luminosity

A heaping teaspoon, and the scale reads a billion tons. That's roughly what a teaspoon of neutron star matter would weigh if you could scoop it up and put it on a scale. Such objects are born after a supernova explosion: the star's core collapses into a sphere the size of a city, and the density exceeds that of an atomic nucleus.

Two thousand years ago, a brilliant beacon shone in the constellation Eridanus, recorded in the registers of ancient astronomers. Hipparchus in 129 BCE noted it as a first-magnitude star, Ptolemy confirmed its brightness in the Almagest, and the Persian scholar Al-Sufi still saw it among the brightest in 964.

Hydrogen is the most common element. Its atoms are like antennas: they emit and absorb light at very specific frequencies. Einstein predicted that spacetime can ripple: these are gravitational waves.

In the scorching solar corona, where temperatures soar past a million degrees, float cold, dense clouds — solar prominences. They hang for weeks, neither falling nor dissolving, like icebergs in a boiling ocean. How they got there is a question that has puzzled astronomers for decades.

Ancient stars, nearly devoid of heavy elements, are like fossilized remnants of the first cosmic flashes. For a long time, the odd ratio of carbon, hydrogen, and helium in three such stars was thought to require a hypernova — an ultra-bright supernova with hundreds of times more energy than a regular one.

Neutrinos are tiny particles that barely interact with matter. They pass straight through a star like bullets through fog. When a massive star is gearing up to explode, its core contracts, temperatures soar, and neutrinos start streaming out.

Cosmic rays are charged particles that constantly bombard Earth from deep space. When one of these particles enters the atmosphere, it collides with air nuclei and spawns a whole cascade of secondary particles: electrons, muons, photons.

When a bright spot flares up on a star, astronomers want to know how much energy was released into space. They used to picture a flare as a growing campfire: the area of the fire increases, but the heat remains the same. That made calculations simpler, but reality turned out to be different.

A neutron star is the ultra-dense remnant of a supernova explosion, whose existence was predicted by Fritz Zwicky back in the 1930s. Later, Jocelyn Bell Burnell detected them as pulsars — rotating sources of strictly periodic radio signals.

The Sun’s gravity creates an invisible goblet, in which dark matter of a special kind — ultralight — doesn’t splash around chaotically, but occupies strict energy steps, like transparent layers of liquid. So around the Sun, a natural spectroscope emerges, sorting the invisible substance into levels, just like electrons in an atom.

The Solar System takes 210 million years to complete one orbit around the center of the Milky Way. The last time we were on this same side of the Galaxy, early dinosaurs were roaming the Earth. That number, 243.72 km/s, has now been refined thanks to rare stars that streak through the Galaxy like cannonballs.