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PHYS 284 - INTRO TO ASTRONOMY > Lesson 1 > Flashcards

Lesson 1 Flashcards

Know where Earth is in the solar system and where the solar system is in relation to the rest of the universe; to understand the concept of space-time and of the history of the universe

1
Q

Approximately how many stars are there in the Milky Way galaxy?

A

More than 100,000,000,000 (100 billion)

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2
Q

How big is the Milky Way in comparison to the other nearby galaxies?

A

It is the second largest in the local group of about 40 galaxies

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3
Q

What is the name of the Milky Way’s local group?

A

Laniakea

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4
Q

What is the unit of measurement used inside the solar system?

A 
Astronomical units (AU)
1 AU = 150 million km
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5
Q

What is the unit of measurement used outside of the solar system?

A 
Light years (ly)
1 ly = 9.46 trillion km
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6
Q

What is 1 light second equivalent to?

A

300,000 km/second

- 300,000km/s x 60 seconds x 60 minutes x 24 hours x 365 days = 1 light year

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7
Q

How is observing the light from stars like looking into the past?

A

When we say that a star is 2,000 light years away (distance) we mean that the star’s light has taken 2,000 years to reach us, and thus it is like looking 2,000 years into the past

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8
Q

How old is the Universe?

A

Approximately 13.7 billion years old
- this is based on how long it has taken us to see the light from the farthest point in the observable universe (the horizon of the universe)

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9
Q

What is a galaxy?

A

Many stars and planets that orbit a common centre

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10
Q

What is a galaxy cluster?

A

When there are approximately a dozen galaxies in close proximity to one another

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11
Q

What is a supercluster?

A

The regions in which galaxies and galaxy clusters are most tightly packed

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12
Q

What is the definition of the Universe?

A

The sum total of all matter and energy

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13
Q

Describe what the Voyage scale model does?

A

It shrinks the universe to 1:10,000,000,000 its size

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14
Q

What is the formula for distance?

A

D= speed x time

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15
Q

What is nuclear fusion?

A

The process in which light atomic nuclei fuse to make heavier ones

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16
Q

What is Earth’s rotational speed? How do we perceive this?

A

Earth rotates at 1,670km/h at the Equator, approximately 1,100km/h towards the poles and 0km/h at each pole
- each time the earth rotates, we perceive that one day has passed

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17
Q

What is Earth’s orbital speed? How do we perceive this?

A

107,000km/h

- we perceive each orbit around the Sun as one year

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18
Q

What is the ecliptic plane?

A

Earth’s orbital path around the Sun

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19
Q

What angle is the Earth tilted at in reference to its ecliptic plane?

A

Earth’s axis is pointed 23.5 degrees from a line perpendicular to the ecliptic plane; the axis of the North Pole lines up with Polaris (the north star)

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20
Q

How did scientists calculate the age of the universe?

A

By looking at the rate of expansion in the Universe

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21
Q

What are Doppler Shifts?

A

A technique used to calculate the rate of expansion of the universe

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22
Q

Where is our solar system located in the Milky Way galaxy?

A

In the arm of Orion; 27,000 ly from the centre of the Milky Way

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23
Q

What are terrestrial planets? Where are they located? Name them all.

A

These are the planets closest to the Sun and are therefore made up of heavier elements

  • These include Mercury, Venus, Earth and Mars
  • terrestrial planets are made up of iron and silicon (rocky materials)
24
Q

How many planets are there in the solar system?

A

8

25
Q

What are the Jovian planets? What are they made of?

A

The Jovian planets include Saturn, Uranus and Neptune

  • Jovian means “like Jupiter”
  • the Jovian planets are made up of gasses and frozen material
26
Q

When is a planet considered a planet?

A

When a large enough object has a big enough gravitational field as to make other objects move away from it

27
Q

What is the Alpha Centauri system? Where is it located?

A

The Alpha Centauri system is the star system closest to us

  • it contains the stars Proximus Centauri, Alpha Centauri A and Alpha Centauri B
  • Alpha Centauri system is located approximately 270,000 AU from us
28
Q

How far is Mercury from us?

A

0.4 AU (or 40% the distance from the Earth to the Sun)

29
Q

How far away is Venus from us?

A

0.7 AU

30
Q

How far away is Mars from us?

A

1.5 AU

31
Q

How far away is Jupiter from us?

A

5.2 AU

32
Q

How far away is Saturn from us?

A

9.6 AU

33
Q

How far away is Uranus from us?

A

19.2 AU

34
Q

How far away is Neptune from us?

A

30.1 AU

35
Q

What are Jupiter and Saturn both known as?

A

The gas giants

- they are made up mostly of hydrogen and helium

36
Q

What are Uranus and Neptune both known as?

A

The ice giants

- they are made up of water, ammonia and methane

37
Q

Where is the farthest dwarf planet in our solar system located?

A

96.3 AU

38
Q

What is the definition of cosmology?

A

It is the scientific study of the origin, evolution and future of our universe

39
Q

Where is the asteroid belt located?

A

From the Sun to Mars

40
Q

What is the Kuiper Belt? Where is it located?

A

It is a belt of icy objects about 20 times as heavy and 20 times as wide as the asteroid belt

  • the Kuiper Belt is located near Neptune, about 30-50 AU away
  • the Kuiper Belt also contains Pluto
41
Q

Describe the Hubble Law:

A

The speed of recession of a galaxy is proportional to its distance from an observer

42
Q

What is the Oort cloud? Where is it located?

A

The Oort cloud is a collection of smaller icy objects

- these are farther away from us than Pluto

43
Q

What does t=0 describe?

A

The point at which the universe began expanding (i.e. post big bang)

44
Q

What is the diameter of the Milky Way galaxy?

A

Between 6 - 10 billion AU

45
Q

What is the cosmic calendar?

A

The history of the universe, scaled down to a single year

  • 1 second = 438 years
  • 1 hour = 1.58 million years
  • 1 day = 37.8 million years
46
Q

What is the thickness of the Milky Way?

A

Approximately 120 million AU

47
Q

What are the closest stars to Earth?

A

The Alpha Centauri system

48
Q

How can we find the Andromeda galaxy from our observation of the sky?

A

Cassiopeia (the W shaped constellation) lines up at its right side with a star in the constellation Pegasus (at a point near his neck)
- to the right of these two points is the Andromeda galaxy

49
Q

What is the Andromeda galaxy also called?

A

M31

50
Q

What are Hubble’s observations?

A

These observations happen outside of the local group

(1) Almost every galaxy is moving away from us
(2) The farther away the galaxy, the faster they appear to move

51
Q

Where is the Andromeda galaxy located?

A
  1. 5 million light years away
    - the area of the galaxy is 100,000 ly x 100,000 ly, meaning that the light from the far side of the galaxy takes 2.5 million light years + the additional 100,000 light years to reach us (compared to only 2.5 million on the near side)
52
Q

Describe the history of the Universe immediately following the big bang:

A
  1. expansion and cooling of the universe
  2. formation of atoms, stars and planets
  3. stellar nuclear fusion
  4. stars cluster to form galaxies
  5. galaxies form into local groups
  6. large galaxies cluster to form galaxy clusters
53
Q

Describe Earth’s rotation:

A
  • it rotates counter-clockwise
  • Earth rotates from West - East (which makes the Sun appear to rise in the East and set in the West)
  • the axis of the Earth remains constant at 23.5 degrees
54
Q

How often does the Solar System orbit the Milky Way?

A

Once every 230 million years at a speed of 800,000km/h

55
Q

Describe the early astronomer’s ideas about space:

A
  • Aristotle (384 B.C.) said that celestial bodies orbit the Earth
  • Aristarchus of Samos (310 B.C.) presented the first model where the Sun was at the centre with the Earth revolving around it
  • Copernicus (1543) affirmed that the Earth was not at the centre of the Universe
  • Tycho Brahe (1601), Kepler (1630) and Galileo (1642) all supported Copernicus’ theory
  • Isaac Newton (1727) formed the theory of gravity and the laws of motion

PHYS 284 - INTRO TO ASTRONOMY (28 decks)

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