About Us
For Teachers
Most Popular
Most Recent
Astronomy Links
Image Credits
Cornell Astronomy
Ask a Question
Home
Our Solar System
The Earth
The Moon
The Sun
Planets & Dwarf Planets
Comets, Meteors, & Asteroids
The Universe
Extrasolar Planets
Stars & Star Clusters
Supernovae
Black Holes & Quasars
The Milky Way
Galaxies
Cosmology & the Big Bang
Observational Astronomy
Stargazing
Telescopes
Lunar & Solar Eclipses
Timekeeping
SETI & Extraterrestrial Life
Physics
General Physics
The Theory of Relativity
People & Astronomy
Careers in Astronomy
Space Exploration & Astronauts
The History of Astronomy
Astronomy in the Arts
Hydrogen
Enter Part of Title
Display #
5
10
15
20
25
30
50
100
All
Can we harvest H & O from space to make water?
(Intermediate)
Does the Sun have any heavy elements?
(Beginner)
How can a star burn with no oxygen?
(Beginner)
Is it true that the Sun burns off a billion tons of gas every 5 seconds?
(Beginner)
What elements make up the Sun?
(Beginner)
What happens to the helium formed in the Sun?
(Beginner)
What is a nova?
(Beginner)
What is the evidence supporting the nebula theory of Solar System formation?
(Intermediate)
What is the origin of the stellar classification system "OBAFGKM"?
(Intermediate)
What is the physical difference between a star and a planet?
(Intermediate)
Where are stars born?
(Beginner)
Where did all the water in the universe come from?
(Intermediate)
Why doesn't the hydrogen on Jupiter explode?
(Intermediate)
Why is the Cosmic Microwave Background not absorbed by interstellar hydrogen?
(Advanced)
Why will fusion wait until hydrogen is gone before starting to fuse heavier atoms?
(Advanced)
Random Question
Why does the Earth tilt back and forward once a year? (Beginner)
Most Recent
What should I know about the upcoming Solar Eclipse (2017)? (Beginner)
Do galaxies that are receding from us faster than the speed of light disappear from our observations? (Intermediate)
Why are astronomers interested in gravitational waves? (Intermediate)
Can two galaxies move away from each other faster than the speed of light? (Intermediate)
What is a graviton? (Intermediate)
Why are there high tides during a Full Moon? (Intermediate)
Why is Neptune still considered a planet when Pluto crosses its orbit? (Intermediate)
Could there be objects orbiting interior to Mercury? (Intermediate)
Have the inner planets cleared their neighborhood? (Intermediate)
What caused the Big Bang and created the Universe? (Beginner)
Editor's Pick
What is the universe expanding into? (Intermediate)
What do I need to do to become an astronomer? (Beginner)
What's the difference between astronomy and astrology? (Beginner)
Why is looking out into space the same as looking back in time? (Beginner)
Can we find the place where the Big Bang happened? (Intermediate)
Most Popular
Today
This Week
This Month
All Time
What color is each planet? (Intermediate)
How far is each planet from Earth? (Intermediate)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
What is the difference between a "star" and a "sun"? (Beginner)
Can artificial gravity be created in space? (Intermediate)
When was the last time all of the planets were aligned? (Beginner)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
Why do airplanes take longer to fly West than East? (Intermediate)
Can a person go into a black hole and come out alive? (Beginner)
What color is each planet? (Intermediate)
What is the difference between a "star" and a "sun"? (Beginner)
Can artificial gravity be created in space? (Intermediate)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
How far is each planet from Earth? (Intermediate)
Are black holes spherical? (Intermediate)
Why do the planets orbit the sun? (Beginner)
Why do airplanes take longer to fly West than East? (Intermediate)
What color is each planet? (Intermediate)
Can a person go into a black hole and come out alive? (Beginner)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
What is the difference between a "star" and a "sun"? (Beginner)
Can artificial gravity be created in space? (Intermediate)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How far is each planet from Earth? (Intermediate)
Why do airplanes take longer to fly West than East? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
Why can't a plane fly slowly and let the Earth pass underneath? (Beginner)
What's going to happen on December 21st 2012? (Intermediate)
What color is each planet? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
How far is each planet from Earth? (Intermediate)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
How do you measure the distance between Earth and the Sun? (Intermediate)
Why do the planets orbit the sun? (Beginner)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
How long does it take for the Sun's light to reach us? (Beginner)
When was the last time all of the planets were aligned? (Beginner)
Our Reddit AMAs
AMA = Ask Me (Us) Anything
June 2014 AMA
July 2013 AMA
Q&A Categories
Home
Our Solar System
The Earth
The Moon
The Sun
Planets & Dwarf Planets
Comets, Meteors, & Asteroids
The Universe
Extrasolar Planets
Stars & Star Clusters
Supernovae
Black Holes & Quasars
The Milky Way
Galaxies
Cosmology & the Big Bang
Observational Astronomy
Stargazing
Telescopes
Lunar & Solar Eclipses
Timekeeping
SETI & Extraterrestrial Life
Physics
General Physics
The Theory of Relativity
People & Astronomy
Careers in Astronomy
Space Exploration & Astronauts
The History of Astronomy
Astronomy in the Arts