Sun.
Has an icy surface.
Temperature is 37 K.
Very thin nitrogen
atmosphere and solid
and frozen surface
(primarily of water
ice).
Relatively high density
(2050 kg/m3) à
75 % rock and 25 % ice.
In retrograde orbit around
the parent planet. It
spirals slowly inward.
Evidence of internal
activity and resurfacing.
Has plumes.
Trans-Neptunian Objects (TNOs)
Large number of relatively small, icy bodies in the region beyond
Neptune.
Pluto: Percival Lowell tried, Clyde Tombaugh found it.
About 40 AU from the Sun on average. At perihelion, Pluto
crosses Neptune’s orbit.
Has a satellite named Charon (1978), which provided the mass of
the Pluto (just 0.0021 Earth mass) to great accuracy.
Very reflective surface, due to ice material (frozen nitrogen, small
amounts of frozen carbon monoxide and methane).
Pluto: Not a planet anymore!
Defini&on of a planet: •  Orbits a star •  Massive enough for its gravity to give it nearly a round shape •  Has cleared the neighborhood around its orbit Pluto and Eris are dwarf planets! Other TNOs
More than 1200 TNOs are known.
Most of them orbit Kuiper belt (lie between 40 and 50 AU).
Plutoids: Pluto and other dwarf planets (Ceres, Eris) beyond
Neptune.
SMALL SOLAR SYSTEM BODIES
A meteor is a
sudden streak of
light in the sky
caused by friction
between air
molecules in the
Earth’s atmosphere
and incoming piece
of asteroid,
meteoroid or comet.
A given
meteor shower
occurs about
the same date
each year.
Earth crosses
the orbit of the
meteoroids
responsible
for that
shower on the
same date
each year.
Three main kinds:
Stony meteorites:
94%. Most of them
are chondrites. They
contain spheres of
silicate rock.
Iron meteorites: 5%.
Pure alloys of iron
and nickel.
Stony-iron
meteorites: 1%.
Mixtures of silicate
rock and metal.
Asteroids
Asteroeides : like a star.
Asteroids are the multitude of rocky bodies that orbit the
Sun within the planetary system.
Sizes: A few km à 1000 km.
Almost all of them orbit the Sun in the same direction as the
Earth does.
Orbits change in shape and size, but are more eccentric than
the planets.
Location
Most of them are found in the
region known as the asteroid
belt, located between Mars
and Jupiter (between 2.1 and
3.3 AU from the Sun).
Largest are Pallas and Vesta.
They are in the asteroid belt.
Two other groups of asteroids
share Jupiter’s orbit. Known
as Trojan asteroids, located
60° ahead and behind Jupiter.
Most of the asteroids
always remain between
the orbits of Mars and
Jupiter.
There are thousands that
have orbits that cross
Earth’s orbit: They may
have been deflected into
the inner solar system due
to gravitational fields of
Mars and Jupiter.
Comets
Small icy bodies in orbit around the Sun.
They shine by reflected light.
Anatomy
Nucleus: Main frozen solid body. A few km in diameter. Mostly made of frozen water.
Also has frozen CO, CO2 and formaldehyde, with microscopic particles trapped in it.
Coma (halo): A ball of outflowing gas and dust around the nucleus. Tail: can be as big
as 1 AU
Tail
Ion tail (plasma tail): Made of ions and electrons. Blue due to ionized
carbon monoxide.
Dust tail: Broad, diffuse and gently curved. White or yellow. Rich in
microscopic dust particles that reflect sunlight.
Both tails are directed away from the solar wind.
Comet Orbits
Long-period comets: Periods longer than 200
years.
Could go as much as 100000 AU away from the
Sun. Highly elliptical orbits. Orbits exhibit all
inclinations and orientations with respect to the
ecliptic plane, both prograde and retrograde.
The swarm of long-period comets is called the
Oort cloud.
Short-period comets: Periods shorter than 200
years.
Less frequent. Prograde and lie on the ecliptic
plane. Originated in the Kuiper belt. Nearly
circular orbits.
What happens to comets?
On each passage near the Sun, part of the outer dust and ice
layer of the comet is lost.
When all the ice is gone, the nucleus cannot produce a coma or
a tail.
Only the swarm of dust stays, which forms the meteoroids. The
comets with rocky cores become asteroids.