Astrophoto: Nova Centauri 2013 Turns Pink

A recent naked-eye visible nova that erupted the first week in December 2013 is still showing its stuff, and this new “hot off the press” image from Rolf Wahl Olsen in New Zealand reveals its unusual color. “I managed to grab a close-up of Nova Centauri 2013 with my new 12.5″ f/4 scope,” Rolf said via email to Universe Today. “Curiously, I have only so far seen wide field images of this nova, and none that actually show it’s very unusual strong pink colour.”

Nova Centauri 2013 (in the Southern constellation of Centaurus) was discovered by John Seach from Australia on December 2, 2013, and it was visible at about magnitude 5.5. It subsequently brightened to reach a peak at magnitude 3.3.

Rolf’s image was taken today (it’s already Dec. 28, 2013 in New Zealand!) when the nova had faded to around magnitude 4.5. You can see a larger version here on Flickr or click the image above for a larger version on Rolf’s website.

Why is it pink?

“The nova appears pink because we are really viewing the light from an expanding shell of ionized hydrogen which emits strongly in both the red and blue part of the optical spectrum,” Rolf explained. “These emissions give the nova its strong pinkish colour, similar to emission nebulae which are also predominantly pink/magenta in hue.”

A nova is the result of a thermonuclear explosion on the surface of a white dwarf star in a tight binary system. The white dwarf accretes matter from its nearby companion and eventually the pressure from nuclear fusion blows off the accreted layers from the surface of the white dwarf. Contrary to a supernova where the star itself is blown apart and ceases to exist, a nova does not result in the destruction of the host star. The white dwarf may continue to accrete matter from its companion and the process may repeat itself sometime in the future.

Image details:
Date: 28th Dec 2013
Exposure: LRGB: 17:7:6:6 mins, total 36 mins @ -25C
Telescope: 12.5″ f/4 Serrurier Truss Newtonian
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from Auckland, New Zealand

A Naked Eye Nova Erupts in Centaurus

If you live in the southern hemisphere, the southern sky constellation of Centaurus may look a little different to you tonight, as a bright nova has been identified in the region early this week.

An animation showing a comparison between the constellation Centaurus before and after a nova eruption. Credit and copyright: Ernesto Guido, Nick Howes and Martino Nicolini/Remanzacco Observatory. Click for larger version.
An animation showing a comparison between the constellation Centaurus before and after a nova eruption. Credit and copyright: Ernesto Guido, Nick Howes and Martino Nicolini/Remanzacco Observatory. Click for larger version.

The initial discovery of Nova Centauri 2013 (Nova Cen 2013) was made by observer John Seach based out of Chatsworth Island in New South Wales Australia. The preliminary discovery magnitude for Nova Cen 2013 was magnitude +5.5, just above naked eye visibility from a good dark sky site. Estimates by observers over the past 24 hours place Nova Cen 2013 between magnitudes +4 and +5 “with a bullet,” meaning this one may get brighter still as the week progresses.

Nova Cen 2013
Nova Cen 2013 as imaged from the Siding Spring observatory on December 3rd. (Credit: Ernesto Guido, Nick Howes & Martino Nicolini/Remanzacco Observatory).

We first got wind of the discovery via the American Association of Variable Star Observers yesterday afternoon when alert notice 492 was issued. Established in 1911, the AAVSO is a great resource for info and a fine example of amateur collaboration in the effort to conduct real scientific observation.

Follow-up spectra measurements by Rob Kaufman in White Cliffs Australia and Malcolm Locke in Christchurch New Zealand demonstrated the presence of strong hydrogen alpha and hydrogen beta emission lines, the classic hallmark of an erupting nova. Like Nova Delphini 2013 witnessed by observers in the northern hemisphere, this is a garden variety nova located in our own galaxy, going off as seen along the galactic plane from our Earthbound perspective. A handful of galactic novae are seen each year, but such a stellar conflagration reaching naked eye visibility is worthy of note. In fact, Nova Cen 2013 is already knocking on the ranks of the 30 brightest novae observed of all time.

Nova Cen 2013
A narrow field image (inverted B/W) of  Nova Cen 2013. (Credit: Ednilson Oliveira).

This is not to be confused with a supernova, the last of which observed in our galaxy was Kepler’s Supernova in 1604, just before the advent of the telescope in modern astronomy.  Supernovae are seen in other galaxies all the time, but here at home, you could say we’re “due”.

So, who can see Nova Cen 2013, and who’s left out? Well, the coordinates for the nova are:

Right Ascension: 13 Hours 54’ 45”

Declination: -59°S 09’ 04”

That puts it deep in the southern celestial hemisphere sky where the constellation Centaurus meets up with the constellations of Circinus, Musca and the Crux. Located within three degrees of the +0.6th magnitude star Hadar — also named Beta Centauri — it would be possible to capture the southern deep sky objects of the Coal Sack and Omega Centauri with Nova Cen 2013 in the same wide field of view.

Stellarium
The field of view of Nova Centauri 2013 with a five degree Telrad “bullseye” added for scale. Note that magnitude for selected comparison stars are quoted, minus the decimal points. (Created using Stellarium).

Though Nova Cen 2013 technically peeks above the southern horizon from the extreme southern United States, the viewing circumstances aren’t great. In fact, the nova only rises just before the Sun as seen from Miami in December, at 25 degrees north latitude. The Centaurus region is much better placed in northern hemisphere during the springtime, when many southern tier states can actually glimpse the celestial jewels that lie south, such as Omega Centauri.

But the situation gets better, the farther south you go. From Guayaquil, Ecuador just below the equator, the nova rises to the southeast at about 3 AM local, and sits 20 degrees above the horizon at sunrise.

11PM local from latitude (Created by the author using Starry Night Education Software).
11PM local, from latitude 40 degrees south looking to the southeast. (Created by the author using Starry Night Education Software).

The nova will be circumpolar for observers south of -30 degrees latitude, including cities of Buenos Aires, Cape Town, Sydney and Auckland. Remember, its springtime currently in the southern hemisphere, as we head towards the solstice on December 21st and the start of southern hemisphere summer. We’ve been south of the equator about a half dozen times and it’s a unique experience – for northern star gazers, at least – to see familiar northern constellations such as Orion and Leo hang “upside down” as strange a wonderful new constellations beckon the eye to the south. Also, though the Sun still rises to the east, it transits to the north as you get deep into the southern hemisphere, a fun effect to note!

Latitudes, such as those on par with New Zealand, will get the best views of Nova Cen 2013. Based near latitude 40 degrees south, observers will see the nova about 10 degrees above the southern horizon at lower culmination at a few hour after sunset, headed towards 40 degrees above the southeastern horizon at sunrise.

All indications are that Nova Cen 2013 is a classical nova, a white dwarf star accreting matter from a binary companion until a new round of nuclear fusion occurs. Recurrent novae such as T Pyxidis or U Scorpii may erupt erratically in this fashion over the span of decades.

As of yet, there is no firm distance measurement for Nova Cen 2013, though radio observations with southern sky assets may pin it down. One northern hemisphere based program, known as the EVLA Nova Project, seeks to do just that.

Congrats to John Seach on his discovery, and if you find yourself under southern skies, be sure to check out this astrophysical wonder!

Got pics of Nova Centauri 2013? Be sure to send ‘em in to Universe Today!