What percentage of all stars in the sky are part of a binary, or multiple, star system?

The brightest star in the night sky, a luminous blue star, is a visual binary called ___

The only way we know to get accurate measurements of stellar masses, is when ___

The shift in wavelength for an observer who is moving relative to the wave source is called ___

Polaris, the North Star, is actually a pentuple star system, composed of ___

Stars that were born in the same multiple star system would likely have similar ___

In an eclipsing binary, when the fainter star blocks the brighter one, we see ___

Stars that get so close together that they touch each other are called ___

A white dwarf that accrues material and suddenly flares into visibility in the sky is called ___

Astronomers think that most stars are born in groups, called ___

Loosely bound collections of dozens or thousands of stars, usually in an irregular shape, are called ___

Who was the first to discover, or at least record, that clusters were composed of many stars?

In an open cluster, the stars all orbit the cluster's ___

What is the typical distance between stars in an open cluster?

Over time, due to gravitational interactions, which stars are "flicked out" of an open cluster?

Approximately how many open clusters have been observed?

Which famous open cluster is located about 500 light years from Earth?

The Pleiades appear as a tightly-packed collection of stars, and a lot of people call them ___

Clusters of hundreds of thousands of stars that form a roughly spherical shape are called ___

How old are most globular clusters?

What kind of elements are found in the old stars found in globular clusters?

The normal stars that are left in a globular cluster are mostly ___

Earth-like planets likely don't form in globular clusters because the stars ___

"Nebula" is Latin for ___

What are nebulae?

Stars, like our Sun, form from nebulae. How long ago did our Sun form?

In an emission nebula, what is the predominant color of the glow from hydrogen?

In an emission nebula, what is the predominant color of the glow from oxygen?

When astronomers talk about dust, they mean tiny grains with a width of about ___

"Polycyclic aromatic hydrocarbons" are better known as ___

When visible light hits interstellar dust, what happens to blue and red light?

The Orion Nebula is lit by four stars located in its heart, collectively called ___

A flattened disk of dense gas and dust surrounding a young newly forming star is called ___

When viewed in the infrared, what is revealed at the center of protoplanetary disks?

Three giant towers of gas and dust in the Eagle Nebula have been called ___

The dark nebula in the constellation Orion that is shaped like a gigantic chess piece is called ___

Our "hometown" is a vast, flat, disk-shaped collection of gas, dust, and stars called ___

How far is it across the Milky Way Galaxy?

How many stars are in the Milky Way Galaxy?

Where are we, Earthlings, located in the Milky Way Galaxy?

How many major spiral arms are in the Milky Way Galaxy?

The elongated, roughly cylindrical bar at the center of our galaxy is composed mostly of ___

The ancient Greeks called the glowing pathway of stars in the sky "galaxius", which means ___

Which astronomer discovered that the glowing cloudy Milky Way was actually made up of stars?

Interstellar dust restricts our view, so the structure of the Milky Way was determined by measuring ___

The spiral arms of our galaxy can best be thought of as ___

How long does our Sun take to orbit the galaxy?

Collisions of nebula in the spiral arms form massive, luminous, hot stars that make the arms appear ___

Our Sun is located just outside one of the smaller arms called ___

What object sits at the very center of our galaxy?

The black hole at the center of our galaxy has a mass of ___

The vast spherical cloud of old stars surrounding the Milky Way is called ___

What is the name of our home galaxy?

In the 1920's, what type of pulsating stars were observed in the spiral nebula M31 in Andromeda?

It was known, for Cepheid variables, that the time it took them to pulse was directly related to their ___

If you can measure the period of Cepheid variables, you can determine how far away they are simply by ___

In the 1920's it was determined that the "Great Andromeda Nebula" was actually ___

We still classify galaxies according to Hubble's original system, based on ___

What type of galaxy is the Milky Way?

What type of galaxy is characterized by a broad, flat, rotating disk of stars, gas and dust, and a central bulge?

What type of galaxy often has a bar of stars extending across the central part of the galaxy?

What type of galaxy is puffy, with no overall structure and populated with older stars?

Current thinking is that elliptical galaxies are the products of ___

Colliding galaxies can glow blue and pink as stars are born and ___

We think most large galaxies, including our own Milky Way, grew to their current bulk by ___

What type of galaxy has a shape that's weird and distorted, essentially all due to collisions?

What type of galaxy tends to be small and are truly shapeless?

The words "elliptical", "irregular" and "peculiar" are used to classify galaxies based on ___

The most powerful energy source in the entire cosmos was dubbed, for short, a ___

Galaxies that emit x-rays and gamma rays were given the generic name ___

Which telescope was first used to search for evidence of black holes at the cores of galaxies?

What appears to be at the heart of every big galaxy we see?

The flat disk of material that swirls around a black hole at ferocious speeds is called ___

In which direction do active galaxies launch beams of matter and energy?

If the poles of an active galaxy are aimed right at us, we see ___

One way to flip a quiescent black hole from a baby to a monster is through ___

Our Milky Way is part of a small knot of a few dozen galaxies that we call ___

Which two galaxies completely overpower the Local Group?

The spectrum of the Andromeda Galaxy is blue-shifted, which means it's ___

Located about 50 million light years away, what is the nearest galaxy cluster to us?

What sits right at the center of many galaxy clusters?

Clusters of galaxies themselves fall into even bigger groups called ___

Superclusters appear to fall along tremendously long, interconnected and intersecting ___

What image, taken in 1995, shows a small grain of the sky filled with thousands of galaxies?