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OpenStem
@openstem · Joined Jul 2026
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Flashcards8 cards
What is the name of NASA's current program to send humans back to the Moon?1 / 8
The Artemis program.
Astronomy · L1 · Artemis: Returning to the Moon
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Astronomy · L1 · Artemis: Returning to the MoonFlashcards8 cards
Which planet is the biggest in our Solar System?1 / 8
Jupiter — it is so big that more than 1,000 Earths could fit inside it.
Astronomy · L1 · Jupiter, the Giant Planet
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Astronomy · L1 · Jupiter, the Giant PlanetFlashcards7 cards
Which planet is famous for its rings?1 / 7
Saturn — its wide, bright rings make it one of the most recognizable planets.
Astronomy · L1 · Saturn's Rings
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Astronomy · L1 · Saturn's RingsFlashcards7 cards
What is the Milky Way?1 / 7
The huge collection of stars, gas, and dust that our Sun and Solar System belong to — our home galaxy.
Astronomy · L1 · Spotting the Milky Way
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Astronomy · L1 · Spotting the Milky WayFlashcards7 cards
What is a black hole?1 / 7
A place in space where gravity is so strong that nothing — not even light — can escape it.
Astronomy · L1 · Black Holes
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Astronomy · L1 · Black HolesFlashcards7 cards
What are Uranus and Neptune called as a pair?1 / 7
The ice giants — the two outermost, coldest planets in our Solar System.
Astronomy · L1 · Neptune and Uranus, the Ice Giants
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Astronomy · L1 · Neptune and Uranus, the Ice GiantsFlashcards5 cards
Where are stars born?1 / 5
Stars are born inside giant clouds of gas and dust called nebulae. Gravity pulls the gas together until it is dense and hot enough to start nuclear fusion.
Astronomy · L2 · The Life Cycle of Stars
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Astronomy · L2 · The Life Cycle of StarsFlashcards6 cards
What is the solar system?1 / 6
The solar system is the Sun and everything that orbits it — eight planets, their moons, asteroids, and comets. An orbit is the path an object takes as it travels around the Sun.
Astronomy · L2 · The Solar System
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Astronomy · L2 · The Solar SystemFlashcards8 cards
Who was Johannes Kepler?1 / 8
A German astronomer in the early 1600s who used incredibly precise position data recorded by Tycho Brahe to work out the actual mathematical rules planets follow as they orbit the Sun.
Astronomy · L2 · Kepler's Laws of Planetary Motion
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Astronomy · L2 · Kepler's Laws of Planetary MotionFlashcards8 cards
If gravity is always pulling planets toward the Sun, why don't they fall in?1 / 8
Planets are also moving sideways very fast. Gravity constantly bends that sideways motion into a curve, but the planet keeps moving forward fast enough to 'miss' the Sun over and over — that continuous falling-and-missing is an orbit.
Astronomy · L2 · Gravity and Orbital Motion
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Astronomy · L2 · Gravity and Orbital MotionFlashcards7 cards
Why don't astronomers measure the solar system in kilometres?1 / 7
They can, but the numbers get awkwardly huge — Neptune is over 4 billion km from the Sun. Bigger, more convenient units make distances easier to compare.
Astronomy · L2 · The Scale of the Universe
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Astronomy · L2 · The Scale of the UniverseFlashcards8 cards
What is the Kuiper Belt?1 / 8
A vast, disc-shaped region of icy bodies beyond Neptune's orbit, stretching from about 30 to 50 AU from the Sun. It's home to Pluto and many other small icy worlds.
Astronomy · L2 · Dwarf Planets and the Kuiper Belt
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Astronomy · L2 · Dwarf Planets and the Kuiper BeltFlashcards8 cards
What is an asteroid made of?1 / 8
Mostly rock and metal. Asteroids are leftover building blocks that never joined together to form a planet, and most orbit the Sun in the asteroid belt between Mars and Jupiter.
Astronomy · L2 · Comets, Asteroids, and Meteoroids
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Astronomy · L2 · Comets, Asteroids, and MeteoroidsFlashcards7 cards
What shape is the Milky Way galaxy?1 / 7
It's a barred spiral galaxy — a flat, rotating disc with curving spiral arms, and a bar-shaped structure of stars crossing through its central bulge.
Astronomy · L2 · The Milky Way and Other Galaxies
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Astronomy · L2 · The Milky Way and Other GalaxiesFlashcards8 cards
What happens in the Sun's core?1 / 8
Nuclear fusion — hydrogen nuclei fuse into helium under crushing pressure and heat of about 15 million °C, releasing the energy that powers the entire Sun.
Astronomy · L2 · The Sun's Structure and Activity
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Astronomy · L2 · The Sun's Structure and ActivityFlashcards8 cards
What was Sputnik 1, and why did it matter?1 / 8
The first artificial satellite, launched by the Soviet Union in October 1957. It shocked the world and kicked off the Space Race between the USSR and the United States.
Astronomy · L2 · The Space Race
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Astronomy · L2 · The Space RaceFlashcards7 cards
What is the International Space Station (ISS)?1 / 7
A large research station orbiting about 400 km above Earth, built and operated by multiple countries. It has been continuously crewed by rotating astronaut teams since November 2000.
Astronomy · L2 · Modern Space Missions and Rovers
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Astronomy · L2 · Modern Space Missions and RoversFlashcards8 cards
What is an exoplanet?1 / 8
A planet that orbits a star other than our own Sun.
Astronomy · L2 · Exoplanets
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Astronomy · L2 · ExoplanetsFlashcards7 cards
What mainly causes ocean tides?1 / 7
The Moon's gravity pulls on Earth's oceans, creating a bulge of water on the side of Earth facing the Moon.
Astronomy · L2 · Tides and the Moon's Pull
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Astronomy · L2 · Tides and the Moon's PullFlashcards8 cards
What is the celestial sphere?1 / 8
An imaginary giant sphere surrounding Earth, onto which we project the positions of stars, as if they were all painted on its inside surface. It's a useful tool for mapping the sky, even though it isn't physically real.
Astronomy · L2 · Navigating the Night Sky
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Astronomy · L2 · Navigating the Night SkyFlashcards7 cards
What is a Near-Earth Object (NEO)?1 / 7
An asteroid or comet whose orbit brings it within about 195 million km of Earth's orbit — close enough that astronomers keep a careful watch on it.
Astronomy · L2 · Near-Earth Objects and Impact Risk
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Astronomy · L2 · Near-Earth Objects and Impact RiskFlashcards8 cards
What is Earth's magnetosphere?1 / 8
The region of space around Earth controlled by its magnetic field. It is squashed on the side facing the Sun and stretched into a long tail on the far side.
Astronomy · L2 · Auroras and Earth's Magnetosphere
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Astronomy · L2 · Auroras and Earth's MagnetosphereFlashcards8 cards
What is Low Earth Orbit (LEO)?1 / 8
An orbit roughly 160 to 2,000 km above Earth's surface, with an orbital period of about 90 minutes. The International Space Station and many imaging satellites use LEO.
Astronomy · L2 · Satellite Orbits and GPS
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Astronomy · L2 · Satellite Orbits and GPSFlashcards8 cards
What part of the electromagnetic spectrum do radio telescopes observe?1 / 8
Radio waves — the longest-wavelength, lowest-energy form of light, invisible to the human eye.
Astronomy · L2 · Radio Astronomy Basics
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Astronomy · L2 · Radio Astronomy BasicsFlashcards8 cards
What was the geocentric model?1 / 8
The idea that Earth sits at the center of the universe, with the Sun, Moon, planets, and stars all orbiting around it. It was the accepted view for roughly 1,400 years.
Astronomy · L2 · The Copernican Revolution
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Astronomy · L2 · The Copernican RevolutionFlashcards9 cards
Why is Mars called the 'Red Planet'?1 / 9
Its surface is covered in iron oxide dust — essentially rust — which gives it a reddish color.
Astronomy · L2 · Mars in Depth
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Astronomy · L2 · Mars in DepthFlashcards8 cards
What is comparative planetology?1 / 8
The practice of comparing planets to each other to understand why they turned out the way they did — and what that reveals about the rules governing all planets.
Astronomy · L2 · Comparative Planetology
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Astronomy · L2 · Comparative PlanetologyFlashcards8 cards
What is a star cluster?1 / 8
A group of stars that formed together from the same giant cloud of gas and dust, and are held together by their mutual gravity.
Astronomy · L2 · Star Clusters
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Astronomy · L2 · Star ClustersFlashcards8 cards
What is light pollution?1 / 8
Excessive or poorly directed artificial light that brightens the night sky, making it harder to see stars and other faint objects.
Astronomy · L2 · Light Pollution and Dark Skies
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Astronomy · L2 · Light Pollution and Dark SkiesFlashcards8 cards
Where are stars born?1 / 8
Inside giant clouds of gas and dust called nebulae, where gravity pulls material together.
Astronomy · L2 · The Life Cycle of Stars
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Astronomy · L2 · The Life Cycle of Stars