(A) Topic 11 study these Flashcards
What are asteroids between Mars and Jupiter thought to be formed from?
Debris of an old planet or raw materials of a forming planet that failed due to Jupiter’s gravitational influence
Describe the composition of asteroids
Consist of iron, rock and silicate
Name the parts of a comet
Nucleus, coma, ion tail, dust tail
When does a comet form its tails?
As it gets closer to the sun
What are the names of comet tails and how are they formed?
Dust tail: radiation pressure
Ion tail: particles from solar wind hit the comet
What are the differences between the comets two tails?
Dust tail is brighter and more curved, whereas ion tail is more coloured but straighter than the dust tail
What is unusual about the orbit of comets compared to those of planets?
Comets have an inclined orbit: at a higher/lower angle to the elliptical
Explain the position of the Kuiper Belt
Outside Neptune’s orbit. Possibly 100-1000 AU
Explain the position of the Oort cloud
Spherical region 10,000 to 20,000 AU
Explain the type of bodies thought to originate from the Kuiper Belt and Oort Cloud
Kuiper Belt: where large bodies such as Pluto reside temporarily + short period comet origin
Oort cloud: source of long period comets
What is the heliosphere?
Extended feature of the sun’s influence. Bubble surrounding the solar system created by solar wind
What are the three ways a satellite can be formed?
1) Forms in the same space as the planet
2) Captured by the planet
3) Evolves from the debris of the planet
Describe the composition of Gas Giants
Rocky core and the largest have an outer core of liquid metallic hydrogen (larger) or ammonia (smaller)
How were gas giants formed?
Gas from the Sun’s formation travelled further and further, gas giants evolved by accreting more gas
What are meteoroids?
An object in space that will eventually become a meteor. There are two main kinds:
cometary meteoroid: small particles shed by the comet
asteroidal meteoroid: particles fallen off/ chipped off asteroids
What are meteorites?
Meteor which survives entry into the Earth’s atmosphere.
- Most aren’t observed + fall into the ocean
- made of stone or iron with smooth exteriors
What is the difference between elliptic and ecliptic?
Ecliptic: imaginary line between Earth and the Sun
Elliptic: oval shape, rounded like an egg
What are ingress and egress points?
The moment a body starts and ends its transit
How did scientists come up with an accurate measurement of the AU?
By taking multiple observations of the transit of a body and using geometry based on said observations, we can calculate the AU
Why is liquid water important for life?
It is a solvent and allows various chemicals to form
What are the two main theories about the origin of water?
Comets: since the Earth was heavily bombarded by comets, the comets containing large amounts of ice would’ve fed our oceans on impact
Condensation: claims water was part of the Earth’s body when it formed
Why is our eye limited when it comes to naked eye observations?
Due to the size of our pupils
What do telescopes allow us to do?
To see finer details of objects far away such as the moon or planets
What do telescopes contain to help us see far objects?
Lenses or mirrors which are placed at the end of the tube
Compare and contrast convex and concave lenses
Convex lens: enlarge an image + viewed in another convex lens
Concave lens: mirror can capture light and focus it onto a point where it is viewed by a convex lens
Compare and contrast reflectors and refractors
Refractors: uses a convex lens to capture and focus light - glass coated in a film
Reflectors: use a mirror (concave) to capture a focus light - made of glass with an aluminium coating
Describe Galilean refracting telescopes
G uses a concave lens as an eyepiece, fixed focus, and a limited FOV
Describe Keplerian refracting telescopes
K uses a convex lens, is larger or heavier - focusable but photos are inverted
Describe Newtonian reflecting telescopes
N has two mirrors, a concave mirror + another mirror further up the tube at a 45-degree angle
Describe Cassegrain reflecting telescopes
C reflects light onto a secondary mirror as well, which faces the primary mirror + reflects light onto it but focused through a small hole behind the primary
Define aperture
The amount of light a telescope receives, diameter of its objective lens or mirror
Why is the size of the aperture important?
The larger it is, the more light that enters the telescope, making objects brighter and increasing resolution
What is light grasp?
The measure of a telescope’s ability to capture light by its objective element
What is the equation for light grasp?
light grasp is directly proportional to area, which is directly proportional to the diameter of its objective lens squared
What is the field of view?
the circle of sky visible through a telescope’s eyepiece
Define the two types of FoVs
Apparent FoV: when it’s not connected to the telescope
Real FOV: when the eyepiece is attached to the telescope
How do we calculate the real FOV?
apparent FOV/ magnification
What is resolution of a telescope dependant on?
the objective element and proportional to its diameter
What is used to determine the resolution of a telescope?
- wavelength
- diffraction of light
- the quality of the telescope
- contrast
- brightness
- observer’s eyesight
How might astronomers test out angular resolution?
Seeing how closely related objects such as double stars can be separated by arc seconds
How is resolution calculated?
wavelength/ diameter
How is magnification calculated?
focal length of objective lens/ focal length of eyepiece
What does magnification depend on?
Ratio of focal lengths
What is the focal length of a telescope?
How far light travels inside the telescope before it reaches a focus point
How does the focal point of a telescope affect its magnification?
Shorter the focal length, the greater the magnification
Name some of the principal astronomical theories associated with Galileo
- Galilean Moons - Jupiter’s Moons
- Moon’s uneven and rugged surface of mountains and craters
Which is more popular: reflectors or refractors?
Reflectors because:
- lenses suffer from lens sagging and are more expensive
- refractors suffer from chromatic aberration, which makes images blurred and unclear. Reflectors reduce said problem
- Focal length can be increased whilst maintaining a practical, smaller tube
- multiple mirrors reduce the amount of wavelengths absorbed and have less maintainance
What is a fly-by and what are the pros and cons of one?
Sending a probe past bodies in space to find information about the body, eg: Voyagers 1
pro: array of sensors - measure + take images
cons: not all parts of the body can be measured
What is an orbiter and what are the pros and cons of one?
Probe sent to the body and continually orbits it for the duration of its mission eg: Magellan (Venus)
pro: usually can observe the whole body
con: limited information about surface features
What is an impactor and what are the pros and cons of one?
The probe sent to hit the body + usually an accompanying probe will analyse the impact. eg: Temple 1
pro: allows us to find the composition of the body
con: 2 probes are expensive
What is a lander and what are the pros and cons of one?
Craft that can land on another object and explore the surrounding area, eg: Huygens on Titan
pro: can study immediate environment + take precise geological and meteorological readings
con: may have limited capacity
What are ALSEPs?
Apollo Lunar Surface Experiments Package
