Most nights the sky just turns, slowly and predictably. But every so often two things line up, or one slides into another's shadow — and those nights are worth staying up for. Here is what each of them is.
Earth casts a shadow into space, a long dark cone pointing away from the Sun. Usually the Moon sails past above or below it. Occasionally it goes straight in.
When it does, the Moon does not vanish — it turns a deep, dusty red. That colour is the best part. The only light reaching it has grazed the edge of Earth and been bent through our air, which strips out the blue. So the red you are looking at is every sunrise and every sunset happening on Earth at that moment, all at once, projected onto the Moon.
Anyone on the night side of Earth sees the same thing at the same time, and it lasts for hours. This is the easiest spectacular sight in the sky.
Find my next lunar eclipseThe same idea the other way round: the Moon passes between us and the Sun and drops its shadow on us. But the Moon is small, so its shadow is a dark spot only a hundred or so kilometres wide, racing across the ground. Stand in that spot and the Sun disappears completely. Stand outside it and you only see a bite taken out.
There is a lovely coincidence behind this. The Sun is about 400 times wider than the Moon — and also about 400 times further away. So from here the two look almost exactly the same size. That is why the Moon can cover the Sun so neatly, and it is pure luck.
"Almost" is the interesting word. The Moon's distance varies, so:
Total — the Moon is near enough to cover the Sun completely. The sky goes twilight-dark in the middle of the day, the temperature drops, birds go quiet, and the Sun's faint outer atmosphere comes out. Ring — the Moon is a little too far away, so a bright ring is left all around it. Partial — you are off to one side of the shadow and only part of the Sun is covered.
A partial eclipse is far less dramatic than the numbers suggest. Even with 95% of the Sun hidden, the remaining sliver is so blindingly bright that the day looks merely a bit odd. The step from 99% to 100% is not a small last step — it is the whole show.
Only through a filter made for looking at the Sun, checked for damage every single time — or by projecting its image onto card, which is safer still.
The Sun can burn the back of your eye permanently, and it does not hurt while it happens, so there is no warning to react to. An adult must be in charge of this.
The Moon goes round us once a month, so you might expect an eclipse every month — one of each, in fact. We don't get them, and this diagram is the reason.
Five degrees does not sound like much, but the Sun and Moon are only half a degree wide. Missing by five degrees is missing by ten times their own width. Only when the Moon happens to cross the flat line at the same moment it lines up with the Sun does a shadow actually land — which is why eclipses arrive in clusters a few times a year rather than monthly.
A comet going round the Sun sheds grit all along its path, and that grit stays in orbit long after the comet has gone. Every year Earth ploughs through the same trails on the same dates — which is why these are the only sky events you can put in a calendar years ahead with no calculation at all.
The grains are mostly the size of a grain of sand. They hit our air at thirty or sixty kilometres a second and burn up sixty miles above your head. Nothing lands. What you see is a bright line drawn across the sky in under a second.
A shower is named after the constellation its radiant sits in — Perseids from Perseus, Geminids from Gemini. But you do not look at the radiant. Meteors near it are coming almost straight at you and leave short stubby trails; the long dramatic ones appear well away from it.
The ones worth staying up for, the same dates every year:
| Shower | Peak night | Per hour | Worth knowing |
|---|---|---|---|
| Quadrantids | 3–4 January | 110 | Sharp peak, only a few hours wide. Bitterly cold. |
| Lyrids | 22–23 April | 18 | Modest, but the first after the winter. |
| Perseids | 12–13 August | 100 | The one for children. Warm nights, school holidays. |
| Orionids | 21–22 October | 20 | Grit shed by Halley's Comet. |
| Leonids | 17–18 November | 15 | Every few decades it erupts into thousands. |
| Geminids | 13–14 December | 120 | The richest of all, slow and bright. Freezing. |
"Per hour" assumes a perfect black sky with the radiant overhead. From a garden with streetlights, expect a quarter of that. It is not a disappointment, it is arithmetic — and a meteor every few minutes is still a good night. The Moon matters more than anything else: a full Moon will wash out all but the brightest, so check its phase before you plan.
Find my next meteor showerMeteor counting is real science that needs no equipment whatsoever, and people have been sending in counts for more than a century.
Getting set up. Lie on your back — a reclining chair or a mat, warm clothes, something hot to drink. Face about halfway up the sky, away from the radiant and away from any streetlight. No telescope, no binoculars: they show a patch of sky far too small. And no phone. Your eyes take twenty minutes to adapt to the dark and one glance at a screen undoes all of it.
Then count. Write down the time you start, and make a tally mark for every meteor for one full hour. Note anything odd — a colour, a trail that hangs in the air afterwards, one far brighter than the rest. Then compare your hour with the table above, and you have measured how dark your own sky is. Two people lying head to head facing opposite ways will get different numbers, and working out why is half the fun.
Two planets, or a planet and the Moon, appear right next to each other — sometimes close enough to hide behind a fingertip held at arm's length.
They are not close. Not remotely. When Jupiter and Venus sit side by side they can still be half a billion kilometres apart; you are simply looking along a line that passes near both. It is exactly like two lamp posts, one down the road and one on the horizon, seeming to touch because of where you happen to be standing.
That does not make it less worth seeing. A bright pair a fingertip apart in a deepening blue twilight is one of the prettiest things the sky does, and it needs nothing but your eyes.
Find my next conjunctionFor the planets further out than us — Mars, Jupiter, Saturn — opposition is when Earth passes directly between that planet and the Sun. We are on the inside track and we overtake them, the way a faster runner laps a slower one.
Three good things happen at once. The planet is at its closest, so it looks biggest. It is fully lit from our point of view, so it looks brightest. And because it is opposite the Sun, it rises as the Sun sets and stays up all night. If you are only going to look at Mars once, look near opposition.
Find my next oppositionMercury and Venus orbit closer to the Sun than we do, so from here they can never wander far from it. They are stuck near the glare, rising just before dawn or setting just after dusk, and never visible in the middle of the night.
Greatest elongation is the moment one of them reaches the furthest from the Sun it can get — the top of its swing. That is your best chance to catch it: highest above the horizon, in the darkest sky it will manage. Mercury in particular is a planet many adults have never knowingly seen, and these are the few weeks a year when you can.
Find my next elongationOccasionally Mercury or Venus passes exactly between us and the Sun, and you can watch a tiny perfectly round black dot creep slowly across the Sun's face over several hours.
These are properly rare. Mercury manages it about thirteen times a century. Venus is far rarer: they come in pairs eight years apart, then nothing for over a century. The last pair was 2004 and 2012, and the next transit of Venus is in 2117. If you want to be the one who watches it, the trick is to be born at the right moment — and some of the people who will see it are alive already.
They matter more than they look. Timing a transit of Venus from two distant places on Earth was how people first measured the real size of the solar system — the whole story is on the distances to the Sun and planets.
Find my next transitThe Moon is always moving eastwards against the stars — about its own width every hour, which is far too slow to notice by staring. Once in a while it drives straight over a bright star or a planet, and that is the moment you can see it moving.
What surprises everyone is how it goes. There is no fading and no dimming. The star is there, and then between one blink and the next it is gone. That is a real measurement, not a trick of the eye: it means the Moon has no air. Anything with an atmosphere would smear the star out over several seconds as it sank through the haze, the way the Sun reddens at sunset.
The Moon is close enough that where you stand changes where it appears to sit — by up to a degree, which is nearly four times its own width. So an occultation is never a fact about the night, only about your town. This is the same effect, and the same maths, that decides who stands in the shadow during a solar eclipse.
Only four bright stars can ever be hidden: Aldebaran, Regulus, Spica and Antares. The Moon never wanders more than about six degrees from the ecliptic, and they are the only bright stars inside that lane. The planets are all in the same lane, so any of them can be covered too — and a planet is a tiny disc rather than a point, so it takes a second or two to go, which is worth watching for on its own.
Sometimes the star only clips the very edge of the Moon. Then it can wink out and back several times in a minute, hidden behind lunar mountains and reappearing down the valleys between them. Amateur astronomers time these to map the Moon's profile, and have done since long before anyone went there.
Find my next occultationNot really an astronomical event at all. The aurora happens in our own air, about a hundred kilometres up, where particles blown off the Sun spiral down Earth's magnetic field and make the gases glow: green from oxygen low down, red from oxygen higher up, purple-blue from nitrogen.
From Iceland or northern Scandinavia it is a common sight. From central Europe it takes a strong solar storm, and happens a handful of times in each eleven-year solar cycle — usually as a red glow low in the north rather than the curtains overhead you see in photographs. When one is forecast, it is worth driving somewhere with a flat northern horizon and no towns.
Comets are dirty snowballs a few kilometres across on long looping orbits. Most spend thousands of years out in the dark and are never seen at all. When one falls close to the Sun its ice turns straight to gas, and it grows a glowing head and a tail that can stretch right across the sky.
The tail always points away from the Sun — not backwards along the comet's path, which is what everyone expects. It is being blown, not dragged. So on the way out, a comet flies tail-first.
Comets on short orbits, like Halley's, can be predicted to the day. But the bright ones are nearly always newcomers, found only months ahead, and whether one turns spectacular or fizzles out is genuinely not knowable until it arrives. Roughly one a decade is worth going outside for. That is why this site only lists a comet once a real one is on its way.
There is no button for this one: a bright comet is normally found only months before it arrives, so nobody — not this site, not any observatory — has a list of the next one.
Everything else on this page can be worked out in advance, some of it for a thousand years. This one cannot be predicted at all.
When a massive star runs out of fuel, its core collapses in about a second and the star tears itself apart, briefly outshining every other star in its galaxy put together. A star that has sat quietly in a constellation for the whole of human history simply becomes the brightest thing in the sky, and stays for weeks.
It has happened twice in recorded European history where anyone could see it plainly: 1572, watched by Tycho Brahe, and 1604, by Johannes Kepler. Both are in this site's database, and both are now nothing whatever to the eye. We are long overdue another.
Nobody knows which star, or when. It could be tonight. There is no preparing for it beyond knowing the sky well enough to notice that something is there which was not there yesterday — and it is amateurs, not professionals, who usually spot them first.
No button here either, and there never can be. Nobody knows which star, or when.
Two of the things on this page — a bright comet and a supernova — cannot be listed in advance by anybody, because nobody knows about them yet. Everything else here is already worked out.
The Planetarium has a button marked Worth seeing in the next 30 days. It knows where you are and what time it gets dark there, so it only lists things you can genuinely see from your own garden — and it will set the sky to that moment so you can check which way to face before the night arrives.