On March 18 this year, amateur astronomer Yuji Nakamura of Japan discovered a "new star" in Cassiopeia in pictures he took with a digital camera and 135-mm lens. At the time you needed a small scope to see it, but then the star quickly rose to magnitude 8, bright enough to see faintly in binoculars. Officially named V1405 Cassiopeiae (or simply V1405 Cas), it hovered around that brightness until the past week, when it suddenly vaulted into naked-eye visibility. I figured it was high time to share the news.

This close-up of V1405 Cas was taken in early April before its current outburst in brightness. (John Chumack)
This close-up of V1405 Cas was taken in early April before its current outburst in brightness. (John Chumack)

While the nova still appears dim without optical aid — magnitude 5.5 as of May 8 — it's super easy to see in any pair of binoculars. It's also located in the familiar W of Cassiopeia, one of the northern circumpolar constellations that circles around the North Star without setting. That means it's in view the entire night. Just before dawn is the best time because the nova is higher up than during the evening hours. But as long as you can find an open view of the northern sky and see Cassiopeia, it's within your reach.

When you hear the word "nova," you might think V1405 Cas is either a brand new star or an old star that blew up, similar to a supernova. Neither is true. A nova is an event that occurs in a pair of closely orbiting stars comprised of a Earth-sized, super-dense white dwarf and a star similar to our sun.

In this illustration, the white dwarf star is siphoning hydrogen gas from the atmosphere of its sun-like companion star. sun-like star. The material first flows into a disk around the dwarf before spiraling down to its surface, where it can later detonate in a thermonuclear explosion. (NASA / CXC / M. Weiss)
In this illustration, the white dwarf star is siphoning hydrogen gas from the atmosphere of its sun-like companion star. sun-like star. The material first flows into a disk around the dwarf before spiraling down to its surface, where it can later detonate in a thermonuclear explosion. (NASA / CXC / M. Weiss)

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The dwarf’s powerful gravity siphons hydrogen from its partner into a whirling disk of material. Like water going down a bathtub drain, the gas funnel down to the dwarf’s surface, where it’s compacted and heated to millions of degrees, hot enough for nuclear fusion to occur. Just like it does in a thermonuclear bomb, fusion releases gobs of energy, triggering a titanic explosion.

I took this photo on Saturday night, May 8 around 11:30 p.m. from Duluth, Minn. when the nova was faintly visible with the naked eye. It's located to the right and above the star Caph in Cassiopeia. Magnitudes (star brightness) are shown for the circled stars. The larger the magnitude the fainter the star. Use the map below to star-hop to the nova with binoculars. (Bob King)
I took this photo on Saturday night, May 8 around 11:30 p.m. from Duluth, Minn. when the nova was faintly visible with the naked eye. It's located to the right and above the star Caph in Cassiopeia. Magnitudes (star brightness) are shown for the circled stars. The larger the magnitude the fainter the star. Use the map below to star-hop to the nova with binoculars. (Bob King)

Only a relatively small amount of the stolen hydrogen burns; the majority of the material is blasted into space in a rapidly expanding shell. What was a faint, unassuming star a moment ago can brighten from 50,000 to 100,000 times in a matter of hours. This is what we see when we look at a nova. Through it all, the white dwarf survives intact and starts the whole process again, greedily gathering more hydrogen for a future blast.

Begin your binocular journey to V1405 Cas at Caph, located at the far end of the W. From there, work your way from one star to the next (connected by the yellow lines) until you arrive at the nova. I included the magnitudes of several stars so you can judge the nova's changing brightness. For example, if it's halfway between 5.0 and 5.6, then its magnitude would be 5.3. Write your observations down, and after a few weeks you'll see a trend. (Stellarium with additions by Bob King)
Begin your binocular journey to V1405 Cas at Caph, located at the far end of the W. From there, work your way from one star to the next (connected by the yellow lines) until you arrive at the nova. I included the magnitudes of several stars so you can judge the nova's changing brightness. For example, if it's halfway between 5.0 and 5.6, then its magnitude would be 5.3. Write your observations down, and after a few weeks you'll see a trend. (Stellarium with additions by Bob King)

Last night (May 8) I spotted the nova without optical aid, which I found thrilling. Naked-eye novae are relatively rare. Of course, it appeared faint. That's why I suggest you find it first in binoculars. Once you know precisely where to look, try to spot the star unassisted. Observe V1405 Cas as often as you can. Novae brighten, fade, and often re-brighten (as this one did), so there's always a potential surprise awaiting each clear night. The maps include the magnitudes of several stars to help you to document the V1405 Cas's changing brightness.

As you do, relish the pleasure of watching one of the biggest bombs in the universe detonate from a safe distance.

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.