It’s official. The new nova has been christened Nova Delphini 2013. Even better, it’s brightened since discovery. Last night a group of stargazers and I saw the pale yellow star with ease through the telescope. Later, when the moon had set, I was even able to spot the nova faintly with the naked eye at magnitude 5.8.
It’s been years since we’ve had an exploding star of this variety reach naked eye brightness. About 6-10 novae are discovered each year, most of them needing at least a small telescope to see. This year novae have popped off in Cepheus, Scorpius and possibly one in Aquila. Amateur astronomers are the nova finders, training cameras on swaths of the Milky Way night after night hoping to catch one in outburst.
The brightest nova ever recorded blew its top in Aquila the Eagle in 1918. V603 Aquilae shot all the up to -1.4 magnitude or nearly as bright as Sirius, the brightest star. You can still see it today in a 6-inch or larger telescope biding its time around magnitude 12 patiently waiting for another chance at nova-hood. Click HERE to get a finder chart.
The Milky Way is the most lucrative hunting ground for novae hunting because stars are greatly concentrated along its length; that’s what creates the familiar hazy ribbon of light. You’re much more likely to spot one pointing your camera at millions of stars than at sparsely-strewn star fields outside the Milky Way band. Favorite hunting grounds include the Milky Way-streaked constellations of Scorpius, Sagittarius and Cygnus. I’ve never heard of one being found in the Big Dipper which is located well away from the galactic plane.
Just as there’s more than one type of tea, there are different kinds of novae. All involve close binary stars with a compact white dwarf stealing gas from its companion. The gas ultimately funnels down to the surface of the dwarf where it’s compacted by gravity and heated to high temperature on the star’s surface until it ignites in an explosive fireball. This is what you see when you look at a nova – a gigantic bomb going off.
Just to be clear, a nova doesn’t involve the destruction of the star, only a “shock to the system”. A supernova is a different beast entirely, resulting in the complete annihilation of a white dwarf or supergiant star. If a white dwarf accumulates too much matter from a companion and crosses the Chandrasekhar Limit, it can sidestep the nova stage and go straight to supernova.
Looking more closely we discover that novae come in two basic types – fast and slow. Fast ones rise abruptly to maximum brightness, some of them vaulting 10 magnitudes a day. Their decline can be equally swift.
Slow novae behave as you might expect, sometimes taking several months to reach peak brightness and often lingering for months. Fast novae, which arise from more massive white dwarfs, are concentrated in our galaxy’s flat disk; slow ones from smaller dwarfs are found in the central bulge. I suspect this recent nova is the fast variety.
Nova Delphini is still in the fireball stage engulfed by incandescent hydrogen gas. Astronomers have spectroscopically measured the speed of the ejecta from the blast at 1,250 miles (2,000 km) per second. That’s 4.5 million miles per hour. Think about that for a second. Now picture the scene in your mind’s eye when you see the nova for yourself.
I’ve included a fresh map above. The numbers in gold are star magnitudes to help you track the nova’s brightness as it brightens or fades in the coming nights. The larger the number, the fainter the star. Click HERE for a nice explanation of star magnitudes. For more maps, please see my earlier Universe Today post.
Update 8/16: Last night Aug. 15 I saw the nova at magnitude 4.8 and it was even brighter this morning. That means it’s nearly ten times brighter than at discovery a two days ago.