cosmic microwave background obscuration

Light from the hottest stage of the universe has been traveling toward us for nearly 14 billion years. This is the cosmic microwave background — a faint glow filling the entire sky.

Cosmologists are facing a curious situation: two reliable tools draw slightly different maps of the same universe. One tool is the map of ancient light (the cosmic microwave background), and the other is the map of galaxy distribution. They broadly agree, but in details they diverge.

In the first moments after the Big Bang, the universe expanded at an incredible rate — a phase known as inflation. Even the vacuum was restless back then: quantum jitters shook the fields like wind rustling through a wheat field.

The universe is like a vast invisible scaffold. We don't see it directly, but we know it's there: galaxies and clusters hold together thanks to it. This scaffold is dark matter. The most popular version says it is "cold," made of heavy, slow-moving particles.

264 kilometres per second — that's how fast the Solar System hurtles through the cloud of dark matter. Its existence was given away by galaxies: they spun too fast to be held by visible mass, and Vera Rubin was first to suspect a hidden scaffolding.

The universe cooled like a giant bathtub after a hot start. At 400 000 years after the Big Bang, hydrogen was ready to recombine — protons capturing electrons to become neutral atoms. But somewhere in this dark water, a tap kept dripping.

In the first seconds after the Big Bang, the Universe left us not only light but also something far more elusive — the relic neutrino background. This echo of creation permeates every cubic centimeter, yet we barely notice it.

Two million years away, around the young star CI Tau, a gas-dust disk whirls — a protoplanetary cradle. ALMA observations have already shown rings and gaps in it, but the finest details remained invisible: their width is smaller than the instrument's resolution.

The standard cosmological model ΛCDM, where dark matter and dark energy act as the chief architects of the cosmos, has predicted astronomical data with Swiss-watch precision for decades. Its foundation was laid by three geniuses.

Cosmology is like an orchestra where different sections suddenly start playing out of sync. Measurements of the universe's expansion rate (the Hubble constant) from the early and late universe give different numbers.

The universe is like a vast warehouse where a strict inventory was taken long ago. The cosmic microwave background is an ancient record of everything in stock 380,000 years after the big bang. According to it, the fraction of matter in the cosmic 'budget' (the parameter Omega_m) is known with high precision.

A giant cloud of invisible matter acts like a funhouse mirror — distorting the light from a distant galaxy. From these distortions, astronomers can weigh the cloud and peer into its depths.

At the center of the Milky Way, like a matryoshka doll within a matryoshka doll, lies a supermassive black hole, surrounded by a swarm of stars and an invisible shell of dark matter. This shell, or "spike," is expected to be extremely dense right at the horizon.

The Universe grows like a metropolis: galaxies skyscrapers are erected on an invisible scaffold of dark matter: its gravity pulling in construction material. Meanwhile, dark energy makes the city itself continuously expand.

An old photograph taken at the moment of the universe's birth has been carrying its light to us for nearly 14 billion years. This snapshot is the cosmic microwave background, the cooled echo of the Big Bang. It captures the tiny inhomogeneities from which galaxies later grew.

On the kitchen counter, there's a flour scale and a measuring cup for water. Individually, they're precise, but when you bake bread, the recipe calls for the perfect ratio. Astronomers have a similar dispute about the universe's expansion rate.

The cosmic microwave background is the afterglow of the Big Bang, which we see at millimeter wavelengths. But it also has a long-wavelength tail extending into the radio range.

A spotlight shines through a dark hall. Between the lamp and the wall, an invisible lens drifts by, and the spot of light briefly brightens and shifts. That is exactly what the DECam telescope, aimed at the Large Magellanic Cloud, a satellite galaxy of our Milky Way, was watching for five consecutive nights.

Black holes come in lightweights, born from dying stars, and supermassive ones at galactic cores. The missing intermediate link had been hiding. Fast radio bursts, cosmic signals lasting milliseconds but carrying the energy of days of sunlight, helped crack the case. Think of these bursts as cries from the depths of the universe.

A flashlight beam glides over uneven glass. The glass is massive galaxy clusters, and the flashlight is ancient light born shortly after the big bang. Passing by such clusters, light doesn't just bend around them like water around a rock. Its path shifts slightly sideways, and the amount of shift depends on how the light is 'twisted'—right or left.

Frozen cake batter is dotted with tiny raisins. If the batter is uniform, all the raisins will puff up evenly, and the cake will be smooth. But if the batter has denser spots (some sweeter, some more bland) the raisins will be distributed unevenly: dense in some places, sparse in others.

A dust storm that has raged for millions of years is not in a desert but between the stars. There, clouds of tenuous gas drift, threaded by magnetic fields. These fields align dust grains like compass needles along field lines. When such dust emits, its light becomes polarized: it oscillates in a single plane, like a rope shaken only up and down.

A giant cloud of gas and dust, so cold that its warmth barely flickers, just a few degrees above absolute zero. This is TMC-1 in the constellation Taurus, one of the darkest and densest cradles of molecules in our Galaxy. In recent years, it has become a true treasure trove for astrochemists: the number of substances found there has more than doubled.

The universe resembles a giant sponge: bright filaments of galaxies weave around enormous dark voids. Inside these filaments and walls hide clumps of invisible dark matter — halos. When dark matter particles collide and decay, they produce ordinary particles that telescopes can catch.

Five galaxies that long ago stopped igniting new stars look like houses with darkened windows. But the ALMA radio telescope and the James Webb Space Telescope peered inside and saw that in these 'sleeping' houses, a fire still smolders.

Light from a distant star, passing through the atmosphere of planet K2-18b, left unusual "fingerprints" in its spectrum. Astronomers spent 420 hours collecting this light with the James Webb Space Telescope and split it into colors, like a rainbow.

Light that has traveled to us for nearly 14 billion years is like an old photograph whose details emerge with careful processing. The cosmic microwave background (the afterglow of the Big Bang) holds the imprint of the universe's first moments, but its signal is faint and distorted.

Radio waves passing through magnetized gas have their polarization slightly rotated, like a compass needle deflecting near a magnet. This rotation, called the Faraday effect, revealed the invisible environment around the supermassive black hole in galaxy NGC 1275.

Astronomers are trying to capture the radio echo of the Big Bang — a faint glow that fills the entire universe. But the receiver is choking with noise: our Galaxy is packed with glowing interstellar dust, whose emission can easily be mistaken for a signal from the distant past.

When a massive star runs out of fuel, its core collapses and a shock wave races outward. But even before the star tears apart, particles that barely interact with ordinary matter may be born in its depths. If they decay into light, that energy leaks into the dense gas around the star. This gas, like a blanket, wraps the star.

Globular clusters are dense stellar archives, where the youth of the Galaxy is recorded. But reading this chronicle was hindered by imprecise chronometers: age estimates diverged by a billion years.

Deep in the constellation Ophiuchus lies the galaxy NGC 6447. Until recently, it was quiet and unremarkable, like a house with its windows dark. But over the past 14 years, something has ignited at its center, and now it's visible in infrared light.

The universe is like an ocean, where waves of different lengths roll onto the shore. The longest waves are the giant fluctuations in the distribution of matter that we see in the cosmic microwave background. Standard theory says such waves should exist on all scales.

The cosmic microwave background is a faint glow left over from the Big Bang, like the cooling embers of a campfire. It encodes gravitational waves that may have arisen in the first fractions of a second, when the universe inflated faster than light.

Light from distant galaxies passes through clumps of matter, and the gravity of those clumps slightly bends its path, like a lens. By measuring how much the images of distant galaxies are distorted, we can infer the distribution of matter and how gravity affects light.

Light from a distant lantern reflects off the surrounding fog, and from the delay of the reflection you can infer the distance. If the fog is uneven, the reflection arrives earlier or later, and the distance comes out wrong.

In the Large Magellanic Cloud, a galaxy that orbits our Milky Way, astronomers have caught five stars that look like fossils from the very distant past. They contain almost no metals, only one-hundredth to one-thousandth of what the Sun has, but they have tens of times more carbon.

The night sky is full of stars, but they are only a small part of everything that exists in the universe. Astronomers have long noticed a strange thing: galaxies rotate so fast that they should fly apart, yet they don't. Something invisible holds them together, like invisible threads linking beads on a spinning wheel. This "something" was named dark matter.

Dark energy and dark matter are the invisible conductors of the cosmos. Usually considered independent, new research proposes seeing them as dance partners. The lead — dark energy — changes the mass of dark matter particles. Like a dancer who lifts and lowers their partner, dark energy increases or decreases the weight of dark matter.

A black hole merger gives birth to a gravitational wave. Sometimes the wave’s path is blocked by a galaxy or a clump of dark matter, predicted by Zwicky and discovered by Rubin.