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Astronomy
The most important diagram in astronomy was drawn twice, independently, by two people who never collaborated
The Hertzsprung-Russell diagram plots stellar luminosity against temperature and organizes every type of star into a coherent pattern that reveals the physics of stellar evolution. Published independently around 1910 by Ejnar Hertzsprung and Henry Norris Russell, it remains the foundational tool of stellar astrophysics.
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Astronomy
The universe has a skeleton. It is made of gas, dark matter, and time.
The largest structures in the universe are not galaxies or galaxy clusters — they are the filaments connecting them and the voids between them. This cosmic web, predicted by simulations, has been mapped across billions of light-years and continues to yield surprises.
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Astronomy
Gold and platinum were made in the collision of two neutron stars. We watched it happen.
On August 17, 2017, gravitational wave detectors caught two neutron stars merging. The electromagnetic flash that followed — a kilonova — was observed by dozens of telescopes worldwide and confirmed that collisions between neutron stars produce most of the heavy elements in the universe.
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Science & Discovery
Three moons in the outer solar system have conditions that could support life. We've barely started looking.
Enceladus has a liquid ocean venting organics and hydrogen into space. Europa has a global ocean under an ice shell. Titan has lakes of liquid methane and a complex organic chemistry. All three are active targets for future astrobiology missions.
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Science & Discovery
The Oort Cloud is the solar system's outer shell. We've never directly observed it.
The Oort Cloud — a spherical shell of icy bodies at distances up to 100,000 AU from the Sun — is inferred from the orbits of long-period comets. It may contain trillions of objects and is thought to be the source of most comets that visit the inner solar system.
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Science & Discovery
Saturn's rings exist because of a mathematical boundary. Anything inside it cannot hold itself together.
The Roche limit is the distance at which a planet's tidal forces overcome a satellite's self-gravity, preventing it from accreting or tearing it apart. Saturn's rings sit inside this boundary for water ice, which is why they exist as rings rather than as one large moon.
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Science & Discovery
Every atom heavier than hydrogen was forged inside a star. Here is how that happened.
Stellar nucleosynthesis is the process by which stars manufacture every element from helium to iron in their cores, and supernovae and neutron star mergers produce everything heavier. The atoms in your body have a detailed provenance that astrophysicists have largely worked out.
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Science & Discovery
In the first fraction of a second after the Big Bang, the universe grew by a factor of 10 to the 26th power. Here's what we know about that.
Cosmic inflation — a period of exponential expansion in the universe's first 10^-32 seconds — was proposed in 1980 to solve three problems with the standard Big Bang model. Evidence for it is strong; direct detection of its signature in gravitational waves remains the goal.
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Science & Discovery
Frank Drake wrote seven terms on a blackboard in 1961. Here's what we know about each of them now.
The Drake Equation estimates the number of communicating civilizations in the galaxy from seven factors. In 1961, most were guesses. In 2026, exoplanet surveys, astrobiology, and SETI experiments have turned several of them into data. The answer is still unknown — but for different reasons than before.
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Commercial
Some things can only be made in zero gravity. A small industry is building the infrastructure to make them.
Microgravity enables manufacturing processes impossible on Earth: near-perfect optical fibers, protein crystals for drug development, organs grown without scaffolding, and alloys that separate under gravity. A nascent commercial sector is building the satellites and ISS platforms to exploit these properties.
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Commercial
SpaceX has launched more than 6,000 satellites. Astronomers are not happy about it.
Starlink is the largest satellite constellation in history — and the most disruptive to ground-based astronomy. SpaceX has made mitigation efforts, but the fundamental tension between dense LEO constellations and telescope surveys remains unresolved as competitors plan their own systems.
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Commercial
SpaceX cut the cost of reaching orbit by 90 percent. Here's what that has and hasn't changed.
The cost of putting a kilogram in low Earth orbit dropped from roughly $50,000-$70,000 in the Space Shuttle era to under $3,000 on a Falcon 9 rideshare. This 90-percent price reduction has transformed who can access space — but it hasn't yet transformed what they do there.
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