An undated handout image made available by European Southern Observatory in September 2013 showing the ESO 3.6-meter telescope at La Silla, Chile, during observations. (European Pressphoto Agency)

By now you’ve been inundated with stories, analyses, maps, illustrations, tweets and other messages about the Great American Eclipse on Aug. 21.

You have likely learned that on that day, the moon will pass between the sun and Earth, and all of North America will see an eclipse of the sun.

Those in the “path of totality” will see a total solar eclipse, when the moon covers the sun and all that can be seen is the sun’s corona, or atmosphere, while those outside the path of totality will see the moon cover part of the sun. Of course, the sun is 400 times wider than the moon, but it is also 400 times farther away, so they will appear the same size in the sky.

But how much do you remember learning about other things astronomical? Here’s a chance to test your astronomy smart. The questions are first, followed by all of the answers with plenty of interesting details from NASA and other sources.

1) On July 20, 1969, two astronauts landed the Eagle lunar module on the surface of the moon, the first time human beings had made it there. What were the first human words spoken after the Eagle made contact with the surface?

a) “Houston, Tranquility Base here. The Eagle has landed.”
b) “Contact light.”
c) “Shutdown.”
d) “That’s one small step for (a) man, one giant leap for mankind.”


2) A light-year is the distance that light can travel in vacuum in 365 days. How fast is that?

a) 900 million miles
b) 80.4 billion miles
c) 5.9 trillion miles
d) 1 quadrillion miles


3) True or false. The hottest planet in our solar system is Mercury, the planet closest to the sun.


4) Total solar eclipses occur:

a) once every 10 years or so
b) once every 100 years or so
c) twice every 1½ years or so
d) twice every 10 years or so

Here's how the Earth, moon and sun move during a solar eclipse. (NASA)


5) True or false. For as long as humans are on Earth, they will be able to experience solar eclipses.


6) What’s a major difference between a comet and an asteroid?

a) There isn’t any; they are different names for the same thing.
b) Comets are much older than asteroids.
c) Asteroids are always larger than comets.
d) They are made of different materials.


7) What makes up most of the universe?

a) plasma and gases
b) ice and rock
c) energy
d) scientists don’t know


8) Data from the Hubble Space Telescope has recently revealed something new about galaxies in the universe:

a) The established estimate of 200 billion galaxies in the observable universe is correct.
b) The estimate of 200 billion galaxies turns out to be 10 times too high.
c) The estimate of 200 billion galaxies is at least 10 times too low.
d) All galaxies have about 200 billion stars.


9) What is not true about black holes?

a) The pulling force of gravity is so strong that the only thing that can escape it is light.
b) If our sun turned into a black hole, Earth would not be sucked into it.
c) The Milky Way has a supermassive black hole with a mass equal to about 4 million suns.
d) The smallest black holes can be as small as a single atom but with the mass of a large mountain.


10) In 4 billion years, something is predicted to happen to the Milky Way galaxy. What is it?

a) It will come apart as the universe continues to expand.
b) It will collide/merge with the Andromeda galaxy.
c) The black hole in the center will absorb all of its matter.
d) Nothing, actually.


1) The correct answer is B. The first conversation that took place was just after at least one of the probes hanging from three of the footpads on the Eagle lunar module ad made contact with the moon’s surface. The discussion was procedural. Astronaut Buzz Aldrin said, “contact light.” Neil Armstrong then said “shutdown.” Some time later, Armstrong became the first person to walk on the moon and his first words, upon setting foot, were “That’s one small step for (a) man, one giant leap for mankind.”

2) The correct answer is C. According to the International Astronomical Union, a light-year is 9,460,730,472,580.8 km, which is close to 5.9 trillion miles.

3) It would seem to make sense for the closest planet to the sun to be the hottest in our solar system, but it’s not true. Venus, the second planet closest to the sun is hotter than Mercury. Mercury has no atmosphere, which can hold and trap heat. Venus has a very thick atmosphere made mostly of carbon dioxide, which traps the heat so that, according to NASA, the temperature on the surface is around 872 degrees Fahrenheit, or 467 degrees Celsius.

4) The correct answer is C. From NASA:

“During the 5,000-year period from -1999 to +3000 (2000 BCE to 3000 CE), Earth will experience 11,898 eclipses of the Sun. The statistical distribution of eclipse types for this interval is as follows: 4,200 partial eclipses, 3,956 annular eclipses, 3,173 total eclipses and 569 hybrid eclipses. That means that, every 1,000 years you have 840 partial eclipses, 791 annular eclipses, 635 total eclipses and 114 hybrid eclipses. That works out to 2-3 eclipses of all kinds each year, and about 2 total solar eclipses every 3 years.”

You can see data on 5,000 years of solar eclipses, here, from NASA.

5) That’s false. According to The Washington Post:

“Earth won’t experience eclipses forever. The moon is drifting away from our planet at a rate of about an inch and a half per year. In approximately 650 million years, the moon will be so distant that it can no longer completely block out the sun. Humans will have seen their last eclipse — if we manage to make it that long.”

6) The correction answer is D. According to NASA, comets are made up of a lot of ice, along with rock and hydrocarbons, while asteroids are made of metals and rock. Both were formed in the early stages of the solar system, about 4.5 billion years ago, though comets are believed to have formed in the outer solar system and asteroids closer to the sun. Both are irregularly shaped. The diameter of comets can range from about six to 25 miles; the diameter of asteroids range from small rocks to 600 miles. Both orbit around the sun, though ice burns off comets as they approach the sun while asteroids remain stable. Scientists believe comets may have brought to Earth a large part of the planet’s water.

7) The correct answer is D. Nobody really knows. Dark energy and dark matter make up 95 percent of the universe — but scientists don’t know exactly what they are. According to NASA:

“When scientists study our universe, they see that it’s expanding. But if the universe is only made of the galaxies, stars, planets, and other things that we know about, it shouldn’t be expanding. Something else is out there. There has to be energy that is making the universe expand. We just don’t know what this energy is. We also don’t know where it comes from. But we can tell that it’s there. Scientists named this energy dark energy. We don’t know much about dark energy, but we do know there is a lot of it. Dark energy makes up 68%, about two-thirds, of the universe. There is also stuff out there in space that has gravity. We can see its pull on matter like stars and galaxies. But it’s not regular matter. It’s not a black hole. It’s not anything that we have ever heard of. But it’s definitely there. Scientists named this stuff dark matter. Just like dark energy, we don’t know a whole lot about dark matter. But it seems that 27% of the universe, or about one quarter, is made up of the strange stuff.

8) The correct answer is C. According to NASA:

One of the most fundamental questions in astronomy is that of just how many galaxies the universe contains. The landmark Hubble Deep Field, taken in the mid-1990s, gave the first real insight into the universe’s galaxy population. Subsequent sensitive observations such as Hubble’s Ultra Deep Field revealed a myriad of faint galaxies. This led to an estimate that the observable universe contained about 200 billion galaxies. The new research shows that this estimate is at least 10 times too low.

This handout illustration courtesy of NASA shows the Cassini spacecraft diving through the plume of Saturn’s moon Enceladus in 2015. (AFP/Getty Images)

9) The correct answer is A. Not even light can escape a black hole. From NASA:

Black holes do not wander around the universe, randomly swallowing worlds. They follow the laws of gravity just like other objects in space. The orbit of a black hole would have to be very close to the solar system to affect Earth, which is not likely. If a black hole with the same mass as the sun were to replace the sun, Earth would not fall in. The black hole with the same mass as the sun would keep the same gravity as the sun. The planets would still orbit the black hole as they orbit the sun now.

The sun does not have enough mass to collapse into a black hole. In billions of years, when the sun is at the end of its life, it will become a red giant star. Then, when it has used the last of its fuel, it will throw off its outer layers and turn into a glowing ring of gas called a planetary nebula. Finally, all that will be left of the sun is a cooling white dwarf star.

10) The correct answer is B. From NASA:

NASA astronomers … can now predict with certainty the next major cosmic event to affect our galaxy, sun, and solar system: the titanic collision of our Milky Way galaxy with the neighboring Andromeda galaxy. The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed.