140 Fun Facts About The Sun

What informal name do astronomers give to a star of the Sun's type?

Yellow dwarf is the informal name for a G-type main-sequence star, one that fuses hydrogen steadily for about 10 billion years before it swells into a giant.

Approximately how long does it take sunlight to reach Earth?

About 8 minutes, or 8 minutes 20 seconds on average, means nobody ever sees the Sun as it is now, only as it was when that light set out.

Which invisible rays in sunlight are the main cause of sunburn?

Ultraviolet rays cause both suntan and sunburn; ozone high in the atmosphere absorbs part of them, so a thinner ozone layer means more reach the ground.

What process powers the Sun and produces its energy?

Nuclear fusion forces hydrogen nuclei together in the core at about 15 million °C, and the energy released then takes many thousands of years to work its way out to the surface.

What color would the Sun appear if viewed from space, without atmospheric interference?

The Sun actually emits white light. It appears yellow or orange from Earth's surface because the atmosphere scatters shorter (blue) wavelengths, making the remaining light look yellowish.

In ancient Egyptian mythology, who was the sun god?

Ra (also spelled Re) was the ancient Egyptian sun god and one of the most important deities in the Egyptian pantheon. He was believed to sail across the sky each day in a solar boat.

What name is given to the huge arches of cooler gas that hang above the Sun's edge, held up by magnetism?

Prominences can hang in place for weeks or months; when the magnetic field holding one up becomes unstable, it can erupt into space as a coronal mass ejection.

What is the approximate surface temperature of the Sun?

About 5,500°C is the visible surface; oddly, the thin corona high above it is far hotter, a million degrees or more, and why remains one of the Sun's unsolved puzzles.

How many Earths could fit inside the Sun?

About 1.3 million Earths would fill the Sun's volume, as it is 109 Earths across; yet it weighs only as much as 330,000 Earths, because the Sun is far less dense.

A solar eclipse can happen only during which phase of the Moon?

New moon puts the Moon between Earth and the Sun, yet most months bring no eclipse, because its orbit is tilted about 5 degrees and its shadow usually passes above or below Earth.

Which layer of the Sun flashes reddish-pink for a few seconds at total eclipses?

The chromosphere glows reddish-pink with hydrogen light but is normally drowned out by the glare beneath it, so it shows only when the Moon hides the Sun's bright disk.

What is the approximate age of the Sun?

About 4.6 billion years ago a spinning cloud of gas and dust collapsed and most of it fell to the centre to make the Sun, which is now roughly halfway through its life.

What will the Sun eventually become at the end of its life?

White dwarf is the end for every low- or medium-mass star: in about 5 billion years the Sun will swell into a red giant, throw off its outer layers and leave a core about the size of Earth.

Roughly how long does a typical coronal mass ejection take to travel from the Sun to Earth?

A few days is typical, though the fastest make the trip in 15 to 18 hours; on arrival a big one can light up auroras and disturb satellites and power grids.

The Sun holds about 99.8% of the solar system's mass; which planet accounts for most of the rest?

Jupiter holds more than twice the mass of all the other planets put together, yet the Sun still outweighs it roughly a thousand times over.

In Greek myth, who fell into the sea after flying too close to the Sun on wings held together with wax?

Icarus flew too high on wings his father Daedalus built so they could escape King Minos of Crete; the island where his body washed ashore was later named Icaria.

What is the visible surface of the Sun called?

The photosphere is not a solid surface at all: the Sun is gas throughout, and this is simply the layer from which its light finally escapes into space.

About how long does one solar cycle of rising and falling sunspot numbers last?

About 11 years separates one sunspot peak from the next, and around each peak the Sun's magnetic field flips, its north and south poles swapping places.

After the Sun, which star lies closest to Earth?

Proxima Centauri is just over four light-years away, roughly 250,000 times farther than the Sun, so the light we see from it set out more than four years ago.

Which of NASA’s spacecraft, launched in 2018, was built to fly through the Sun’s corona?

Parker Solar Probe flies behind an 11 cm carbon heat shield whose Sun-facing side reaches about 1,400°C, while the instruments in its shadow stay near room temperature.

How long does the Sun take to complete one orbit around the centre of the Milky Way?

About 230 million years makes one 'galactic year', so for all its age the Sun has carried its planets around the Milky Way only about 20 times since it formed.

Roughly how fast does the solar wind typically stream past Earth?

About 400 km/s is the usual slow wind, with fast streams near 750 km/s; together they blow a vast magnetic bubble that reaches far beyond the planets.

Roughly how strong is gravity at the Sun's surface compared with Earth's?

About 28 times Earth's pull, roughly 274 m/s², so an 80 kg person would weigh more than two tonnes there, if there were anything solid to stand on.

In which arm of the Milky Way does the Sun sit?

The Orion Arm, also called the Local Arm, was long written off as a mere spur between two major arms, but radio measurements reported in 2013 suggest it is far more substantial.

What was the Carrington Event of 1859?

A solar storm that crippled telegraphs: wires sparked, operators got shocks and paper caught fire, while auroras glowed as far south as Cuba and Hawaii.

How long does the Sun's equator take to spin once around?

About 25 days at the equator, but well over 30 near the poles: the Sun is a ball of gas, not a solid, so different latitudes turn at different rates.

Where does the solar wind give out and interstellar space begin?

The heliopause is where the solar wind can no longer push back the thin gas between the stars; Voyager 1 crossed it in 2012, the first craft ever to do so.

What is the Latin word for the Sun?

Sol is the Latin word for the Sun; it survives in solar, solstice (from sol plus sistere, 'to stand still'), solarium and parasol.

Which spacecraft, launched in December 1995, was built to observe the Sun from the L1 point?

SOHO, the Solar and Heliospheric Observatory, launched on 2 December 1995 and took station at the L1 Lagrange point between Earth and the Sun, far outliving its planned two-year mission.

Roughly how long does a neutrino produced in the Sun's core take to reach the surface and escape?

About 2 seconds, since neutrinos barely interact with matter and fly straight out at nearly light speed, while light itself needs many thousands of years to work its way out.

Since the Sun first began to shine, it has steadily been getting what?

Brighter: the young Sun gave out only about 70% of today's light, which leaves scientists puzzling over why the early Earth was not frozen solid.

Which scientist observed sunspots by telescope around 1612 and argued they were on the Sun itself?

Galileo Galilei made the case in his Letters on Sunspots, written against the Jesuit Christoph Scheiner, who held that the dark spots were small satellites circling the Sun.

What name do scientists give the roughly 1.36 kilowatts of sunlight reaching each square metre at Earth's distance?

Solar constant is a slight misnomer: satellites show the figure creeping up by a fraction of a percent at the peak of each solar cycle and dipping again afterwards.

North of which line does the Sun stay above the horizon for at least one full day every summer?

The Arctic Circle marks the limit because Earth is tilted about 23.5 degrees; the unbroken daylight lasts a day there and stretches to six months at the North Pole.

Which Victorian physicist held that gravity alone fuelled the Sun, giving it an age of only tens of millions of years?

Lord Kelvin's figure left too little time for Darwin's slow evolution, and he argued the point publicly with geologists; what truly powers the Sun was worked out only in the 1930s.

What name is given to studying the Sun's interior through the sound waves that make its surface rise and fall?

Helioseismology works the way earthquake studies reveal Earth's interior: the waves' timing betrays the temperature, make-up and motion of the gas they cross deep inside the Sun.

What are the bright spots called that appear either side of the Sun when its light bends through ice crystals?

Sun dogs form about 22 degrees either side of the Sun as flat ice crystals act like tiny prisms; red light bends least, so their inner edges glow red.

What name is given to the points of sunlight that shine through lunar valleys just before a total eclipse?

Baily's beads are named for the English astronomer Francis Baily, who drew attention to them in 1836; the last one to linger shines out alone as the 'diamond ring'.

Which prehistoric monument in England is aligned with sunrise on the summer solstice?

Stonehenge's axis also points the other way, to the midwinter sunset; its stone circle went up about 2500 BC, and it was long mistaken for a Druid temple.

Which element turned up in the Sun's spectrum before anyone found it on Earth?

Helium first showed up as an unexplained yellow line in sunlight during the 1868 eclipse; Norman Lockyer judged it a new element, and it was not found on Earth until 1895.

Which probe, launched in 1990, used Jupiter's gravity to swing up over the Sun's poles?

Ulysses needed Jupiter's pull to swing it onto a path over the Sun's poles; too far from the Sun out there for solar panels, it ran on a radioisotope generator instead.

Which 1980 NASA solar satellite became the first to be repaired in orbit by astronauts?

Solar Maximum Mission launched in February 1980 and lost attitude control within months; in April 1984 Challenger astronauts captured and repaired it, the first in-orbit satellite repair.

Which kind of eclipse leaves a ring of sunlight because the Moon is too far away to cover the Sun?

Annular eclipses come when the Moon is near its farthest from Earth; because the bright ring never goes dark, eclipse glasses have to stay on the whole time.

With which country did NASA send the twin Helios probes closer to the Sun than any craft before them?

West Germany supplied both spacecraft and NASA the rockets; in 1976 Helios 2 dived to 43 million km from the Sun, a record that stood for four decades.

Which NASA capsule carrying particles caught from the Sun crash-landed in Utah in 2004?

Genesis spent two years collecting solar-wind particles; in September 2004 its drogue parachute never deployed and it hit the Utah desert, yet enough clean material survived to meet the mission's major science goals.

India's first dedicated solar observatory, launched on a PSLV rocket in September 2023, carries what name?

Aditya-L1 reached its orbit around the L1 point, 1.5 million km sunward of our planet, early in 2024; from there nothing ever passes between it and the Sun.

ESA's Solar Orbiter, launched 2020, tilts its orbit using flybys of which planet?

Venus flybys lever Solar Orbiter out of the plane of the planets; by March 2025 a tilt of 17 degrees had already given it the first clear views of the Sun's poles.

Which NASA mission gave the first view of the entire Sun at once, including its far side?

STEREO is a pair of near-identical craft launched in 2006, one drifting ahead of Earth and one falling behind, so that between them they could see round both sides of the Sun.

In Shinto belief, which sun goddess does Japan's imperial family claim as its ancestor?

Amaterasu once shut herself in a cave after a quarrel with her brother Susanoo, plunging the world into darkness until the other gods lured her back out.

The Solar Dynamics Observatory's Sun images appeared on what US item in 2021?

Forever stamps in the 'Sun Science' set don't show the Sun's real colours: the observatory records light our eyes cannot see, and NASA tints each image to mark its wavelength.

Which space station carried the Apollo Telescope Mount, a set of solar telescopes run by its astronauts?

Skylab's solar telescopes recorded on film, so its astronauts had to collect the canisters on spacewalks and carry them home in their Apollo capsules.

Which NASA series put probes 6 to 9 into solar orbit to monitor space weather?

Pioneer 6 was built to last six months, yet NASA was still raising it in December 2000, 35 years after launch; Pioneers 7, 8 and 9 joined it in orbit around the Sun.

Which Soviet craft, launched at the start of 1959, became the first artificial object to orbit the Sun?

Luna 1 was aimed at the Moon but missed it, and so became by accident the first craft to escape Earth's gravity and settle into orbit around the Sun.

In the 1950s, Biermann inferred a particle stream from the Sun from what feature?

Comet tails always point away from the Sun, whichever way the comet is travelling, which led Ludwig Biermann to propose a steady stream of particles blowing outward.

What is each of the two days a year called when the Sun stands directly over the equator?

Equinox days fall in March and September; even then day and night are not quite equal, because the air bends sunlight and keeps the Sun in view a few minutes longer.

What is the boundary where the Sun's outflowing particles abruptly slow, beyond Pluto?

At the termination shock the solar wind abruptly drops from supersonic to subsonic speed; beyond it lies the heliosheath, which the two Voyager probes spent years crossing before leaving the bubble.

The 4-metre Daniel K. Inouye Solar Telescope stands on which Hawaiian volcano?

Haleakalā means 'house of the sun'; in Hawaiian legend the demigod Māui caught the Sun there and made it cross the sky more slowly, to lengthen the day.

Which German amateur astronomer first spotted the sunspot cycle, in 1843?

Heinrich Schwabe counted sunspots almost daily for 17 years; astronomers had watched them for over two centuries without noticing that their numbers rise and fall.

What name is given to the decades from about 1645 to 1715 when sunspots all but vanished?

The Maunder Minimum overlapped the coldest stretch of the Little Ice Age, when Europe and North America shivered through bitter winters, though how far the quiet Sun was to blame is unsettled.

Who showed in 1908 that sunspots are intensely magnetic?

George Ellery Hale read the magnetism from the way it splits the lines in a sunspot's spectrum, working at Mount Wilson, one of four observatories he founded.

What is the dark central part of a sunspot called?

The umbra is dark only by contrast: it is more than a thousand degrees cooler than the gas around it, yet alone in the night sky a sunspot would shine about as brightly as the full Moon.

The largest sunspots can reach diameters of roughly how many kilometres?

160,000 km is more than twelve Earths side by side; spots that large can be seen without a telescope when mist or thin cloud dims the Sun.

The oldest known sunspot records, made around 800 BC or earlier, come from which civilisation?

Chinese court astronomers logged sunspots for many centuries, while in Europe, where the heavens were held to be perfect, a large spot seen in 807 was taken for a planet crossing the Sun.

Solar flares are ranked on a letter scale by their peak flux in what kind of radiation?

Soft X-rays measured by GOES weather satellites set a flare's class, each letter ten times stronger than the last; the biggest can black out shortwave radio on Earth's sunlit side.

The series of solar storms that struck in 2003 is nicknamed after which holiday?

Halloween 2003 brought a run of giant flares; one on 4 November overloaded the satellite sensors meant to measure it, so its true strength could only be estimated.

A huge solar storm in July 2012 missed Earth by roughly how long?

About a week: the blast tore through Earth's orbit where the planet had been days before and hit a NASA spacecraft instead; a direct hit, one researcher said, would have left us 'still picking up the pieces'.

Which amateur astronomer independently saw the 1 September 1859 white-light flare alongside Carrington?

Richard Hodgson independently recorded the same white-light flash as Carrington on 1 September 1859, and both accounts appeared together in the Monthly Notices of the Royal Astronomical Society.

Which cycle of 18 years and 11 days brings near-identical eclipses round again?

The Saros cycle runs a third of a day over its 18 years and 11 days, so the Earth has turned further and each repeat falls about 120 degrees to the west of the last.

What is roughly the longest that totality can last in a total eclipse of the Sun?

About 7.5 minutes is the ceiling, because the Moon's shadow never stops racing across the ground; the longest eclipse yet calculated, on 16 July 2186, will last 7 minutes 29 seconds.

The 2017 'Great American Eclipse' reached land in Oregon and left from the coast of which state?

South Carolina was where the Moon's shadow slid out to sea about an hour and a half after reaching Oregon; no total eclipse had crossed the whole country since 1918.

The April 2024 total eclipse crossed North America; in which country did its totality last longest?

Mexico had the longest view, 4 minutes 28 seconds near Torreón; the Moon was closer to Earth than in 2017, when totality peaked at 2 minutes 42 seconds.

The 1919 relativity eclipse was observed from Sobral, Brazil, and which African island?

Arthur Eddington led the party on Príncipe, in the Gulf of Guinea; measuring how much the Sun's gravity bent starlight confirmed general relativity and made Einstein famous overnight.

Who catalogued the dark absorption lines in the Sun's spectrum in 1814?

Joseph von Fraunhofer, a Bavarian lens-maker, came upon the lines while testing how different glasses bend light and went on to plot more than 500 of them.

Whose 1925 thesis showed stars are overwhelmingly made of the lightest element?

Cecilia Payne's 1925 Harvard thesis found stars are mostly hydrogen; Henry Norris Russell talked her into calling the result 'almost certainly not real', then conceded in 1929 that she was right.

Which physicist won the 1967 Nobel Prize for explaining how stars generate energy?

Hans Bethe worked out the nuclear reactions that keep stars shining; dismissed from his German university post in 1933 because of his Jewish grandparents, he later led the theory division at Los Alamos.

Who showed in 1859 that the Sun's dark spectral lines come from absorbing elements?

Gustav Kirchhoff, working with Robert Bunsen in Heidelberg, found that the dark lines fall exactly where heated elements give off bright ones, which opened the way to a chemical analysis of the Sun.

Which English scientist passed sunlight through a prism to show it is made up of light of many colours?

Isaac Newton's prism split sunlight into its colours; more than a century later, in 1800, William Herschel found infrared lurking beyond the red end of the same spectrum.

The Homestake solar-neutrino experiment ran deep in a gold mine in which US state?

Raymond Davis Jr. ran the experiment 1,500 m down in the Homestake gold mine at Lead, South Dakota, finding only about a third of the predicted neutrinos; he shared the 2002 Nobel Prize.

Which Greek, c. 310–230 BC, proposed the first known Sun-centred model of the universe?

Aristarchus of Samos's own account is lost; we know it because Archimedes described the theory in The Sand Reckoner, noting that it would make the universe far larger than anyone believed.

Which Greek philosopher called the Sun a fiery mass larger than the Peloponnese?

Anaxagoras is said to have been tried for impiety in Athens over the claim, perhaps as a blow at his friend Pericles, and to have died in exile.

Who used sightings of Mars from Paris and South America in 1672 to measure the distance to the Sun?

Giovanni Cassini stayed in Paris and sent Jean Richer to Cayenne in French Guiana; sighting Mars from both at once gave its distance, and the known proportions of the orbits gave the Sun's.

James Cook's 1769 voyage to observe a transit of Venus took him to which island?

James Cook carried Royal Society observers to Tahiti aboard HMS Endeavour to time the transit on 3 June 1769; that done, his orders were to search for a great southern continent.

Every second, the Sun converts roughly how much mass into energy?

4.26 billion kg vanish every second, yet the Sun is so vast that in its whole life so far it has used up only about 0.03% of its mass this way.

The Sun is made of plasma, the state of matter also seen in which of these on Earth?

Lightning is a flash of plasma, the electrically charged gas that makes up the whole Sun; in the Sun's core it is squeezed far denser than lead and yet is still not a solid.

What measure of length, about 150 million km, is based on Earth's average distance from the Sun?

The astronomical unit used to be measured, but since 2012 it has been fixed by definition at exactly 149,597,870.7 km, so it no longer shifts as measurements improve.

The Sun outshines most stars in the Milky Way because the great majority are which dim type?

Red dwarfs are by far the commonest stars, yet they are so faint that not a single one, not even the nearest, can be seen from Earth with the naked eye.

When the Sun swells into a red giant billions of years from now, which planet will it engulf first?

Mercury goes first and Venus is expected to follow; Earth's fate is too close to call, because the swollen Sun will shed mass and loosen its hold, letting our world drift outward.

In which month, oddly for northerners, does Earth reach perihelion, its closest point to the Sun?

January puts Earth about 5 million km nearer the Sun than July does, in the depth of northern winter; the seasons come from the planet's tilt, not its distance.

In Norse myth, which wolf chases the Sun across the sky?

Sköll runs after the Sun in Snorri's Edda while his fellow wolf Hati hunts the Moon; another old poem has Fenrir, not Sköll, seize the Sun at Ragnarök.

Which Roman emperor revived the cult of the Unconquered Sun in AD 274 and built it a grand temple?

Aurelian hoped one shared sun cult would bind together an empire of many faiths; he gave the god a new college of senatorial priests and games held every four years.

Which is the only US state where the Sun can pass directly overhead, leaving upright poles with no shadow?

Hawaii is the only US state in the tropics, and a 1990s Bishop Museum contest named the shadowless moment Lāhainā Noon, from words meaning 'cruel sun'.

Volume for volume, the centre of the Sun gives off heat at about the same rate as which garden feature?

A compost heap makes heat about as fast per cubic metre as the Sun's centre, under 300 watts; the Sun blazes only because it is so enormous.

Which colour is the brief flash sometimes seen on the Sun's upper rim at the last instant of sunset?

Green appears because the air scatters the Sun's blue light out of view, and the flash usually lasts no more than two seconds.

Which constellation does the Sun cross each year, though astrology's twelve star signs leave it out?

Ophiuchus sits between Scorpius and Sagittarius, so the Sun's yearly route really crosses thirteen constellations rather than astrology's twelve.

Which everyday molecule can survive in the coolest layer of the Sun, about 4,100 K, just above the visible surface?

Water and carbon monoxide can hold together there because, oddly, the Sun's atmosphere cools for the first 500 km above the surface before heating up again.

Which part of the Sun, normally lost in the glare, shows as a pearly halo around the Moon during a total eclipse?

The corona was only pinned on the Sun in 1724, when Giacomo Maraldi recognised that the eclipse halo does not belong to the Moon.

For someone in Sydney, Australia, the midday Sun always stands in which part of the sky?

The north is where the midday Sun sits across the Southern Hemisphere's mid-latitudes, so homes there catch winter warmth through north-facing windows.

Moreton waves, shock fronts that race across the Sun after a big flare, are nicknamed after which ocean hazard?

A tsunami is the usual comparison for these ripples in the Sun's lower atmosphere, which Gail Moreton clocked at 500 to 1,500 km a second.

The Sun's daily journey from east to west across the sky is an illusion caused by which motion of Earth?

Spinning on its axis, Earth turns once every 23 hours 56 minutes measured against the stars, which makes the Sun, Moon and stars all seem to wheel westward.

Which name do astronomers give the path the Sun appears to trace against the background stars over one year?

The ecliptic takes its name from eclipses, because the ancients noticed they happen only when the Moon is crossing that line.

Photographing the Sun at the same clock time all year reveals which figure-eight curve in the sky?

An analemma was first caught on film in 1978–79, when Dennis di Cicco made 44 exposures on a single frame over Massachusetts.

On the June solstice the noon Sun stands directly overhead along which line of latitude?

The Tropic of Cancer was named when the Sun sat in the constellation of the Crab at that solstice, and the line is drifting south by about 15 metres a year.

Which part of a sundial casts the shadow that follows the Sun's movement through the day?

The gnomon has a Greek name meaning 'one that knows', and the philosopher Anaximander is credited with introducing the device to the ancient Greeks.

Which bending of light by Earth's air keeps the Sun in view after it has really dropped below the horizon?

Refraction lifts the Sun's image so far that when its lower edge seems to touch the horizon, the whole disc is geometrically already below it.

The Sun has no solid surface because it is a giant ball of what?

Plasma, a gas so hot that its atoms are stripped of electrons, is rare on Earth yet makes up an estimated 99.9% of the ordinary matter in the universe.

Which layer of the Sun, lying just under the visible surface, churns like boiling soup as hot gas rises and sinks?

The convection zone fills roughly the outer 30% of the Sun's radius, where the gas is thin enough to carry heat upward in bulk rather than as light.

Which layer of the Sun, the thickest of them all, rotates as a single rigid shell beneath the churning gas above?

The radiative zone is packed so tightly that its density falls a hundredfold from bottom to top, and energy can only work its way out as radiation.

Which bright patches between the granules on the Sun's surface more than offset the dimming caused by dark sunspots?

Faculae are larger and longer-lived than the spots they accompany, so the Sun's total output actually rises slightly when it is at its most spotted.

A prominence seen against the Sun's bright face rather than at its edge shows up dark and is called a what?

A filament and a prominence are the same cloud of cooler gas: it glows against black space but looks dark against the hotter surface behind it.

Which dark patches in ultraviolet images of the Sun let the fast solar wind pour out along open magnetic field lines?

Coronal holes were only understood in the 1970s, once telescopes flown above Earth's atmosphere could map the Sun's outer layer in detail.

Which name is given to the vast bubble, blown by the Sun's outflowing wind, that encloses all the planets?

The heliosphere is not a neat ball: it takes the shape of a vast, tailed bubble, kept inflated by the stream of charged gas flowing off the Sun.

Which thin layer of the Sun's atmosphere, about 200 km deep, sees the temperature leap from 20,000 K to 1,000,000 K?

The transition region is not a smooth shell but a restless, ragged halo around the jets below, and physicists liken its sudden heating to a liquid boiling into steam.

Energy made at the centre of the Sun starts out as which radiation, long before it emerges as visible light?

Gamma rays are swallowed after travelling only a few millimetres, and each one is eventually broken down into several million particles of visible light.

A mystery line in the spectrum of the eclipsed Sun's halo, long blamed on an unknown element, comes from which metal?

Iron stripped of half its electrons gives off the line, a state so extreme that the puzzle lasted until the 1930s and proved how fiercely hot the halo is.

Which effect makes the Sun's disc look dimmer toward its rim, where our slanting view reaches only higher, cooler gas?

Limb darkening gave early astronomers a way to work out how the Sun's temperature climbs with depth, spurring the theory of how radiation travels through gas.

Which giant churning cells, about 30,000 km wide and lasting a day or so, tile the whole surface of the Sun?

Supergranules carry gas sideways at only 300 to 500 metres a second, a tenth of the speed seen in the far smaller cells that crowd the surface.

Which temperature does the centre of the Sun reach, thousands of times hotter than its visible surface?

About 15 million °C is only the peak: moving outward through the thick middle layer, the temperature slides from roughly 7 million to 2 million degrees.

Which kind of vibration, trapped inside the Sun and making its surface throb, lets astronomers map its hidden layers?

Sound waves, stirred up by the churning gas just under the surface, bounce around inside the Sun, and their pitch depends on the layers they pass through.

Which famous equation explains how the Sun shines by steadily turning a little of its own mass into light?

E = mc² was Albert Einstein's essential clue: about 0.7% of the fuel's mass vanishes in the Sun's reactions and reappears as energy.

Astronomers call every element heavier than the two lightest a 'metal'; which is the most abundant 'metal' in the Sun?

Oxygen leads the Sun's heavier elements, ahead of carbon and neon, yet all of them together make up less than 2% of its mass.

The huge wavy sheet where the Sun's magnetic field switches direction is often likened to which twirling garment?

A ballerina's skirt is the usual comparison because the Sun's spin twists the sheet into a rippling spiral, much as a rotating lawn sprinkler curls its jets.

Which bright, pointed structures seen around the eclipsed Sun are magnetic loops stretched outward by the solar wind?

Helmet streamers hug the Sun's equator when it is quiet but sprout all around it when it is most active, changing the look of every eclipse.

The centre of the Sun is too cool for its nuclei to merge by brute force; which strange effect lets them through?

Quantum tunnelling gives each nucleus only a tiny chance of slipping through the barrier, but the Sun holds so many nuclei that the reactions never stop.

Which English astronomer, founder of the journal Nature, named the thin red layer just above the Sun's visible surface?

Norman Lockyer coined the name after systematic observations, wanting to set the coloured layer apart from the dazzling surface beneath it.

Which boundary, named after a Nobel-winning physicist, marks where the Sun's atmosphere ends and the solar wind begins?

The Alfvén surface lies where the outflowing gas first matches the speed of the magnetic waves running through it; no spacecraft crossed it until this century.

Which balance between gravity pulling inward and hot gas pushing outward keeps the Sun a steady size?

Hydrostatic equilibrium regulates itself: if the Sun's reactions slowed, its centre would cool and shrink, squeezing the gas until they sped back up.

Which term describes the way the Sun's surface turns faster at its equator than it does near its poles?

Differential rotation shows the Sun is no solid ball: gas near its poles needs about a week longer to complete one turn than gas around its middle.

The Sun's magnetic field is generated by churning, electrically charged gas acting like which kind of machine?

A dynamo is the physicists' comparison because moving, electrically conducting gas creates currents and a magnetic field; the detailed mechanism has yet to be worked out.

Which English astrophysicist first correctly guessed, around 1920, what really keeps the Sun and other stars shining?

Arthur Eddington made the leap when the source of starlight was a complete mystery, the year after his eclipse expedition tested Einstein's general relativity.

Which set of reactions, dominant in stars heavier than the Sun, supplies only around 1% of the Sun's own power?

The CNO cycle uses three heavier elements as catalysts and takes over in stars more than about 1.3 times the Sun's mass; its share will grow as the Sun ages.

Which term do astronomers use for the total power the Sun pours out, also their yardstick for rating other stars?

Luminosity measures a star's whole output rather than how bright it looks from Earth, and the Sun's is fixed by convention at 3.828 × 10²⁶ watts.

Which long, stable stage of a star's life, named after a band on a famous diagram, is the Sun about halfway through?

The main sequence is the diagonal band on plots of star colour against brightness, and the Sun should stay on it for roughly another 5 billion years.

Roughly how many Earths, lined up side by side, would it take to span the full width of the Sun?

109 Earths span the Sun's 1.39-million-km diameter, which also makes the Sun about ten times as wide as Jupiter.

On the scale that sorts stars from hot blue O to cool red M, which spectral class is the Sun?

G-type stars like the Sun are loosely called yellow dwarfs, and its full label, G2V, adds a V that marks it as a dwarf rather than a giant star.

Which process converts energy stored in the Sun's tangled field lines into the sudden blast of a flare?

Magnetic reconnection happens when oppositely directed field lines are forced together and rearrange, and countless tiny versions may help heat the Sun's outer atmosphere.

Twice a year the setting Sun lines up exactly with the cross streets of which New York City borough?

Manhattan gets the show around May 28 and July 13 because its street grid is turned 29° away from true east–west.

Which name is given to the midwinter spell inside the Arctic Circle when the Sun stays down for over 24 hours?

Polar night lasts just 24 hours at the edge of the polar circles but stretches to 179 days at the poles themselves.

Which astronomer's 1543 book argued that the Sun's motions across the sky are really Earth's own?

Nicolaus Copernicus saw his book, On the Revolutions of the Celestial Spheres, into print only just before his death that same year.

Which French astronomer escaped the Siege of Paris by balloon in 1870 to chase an eclipse of the Sun?

Pierre Janssen had already found, in 1868, a way to study the flaming arches at the Sun's edge on any clear day, with no eclipse needed.

Roughly how many planets the mass of Earth would it take to balance the Sun on a giant set of scales?

330,000 Earths would be needed, and astronomers treat that bulk as a unit of its own, the solar mass, for weighing other stars and galaxies.