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Explanation: Spectacular explosions keep occurring in the binary star system named RS Ophiuchi. Every 20 years or so, the red giant star dumps enough hydrogen gas onto its companion white dwarf star to set off a brilliant thermonuclear explosion on the white dwarf's surface. At about 5,000 light years distant, the resulting nova explosions cause the RS Oph system to brighten up by a huge factor and become visible to the unaided eye. The red giant star is depicted on the right of the above drawing, while the white dwarf is at the center of the bright accretion disk on...

If you look carefully into the night sky, you might see a star that wasn't visible last week. In the equatorial constellation of Ophiuchus, a star named RS Ophiuchi about 4,566 light-years away has just had an epic eruption. This nova was so bright that the star is now visible to the naked eye, at a magnitude of around 4.8 – a whopping seven magnitudes brighter than its usual 12th magnitude dimness. Novae are rare enough to spot at the best of times, but what makes this occasion so special is the rarity of the star. RS Ophiuchi is what...