Topic Two: Planetary Systems Flashcards
Name the 4 Rocky/Terrestrial Planets:
Mercury, Venus, Earth and Mars
Name the 4 Gas Giants:
Jupiter, Saturn, Uranus, Neptune
What is the definition of a planet?
A planet is a body that:
- Is in orbit around a Star
- Is large enough to be Spherical
- Has cleared its orbit of other objects
Name 6 other types of body in our Solar System except Planets:
Asteroids (minor planets) Comets Centaurs Moons/satellites Dwarf Planets TNOs (Trans Neptunian Objects)
What size are asteroids?
bigger than 10m but smaller than a few hundred kilometres
Where are asteroids usually in our solar system? Name a few.
The Asteroid Belt
Vesta and Pallas
What is the brightest asteroid in the asteroid belt?
Vesta
What can comets be described as? And what do they consist of?
Icy snowballs
Consists of:
Dust, Rock and Ice
What are centaurs?
Half comet, half asteroid.
Where do centaurs orbit?
Between Jupiter and Neptune
Give examples of centaurs:
Chiron, Hidalgo and Absolus
Give examples of Dwarf Planets:
Pluto, Ceres and Eris
What is the IAU?
International Astronomical Union
What were the 2 decisions the IAU made in 2006?
Ceres promoted from Asteroid to dwarf planet
Pluto demoted from planet to dwarf planet
What is 1AU?
Unit of Measurement
Based on distance between Earth and Sun (150 million km)
Describe Mercury:
Closest to the Sun Fastest orbital period Heavily cratered Highlands and lava filled basins Smallest Planet
What is odd about Venus?
It spins backwards (retrograde rotation)
Describe Venus:
Similar Size to Earth Clouds of Sulphuric Acid Atmosphere of mostly Carbon Dioxide Runaway Greenhouse Effect Temperature: 470 degrees Celsius Pressure: 90x Earth's
Describe Mars:
Iron rich rocks (red planet)
450km long water carved canyons
Highest volcano is solar system
What is the Great Red Spot?
The anticyclone weather system greater in size the Earth on Jupiter
How many times bigger than Earth is Jupiter?
11
Describe Jupiter’s equatorial budge:
Dynamic wind system splits atmosphere into belts and zones
Why does Jupiter have an equatorial budge?
Extremely fast rotation (once in only 10hrs)
How long is a Venus day?
243 Earth days
Name some similarities between Uranus and Neptune:
They are both cold Gas Giants
Similar in size
Describe some similarities between Jupiter and Saturn:
Both have ring systems
Both are gas giants
Similar rotational periods
Describe two differences between Jupiter and Saturn:
Saturn has less visible structure to its atmosphere unlike Jupiter, which as the great read spot, red/brown belts and yellow/white zones
Jupiter’s rings aren’t as reflective as Saturn’s
Name some differences between Uranus and Neptune:
Uranus is almost featureless
Uranus spins on its side
Neptune has a Great Dark spot
Neptune has clouds of frozen methane
Name 5 problems Astronauts could face is venturing beyond the moon:
Time
Space adaptation syndrome
Physiological problems
Psychological problems
Communication delays
Radiation risk
Describe Space Adaptation Syndrome:
- No up and no down
- Disorientation
- Headaches
- Vomiting
- Poor concentration
Describe Physiological problems from venturing beyond the moon:
Prolonged zero gravity causes:
- Muscle wasting
- Brittle bones
- Reduced red cell count
Name some advantages of robotic planetary exploration:
- Less expense
- No loss of life
- Safer
Name one advantage of human planetary exploration:
Hype -publicity, etc
Name Mars’ two small moons:
Deimos
Phobos
Why do astronomers believe that Deimos and Phobos are captured Asteroids?
Heavily cratered
Irregular in shape
Densities half that of Mars
Compositions similar to asteroids
Name 3 moons of Neptune:
Triton
Dark Proteus
Nereid
Describe Dark Proteus
Largest irregular moon of the Solar System
Orbits in the plane of Neptune’s equator
Describe Nereid:
Highly eccentric orbit:
- 1 orbit is 1 Earth year
- probably captured Kuiper Belt object
Why do astronomers believe Triton is also a captured body?
Revolves around Neptune in the opposite direction to Neptune’s rotation
Highly inclined orbit
It is thought that Triton’s capture is the result of a collision with Neptune or one of its moons
Name 4 planets that have ring systems:
Saturn
Jupiter
Neptune
Uranus
Why aren’t Jupiter’s rings visible like Saturn’s rings?
Saturn’s rings are made out of highly reflective ice particles
Jupiter’s rings are made out of dark dust
What are the gaps in Saturn’s rings called?
The Cassini Division
Which planets have incomplete rings (arcs)?
Neptune
Uranus
Give 4 theories on the origin of rings:
Debris left over from planet formation
Large impacts between moons
Moons torn apart through tidal gravitational forces
Meteors striking moons creating debris
Are the orbits of planets circular?
No they are elliptical
What is the plain on which the planet’s orbit called?
The ecliptic
What is the Zodiacal band?
Because all the planets orbit on the ecliptic they appear to move through a narrow region of the sky called the Zodiacal band
What are the inferior planets?
Mercury and Venus
What are the Superior Planets?
Mars to Neptune
Where do the inferior planets appear in the sky?
Near the sun
Best observed during sunsets and sunrises
At what time in their orbit is it best for us to see Mercury and Venus?
At their Greatest Elongation
What is an inferior conjunction?
When the angle of elongation is 0
Planets passes between Sun and Earth
May undergo a transit
What is a superior conjunction?
When the angle of elongation is 0
When the planet passes behind the Sun
May undergo an occultation
What is an occultation?
When the planet disappears behind the sun
When are superior planets most favourably placed for observation?
Give two reasons why:
At opposition
Brighter (fully illuminated by sun throughout night) and better resolution (closest to Earth)
Which directions do planets seem to move in the night sky?
From west to east
Explain retrograde motion:
Direct motion of planet seems to stop and move backwards
It is because Planets orbit the sun at different speeds (Angular and Actual)
We therefore see planets from different viewpoints (as we also orbit the sun)
What kind of orbits do comets have?
Highly elliptical
Describe the ion tail of a comet:
Blue coloured
Fluorescence
Ionised carbon monoxide
Ionised by solar wind
What direction does the ion tail point in?
Away from the sun
Describe the dust tail of a comet:
Lighter coloured Broader Curvier Produced by radiation pressures pushing particles out of the nucleus Reflects sunlight
What direction does the gas tail point in?
Away from the path of the comet
Name two categories of comets:
Short period
Long period
Describe short period comets:
<200 years
Originate from Kuiper Belt
Describe long period comets:
Originate from Oort Cloud.
Paths clockwise or anticlockwise.
Orbits highly inclined to the ecliptic.
Originate vast distances from the sun.
What is the Kuiper belt?
Where short period period comets originate
Disc shaped region of icy bodies
Beyond Neptune
30-50 AU from Sun
What is the Oort Cloud?
Where long period comets originate
Spherical region of cometary nuclei
Roughly 50000AU from Sun
What is the difference between a meteoroid and meteorite?
A meteroid is a small rocky irregular lump in the solar system
Meteroids are between micrometres and several meters
When a meteroid enters the earth’s atmosphere it turns into a meteor
If it survives the atmosphere and impacts the grounds is a meteorite.
METEOROID - METEOR - METEORITE
Name three origins of meteroids:
Broken fragments of clodding asteroids
Impacts with the surface of the moon or Mars
The dust tails of comets
How fast can a meteoroids orbit be?
40km/s
What is a meteoroid shower?
A dramatic increase in the number of meteors observed when the Earth passes through a meteoroid stream left by a comet
What causes meteors to appear as light streaks in the sky?
Friction between a meteor and the surrounding air product heat and light
What is a fireball?
Meteors with a bright magnitude of -3 or less
What is the radiant?
A point in the night sky from which meteors appear to diverge from
Describe the classification of meteorites:
Stones, Irons, Stony Iron
How do we name meteor showers?
Named after the constellation in which the radiant is found
Name 4 annual meteor showers and when they occur:
Perseids - in August
Leonids - in January
Geminids - in December
Quadrantids - in January
What is the definition of an NEO?
A near Earth object is an asteroid or comet whose path might bring them closer to Earth than 0.3AU
What is a PHO?
A potentially hazardous object
Comes closer than 0.05AU
Give examples of collisions between astronomical bodies in the solar system:
Craters
Unusual rotations
Giant Impact Hypothesis
Comet Shoemaker-Ievy
Tunguska event (explosion of comet/asteroid in the sky)
Why do we need to monitor PHOs?
Because it could have catastrophic consequences
Especially if the PHO’s are larger than 1km
What is the Torino Scale?
Used to assess asteroid/comet impact predictions
Who was Ptolemy?
First Geocentric Model of the universe
Ancient Greece
Who was Copernicus?
First Heliocentric model of the universe
Who was Kepler?
Tycho’s assistant
Formulated laws of planetary motion
Describe Kepler’s 1st law:
Planets move in elliptical orbit around a Star
Star was at one focus of each ellipse
Describe Kepler’s 2nd Law:
Planets speed is related to distance from Sun
The closer the sun the faster the orbit
Describe Kepler’s 3rd Law:
The orbital period of a planet is directly proportional to its mean distance from the sun
T squared = R cubed
Where T =number of Earth years to orbit the sun
Where R = the average distance from the Sun in AU
Name some of Galileo’s discoveries:
The moon was not spherical
Venus’s phases
Four of Jupiter’s moons
Name the four galilean moons:
Callisto, Europa, Ganymeade and Io
Who was Newton?
Came up with the theory of Gravity
Inverse Square Law
What is the inverse square law?
two objects are inversely proportional to the square of their distance
Distance between two object doubles, force is one quarter of original value
Who discorvered Uranus?
William Herschel in 1781
Mistook Uranus for a star
Tracked the star to find an orbit
Who found Ceres?
Giuseppe Piazza in 1801
Astronomers predicted another planet between Mars and Jupiter
Who found Neptune?
Johann Galle and Henrick D’arrest
Based on a mathematical prediction by Le Verrier
Describe Astrometry:
When stars wobble due to exoplanet’s gravity.
Astronomers monitor stars to see if they wobble, to indicate whether their are exoplanets orbiting
Describe Transit method:
When exoplanets move across the star the brightness is reduced.
Astronomers monitor star’s brightness and observe light curves.
What is a “Hot Jupiter”?
Large planets orbiting at extremely close distances to the parent star
What is the main problem with the current methods used to find exoplanets?
We cannot find rocky, Earth-like exoplanets
What is the Kepler spacecraft?
NASA space observatory, aiming to find earth sized planets in habitable zone
What is the problem with using the Transit method?
We must be in the plane of the exoplanets to detect changes in light
What are the two essential chemical ingredients for life (as we know it)?
Carbon and liquid water
Where is water on earth thought to have come from?
Deposited by ice containing comets striking Earth
What is the habitable zone?
Narrow range of distances from star
Temperature allows liquid water
Goldilocks zone (neither too hot or too cold)
What is the Drake Equation?
The estimated probability of life existing elsewhere in our Galaxy
N = R* Fp Ne Fl Fl Fc L
List some factors considered in the Drake Equation:
Number of stars in our galaxy
Fraction of stars with planetary system s
Number of planets capable of sustaining life
Fraction of life forms that are intelligent
Fraction of these that can and wish to communicate
Fraction of planets lifetime of which such civilisations can live
Where else in our solar system is life most likely?
Mars
Europa (one of Jupiter’s moons)
Name 3 techniques astronomers use to search for signs of life on other planets:
Space probes
Spectral analysis of planetary atmospheres of rocky planets
Analysis of radio waves
Name 2 potential dangers of finding extra-terrestrial life:
Potential Foes
Diseases
