Astronomy Picture of the Day

🌌Lightning over the Volcano of Water Have you ever watched a lightning storm in awe? You're not alone. Details of what causes lightning are still being researched, but it is known that inside some clouds, internal updrafts cause collisions between ice and snow that slowly separate charges between cloud tops and bottoms. The rapid electrical discharges that are lightning soon result. Lightning us ...

© Leo Shatz

🌌Globular Cluster Omega Centauri Globular star cluster Omega Centauri packs about 10 million stars much older than the Sun into a volume some 150 light-years in diameter. Also known as NGC 5139, at a distance of 15,000 light-years it's the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the sam ...

© Petr Horálek

🌌Twelve Years of Kappa Cygnids Meteors from the Kappa Cygnid meteor shower are captured in this time-lapse composite skyscape. The minor meteor shower, with a radiant not far from its eponymous star Kappa Cygni, peaks in mid-August, almost at the same time as the much better-known and better-observed Perseid meteor shower. But, seen to have a peak rate of only about 3 meteors per hour, Kappa Cyg ...

© Every 15 years or so

🌌Titan Shadow Transit very 15 years or so, Saturn's rings are tilted edge-on to our line of sight. As the bright, beautiful ring system grows narrower and fainter it becomes increasingly difficult to see for denizens of planet Earth. But it does provide the opportunity to watch transits of Saturn's moons and their dark shadows across the ringed gas giant's still bright disk. Of course Saturn's l ...

© Jason Rice

🌌Fireball over Cape San Blas Have you ever seen a fireball? In astronomy, a fireball is a very bright meteor -- one at least as bright as Venus and possibly brighter than even a full Moon. Fireballs are rare -- if you see one you are likely to remember it for your whole life. Physically, a fireball is a small rock that originated from an asteroid or comet that typically leaves a fading smoke tra ...

🌌A Double Detonation Supernova Can some supernovas explode twice? Yes, when the first explosion acts like a detonator for the second. This is a leading hypothesis for the cause of supernova remnant (SNR) 0509-67.5. In this two-star system, gravity causes the larger and fluffier star to give up mass to a smaller and denser white dwarf companion. Eventually the white dwarf's near-surface temperatu ...