Astronomy > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

Newtons First Law

A

An object at rest, or in motion in a straight line at a constant speed, will remain in
that state unless acted upon by a force.

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2
Q

Newtons Second Law

A

The acceleration of a body due to a force will be in the same direction as the force,
with a magnitude inversely proportional to its mass.

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3
Q

Newtons Third Law

A

For every action, there is an equal and opposite reaction

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4
Q

What causes day and night?

A

Rotation of the Earth on its axis

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5
Q

How does the Sun appear to move in the sky in the course of a day?

A

East to West, because of Earth’s rotation. The stars and planets move in the same
way from

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6
Q

What happens to the Earth in one year?

A

It orbits the Sun, once (also referred to as one complete revolution about the Sun).

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7
Q

Why do we have seasons?

A

The tilt of the Earth’s axis of rotation, with respect to the plane of its orbit around
the Sun (and not because of changing distance from Sun).
The Earth’s tilt is about 23 degrees

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8
Q

How is the Earth’s axis tilted when we have summer in the Northern hemisphere?

A

With the North Pole toward the Sun.

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9
Q

What season is it in the Southern hemisphere when it is summer in the
Northern hemisphere?

A

Winter

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10
Q

When do the seasons begin?

A
  • Winter begins on or about Dec. 21 = in the Northern hemisphere, the
    nights are longer than days
  • Spring begins on or about March 21 = days and nights have equal length
  • Summer begins on or about June 21 = days longer than nights in the North
  • Fall begins on or about Sept. 21 = days and nights have equal length
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10
Q

What is the order of the phases of the Moon?

A

New – Waxing Crescent – First Quarter – Waxing Gibbous – Full –
–Waning Gibbous – Third Quarter – Waning Crescent – New (and repeat…)

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11
Q

What happens to the moon in 1 month?

A

It moves once around the Earth

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12
Q

What causes the phases of the moon?

A

The Sun is lighting up different fractions of the part of the Moon we see from Earth.

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13
Q

When is the full moon visible?

A

Only at night. It transits (is highest in the sky, or overhead) at midnight;
the full moon rises 6 hours earlier (at sunset), and sets 6 hours later (at sunrise)

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14
Q

When is the new moon visible?

A

The new moon is visible during the day. It transits at noon; it rises 6 hours earlier
(at sunrise), and sets 6 hours later (at sunset).

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15
Q

How are the Sun, Earth, and Moon positioned when it is new Moon?

A

in a straight line: Sun — Moon — Earth

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16
Q

How are the Sun, Earth, and Moon positioned when it is full Moon?

A

Sun — Earth — Moon

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17
Q

How are the Sun, Earth, and Moon positioned when it is a lunar eclipse, and what
phase is the Moon in?

A

Sun — Earth — Moon (as in a full Moon).

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17
Q

What is a solar eclipse?

A

The Moon is blocking the Sun’s light, or a location on the Earth’s surface is passing
under the Moon’s shadow

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18
Q

How are the Sun, Earth, and Moon positioned when it is a solar eclipse?

A

Sun — Moon — Earth (as in a new Moon).

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19
Q

How many constellations are there?

A

there are 88 of them, in all (dividing up the total celestial sphere)

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19
Q

Zodiac constellations

A

the 12 (or 13) constellations that lie along the ecliptic.

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19
Q

What is a lunar eclipse?

A

Earth’s shadow passes across the moon

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20
Q

Why do eclipses not occur every month on Earth?

A

The Moon orbits the Earth in a slightly different plane than the Earth orbits the Sun.

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20
ecliptic
the apparent path of the Sun over the course of a year, with respect to the distant stars — also refers to the plane in which the Earth orbits the Sun.
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constellation
large defined areas of the sky (like states in a map of a country) * anything visibly within that region is considered "in" that constellation
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Forms of light from high energy to low energy
gamma ray > X-ray > ultraviolet (UV) > visible > infrared (IR) > microwave > radio
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Bluer Color
high-energy light = high frequency = low / short wavelength = a bluer color
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photon
A "particle of light"
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All forms of radiation travel at what..
The speed of light
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Redder Color
low-energy light = low frequency = high / long wavelength = a redder color
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Wavelengths of radio waves
Meters and Centimeters
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Wavelengths of visible light
Ten-billionth of a meter
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Wavelengths of x-ray
Even smaller
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What kinds of radiation get through the Earth’s atmosphere?
visible and radio (so, to be able to see other kinds of light with a telescope — e.g., infrared, x-ray — you would need to place that telescope in space
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Blackbody Spectrum
Higher temperature = more light in total, and a peak intensity at a shorter wavelength (or at a bluer color)
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continuum spectrum
Light at all wavelengths
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Absorption Spectrum
shows absorption lines — dark lines in the spectrum at certain wavelengths, superimposed on a continuum spectrum — produced by a (less-energetic) gas cloud in front of a light source
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How are absorption lines produced?
An absorption line is produced when the electrons in atoms absorb photons and remove light of specific energies from the spectrum. Then the electons move from a lower to a higher energy level.
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Emission Spectrum
shows emission lines — bright lines at specific wavelengths, in an otherwise empty (dark) spectrum, due to emission of photons from atoms in gas that have electrons in elevated levels (i.e., an "excited" gas)
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How are emission lines produced?
An emission line is produced when electrons jump from higher to lower energy levels, and emit photons of those specific energies.
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Reflecting telescopes
use a mirror to collect and focus light
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Refracting telescopes
Use a lens to collect and focus light
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Important qualities of telescopes:
light-gathering power, angular resolution, and the quality of the instruments. The magnification is not so important.
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light-gathering power:
Telescopes collect light in proportion to the area of their mirrors
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angular resolution
the ability to distinguish or separate two nearby light sources (with good angular resolution)
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magnification
zooms in on a smaller portion of the sky, to see more detail (but also observes a smaller overall area of the sky)
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Telescopes above Earth’s atmosphere are better because
certain kinds of radiation cannot get through atmosphere all the way to the surface (X-ray, gamma-ray, UV, IR) * conditions give clearer images without atmospheric blurring; i.e., better seeing
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Telescopes above Earth’s atmosphere are worse because
It is hard (and expensive) to get a very large light-collecting area launched into space
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Kelpers 1st Law
The planets orbit the Sun in elliptical orbits with the Sun at one focus. These ellipses tend to be nearly circular for the planets in our Solar System.
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Kelper's Second Law
"A line joining a planet and its star sweeps out equal areas during equal intervals of time." Or, a planet's speed is fastest when the planet is closest to the Sun (at a point called perihelion), and slowest when it is farthest away (aphelion).
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Kelper's Third Law
P 2 = a 3 , where P is the orbital period (a planet's year, given as a mulitple of Earth years) and a is the semimajor axis (average distance from Sun, given in AU).
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Mercury
Closest to the sun and smallest planet in our solar system Mercury orbits the sun in about 88 Earth days Grayish color, and numerous craters. Overall it looks a lot like Earth's moon, but does not have prominent maria, the dark "seas," like the Moon does. Temperature is extremely high on day side and extremely low on night side
41
Venus
Closest planet to Earth, second planet from sun and sixth largest in solar system Takes 243 days to orbit the sun Dense atmosphere -- mostly carbon dioxide Bright, yellowish, and cloud-covered (no sharp surface features visible). A clue that this is not a gas giant is that it does not have rings, which all gas giants (aka "Jovian planets") in our Solar System have.
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Earth
The third planet from the sun and the fifth largest in the solar system Only the habitual planet Atmosphere mostly composed of nitrogen and oxygen molecules
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Aurora
caused by solar wind particles that hit atmospheric gas and lead to emission of different colors; they are prominent near the north and south poles
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Plate tectonics
rocky plates on the surface of Earth float on denser but more-fluid rocky material, and move around — leads to continental drift, mountains caused by collisions of plates; plates sliding past each other cause faults, quakes
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Ozone
Three oxygen atoms bonded together Protects the Earth from UV radiation
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Greenhouse Effect
Energy from the Sun heats Earth
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Earth Moon (LUNA)
Grayish and cratered, and with distinctive large dark maria, the remains of old lava flows that covered large patches of its surface.
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terra
light-colored features, heavily-cratered, high peaks; geologically older; highlands uplifted from impacts in early solar system
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Maria
dark-colored, less cratered, valleys; geologically younger; filled by lava 1 to 4 billion years ago
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Regolith
powdery dust and rocky debris that covers the Moon; broken apart by small meteorites hitting moon continuously
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Impact craters
gouged out from explosions, asteroids or comets that hit the moon
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Mars
Fourth planet from the sun and seventh largest in solar system "The Red Planet," Mars is the color of rust. Has whitish ice caps at its poles, many craters, some prominent old volcanoes, some large valleys, but no significant surface water (lakes, oceans, etc.) Has two moons Phobos and Deimos
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Comets
icy and dusty remnants from the formation of the Solar System. They shine by reflecting sunlight rather than producing their own light. When near the Sun, solar wind causes them to form tails that always point away from it. Comets have highly elliptical orbits, spending most of their time far from the Sun and moving slowly across our sky.
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Asteroid (VESTA)
Asteroids are rocky remnants from the formation of the Solar System, mostly found in the Asteroid Belt between Mars and Jupiter. Their orbits are slightly elliptical, and they come in three main types: carbon-rich, metallic, and silicate (stony). Asteroids are visible only by reflected sunlight and do not produce their own light. Some asteroids have orbits that cross Earth’s path, causing meteors when fragments enter our atmosphere. Most are smaller than 1 kilometer, though some are larger, and they appear to move slowly across the sky from Earth’s perspective.
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Meteors
Meteors, or “shooting stars,” are small pieces of Solar System debris that burn up rapidly in Earth’s atmosphere, creating bright streaks across the sky. Most are tiny dust grains moving at very high speeds (up to 100,000 km/h). A fireball is an unusually bright meteor caused by a larger fragment, while a meteorite is a piece that survives entry and lands on Earth. In the early Solar System, asteroid impacts were common; one such massive impact 65 million years ago (the K/T event) helped cause the extinction of the dinosaurs, mainly due to dust and smoke blocking sunlight.
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Jupiter
Fifth planet from the sun and THE LARGEST in the solar system Made mostly of hydrogen and helium gas Has four Galilean moons (Io, Europa, Ganymede, and Callisto Distinctive stormy stripes, cloud bands in different colors (red or brown, to white or even blue-ish). Also has the Great Red Spot, an Earth-sized circular storm in its southern hemisphere.
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Io
the closest; mostly coppery-yellow with black dots, which are active volcanic sites; overall very volcanically active, due to "tidal heating" from Jupiter; low crater density; yellow color from sulfur
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Europa
water-ice surface; no craters — ice movement wiped them out; liquid water ocean below icy crust
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Callisto
the farthest out of the four large Galilean moons; very heavily cratered —many young craters; does not get heated much, and has not changed much since its formation; about the size of the planet Mercury
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Ganymede
largest moon in the Solar System (larger than the planet Mercury); icy crust; has craters so not active now, but cracks show it once was more active
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Saturn
Sixth planet from the sun and second largest in the solar system Gas giant - made up of mostly hydrogen and helium Has special ring system Has more than 50 moons, Titan is the largest.
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Titan
second largest moon in Solar System; very thick nitrogen-rich atmosphere like the young Earth, but perhaps too cold for life.
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Uranus
Seventh planet from the sun and third largest in solar system Very cold and windy Gas giant - mostly hydrogen and helium, but some methane making it greenish-blue Has extreme seasons due to it's tilt Has 27 known moons - MIRANDA
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Miranda
(one of the larger moons): heavily cratered, with weird valleys and cliffs; appearance caused by upwelling of ices
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Neptune
Eighth furthest planet from the sun and fourth largest planet in the solar system Atmosphere - Hydrogen and Helium and methane Deep blue color Has 14 known moods - Triton
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Trition
(largest): thin atmosphere made of nitrogen and methane; rocky composition; reflective icy surface; ice volcanoes with liquid nitrogen, dust, or methane coming out of them
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Pluto
Dwarf planet Didn't follow all the rules to be a planet
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Rules to be a planet
Orbits the sun Hydrostatic equilibrium/nearly round shape Cleared it's orbital neighborhood
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Formation of solar system
Started 4.5 billion years ago Started with gas that collapsed, spinning cloud makes disk Sun forms and lumps in the disk become planets
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Terrestrial Planets
ROCKY PLANETS Mercury, Venus, Earth, Mars
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Jovian Planets (Gas Giants)
Jupiter, Saturn, Uranus, and Neptune
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Kuiper Belt
Disk-shaped region beyond Neptune
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Oort Cloud
Houses long period comets Is out beyond the Kuiper's Belt
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Order of planets
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
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Astronomy
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