50 Fun Facts About Astrophysics

Which rock guitarist earned a PhD in astrophysics from Imperial College London in 2007, some 37 years after starting it?

Brian May shelved his thesis on interplanetary dust in 1974, when Queen found international success. He later worked with the science team on NASA's New Horizons mission to Pluto.

Which element was first spotted in the Sun's light during an 1868 eclipse, years before anyone isolated it on Earth?

Helium takes its name from helios, the Greek word for the Sun. It was 1895 before the chemist William Ramsay isolated it on Earth, from a uranium mineral.

What name do astrophysicists give the extreme vertical stretching of an astronaut falling feet first into a black hole?

Spaghettification happens because gravity pulls far harder on the feet than on the head. Near a small black hole the difference is strong enough to pull a person into a long thin strand.

Light leaving the Sun's surface crosses about 150 million kilometres of space to reach Earth in roughly how long?

About 8 minutes is all sunlight needs, which means we always see the Sun as it was that long ago. Astronomers describe the distance as roughly 8 light-minutes.

Astronomers watching the 2017 neutron-star collision GW170817 saw the creation of several Earth masses of which element?

Gold and platinum amounting to about ten Earth masses formed in the collision, by one estimate. Such mergers are now seen as a main cosmic source of both metals.

Which physicist, later director of the Los Alamos atomic bomb laboratory, co-wrote a 1939 paper predicting black holes?

Robert Oppenheimer and his student Hartland Snyder showed that a heavy enough star must keep collapsing without limit. The name black hole did not catch on until the 1960s.

IceCube, a detector frozen into a cubic kilometre of ice at the South Pole, was built to catch which elusive particles?

Neutrinos interact so weakly that about 65 billion from the Sun cross every square centimetre of Earth each second. IceCube records the faint flash when one finally hits the ice.

After swelling and shedding its outer layers billions of years from now, the Sun will end as which Earth-sized remnant?

A white dwarf packs about a Sun's worth of mass into a ball the size of Earth. The Sun is far too light to explode as a supernova or collapse into a black hole.

Which unit of distance, equal to about 3.26 light-years, does Han Solo wrongly use as a measure of time?

Parsec is a real unit, worth about 31 trillion kilometres. The nearest star beyond the Sun, Proxima Centauri, lies just 1.3 of them away.

Which Cambridge physicist argued in 1974 that black holes are not truly black but slowly leak radiation and evaporate?

Stephen Hawking's radiation is so feeble that a black hole with the Sun's mass would take far longer than the age of the universe to evaporate.

The Sun and other stars are made of which state of matter, rare on Earth but seen in lightning and neon signs?

Plasma accounts for an estimated 99.9% of the ordinary matter in the universe. It forms when a gas is heated until electrons break free of their atoms.

Which famous equation explains how the Sun's core turns four million tonnes of matter into energy every second?

E = mc² says a tiny amount of mass equals a huge amount of energy, because the speed of light squared is an enormous number. The Sun can keep paying that bill for billions of years.

Vera Rubin's finding that outer stars in spiral galaxies orbit far too fast was key evidence for the existence of what?

Dark matter seems to make up about 85% of all the matter in the universe. It gives off no light, so astronomers can trace it only through the pull of its gravity.

Which Northern Irish scientist found the first pulsar as a student in 1967 but was passed over for the Nobel Prize?

Jocelyn Bell Burnell's radio pulses were so regular that the source was at first dubbed Little Green Man 1. In 2018 she won a $3 million prize and gave it all away to fund physics students.

Which Nobel-winning Caltech physicist advised Christopher Nolan on the black hole in the film Interstellar?

Kip Thorne's equations drove the film's visual effects, and the images were accurate enough to yield three scientific papers. He shared the 2017 Nobel Prize for detecting gravitational waves.

The James Webb Space Telescope has to stay below minus 220 °C because it observes mainly which kind of light?

Infrared light passes through the dust clouds that hide newborn stars, and it carries the stretched glow of the earliest galaxies. A warm telescope would drown both in its own heat.

Which astrophysicist took over New York's Hayden Planetarium in 1996 and later hosted Cosmos: A Spacetime Odyssey?

Neil deGrasse Tyson received hate mail, much of it from children, after his planetarium stopped listing Pluto among the planets. The show revived a 1980 series by Carl Sagan.

By the Planck satellite's measurements of the oldest light in the cosmos, the universe is roughly how old?

13.8 billion years makes the universe about three times as old as the Sun and Earth. Planck's team pinned the figure down to better than one percent.

Which hypothetical shortcut through spacetime got its name in a 1957 paper co-written by the physicist John Wheeler?

Wormhole tunnels are consistent with general relativity, but nobody knows whether any exist. Keeping one open for a traveller would seem to need exotic matter with negative energy.

Earth squeezed into a black hole would have which boundary of no return, just 9 millimetres in radius?

The event horizon is not a solid surface, and an astronaut crossing a big black hole's would feel nothing special at that moment. The Sun's would have a radius of about 3 km.

Which Oxford mathematician shared the 2020 physics Nobel for proving that general relativity demands black holes?

Roger Penrose and his father also devised the impossible Penrose triangle and Penrose stairs, which inspired Escher's prints Waterfall and Ascending and Descending.

The international ITER reactor aims to recreate on Earth which process that makes the Sun and other stars shine?

Nuclear fusion in the Sun's core joins hydrogen nuclei at about 15 million degrees. Hans Bethe won the 1967 Nobel Prize in Physics for working out how stars do it.

Which phenomenon, heard as a passing siren drops in pitch, lets astronomers clock stars approaching or receding?

The Doppler effect is named after Christian Doppler, who proposed it in 1842 in a paper about the colours of double stars. It was first tested, on sound, three years later.

Which outer layer of the Sun, seen as a pale halo during total eclipses, mysteriously exceeds a million degrees?

The corona is some 200 times hotter than the Sun's visible surface beneath it. Physicists still argue over what heats it.

Supernova surveys revealed in 1998 that the universe's expansion is speeding up, driven by which mysterious ingredient?

Dark energy accounts for roughly 68% of everything in the universe, yet nobody knows what it is. The discovery won three astronomers the 2011 Nobel Prize in Physics.

Which astronomer showed in the 1920s that Andromeda lies beyond the Milky Way and that distant galaxies are receding?

Edwin Hubble had studied law at Oxford as a Rhodes Scholar before turning to astronomy. His discoveries came at Mount Wilson's 100-inch telescope, then the world's largest.

Which British astrophysicist coined the name Big Bang on BBC radio in 1949 for a theory he himself rejected?

Fred Hoyle argued instead for a steady-state universe with no beginning, and went on defending it for decades. He also showed how stars could forge carbon.

Arno Penzias and Robert Wilson first blamed pigeon droppings for a radio hiss that proved to be which Big Bang relic?

The cosmic microwave background is light set free about 380,000 years after the Big Bang, now cooled to 2.7 degrees above absolute zero. The find won the pair the 1978 Nobel Prize.

Which observatory's twin L-shaped detectors in Louisiana and Washington state first caught gravitational waves in 2015?

LIGO measures changes in the 4 km gap between its mirrors that are far smaller than the width of a proton. The first signal came from two black holes merging over a billion light-years away.

The four-million-solar-mass black hole at the centre of the Milky Way is named after which constellation?

Sagittarius A* is the black hole's full name. The first image of it, released in 2022, took five years of calculations to process.

Which small, cool stars are the most common kind in the Milky Way and can shine for trillions of years?

Red dwarfs make up fifty of the sixty stars nearest the Sun, yet not one is bright enough to see with the naked eye.

The core of a massive star dies when it fills with which element, whose nuclei release no energy when forced together?

Iron marks the end: with nothing left to hold it up, the core falls inward at up to 23% of the speed of light and the star explodes as a supernova.

Which supernova remnant grew from an explosion that Chinese astronomers recorded as a daytime guest star in 1054?

The Crab Nebula owes its name to an 1840s sketch by the Earl of Rosse that made it look like a crab. At its heart, a pulsar spins about 30 times a second.

Which objects, first identified in 1963 from the radio source 3C 273, can outshine the entire galaxies around them?

Quasars are the blazing cores of distant galaxies, lit by gas falling toward a supermassive black hole. The name is a contraction of quasi-stellar radio source.

Which rare type of neutron star unleashed a 2004 flare that disturbed Earth's ionosphere from far across the Milky Way?

The magnetar, SGR 1806-20, released more energy in a tenth of a second than the Sun gives off in 150,000 years, from a star no more than about 20 km across.

Which Belgian Catholic priest proposed that the universe is expanding and traced it back to a single primeval atom?

Georges Lemaître first set out an expanding universe in 1927, in a Belgian journal few astronomers read. Einstein accepted the mathematics but scorned the physics.

Whose 1925 doctoral thesis showed that stars are mostly hydrogen, a result a senior astronomer urged her to disown?

Cecilia Payne was pressed by Henry Norris Russell to play down her own finding. Four years later he reached the same result himself and was widely given the credit.

Which NASA X-ray telescope, launched in 1999, is named after the astrophysicist who found a mass limit for dying stars?

Chandra was the nickname of Subrahmanyan Chandrasekhar, and fittingly means moon in Sanskrit. His limit, about 1.4 times the Sun's mass, helped earn him a share of the 1983 Nobel Prize in Physics.

Which British astronomer travelled to Príncipe for the 1919 eclipse that confirmed Einstein's general relativity?

Arthur Eddington was a Quaker and a conscientious objector, and news of his result turned the German-born Einstein into an international celebrity just after the First World War.

Which Harvard astronomer found that brighter Cepheid stars pulse more slowly, a rule used to measure cosmic distances?

Henrietta Swan Leavitt's rule turns a pulsing star's rhythm into its true brightness, and so its distance. A Swedish academician later tried to nominate her for a Nobel Prize, unaware she had died.

Which technique, built on the dark lines Joseph von Fraunhofer mapped in sunlight, reveals what stars are made of?

Spectroscopy works because each element absorbs its own set of colours, leaving a barcode of dark lines in a star's light. Fraunhofer, a glassmaker, counted 574 of them in sunlight.

Vesto Slipher found in the 1910s that light from most spiral nebulae is stretched to longer wavelengths, known as what?

Redshift later became the first evidence that the universe is expanding. Oddly, the first galaxy Slipher measured, Andromeda, turned out to be rushing toward us instead.

Which apparent shift of nearby stars as Earth orbits the Sun gave Friedrich Bessel a distance to 61 Cygni in 1838?

Parallax is the same effect that makes a raised finger jump when you look with one eye and then the other. Bessel's sums put 61 Cygni about 10 light-years away.

Stars spend about 90% of their lives in which hydrogen-burning phase, with the Sun roughly halfway through its own?

The main sequence will be the Sun's home for roughly ten billion years in all. The heaviest stars race through theirs in just a few million.

The Hertzsprung–Russell diagram sorts stars by plotting their luminosity against which other property?

Surface temperature runs backwards on the chart, with the hottest stars on the left. Ejnar Hertzsprung and Henry Norris Russell each devised it independently in the early 1910s.

Cepheid stars and Type Ia supernovae serve as which distance markers, objects whose true brightness is known?

Standard candles work like a light bulb of known wattage: the dimmer one looks, the farther away it must be. Standard sirens do the same job using gravitational waves.

Which effect can smear the image of a distant galaxy into a circle of light known as an Einstein ring?

Gravitational lensing happens because mass curves space, bending light that passes a galaxy as if through glass. Einstein wrote in 1936 that there was no hope of ever seeing such a ring.

Which cosmic explosions were first detected in 1967 by US Vela satellites built to spot covert nuclear weapons tests?

Gamma-ray bursts pack as much energy into a few seconds as the Sun will release in its ten-billion-year life. The puzzling flashes were not published until 1973.

Victor Hess took a balloon to 5,300 metres in 1912 and found radiation rising with altitude, the discovery of what?

Cosmic rays are mostly protons arriving from deep space. Hess flew during a near-total eclipse to rule out the Sun as their source, and won the 1936 Nobel Prize in Physics.

Which German physicist found the first exact solution of general relativity while serving on the Russian front in 1915?

Karl Schwarzschild sent his answer to Einstein by letter from the front, amid gunfire. It describes what is now called a black hole, though he died the next year, aged 42.