STARS, GALAXIES, AND THE UNIVERSE

Flashcards covering constellations, star properties, H-R diagrams, calculating distances, star life cycles, massive star life cycles, black holes, star systems, quasars, Big Bang Theory, evidence, and the future of the universe.

What are constellations?

Groups of stars that form images.

How many constellations are there?

88

What is the Zodiac?

12 constellations found in the same plane as the Earth’s orbit (ecliptic).

What does magnitude measure in relation to a star?

A measure of how bright that star is.

How does the negative number relate to Magnitude?

The larger the negative number, the brighter the star.

What is apparent magnitude?

How bright the star appears to us from Earth.

What is absolute magnitude?

How much light is actually given off by the star.

What does Luminosity measure?

The amount of energy given off by a star.

What does the color (spectral class) of a star indicate?

How hot it is. A blue star is the hottest.

What does the H-R diagram show?

The relationship between star temperature and magnitude.

What percentage of stars, including our Sun, fall into he main Sequence on the H-R diagram?

90%

What is parallax?

The apparent shift in position of an object when viewed from two different positions; used to measure the distance of (closer) stars.

What is a light-year?

A measurement of the distance light travels in one year (about 9.5 trillion km).

How many astronomical units are in one light year?

63,000

How many light years are in one parsec?

3.26

What is nuclear fusion?

The process of hydrogen atoms combining to form a helium atom, converting mass into energy.

What is a nebula?

A cloud of dust and gases (mostly hydrogen) where all stars start out.

What is a protostar?

The dust cloud becomes compacted into a central region, increasing the temperatures.

What element is created last in the core of a main sequence star?

Carbon.

What is a red giant?

When the core of the star is completely made up of helium, a thin shell of hydrogen surrounds the core and continues to fuse, expanding the star.

What is a white dwarf?

The hot core of the star left after fusion stops, which will continue shining as it cools down.

For massive stars, what element is formed last during the fusion process?

Iron.

What is a Nova?

An exploding star due to the core becoming unstable.

What is a neutron star?

A small and extremely dense star caused by the collapse of a star's core.

What are pulsars?

Neutron stars that give off strong beams of energy.

What is a black hole?

A neutron star that is greater than 3 times the mass of our sun.

What is a singularity?

A single point that black holes contract into.

What is the event horizon?

The radius around a black hole whereby anything that comes within that radius will not escape its gravity.

What are binary stars?

Star systems that contain two stars.

What are galaxies?

A system of billions of stars held together by gravity.

What are the 3 main galaxy types?

Elliptical, spiral, and irregular.

What type of galaxy is the Milky way?

Spiral Galaxy

What are quasars?

The brightest objects that emit enormous amounts of radio wave energy found at the edges of the universe.

What does the Big Bang Theory state?

That 10-14 billion years ago a small but very dense mass exploded and sent matter and energy throughout space.

What are the two things that provide evidence of the Big Bang Theory?

Red shifts and background radiation.

What does a red shift indicate?

That something is moving away from us.

What is background radiation?

Radio wave energy left over from the original explosion of the big bang, which can be detected all across the universe.

What are the three possible futures for the universe?

Open universe model, closed model, and flat model.

What is the open universe model?

The expansion is so rapid that it will continue expanding forever.

What is the closed universe model?

Gravity will cause the universe to stop expanding and contract it back in on itself.

What is the flat universe model?

The universe will slowly stop expanding over an infinite amount of time, but will never collapse.