200 most important Astronomy topics - Sykalo Eugen 2023

The Quasars

A Question From the Darkness: What Could Outshine a Galaxy?

Imagine staring at a black sky and seeing a single dot that outshines an entire galaxy—a pinprick of light so intense it drowns the glow of hundreds of billions of stars. It almost sounds like science fiction, like a rogue lighthouse beaming across the void. And yet, that’s a quasar.

Quasars, short for "quasi-stellar radio sources," were first spotted in the 1950s as faint radio signals with no clear source. Then, in 1963, astronomer Maarten Schmidt decoded the spectral lines of one such object (3C 273), realizing its redshift was astronomical—literally. This thing was so far away, it should have been invisible. And yet, it shone.

Here's the kicker: it wasn't a star, though it looked like one. It was a supermassive black hole, devouring matter at the center of a galaxy.

The Hungry Hearts of Galaxies

At the core of most galaxies, including our own Milky Way, sits a supermassive black hole. In some, it snoozes quietly. In others, it awakens in a feeding frenzy. When gas, dust, and even stars spiral into its gravitational grip, they don't vanish quietly. No. They scream.

The process is called accretion, and it's beautifully violent. As matter falls inward, it heats up due to friction and gravitational compression, forming a swirling disk hotter than the core of the Sun. Some of that energy escapes before the matter crosses the event horizon, blasting into space as jets of radiation. This is what we see as a quasar.

It’s ironic, isn’t it? The darkest objects in the Universe give rise to its brightest lights.

Time Capsules from the Infant Universe

Quasars are not just bright; they are ancient. Most live in the early Universe, formed just a few hundred million years after the Big Bang. When we observe a quasar today, we’re seeing light that left it 10 to 13 billion years ago. We are literally looking back in time.

I remember once looking at a Hubble image of a quasar labeled ULAS J1342+0928—discovered in 2017. It lived just 690 million years after the Big Bang. That blew my mind. This thing was already a fully-formed black hole the size of a billion Suns, lighting up a young, chaotic Universe. It felt like hearing a toddler roar like a lion.

Astrophysicists still grapple with how such massive quasars formed so quickly. Some theories suggest direct collapse black holes, others posit fast-track growth with super-efficient accretion. No one's sure. The Universe, cheeky as ever, loves a mystery.

A Cosmic Web of Influence

Think quasars are just passive lighthouses? Think again. Their light sculpts the cosmos.

The radiation they emit can ionize surrounding gas, altering star formation in their host galaxies. Some blast powerful winds that sweep away galactic gas—like cosmic leaf blowers, quenching further star birth. Others might even trigger star formation by compressing nearby clouds.

In this way, quasars are architects and destroyers. Their ferocity helps shape the galaxies they inhabit, perhaps even defining their evolution.

And here's a spicy idea: some scientists think quasars helped reionize the Universe—that is, ended the cosmic Dark Ages by blasting the fog of neutral hydrogen with ultraviolet radiation, making the Universe transparent.

The Quiet Deaths and Hidden Remnants

Quasars don’t last forever. Eventually, the black hole consumes all available fuel, or the galaxy’s internal dynamics stabilize. The blazing light dims. The jets cease. The lighthouse turns off.

But the black hole remains—silent, immense, and hungry still. The Milky Way's Sagittarius A* might once have been a quasar. Maybe it whispered with light like its ancient siblings. We may never know.

And yet, their ghosts remain. Astronomers can spot ancient quasars by studying galactic fossils and intergalactic gas clouds that still bear the scars of quasar storms.

Humanity and the Lighthouses of Time

Sometimes I imagine what it would be like to stand on a planet near a quasar—the sky a wild aurora of radiation, the night lit as if by a million suns. Terrifying? Absolutely. But awe-inspiring too.

Here’s the thing. Quasars aren't just distant fireworks. They’re reminders. Reminders that even in the early, chaotic Universe, beauty erupted from darkness. That black holes—those ultimate devourers—can, in their hunger, paint the cosmos with light.

Quasars teach us about extremes: of gravity, of brightness, of time. And through them, we see the grand machinery of the cosmos grinding ever onward.

Have you ever looked up and wondered where we came from? Follow a quasar's light back through time, and you might just find a part of the answer.