Astronomy 311 midterm 1

Jovian Planets

almost entirely gas(no fusion) Jupiter, Saturn, Uranus, Neptune.

Terrestrial planets

rocky surfaces, maybe an atmosphere. Mercury, Mars, Earth, Venus

During a year how many different constellations does the Sun pass through? What term describes the path of the Sun through the celestial sphere?

13 Constellations. The ecliptic is an imaginary line on the sky that marks the annual path of the sun.

What is a Zodiac constellation? How many Zodiac constellations are there?

13.

When we look at two galaxies, one that is 5 billion light years away and one that is 10 billion light years away, which one APPEARS younger?

5 billion light years

Which one, if either, actually IS younger? Explain.

5 billion light years. It take 5 billion years to be able to see it as it did 5 billion years ago.

When we look at a galaxy 5 billion light years away we see it as it looked _____________ years ago. This is (younger, older, the same as) it looks now.

5 billion years ago. It's younger than it looks now.

To describe where a star is, you need to give both a direction and altitude. What is the direction and altitude of: a star at the zenith?

90, directly overhead

comet

A ball of frozen dust and rock that orbits the sun, or a star, and has a tail that glows

Galaxy

A huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.

nebula

A large cloud of dust and gas in space

Star

A large, glowing ball of gas that generates heat and light through nuclear fusion in its core. our Sun is a Star!

Define the term Light-Year?

A unit of astronomical distance equivalent to the distance that light travels in one year, which is about 10 trillion kilometers. Light-years are used to describe the distances of stars and galaxies.

Altitude

Above the horizon.

Which is the closes star to us, other than the Sun?

Alpha Centauri

Describe how stars would appear to move in the sky if you are living at the North Pole.

At the North Pole, the stars circle the zenith and do not rise and set.

What galaxy are we in? What group? What supercluster?

Milky Way Galaxy, the Local Group, Local Supercluster

Moon

Natural/satellite object that orbits a planet. smaller rocky or icy.

Out of the following groups, which is the largest and which is the smallest? Radius of the Sun, Radius of the Galaxy, Radius of the Earth.

Radius of the Galaxy, Radius of the Sun, Radius of the Earth.

What is the rough direction in the sky where you'll find a star when it is rising? Setting?

Rising: East Setting: West

Which distance is larger: the distance to the closest star or the size of our galaxy?

Size of our galaxy.

asteroid

Small rocky bit, too small for gravity to make into a sphere. Orbits a star.

Circumpolar Stars

Stars near the north celestial pole.

Rise

Stars rise in the East.

Set

Stars set in the West.

Describe how to find Polaris in the sky from Los Angeles. What direction do you look?

Zenith.

Out of the following groups, which is the largest and which is the smallest? 1 light year, 1 astronomical unit, distance from Earth to the Moon.

1 light year (distance light travels in one year), Astronomical unit (earth's average distance from the sun), distance from Earth to Moon.

If the Sun all of a sudden stopped giving off light, when would we notice it?

Because light from the Sun takes eight and a half minutes to reach Earth, we wouldn't notice immediately if the Sun suddenly went out. Without the Sun's warmth, Earth would quickly become a much colder place. Fortunately, Earth retains heat fairly well, so humans wouldn't freeze instantly.

If the universe is 14 billion years old, why can't we see a galaxy 15 billion light years away?

Because looking 15 billion light-years away means looking to a time before the universe existed.

Out of the following groups, which is the largest and which is the smallest? Distance from the Sun, Distance to the Moon, and Distance to the nearest Star.

Distance to the Sun, distance to the nearest star, distance to the Moon.

Planet

Doesn't create their own light. They reflect light which makes them visible. Not fusing hydrogen in the core. Orbits a star, large enough to make its own gravity to make it round, and has cleared objects from its orbital path.

Astronomical Unit

Earth's average distance from the Sun, which is approximately 150 million kilometers. We commonly describe distances within our solar system.

Describe briefly why we have the seasons.

Earth's tilted axis causes the seasons. Throughout the year, different parts of Earth receive the Sun's most direct rays. So, when the North Pole tilts toward the Sun, it's summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it's winter in the Northern Hemisphere.

Put these sizes in order from smallest to the largest: Size of the Earth, Size of a galaxy cluster, Size of a galaxy supercluster, Size of the Sun, Size of the Milky Way, Size of the solar system.

Earth, Sun, Solar System, Milky Way, galaxy cluster, galaxy supercluster

During what season do the Sun's rays hit the Earth most directly?

Equinox

T/F: All stars pass through the Zenith each day?

False ?

Explain why different constellations are visible at different times of the year.

If you look at the night sky different times of the year you see different constellations. This change is due to the motion of the Earth in its orbit around the Sun.

Celestial Equator

Is a projection of Earth's equator into space, makes a complete circle around the celestial sphere.

What is a constellation? How many constellations are there? How are they used by astronomers today?

Is a region of the sky with well-defined borders; the familiar patterns of stars merely help us locate these constellations. There are 88 constellations!

Meridian

Is an imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon.

Elliptic

Is the path the Sun follows as it appears to circle around the celestial sphere once each year. It crosses the celestial equator at 23 1/2 angle, because that is the tilt of the Earth.

Celestial North Pole

Is the point directly over the Earth's North Pole.

Celestial South Pole

Is the point directly over the Earth's South Pole.

Universe

Sum total of all matter and energy encompassing the superclusters and voids and everything within them.

Solar (Star) System

The Sun and all its materials that orbits it, including planets and dwarf planets.

Horizon

The boundary between earth and sky.

What two points on the celestial sphere do not move in the sky? What two locations on Earth could you be in to find one of these points directly overhead?

The north and south celestial pole...

Explain how the signs of the zodiac are related to the Sun's path through the celestial sphere. Are the dates of the zodiac accurate now? Explain

The signs are derived from the constellations that mark out the path on which the sun appears to travel over the course of a year. the dates are no longer accurate.

What is special about the speed of light?

The speed of light is a physical constant of our universe. The speed of light travels 300,000 kilometers per second. Speed of light is special because it can help us calculate distances of other stars.

Zenith

the point directly overhead.