Early on 20th March, professional theoretical cosmologist and amateur astrophotographer Peter Dunsby of the University of Cape Town was imaging a beautiful part of the sky, in the constellation of Sagittarius. When you look at this part of the sky, you’re staring toward the centre of the galaxy, and your view is filled with beautiful nebulae and clusters. Dunsby was using a small telescope, with a lens just a few inches across, yet he saw within it something that shouldn’t be there – a bright, new object, glowing red next to the nebula itself.
Dunsby checked previous images of the same region, both his own, from a few weeks earlier, and from the Sloan Digital Sky Survey, a survey of the sky carried out a decade ago from an observatory in New Mexico. Neither showed any sign of the object, and so Dunsby took the next, obvious step. Something as brilliant as this object – brighter than all but a handful of stars – would soon be spotted by others; only by announcing quickly what he’d found could Dunsby secure the credit. More importantly, the only plausible explanation for such a bright transient would be a supernova in the Milky Way galaxy, in which case observations while it was still brightening would be essential.
Dunsby turned to the
Astronomer’s Telegram, or ATel, service to announce his discoveries. These bulletins, issued to observatories around the world are web based, rather than physical telegrams, but their terse reports still attract the same attention you’d expect if a uniformed courier rapped on the door. Early next morning, astronomers all over the world were reading of what Dunsby had found, and deciding whether to interrupt their observations to follow-up the discovery of the century.
Forty minutes later, a second telegram – number 11449 – was released. It was brief: ‘The object reported in ATel 11448 has been identified as Mars. Our sincere apologies for the earlier report and the inconvenience caused.’
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