On 27 December 2004 a magnetar called SGR 1806-20, tens of thousands of light-years away, released a giant flare that for about 0.2 seconds was brighter than the full Moon in gamma rays. It overwhelmed detectors on spacecraft from Earth orbit to Mars, bounced off the Moon and disturbed Earth's upper atmosphere. This is the true story of the brightest flash ever recorded from beyond the Solar System, and of the dead stars called magnetars.

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Chapters

0:00 The day the satellites were blinded

0:32 The flash

1:13 An echo from the Moon

1:40 It reached our sky

2:11 Where did it come from?

2:43 What is a magnetar?

3:23 A starquake

3:59 How much energy?

4:19 Giant flares in other galaxies

5:09 Should we worry?

5:27 Another one is on its way

The magnetar's distance is uncertain; modern estimates are lower than the 50,000 light-years often quoted.

Sources

• Palmer et al. 2005, Nature (the giant flare): https://arxiv.org/abs/astro-ph/0503030

• Hurley et al. 2005, Nature: https://arxiv.org/abs/astro-ph/0502329

• Gaensler et al. 2005 (radio afterglow): https://arxiv.org/abs/astro-ph/0502393

• Mereghetti et al. 2005 (INTEGRAL and the Moon echo): https://arxiv.org/abs/astro-ph/0502577

• Inan et al. 2007, GRL (Earth's ionosphere): https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006GL029145

• Svirski, Nakar & Ofek 2011 (distance): https://arxiv.org/abs/1103.0006

Labels: in the video every claim carries an on-screen label (FACT, THEORY, ESTIMATE, HYPOTHESIS, SPECULATION); in this audio edition the narration says out loud when something is an estimate or a thought experiment.

Narration: synthetic voice. Music: original.

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