Topic 11: Exploring the Solar System Flashcards
What is refraction?
The bending of light when it passes from one medium to another, for example from air to water or air to glass.
Draw a basic diagram of Galileo’s refracting telescope
How did Kepler improve Galileo’s refracting telescope design?
He swapped the concave lens that Galileo used at the eyepiece with a convex lens.
This meant that rays of light emerging from the eyepiece are converging. This made for a clearer image.
What is meant by the term ‘field of view’?
is the circle of sky visible through the eyepiece
What is meant by the term light-grasp and how is it calculated?
- The amount of light a telescope can take in.
- The light grasp of a telescope is directly proportional to the square of the diameter of the objective element.
How do you calculate the magnification of a telescope?
magnification = objective focal length ÷ eyepiece focal length
How do you calculate the magnification of a telescope?
magnification = objective focal length
What is dispersion?
the splitting of light in to its component colours, as different colours of light have different wavelengths they refract different amounts.
What is chromatic aberration?
Chromatic aberration occurs when a lens fails to focus the different wavelengths of light at the same point making the image blurry and unclear.
Only a problem with refracting telescopes.
Give 3 advantages of reflecting telescopes.
- larger objective apertures
- mirrors reflect light with almost no loss of intensity, unlike lenses
- don’t suffer from chromatic aberration
- tend to be smaller in size and therefore more practical to use
What is the basic difference between a refracting and reflecting telescope?
- Refracting telescopes use a convex (converging) lens to capture and focus light.
- Reflecting telescopes use a parabolic concave (mirror) to capture and focus light.
Describe how an optical telescope works.
- The objective element collects as much light as possible and focuses the light to a small bright image.
- The image is the magnified by an eyepiece lens so that the astronomical object can be observed in much more detail (higher resolution) and brighter than when looking with the naked eye.
What is meant by a telescope’s size or aperture?
The diameter of the telescopes objective lens or mirror
Give 2 advantages of having a telescope with a larger aperture.
- more light enters the telescope, making the images brighter
- you get ‘sharper’ images, higher resolution images
Why is the human eye a poor tool for astronomical observations?
The human eye has a small aperture so it does not let in very much light so it is bad at seeing dim objects.
Draw a diagram of the objective lens of a refracting telescope.
A curved lens, it focuses light to an image at the focal point. See diagram
Explain the position of the eye piece in a refracting telescope.
The eye piece needs to be after the focal point.
The light rays diverge at the focal point before hitting the eye piece and becoming parallel again before entering the eye
Draw a diagram of a concave mirror, label the focal point and focal length
F is the focal point (ignore the c)
Draw a diagram of a reflecting telescope and explain where the position of the eyepiece needs to be.
The eyepiece is on top of this Newtonian reflecting telescope.
Where the light rays converge.
Which can support a bigger aperture; a refracting or reflecting telescope?
A reflecting telescope because the objective lens is at the back end of the telescope giving it a lower centre of mass. This makes the telescope more stable and able to support a bigger aperture.
Mirrors are also cheaper and easier to manufacture than lenses.
A student has 2 telescopes of the same size and tube length. One telescope is a reflector and the other is a refractor. The student say ‘ the reflector has a longer focal length than the refractor.’ Is the student correct? Explain your answer
Correct because a reflector has more mirrors. The more mirrors you add the greater the focal length.
What benefit does having multiple mirrors in a reflecting telescope have?
More mirrors = greater focal length
greater focal length of the objective = greater magnification
Give 4 disadvantages of refracting telescopes.
- Lenses absorb light making images dimmer
- Lenses do not refract different wavelengths of light to the exact point (chromatic aberration), causing images to be blurry
- Lenses can sag under their own weight, altering their shape and causing distorted images
- It is also difficult to manufacture clear glass lenses that have no blemishes
Explain why bigger is better when it comes to telescopes
- brighter the image
- shorter time needed to collect data from the astronomical object
- better resolution (ability to see fine detail in the image)
What is the approximate diameter of the pupil of the human eye in bright light?
3mm
Which photoreceptors in the human eye respond to bright lights?
cones
What is the name of the naked eye observing technique in which an observer first spends about 30 minutes outside to allow the retina’s rods to desensitise.
Dark adaptation
Which part of the human eye allows light to enter?
pupil
Describe the composition of the Earth’s atmosphere
Thick
78% nitrogen
21% oxygen
1% other gases including CO2, argon, water vapour
What is the mean distance from the Earth to the Sun?
150 million km or 1 astronomical unit (AU)
Why is there life on Earth?
Because it lies in the Goldilock’s Zone of the solar system. The Goldilock’s Zone is a habitable zone just the right distance from a ‘sun’
What colour is Mars and why?
Mar is an orange/red colour because of the iron oxide (rust) on its surface
What is the significance of the colour of Mars?
For rust to form you need iron, water and oxygen. This tells us that at some point in Mars’ past there was a lot of flowing water
Describe Mars’ atmosphere
thin
mainly carbon dioxide (CO2)
Name the moons of Mars
Deimos
Phobos
Give 2 facts about the moons of Mars
Thought to be captured asteroids
Phobos is getting closer and closer to Mars
What is Ceres?
Dwarf planet in the asteroid belt between the orbits of Mars and Jupiter.
What are the 3 conditions for something to be classed as a planet?
- must orbit the Sun independently
- must be in hydrostatic equilibrium - must form a sphere under its own gravity
- must have cleared its orbital path of smaller debris (unless the debris is at a Lagrange point)
Describe Jupiter’s atmosphere
primarily hydrogen
small amount of helium
Give 3 facts about Jupiter
- thought to be entirely a gas planet
- may have a solid core
- key feature is Great Red Spot
How many moons does Jupiter have?
79
What are the 4 biggest moons of Jupiter called?
The Galilean moons:
Io, Europa, Ganymede, Callisto
What is the Great Red Spot?
A storm on the surface of Jupiter.
Longest storm in the Solar System - has been raging for 100s of years
Where is the asteroid belt located?
Between the orbits of Mars and Jupiter
How many planets are there in our Solar System?
Name them in order…
8
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
How are the planets sometimes divided?
4 terrestrial planets: Mercury, Venus, Earth and Mars
4 Gas Giants: Jupiter, Saturn, Uranus and Neptune
Main characteristics of the terrestrial planets
- relatively small
- rock surrounding an iron core
Main characteristics (4) of the gas giants
- liquid interiors
- substantial atmospheres of hydrogen & helium with traces of methane &ammonia
- Accompanied by complex ring systems
- large number of moons
How is a dwarf planet different to a true planet?
Dwarf planets have sufficient mass to be spherical, but lack the gravitational force needed to sweep their orbits clear of other debris. (*with the exception of Ceres)
Where are most dwarf planets found?
Most dwarf planets inhabit the cold outer limits of the Solar System; known as the Kuiper Belt.
Name 3 notable dwarf planets.
- Pluto
- Eris
- Makemake
What are Small Solar System Objects (SSSO)?
Asteroids
Meteoriods
Comets
What are asteroids?
Small, irregular rocky objects
diameter roughly between 10m and 1000km
mostly reside in the doughnut shaped main asteroid belt
What are meteoroids?
- particles of dust,
- larger grit-sized chunks of rock
- boulder-sized mixtures of stone, ice and metal
- they can be classified as either iron, stony, or stony-iron
- orbit the sun
What are comets?
mixtures of compacted dust, rock and ice
mainly found in the outer regions of the solar system
can be classified as ‘short period comets’ or ‘long period comets’
4 facts about ‘short period’ comets
- have orbital periods of less than 200 years
- tend to ‘hug’ the plane of the solar system
- thought to originate in the Kuiper belt (from where the gravitational influence of Neptune might have nudged some into elliptical solar orbits)
- A subset have an orbital period of less than 20 years and do not venture much further away from the sun than Jupiter
Facts about ‘Long Period’ Comets
- Have orbital periods of greater than 200 years
- Originate in the Oort Cloud
- unpredictable orbits - some highly inclined to the plane of the solar system and others orbiting in the opposite sense to that of the planets.
What is the Oort Cloud?
A spherical distribution of icy bodies about half of the way to the nearest star.
What happens as a comet approaches the Sun?
- a coma of thin gases and dust envelopes the small nucleus (about 10km) of rock and ice
- eventually one or more tails develops and that can be several million kilometres long.
- as the comets rounds and begins to move away from the Sun the tails become less visible
- eventually the comet, no depleted of some of its content) ceases to be influenced by the solar radiation, it fades from view
- returns to the outer Solar System
2 facts about comet tails
- The Sun is primarily responsible for the formation of comet tails
- comets tails generally point away from the Sun
Describe a comet’s ion tail
- long
- straight
- predominantly blue in colour
- consists of charged atoms (ions) that have been excited by the particles in the solar wind
- the emit light by fluorescence when then de-excite
Describe a comets dust tail
- broad
- curved
- produced by solar radiation pressure that pushes particles out of the comet’s nucleus (these particles reflect sunlight making the tail visible)
- curve is due to the individual grains of dust following their own independent solar orbits, having been ‘freed’ from the comet
Water is an essential ingredient for life, but what is its origin?
Scientists have long argued about the origin of water on Earth.
One theory is that water was produced by the outgassing of hydrogen and oxygen from primordial volcanoes
An alternative theory is that it was deposited here by the impacts with comets and/or giant asteroids.
What happens when a meteoroid enters the Earth’s atmosphere?
- Speed range usually 20-70 km/s
- air resistance turns kinetic energy in to thermal energy
- which heats smaller particles to incandescence resulting in a streak of light visible in the night sky.
- These are known as ‘shooting stars’ or meteors
What is a meteor shower?
A meteor shower occurs when the Earth passes through a dusty meteoroid stream in the wake of a comet, this means many more meteors are visible at one time.
*During a meteor shower, individual meteors appear to diverge from the same vanishing point, called the radiant. This is simply due to perspective.
The meteor shower is named after the constellation in which the radiant lies.
What are larger meteoroids called and what happens when they enter the Earth’s atmosphere?
- Larger meteoroids produce very bright meteors called fireballs.
- They survive their journey through the Earth’s atmosphere, when they have reached the Earth’s surface they are known as meteorites.
Name 3 famous meteor showers
- The Perseids (every year in mid-August)
- The Geminids (in November)
- The Quadrantids (in January)
What unit are distances within the solar system measured in?
Astronomical Units (AU)
1 AU = 150 million km (1.5 x 108 km)
What are the inferior planets?
Mercury and Venus
Because their orbits are closer to the Sun than that of the Earth
What are the superior planets?
Those planets with orbits further from the Sun than Earth
How did Halley use the transit of Venus to determine the size of the astronomical unit and thus the size of the Solar System?
- On rare occasion, one of the inferior planets crosses the solar disc, an event called a transit. Halley took advantage of the transit of Venus in 1761 and 1769.
- It is known that the observed paths (Halley called them chords) taken by Venus would vary from place to place because of parallax.
- Halley used geometry to show that the angle between two chords could be calculated from the difference in their lengths; this in turn could be found by the difference between the times taken for Venus to cross the solar disc.
- Halley showed that if the latitude distance between the 2 observing locations was known, simple triangulation could then be used to calculate the distance from the Earth to Venus, and therefore from the Earth to the Sun.
- In 1716, Halley urged astronomers to travel to different latitudes to observe and time the forthcoming transit of Venus in 1761 and 1769.
- The request was taken up by the global scientific community, eventually allowing the astronomical unit to be determined to within 2.5% of its modern day value.
What are the four main types of space probes?
- fly-by
- orbiters
- impactors
- landers
Describe a fly-by space probe and give examples of fly-by probe missions
Where the space probe explores many targets.
- Voyager I and II - visited outer planets
- New Horizons - explored Pluto and outer Solar System
Give examples of orbiter space probe missions
- Magellan probe - mapped Venus using radar
- Dawn probe - made detailed studies of asteroids Ceres and Vesta
- Juno probe - measured Jupiter’s composition and magnetosphere
Give examples of impactor space probe missions
- Saturn V rockets were impacted onto the lunar surface to cause artificial moonquakes during its third stage
- Deep Impact Probe - impacted on Comet Temple 1 to study the internal composition of a comet
Describe the purpose soft lander space probes and give examples
Where the impact is controlled and the probe touches down intact on the surface
- Huygens - landed on Saturn’s moon Titan
- the Spirit and Opportunity rovers were landed on Mars and Philae
Mercury
Venus
