Earth and Space: Astronomy Flashcards

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1
Q

What does HR stand for in the HR diagram?

A

Hertzsprung-Russell

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2
Q

What two values does the HR diagram compare?

A

Luminosity and temperature

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3
Q

A star that is very bright and hot would be found in what part of the HR diagram?

A

Upper left corner (main sequence)

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4
Q

A star that is dim and somewhat hot would be found in what part of the HR diagram?

A

Bottom left corner (white dwarves)

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5
Q

A star that is very bright and cool would be found in what part of the HR diagram?

A

Upper right corner (supergiants and giants)

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6
Q

A star that is dim and cool would be found in what part of the HR diagram?

A

Bottom right corner (main sequence)

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7
Q

Most stars are classified under what system?

A

Morgan-Keenan system (MK)

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8
Q

The Morgan-Keenan system classifies stars by letters and numbers, which are?

A

O, B, A, F, G, K, M (O being hottest and M being coolest).

0 - 9 (0 being hottest and 9 being coolest).

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9
Q

In the MK system, Roman numerals indicate what?

A

Luminosity

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10
Q

Our sun has the spectral classification of what?

A

G2V

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11
Q

Several new classifications have been added to the MK system. What are some of these?

A

Class L (very red dwarf), Class T (brown dwarfs with methane in their emission spectra), Class Y (brown dwarfs with ammonia in their emission spectra), Class C (carbon star).

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12
Q

What is found on the y-axis of the HR diagram?

A

Luminosity

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13
Q

What is found on the x-axis of the HR diagram?

A

Temperature

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14
Q

What are Kepler’s three laws of planetary motion?

A
  1. All planets move around the sun in elliptical orbits, with the sun as one of the foci.
  2. A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time.
  3. The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun.
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15
Q

What is the brightest constellation?

A

Crux (or The Southern Cross)

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16
Q

Which constellation has the largest number of visible stars?

A

Centaurus

17
Q

The Big Dipper and the Little Dipper are not constellations; they are _________.

A

Asterisms (groups of stars within a constellation, in this case Ursa Major and Ursa Minor).

18
Q

The brightest star in the sky is _________, found in the ________ constellation.

A

Sirius, Canis Major

19
Q

What northern constellation appears to circle Polaris and straddle the Milky Way?

A

Cassiopeia

20
Q

Which northern constellation named after a famous Greek king never dips below the horizon (circumpolar)?

A

Cepheus

21
Q

Which southern constellation is found on Australia’s flag and surrounded by Centaurus on three sides?

A

Crux (The Southern Cross)

22
Q

What is the scientific name for The Swan northern constellation?

A

Cygnus. Also colloquially referred to as The Northern Cross.

23
Q

The stars Castor and Pollux are found in what constellation?

A

Gemini.

24
Q

The twelve Zodiac constellations are unique how?

A

They are located on the ecliptic.

25
Q

What constellation contains Vega, the 5th brightest star in the sky?

A

Lyra (The Lyre) (northern constellation).

26
Q

The three brightest stars in the northern constellation Orion are what?

A

Rigel, Betelgeuse, and Bellatrix. Betelgeuse is the left shoulder, Bellatrix is the right shoulder, and Rigel is his right foot.

27
Q

What is a Barlow Lens?

A

A lens that’s placed into the focusing tube to effectively double or triple a telescope’s focal length and, in turn, the magnification of any eyepiece used with it.

28
Q

Describe a compound telescope.

A

A telescope with a mirror in the back and a lens in the front.

29
Q

A system of two stars orbiting each other is called a what?

A

Binary star

30
Q

Define declination.

A

The celestial equivalent of latitude, denoting how far (in degrees) an object in the sky lies north or south of the celestial equator.

31
Q

What is the ecliptic?

A

The path among the stars traced by the Sun throughout the year. The Moon and planets never stray far from the ecliptic.

32
Q

Define inclination.

A

The angle between the plane of an orbit and a reference plane. For example, NASA satellites typically have orbits inclined 28° to Earth’s equator.

33
Q

The Moon tips slightly from week to week, caused by the Moon’s inclination and elliptical shape of orbit. This phenomenon is called what?

A

Libration

34
Q

What is an occultation?

A

The moon or a planet passing in front of a more distant planet or star.

35
Q

What is The Terminator?

A

The dividing line between dark and light sides of the Moon. (Disappointing answer, but it’s true.)