Tabby's Star · 1,470 light-years
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The most mysterious star
In 2015 volunteers checking Kepler data found that Tabby's Star sometimes dims by up to 22%, in uneven dips no planet could cause. Ideas ran from comets to alien megastructures; how the dimming changes with colour now points to clouds of fine dust.
1,470 light-years light left 1,470 years ago, around AD 556
SGR 1806-20 · 40,000 light-years
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A flash that reached Earth
On 27 December 2004 a burst of gamma rays from this magnetar, about 40,000 light-years away, briefly lit up Earth's upper atmosphere. In a fraction of a second it gave off more energy than the Sun does in 100,000 years.
40,000 light-years light left 40,000 years ago
Przybylski's Star · 356 light-years
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A star full of rare elements
Przybylski's Star has puzzled astronomers since 1961. Its light shows huge amounts of rare heavy elements and, possibly, traces of some that decay so fast they should not be there at all.
356 light-years light left 356 years ago, around AD 1670
Hoag's Object · 600 million light-years
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A perfect ring
Hoag's Object is a nearly perfect ring of young blue stars round an old yellow core, with a dark gap between them. About 600 million light-years away, how it formed is still debated; by chance, another ring galaxy can be seen through its gap.
600 million light-years light left 600 million years ago
Einstein Cross · 8 billion light-years
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One quasar, four images
A galaxy between us and a quasar 8 billion light-years away bends the quasar's light into four images round its core: gravitational lensing, as Einstein predicted.
8 billion light-years light left 8 billion years ago
SS 433 · 18,000 light-years
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A spinning-top jet
SS 433 is a star being eaten by a black hole or neutron star that fires two jets at about a quarter of the speed of light. The jets wobble round like a spinning top every 162 days, tracing corkscrews on the sky.
18,000 light-years light left 18,000 years ago
Swift J1644+57 · 3.9 billion light-years
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A star torn apart
In 2011 a star strayed too close to the black hole at the heart of a distant galaxy and was torn apart. Some of its gas was flung out in a jet pointing straight at us, which shone in X-rays for months.
3.9 billion light-years light left 3.9 billion years ago
TON 618 · 10.8 billion light-years
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A monster black hole
TON 618 is a quasar whose black hole is thought to weigh about 40 billion Suns, among the heaviest known. The glow of the gas falling into it is seen across about 10 billion light-years.
10.8 billion light-years light left 10.8 billion years ago
FRB 121102 · 3 billion light-years
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Bursts we can't yet explain
Fast radio bursts arrive with their low radio notes slightly late, delayed by the gas they crossed, which tells us how far they came. FRB 121102 repeats; most never do, and what makes them is still an open question. The squares are bursts caught by the CHIME telescope.
3 billion light-years light left 3 billion years ago
Sky photographs: CDS hips2fits (DSS2, Mellinger and other surveys) or a backup survey · All guided tours