Bright Supernova Erupts in NGC 5643 in Lupus

A recently discovered supernova in Lupus now shines around magnitude +11.5, bright enough to see in a modest telescope. With photos and maps, we’ll get you there.

Supernova 2017cbv in the +10.7 magnitude southern galaxy NGC 5643 has bolted to magnitude +11.5 in recent days, making it a fine amateur target.
Joseph Brimacombe

I wished I lived in Georgia and not just for the peach trees and warmer weather. No, I’d be able to get up early tomorrow morning to marvel at a new, bright supernova too far south to see from my home in northern Minnesota.

Supernova 2017cbv in the spiral galaxy NGC 5643 was discovered by a team of astronomers on March 10 during the D<40 Mpc (DLT40) supernova search. NGC 5643 lies 55 million light years from Earth and sits in the far western corner of the constellation Lupus. At discovery, the stellar explosion was only magnitude +15, but in recent days it’s brightened to magnitude +11.5 and is now within easy reach of a 6-inch telescope.

Spectra indicate this so-far brightest supernova of the year is a Type Ia, the aftermath of the explosion of a white dwarf star in a doomed relationship with a close companion sun. After millennia of siphoning material from the companion to its surface, the dwarf exceeded the Chandrasekhar Limit of 1.4 solar masses and underwent uncontrolled gravitational collapse. Dire consequences followed as a runaway fusion reaction from the crushing heat and pressure raced through the star, destroying it in one titanic blast.

Out With a Bang

This illustration shows the stages of a Type Ia supernova explosion like that which occurred in 2017cbv. From left: a white dwarf accretes matter from a close companion until it reaches a super-critical state when it exceeds 1.4 solar masses; a thermonuclear explosion ensures leaving an expanding cloud of debris.
Credit: NASA / CXC / M. Weiss

Now you can see the magnificent explosion with your own eyes simply by setting your alarm clock to 2:30 in the morning, pointing your telescope to NGC 5643 and using the maps and photos to pinpoint the supernova. You can also check for updated photos and magnitude estimates at two of my favorite sites: Dave Bishop’s Bright Supernovae and the AAVSO (Just type in SN 2017cbv in the Pick a Star box).

Supernova Star Hop

Use this map to star hop from Eta Centauri to the galaxy NGC 5643. Once there, the photo below will help guide you directly to SN 2017cbv.
Created with Stellarium

About the only thing required besides a telescope to see the new object is living in a southern clime. NGC 5643 lies at declination –44°08′. Assuming a minimum altitude of 10° to find the galaxy and track down the star, observers located at 36° north latitude and south should be able to see it. This includes the southern and southwestern states Alabama, Georgia, Florida, Texas, Arizona and southern California. If you’re unsure of your latitude, click here to find it.

Tiptoe to a "New Star"

This photo of NGC 5643 and SN 2017cbv was taken on March 22, when the supernova shone at ~11.5 magnitude. Use the two similarly bright stars (at top) just north of the galaxy to complete a flattened triangle with the supernova. The object is currently around peak brightness. North is up.
Guillermo Abramson

To find SN 2017cbv, face south in the early morning hours to face Lupus. NGC 5643 transits the meridian around 3 a.m. local time, so plan your observing session a little before that. The galaxy is located 2° SSW of second magnitude Eta Centauri, and the supernova is found at R.A. 14h 32′ 34″, declination –44°08′ 68″ east and 145″ north of the galaxy’s nucleus.

Alternative Guide

Another option for finding SN 2017cbv is to use this AAVSO chart. Magnitudes of stars near the galaxy will help you track the supernova as it fades. Click for a large version.

Once you’ve brought the galaxy into the field of view, use the photographs and a magnification of around 100x to star-step your way from the center of the galaxy northeast to the supernova. I think you’ll find the two 11th magnitude stars very helpful in nailing it.

SN 2017cbv isn’t the first white dwarf to flame out in NGC 5643. SN 2013aa, another Type Ia, blew its top in early 2013 and peaked at magnitude +11.3 in February that year.

While some of us will never get to see the “new star” because of where we live, I know that a few of you will. Let us know what you see!

The post Bright Supernova Erupts in NGC 5643 in Lupus appeared first on Sky & Telescope.

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