OpenStem

@openstem · Joined Jul 2026

7420 public items8 groups

Note~131 words · 1 min

Getting Ready to Go Landing people on the Moon didn't happen all at once. It took years of smaller missions, each one teaching skills needed for the next, bigger challenge. Three Programs, One Big Goal Before Apollo could land on the Moon,

Astronomy

Astronomy · L1 · Humans on the Moon

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Note~174 words · 1 min

Dust Trails Left Behind by Comets As a comet travels near the Sun, it sheds a trail of tiny dust and rock particles along its path. That trail stays behind in space, long after the comet has moved on. When Earth's orbit happens to cross thr

Astronomy

Astronomy · L1 · Meteor Showers

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Note~166 words · 1 min

A Curtain of Light in the Sky On some nights, especially near the North and South Poles, the sky fills with shifting curtains of green, pink, and purple light. This glow is called an aurora. Even though it happens right here on Earth, the r

Astronomy

Astronomy · L1 · Northern Lights (Auroras)

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Note~138 words · 1 min

Two Kinds of Satellites A satellite is simply anything that orbits a bigger object. Some satellites formed naturally billions of years ago. Others were built and launched by people just decades ago. What Artificial Satellites Do How a Satel

Astronomy

Astronomy · L1 · Satellites: Natural & Artificial

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Note~165 words · 1 min

Exploring the Red Planet with Robots Mars is too far and too harsh for people to visit safely right now, so scientists send robotic rovers instead. These machines drive across the Martian surface, taking photos and testing rocks and soil. W

Astronomy

Astronomy · L1 · Mars Exploration

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Note~171 words · 1 min

You Don't Need a Telescope to Start Some of the best stargazing happens with nothing more than your own eyes. Learning a few simple tricks can help you find stars, planets, and famous patterns in the night sky. Telling Planets from Stars Pl

Astronomy

Astronomy · L1 · Finding Stars & Planets in the Sky

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Note~320 words · 2 min

Two Bulges, Not One The Moon's gravity pulls hardest on the side of Earth closest to it, stretching the ocean there into a bulge. It might seem like that should create just one high tide a day — but there's actually a second bulge on the ex

Astronomy

Astronomy · L2 · Tides and the Moon's Pull

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Note~152 words · 1 min

Earth's Long Trip Around the Sun A 'year' is not just a number on a calendar — it is the real time it takes Earth to travel one full loop around the Sun. Where the Extra Day Comes From Since Earth's real orbit is close to a quarter-day long

Astronomy

Astronomy · L1 · Why a Year Has 365 Days

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Note~160 words · 1 min

A Twin in Size Only Venus is nearly the same size as Earth and made of similar rock, which is why scientists sometimes call it Earth's 'twin'. But that's where the similarity ends. Why So Hot? Venus is not the closest planet to the Sun, yet

Astronomy

Astronomy · L1 · Venus, Earth's Unfriendly Twin

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Note~175 words · 1 min

Looking Up Through History For most of human history, people had only their eyes to study the sky. A few curious thinkers changed forever how we understand our place in the universe. A Slow Change of Mind Big ideas in science rarely change

Astronomy

Astronomy · L1 · Astronomers Who Changed How We See the Sky

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Note~184 words · 1 min

Going Back to Stay, Not Just Visit Humans last walked on the Moon in 1972. Now a new program, named Artemis after the twin sister of Apollo in Greek mythology, is bringing astronauts back — this time to stay longer and prepare for even fart

Astronomy

Astronomy · L1 · Artemis: Returning to the Moon

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Note~216 words · 1 min

The King of the Planets Jupiter is the fifth planet from the Sun and by far the largest. It is so massive that all the other planets combined could almost fit inside it. Unlike Earth, Jupiter has no solid ground. It is a giant ball of gas,

Astronomy

Astronomy · L1 · Jupiter, the Giant Planet

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Note~197 words · 1 min

The Ringed Planet Saturn is the sixth planet from the Sun, and it is best known for the wide, bright rings that circle around it. Through a small telescope, Saturn's rings are one of the most amazing sights in the night sky. Like Jupiter, S

Astronomy

Astronomy · L1 · Saturn's Rings

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Note~227 words · 1 min

A Map Painted on an Imaginary Sphere Stars are scattered through space at wildly different distances, but from Earth they all appear to sit on the inside of one giant dome. Astronomers formalise this useful illusion as the celestial sphere

Astronomy

Astronomy · L2 · Navigating the Night Sky

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Note~220 words · 1 min

Not All Asteroids Stay in the Belt Most asteroids stay confined to the asteroid belt between Mars and Jupiter, but some have orbits that carry them much closer to Earth. Any asteroid or comet whose path brings it within about 195 million km

Astronomy

Astronomy · L2 · Near-Earth Objects and Impact Risk

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Note~221 words · 1 min

An Invisible Shield The Sun constantly releases a stream of charged particles called the solar wind. If it hit Earth's atmosphere unopposed, it could gradually strip the atmosphere away over billions of years — something scientists think ha

Astronomy

Astronomy · L2 · Auroras and Earth's Magnetosphere

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Note~350 words · 2 min

Two Very Different Orbits Not all satellites orbit at the same height, and the altitude a satellite flies at changes everything about how it behaves. A satellite in Low Earth Orbit (LEO), only a few hundred kilometres up, races around the p

Astronomy

Astronomy · L2 · Satellite Orbits and GPS

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Note~281 words · 1 min

Listening, Not Just Looking Visible light — the colors our eyes can see — is only a small slice of the electromagnetic spectrum. Many astronomical objects give off huge amounts of energy at other wavelengths, including radio waves, the long

Astronomy

Astronomy · L2 · Radio Astronomy Basics

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Note~237 words · 1 min

When Shadows Fall in Space The Sun, Earth, and Moon are always moving. Every so often, they line up almost perfectly in a straight line, and one of them casts a shadow on another. That is an eclipse. Solar Eclipse: The Moon Blocks the Sun A

Astronomy

Astronomy · L1 · Solar and Lunar Eclipses

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Note~282 words · 1 min

A Hazy River of Light On a clear, dark night, far from city lights, you might see a pale, cloudy band stretching across the sky. That band is the Milky Way — the galaxy we live in, seen from the inside. The Milky Way is home to our Sun, Ear

Astronomy

Astronomy · L1 · Spotting the Milky Way

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Note~283 words · 1 min

A Place Where Gravity Wins A black hole is a region of space with such powerful gravity that nothing can escape it — not a spaceship, not a planet, and not even light itself. Because light can't get out, a black hole looks completely black,

Astronomy

Astronomy · L1 · Black Holes

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Note~231 words · 1 min

The Outer Edge of the Solar System Beyond Jupiter and Saturn lie two more giant planets: Uranus and Neptune. They are farther from the Sun, colder, and smaller than Jupiter and Saturn, but they are still much bigger than Earth. Because they

Astronomy

Astronomy · L1 · Neptune and Uranus, the Ice Giants

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Note~291 words · 1 min

Telescopes: Windows to the Universe A telescope collects light from distant objects and focuses it so we can see detail that the naked eye cannot. There are two main types: Space telescopes like Hubble orbit above Earth's atmosphere, which

Astronomy

Astronomy · L2 · Telescopes and Eclipses

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Note~243 words · 1 min

A New Shape for the Solar System For centuries, astronomers assumed planets moved in perfect circles because circles were considered the 'perfect' shape. In the early 1600s, Johannes Kepler studied years of careful observations of Mars and

Astronomy

Astronomy · L2 · Kepler's Laws of Planetary Motion

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Note~268 words · 1 min

Falling Around, Not Falling In It seems strange that gravity pulls planets toward the Sun all the time, yet they never crash into it. The trick is that planets are also moving sideways, fast. Gravity bends that sideways motion into a curve

Astronomy

Astronomy · L2 · Gravity and Orbital Motion

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Note~232 words · 1 min

Kilometres Stop Being Useful A kilometre works fine for measuring a road trip. But space is so vast that using kilometres for it quickly produces numbers too large to picture — hence astronomers use two special units built for the job. Stac

Astronomy

Astronomy · L2 · The Scale of the Universe

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Note~195 words · 1 min

A Ninth Planet, Demoted From 1930 to 2006, Pluto was taught as the ninth planet. That changed when astronomers found more and more Pluto-sized objects out beyond Neptune, forcing them to finally define, precisely, what a 'planet' actually i

Astronomy

Astronomy · L2 · Dwarf Planets and the Kuiper Belt

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Note~254 words · 1 min

Three Kinds of Leftovers Not everything orbiting the Sun is a planet or moon. The solar system is full of smaller bodies — leftover material from its formation 4.6 billion years ago — and they come in a few distinct types. Why Comets Grow T

Astronomy

Astronomy · L2 · Comets, Asteroids, and Meteoroids

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Note~190 words · 1 min

Our Galactic Address Every star you can see with the naked eye — and our Sun — belongs to one galaxy: the Milky Way, a huge, rotating collection of stars, gas, and dust held together by gravity. The Milky Way is a barred spiral galaxy: a fl

Astronomy

Astronomy · L2 · The Milky Way and Other Galaxies

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Note~353 words · 2 min

Three Planets, Three Very Different Outcomes Venus, Earth, and Mars all formed in the inner solar system from similar raw materials, at roughly similar times. If you only looked at their ingredients, you might expect three fairly similar wo

Astronomy

Astronomy · L2 · Comparative Planetology

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