All stars shine due to an internal source of energy. Usually, it's nuclear fusion: converting mass into energy. What makes them most bright?

Photons come in every wavelength you can imagine. But one particular quantum transition makes light at precisely 21 cm, and it's magical.

According to Stephen Hawking, spontaneously emitted radiation should cause all black holes to decay. But we've never seen it: not even once.

Empty space itself, the quantum vacuum, could be in either a true, stable state or a false, unstable state. Our fate depends on the answer.

Perhaps no existential question looms larger than that of our ultimate cosmic origins. At long last, science has provided the answers.

The Hubble Space Telescope, launched in 1990, was originally seen as a colossal mistake. This one image, taken in 1995, changed everything.

"Asking the question of, "Where did the entire universe come from?" is no longer a question for poets and theologians and philosophers. This is a question for scientists, and we have some amazing scientific answers to this question."

The most famous Hubble images show glittering stars and galaxies amidst the black backdrop of space. But more was captured than we realized.

25 years ago, our concordance picture of cosmology, also known as ΛCDM, came into focus. 25 years later, are we about to break that model?

Exoplanets can exist anywhere around their parent stars, even so close that they evaporate or disintegrate. Even the rocky ones.

It's difficult to project a sphere onto a flat, two-dimensional surface. All maps of the Earth have flaws; the same is true for the cosmos.

We understand many things about our Universe, and our home within it, extremely well. The number of stars in the Milky Way isn't among them.

Common knowledge says the maximum size of a PDF is as big as 40% of Germany — but that’s a gross underestimate.

The Multiverse isn't just a staple of science fiction; there's real-life science behind it, too. Here are 10 facts to expand your mind.

Large, massive, rotating galaxies like the Milky Way are common today. So how could one form a mere ~2 billion years after the Big Bang?

Over a century after we first unlocked the secrets of the quantum universe, people find it more puzzling than ever. Can we make sense of it?

DESI, by mapping galaxies, has claimed they see evidence for dark energy evolving by getting weaker. But that's only one interpretation.

Someday, we'll look back and see a young galaxy forming stars for the first time. JADES-GS-z14-0, the farthest ever, isn't early enough.

Einstein's general relativity has reigned supreme as our theory of gravity for over a century. Could we reduce it back down to Newton's law?

Our scientific instruments are constantly improving, revealing nature's workings as never before. Without them, we'll remain in the dark.

Some nebulae emit their own light, some reflect the light from stars around them, and some only absorb light. But that's just the beginning.

When we see spiral galaxies, some are face-on, others are edge-on, but most are tipped at an angle. But which side is closest to us?

The tiniest galaxies of all are the most susceptible to violence by their larger, bullying siblings. That's why we need them in isolation.

The Universe is expanding, and individual, bound structures are all receding away from one another. How, then, are galaxies still colliding?

Since the dawn of history, humans have pondered our ultimate cosmic origins. Now in the 21st century, science has gone beyond the Big Bang.

"Asking the question of, where did the entire universe come from, is no longer a question for poets and theologians and philosophers. This is a question for scientists, and we have some amazing scientific answers to this question that have defied even the wildest of our expectations."

Just 165,000 light-years away, the Large Magellanic Cloud is suspected to house a supermassive black hole. At last, evidence has arrived.

There are some 26 fundamental constants in nature, and their values enable our Universe to exist as it does. But where do they come from?

One of the most promising dark matter candidates is light particles, like axions. With JWST, we can rule out many of those options already.

Astronomers see spiral and elliptical nebulae nearly everywhere, except by the Milky Way's plane. We didn't know why until the 20th century.