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Astronomy > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

State the 8 planets in order of closest to furthest from the sun

A

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Neptune

Uranus

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2
Q

Explain what the difference between a planet and a dwarf planet is.

A

To be a planet something must:

  1. Be large enough for its gravity to have cleared its own orbit of other debis
  2. Be large enough for its gravitational pull to have fomed it into a spherical shape

Dwarf planets are bodies orbiting the sun that have not managed to fulfil one or both of these criteria

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3
Q

What are the general differences between the orbit of a planet and the orbit of a dwarf planet?

A
  1. Dwarf planets orbits tend to be more eliptical than a planets (higher eccentricity)
  2. Dwarf planets orbits are inclined from the zodiacal plane but the orbits of planets are not.
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4
Q

What is an asteriod?

A

These are small rockty bodies orbiting the sun, mostly between the orbits of Mars and Jupiter

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5
Q

State 5 dwarf planets

A

Pluto

Ceres

Eris

Haumea

Makemake

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6
Q

What is a comet?

Where to comets originate?

A

A comet is a ball of ice and dust that is orbiting the sun in a very eliptical orbit

Short period comets originate in the kuiper belt, long period comets originate in the Oort cloud.

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7
Q

Define a Trans-Neptunian Object (TNO)

A

This is any body that is orbiting the Sun outside of the orbit of Neptune

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8
Q

What is a centaur?

A

A centaur is a body that orbits between the orbits of Jupiter and Neptune and crosses the orbit of at least one other gas giant (Saturn or Uranus)

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9
Q

State the average distance of each of the planets from the sun in Astronomical Units

A

Mercury - 0.38

Venus - 0.72

Earth - 1

Mars - 1.5

Jupiter - 5.2

Saturn - 9.5

Uranus - 19.1

Neptune - 30

This is exactly the same as how many times further away the planet is from the sun compared to us.

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10
Q

Describe the surface of mercury

A

Lots of craters. contains lots of mountains and lava filled basins

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11
Q

Describe the surface of Venus

Explain why Venus is the hottest planet in the solar system

How is the rotation of Venus differnt to Earth

A

It has an atmosphere containing high level sof carbon dioxide and clouds of sulphuric acid and a surface pressure 90x greater than earth.

Venus is the hottest planet becuase the high levels of carbon dioxde traps infrared radiation and stops it from leaving the surface of the planet in an extreme greenhouse effect. This creates a surface temperature of 470oC.

The rotation of Venus is retrograde, this means that it is in the opposite direction to the other planets in the solar system

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12
Q

What are the features of the surface of Mars?

A

It has iron rich rocks that make it red in colour. It has Ice caps that appear in the winter.

Key features:

Valles Marineris - a 450km long valley carved by flowing water

Olympus mons - the highest volcano in the solar system

Dust stoms can happen on the surface

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13
Q

What are the key features of Jupiter

A

It has bands along its surface where the rapid rotation (period of 10 hours) causes very high winds to seperate the atmosphere.

The creat red spot is a gigantic anticyclone whic is 3x the size of Earth

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14
Q

What are the key features of saturn?

A

The planet is less dense than water.

Its atmosphere is homogenous (all the same) and contains no defining features

It has the mos prominent ring system in the universe.

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15
Q

What are the key features of Uranus?

A

It is made of hydrogen, helium, methane and ammonia

It rotates on its side and has an almost featureless surface.

It also has a ring system inclined in the same plane as its rotation (almost 90o to the zodiac)

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16
Q

What are the key features of Neptune?

A

It is made of hydrogen, helium, methane and ammonia.

It has very fast winds and has many surface features including the Great Dark Spot

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17
Q

What are the problems with sending astronauts on a manned mission to another planet

A
  1. Space adaptation sysndrom - Headaches, poor concentration and vomiting due to having no direction that is down
  2. Brittle bones, muscle wasting and anaemia (low levels of red blood cells) - caused by living in zero gravity for prolonged periods of time
  3. Communication delays - messages will take long periods to transfer from the astronauts to the earth, making it hard to get advice in the event of an emergency
  4. Radiation - Leaving the atmosphere and the Van Allen belts means that astronauts will be exposed to high level of radiation that can result in cancer
  5. Psychological problems - due to working the the same peoplein a small cramped environment for months or years.
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18
Q

What are the benefits of sending humans on a space mission instead of sending a space probe?

A
  1. Large levels of media interest - this will attract a lot of funding
  2. Autonomy - Astronauts can make decisions in real time
  3. Complex experiments - Humans can run and perform much more complicated experiments than robots can
  4. Inspiration - will inspire future generations to beome astronauts and astrophysicists, furthering our knowlede of space
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19
Q

What are the Names of Mars’s two moons

How did Mars get its moons?

A

Phobos and Deimos

It captures asteriods in its gravitational field, so they then became moons of mars

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20
Q

Explain why Neptunes moon Triton has a retrograde orbit (orbits in the other dierction to the planets spin)

A

It was captures by Neptune as a result of a collision with Neptune or one of its moons, forcing it to orbit on the opposite direction

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21
Q

What is the similarity between Neptunes moon Proteus and Saturns moon Pheobe

A

They are both dark moons (do not reflect very much light). They are both believed to have been formed in the same place in the solar system and then captured by the two planets.

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22
Q

Which planets have ring systems?

A

Jupiter

Saturn

Neptune

Uranus

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23
Q

What are the typical sizes of rocks or ice crystals in a ring system?

A

A few micrometers (1000ths of a mm) to a few meters across

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24
Q

State some possible causes of ring systems

A

Formed from the debris left over from planet formation

Moons which have been torn apart by gravitational forces

Material ejected from the surface of a planet or moon (e.g. volcano or due to meteorite impact)

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25
Q

State the planets that are inferior planets

Why are they called inferior planets

A

Mercury and Venus

They are called inferior becuase they orbit the sun closer than earth

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26
Q

State the superior planets

Explain why they are called superior planets

A

Mars, Jupiter, Saturn, Uranus, Neptune

They orbit the sun further away than the Earth

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27
Q

What do the tems ‘greatest eastern elongation’ and ‘greatest western elongation’ mean

Why are these times important

A

These are the times when an inferior planet is the furthest from the sun from our perspective (either east or west)

They are important becuase it is the best time for the planet to be viewed from earth, as glare from the sun does not reduce visibility as much

28
Q

What is a transit?

A

This is when an inferior planet can be seen moving across the sun

29
Q

What is an occultation?

A

This is when an inferior planet cannot be seen becuase it is passing behind the sun compared to us (opposite side of the sun to us)

30
Q

What do each of these labels on the diagram mean?

A
  1. Superior planet at conjunction
  2. Superior conjunction
  3. Inferior conjunction
  4. Superior planet at opposition
  5. Greatest eleongation
31
Q

Define the term retrograde motion

Explain why planets seem to moving in retrograde motion

A

This is when a planet appears to move backwards and travel in a loop during its orbit

Planets move at different speeds to us, when we overtake another palent (further away than the sun than us) or get overtaken (by planets nearer to the sun than us) the relative motion makes the planet appear to move back wards for a short time as our viewpoint changes.

32
Q

What is the ion tail of a comet made out of?

Explain why this always points directly away from the sun

A

This is made up of molecules of gas (mostly carbon dioxide) that have melted off of the comet due to the solar wind. The solar wind ionises (gives energy to) the molecules in the tail which then emit it as light.

It always points away from the sun becuase there is no friction in space to make it fly out behind, so the only force is the solar wind pushing it away from the sun.

33
Q

How is the dust tail of a comet formed

A

When the solar wind melts some of the comet, some of the material is too heavy for the solar wind to push away. this creates a tail that trails beind the direction of motion of a comet.

The tail is slightly curved becuase the dust particles are orbiting the sun in an eliptical path.

34
Q

Label each of these parts of a comet.

A
35
Q

Define each of these terms:

Meteoriod

Meteorite

Meteor

A

Meteoroid - a small piece of rocky debris that is orbiting the sun

Meteorite - This is a small rocky body that has passed through the atmosphere of the earth and has landed on the surface of the Earth

Meteor - This is the firery trail that is made when a meteoroid passes through the atmosphere of the Earth and burns up

36
Q

Explain why meteoroids are much smaller than the meteorites that created it

Why do most meteors not become meteoroids

A

As the meteoroid passes through the atmosphere it burns up (creating a meteor). The process of it burning up causes it to loose material, becoming smaller in the process.

Unless the meteoroid is very large, it will completely burn up in the atmosphere and not hit the surface of the Earth.

37
Q

State the name of a meteor of magnitude 3 or lower (brighter)

A

A fireball

38
Q

Describe how a meteor shower is created

A

A meteor shower is created when the Earth passes through the dust tail of a comet, as it passes through the dust the dust falls towards the earth, creating many meteors all apearing to come from the same place

39
Q

What is the radiant of a meteor shower?

How does this allow astronomers to name the showers?

A

The radiant of the meteor shower is the place where all of the meteors appear to originate.

Showers are named by the constellation that the radiant of the shower is located in (e.g. the perseid metor shower has its radiant in perseus)

40
Q

Explain why meteor showers occur at the same time each year, in the same place

A

After a comet has crossed the orbit of the sun the dust trail remans in orbit around the sun for many years. We pass through this dust trail once a year, creating a metor shower at this time.

41
Q

Define the following terms:

  1. Potentially Hazardous Object
  2. Near Earth Object
A
  1. An object in the solar system where its orbit takes it within 0.05AU of the Earth. This is therefore an object that could hit the Earth
  2. An object where its obit take it within 0.3AU of the Earth.
42
Q

How many PHO’s are we aware of

A

1000

43
Q

Explain why Earth has fewer craters on it than other rocky planets and moons

A
  1. Our thick atmosphere causes most meteoroids to completely burn up before hitting us, unlike some moons and planets with thinner or no atmosphere
  2. Weather conditions on the Earth cause erosion which smooths out the sides of the crater and fill in the centre, making it smaller.
44
Q

How large does a meteoroid need to be to be considered large enough to cause a global catastrophe if it collided with the Earth

A

1 kilometer in diameter

45
Q

Which scale is used to describe the likelyhood and severity of collisisions that a near earth object has with Earth

Describe how it works

A

The Torino scale is used to rank the likelyhood of a collision

The higher the number the more likely and more severe it is for a collision to occur. 0-1 means a very unlikely collisision or a collision that would cause no damage

8-10 is a certain collision that will cause- 8 localised damage, 9 regional devestation, 10 worldwide devestation.

46
Q

What is the heliocentric model of the solar system

How devised this model

A

This is a model of the solar system where all of the planets including the Earth orbit the sun. The moons then orbit the planets

It was devised by Nicholas Copernicus in 1953

47
Q

Which type of motion did the heliocentric model effectively explain?

A

The retrograde motion of the planets

48
Q

What is the Geocentric model of the solar system

A

This is a model where all of the planets, the moon and the Sun all orbit around a stationary Earth

49
Q

What were the contributions made by Tycho Brahe and Johannes Keppler

How did this provide evidence for the heliocentric model

A

Tycho Brahe made incredibly detailed observations of the motion of the planets. These observations were then used by Kepler to formulate his laws of planetary motion, which could be used to predict the motion of the planets in the solar system.

The observations were based on the Heliocentric model, the fact that they then predicted the motion accurately proved that the heliocentric model was correct.

50
Q

What is keplers second law?

What does this tell us about the orbit of the planets?

A

Keplers first law states: An imaginary line from a planet to the sun sweeps out equal areas in equal times.

This tells us that when a planet is closer to the sun in it’s elliptical orbit it must be orbiting at a faster speed than when it is orbiting at a further distance from the sun.

51
Q

State Keplers first law

A

The planets move in eliptical orbits with the sun at one focus of the elipse

52
Q

State keplers third law

Example: How do you use it to calculation the radius of orbit of a planet with a orbital period of 1.8 Earth years

A

Keplers third laws states that the radius of orbit in AU cubed is equal to the orbital period in years squared.

T2 = r3

T = Orbital period (yr - years)

r = Average radius of orbit (AU - Astronomical units)

Example calculation:

First calculate T2 = 1.82 = 3.24

As this is also equal to r3

r3 = 3.24

r = 3√3.24

r = 1.48 AU

53
Q

What were the 3 main discoveries that Galileo Galilei made with a telescope that helped to finally prove the Heliocentric model of the solar system

A
  1. The moon contained craters and mountains proving that it was another world
  2. Venus has pases just like the moon, which occur on a timescale of weeks
  3. Jupiter had 4 moons that orbit it, not the earth - Callisto, Europa, Ganymede and Io (the Galilien moons)
54
Q

State the force that holds the planets in their orbits around the sun

Explain how this force is governed by the inverse square law

A

Weight (the effect of gravity)

The inverse square law means that if the distance of a planet from the sun is doubled the force reduces by 4

F changes by n2 where n is the multiple by which the distance has changed.

55
Q

Who discovered Uranus and when was it discovered

A

Uranus was discovered by William Herschel in 1781 using a telescope

56
Q

Who discovered Ceres (a dwarf planet) and when?

A

It was discovered in 1801 by Giuseppe Piazza, who originally thought it was a commet until Gauss and von Zach proved it was a dwarf planet.

57
Q

Describe how discovered Neptune and how it was discovered

A

Two astronomers, John Crouch Adams and Urbain Le Verrier independantly predicted the existence of a planet that was causing the orbit of Uranus to wobble.

It was then found by German astronomers Johann Galle and Heinrich D’arrest in the position prediced by Le Verrier.

58
Q

Who discovered pluto and when was it discovered.

A

Pluto was discovered by Clyde Tombaugh in 1930

59
Q

Define the term exoplanet

A

An exoplanet is a planet orbiting a star other than our sun

The word Exoplanet is short for ‘Extrasolar planet’

60
Q

Describe the 3 methods of discovering exoplanets

A

Astrometry - Very large exoplanets can cause the star they are orbiting to wobble, very precicely measuring the position of the star can detect the wabble that is being caused by the planet

Transit method - when an exoplanet move across the face of the start they are orbiting it can cause the brightness of the star to drop by about 1%. Measuring this change in brightness can prove the existence of the planet

Radial velocity method - the small wabble seen in Astrometry can also be detected by detecting a doppler shift in the wavelength of the light emitted by the star, this can show very small shifts and is very good at finding exoplanets.

61
Q

Describe two theories on how water appeared on earth

A
  1. Hydrogen and oxygen were ejected from volcanoes which then reacted in the air to form water
  2. It was deposited by ice containing comets that collided with the Earth
62
Q

How can we scientifically test if the water on Earth arrived from comets

A

Send a probe to the comet and check to see if the proportion of isotopes of oxygen in the water is the same as the proportion of oxygen isotopes in water on the Earth

63
Q

Explain what the Goldilocks zone (Habitable zone) is and why it is so important for the presence of life on planets

A

The Goldilocks zone is the region around the sun where planets are the correct distance away for liquid water to be present.

Too close to the sun and the water will evaporate into gas, too far away and it will freeze into ice

It is incredibly important becuase liquid water is believed to be the essential ingredient for life to start to form

64
Q

What is the Drake equation?

How many technically advanced species are there in the galaxy?

A

The Drake equation is an equation that predicts the number of intelligent life forms in the galaxy currently in existence that can communicate with us.

There are predicted to be 50,000 species in the galaxy of approximatly our level of technology or above in the galaxy at any one time

65
Q

How are we trying to search for life on other planets?

A
  1. space probes looking for microorganisms living on other planets or moons in the solar system
  2. Analysing the atmosphere of other planets in the solar system to look for gasses such as oxygen and methane that are produced by living organisms
  3. Analysing radio waves to try to detect signals that have been sent out by other intelligent life forms in the Galaxy
66
Q

What are the pros and cons of the search for life on other planets?

A

Pros

Sharing of technology

Trade and improved economics

Greater knowledge of the univers

Cons

Potential for wars

Alien organisms could out comprete terrestreal ones if they were moved to this planet

We would be ‘less special’ as we are not the only intelligent life forms

Astronomy (4 decks)

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