New nova erupts in Cepheus

The new nova in Cepheus is just below the W of Cassiopeia near the attractive open star cluster NGC 7510. To find Cassiopeia, look halfway up in the north-northwestern sky around 7 p.m. local time. Created with Stellarium

No, I’m not talking about that Chevy Nova you muscled around town years ago. This one’s a tiny star of a thing in the constellation Cepheus the King not far from the W of Cassiopeia. Japanese amateur astronomers Koichi Nishiyama and Fujio Kabashima discovered the “new” star on Feb. 2 shining where no star had been noticed before. They reported their observation and the object was soon given the unwieldy working name of PNV J23080471+6046521.

PNV stands for ‘possible nova’ and the numbers are its celestial coordinates, akin to latitude and longitude. A day later the discovery was confirmed and the new star received the nifty official name Nova Cephei 2013 – our first of the new year.

Want to see the nova in your scope? Click and go to the AAVSO page where you can print a larger version. Just copy and paste the name PNV J23080471+6046521 into the star name box there. Credit: AAVSO

Before you get too excited, this nova is not visible with the naked eye, but a 6-inch telescope will show it. The Japanese astronomers found it shining around magnitude 10.3, plenty bright for a a small telescope, but the star has faded to around 11.7 in the past few days.No worries. Even if you’re not equipped with the right instrument and the burning desire to freeze finger tips in the cold, you can still enjoy what novas are all about.

About half a dozen novae (NO-vee) are found each year along the star rich byways of the Milky Way. These days they’re usually picked up during deliberate photographic patrols of the night sky by amateur astronomers.

Though a nova can happen anywhere in the sky, they’re more likely to be found along the band of Milky Way because that’s where the majority of stars are. Amateurs hunt there to you increase their odds of finding one.

Now that I’ve been blabbing on about the topic for four paragraphs it’s probably time to tell you a nova is NOT a new star despite it hopeful name. It’s an old star really, a very old star, but one that gets an occasional, if explosive, face lift. While we’ve been eating breakfast, lunch and dinner all our lives, a tiny white dwarf star in Cepheus has been dining on the gas of a close companion star for centuries.

A white dwarf with the mass of the sun is about the same size as Earth. Its surface temperatures is about 180,000 degrees (16x hotter than the sun). Unlike the sun, a white dwarf shines by residual heat. Nuclear fusion in its core has ended. Credit: Prof. Richard Pogge

Picture the sun with all its mass compressed to the size of the Earth and you’ve got a white dwarf. Gravity is some100,000 times stronger there than on our “fluffy” planet, so that a teaspoon of matter scooped from a dwarf’s surface weighs 5 tons.

When a white dwarf happens to be in a very close orbit about a normal star, it siphons gas from that star into a swirling accretion disk like cotton candy wound around a paper cone. From there, the material spirals down to the dwarf itself.

Hydrogen gas – the primary ingredient of most stars – gradually builds up on the dwarf’s blazing surface and becomes heated and compressed by gravity until it’s hot enough to burn or fuse. Normally nuclear fusion happens inside of stars; the energy released gradually works its way to the surface and becomes sunshine. On a white dwarf’s surface fusion happens all at once everywhere, created a powerful burst of light and energy as now-incandescent hydrogen is blasted into space. That’s a nova.

Novae happen only in very close binary star systems where a white dwarf pulls matter off its companion. The material spirals down to the dwarf’s surface and eventually ignites. Credit: NASA

We look up and see a star that was otherwise much too faint to notice suddenly become bright enough to spot in a 3-inch telescope. Some novae are brighter or closer and flare to naked eye brightness.

Novae usually flare brightest earliest and then gradually fade back down, but sometimes additional bursts are seen, so it’s fun to keep an eye on them for changes.

The out-of-the-way open cluster NGC 7510 in Cepheus isn’t far from the nova. The cluster’s about 2,400 light years away. Credit: Jim Misti

For amateur astronomers who plan to seek Nova Cephei, you’re in for a treat. Not half a degree away is the rich, box-shaped star cluster NGC 7510. I stumbled on it two nights ago when I got my first look at the nova. It’s worth a look if you’re in the neighborhood.

7 thoughts on “New nova erupts in Cepheus

  1. hey bob.. any concerns we should have with the asteroid 2012 DA14 that will fly by Earth on Feb. 15 and zip within 17,200 miles of the planet ? just a tad nervous. thanks

  2. Thanx Bob for the nice article an explanation. I’d love to take a look in the C8, but 12 magnitude is near the 13-14 limit, and we have rain now. How many days is it estimated it remains at 12?

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