A Bright Nova Appears in Delphinus
Last night a bright nova was discovered in the constellation of Delphinus. It’s bright by nova standards: you normally need telescopes to see novae but this can can be seen with the naked eye – just! – and is easily spottable through binoculars. At the time of writing it has been observed at magnitude 6.3 by Koichi Itagaki, of Yamagata, Japan, and at magnitude 6.0 by Patrick Schmeer, of Bischmisheim, Germany. This means that under dark skies, free from light pollution, with good seeing conditions and good eyesight, it’s within the limit of human eyesight. If you’re in a city though, or if your eyesight isn’t perfect, you’ll need binoculars.
UPDATE 16/08/13 at 1525UT
The British Astronomical Association e-bulletin 00757 is reporting that observations have been submitted to the AAVSO database suggesting the Nova Delphini 2013 has brightened to magnitude +4.5, making it an easy naked-eye object from rural and many suburban sites.
UPDATE 17/08/13 at 0630UT
The AAVSO light curves suggest that Nova Delphini 2013 is dimming, and is currently at magnitude +4.9. This is still naked eye under dark skies and an easy binocular object from cities but get outside as soon as it’s dark and clear; it’s going to keep dimming and soon won’t be naked eye.
UPDATE 18/08/13 at 1430 UT
Although it has dimmed slightly from its maximum brightness of +4.4 magnitudes, it has stayed at +4.9 magnitudes for almost two days now, meaning it’s still naked eye.
UPDATE 22/08/13 at 1330 UT
Nova Delphinus 2013 has dropped below +5.5 magnitude, and will probably drop below human eye detectability in a few days time (it’s already a non-naked-eye object except in very dark sky sites).
Here are some finder charts for the nova, produced using the excellent (free!) Stellarium package.
Your first task will be to locate the small constellation of Delphinus. Luckily, that’s really easy at the moment. It’s high in the south around midnight (SE in the evening), and right next to the prominent stars of the Summer Triangle. The brightest stars in Delphinus make up a tiny diamond shape in the sky. Got it? OK, here’s where it gets a little trickier.
Step 1: Find the diamond shape of Delphinus, shown in the lower left portion of this star chart, with the bright stars of the diamond α, β, γ, and δ labelled (along with ζ nearby).
Step 2: Draw a line from the lower left star of the diamond, δ, past the upper right star, α, but missing it slightly to the “left” of α. Continue for approx. five times the α-δ distance. Here you’ll find another four stars in a diamond of almost exactly the same shape and orientation as (albeit slightly smaller than) the bright diamond of Delphinus. These stars are all really faint. Their magnitudes are marked on the chart above, and they’re all at the very limit of naked eye visibility. Use binoculars if you can’t see them directly.
Step 3: Continue your line onwards, through the lower left star of this fainter diamond to the upper right star, and now take an approximately 45° turn to the “right”, past a very faint star (magnitude 7.85) to the new nova!
(The bright star in the top left of this star chart is 29 Vul, magnitude 4.8)
Nova means “new”, a term coined in 1572 by astronomer Tycho Brahe after he discovered a “new star” in the constellation of Cassiopeia. But these stars aren’t new at all. In fact their brightness is a result of a giant explosion on the surface of a dead white dwarf star.
White dwarf stars form when small stars die and collapse down into a much smaller volume. If there’s another star nearby then the gravity of the white dwarf star can draw some hydrogen gas from the surface of its neighbour onto its own surface. This gas builds up until there is a sufficient quantity of it that it undergoes runaway nuclear fusion, igniting, flaring off, and temporarily brightening the otherwise very faint white dwarf.
No one’s quite sure how this new nova will develop. It might brighten further, or it might begin to dim over the course of days or weeks. All the more reason to get out an find it as soon as you have clear skies. Happy nova hunting!