Naked-Eye Nova in Centaurus

Update Dec. 27:  Nova Centauri 2013 peaked at about magnitude 3.6 on December 5th, faded to 4.3 by the 9th, rebrightened to 3.5 around the 15th, and has been behaving oddly since. As of December 27th it's still naked-eye at magnitude 4.4. See preliminary light curve from the AAVSO.

It’s out of sight from most of the Northern Hemisphere, but a nova has erupted just west of Alpha and Beta Centauri. Nova hunter John Seach in Australia caught it on December 2nd with a DSLR patrol camera at about magnitude 5.5. Nothing there was as bright as 11th magnitude in previous images he took on November 26th. Then Steven Graham in New Zealand checked his wide-sky webcam images and found that the nova came into view between December 1st and 2nd.

A closeup of the presumed Nova Centauri 2013 shining at 5th magnitude on December 3rd. Click on the image for a blink comparison with a Digitized Sky Survey image. The nova is almost exactly on top of a previously 15th-magnitude star.
E. Guido / N. Howes / M. Nicolini
On the 3rd, Ernesto Guido, Nick Howes, and Martino Nicolini used a remotely-operated 20-inch scope to take the close-up image at right. By late on the 3rd UT variable-star observers were calling it magnitude 4.7 or 4.6, and spectra were showing a nova’s strong hydrogen emission lines.

By 6:37 UT on the 4th, Sebastian Otero in Argentina found it to be magnitude 4.3. That's a trace brighter than the much-followed Nova Delphini 2013 at its peak last August. Here's the new nova's current AAVSO light curve.

Will it brighten further? If you’re in the Southern Hemisphere, go out and look! The nova is in the south-southeast before your local start of morning twilight, at right ascension 13h 54m 45s, declination —59° 09.1′. It's at the location of a previously 15th-magnitude star, possibly the progenitor.

Its preliminary designation was PNV J13544700-5909080. Now it's Nova Centauri 2013. Here’s a 10°-wide comparison-star chart from the AAVSO. The nova is centered on the chart, and the bright star is Beta Cen.

A nova happens in a special kind of tightly-orbiting binary star system: one where a relatively normal star pours a stream of hydrogen onto the surface of a companion white dwarf. When the layer of fresh hydrogen on the white dwarf's surface grows thick and dense enough, the bottom of the layer explodes in a runaway hydrogen-fusion reaction — a hydrogen bomb in the shape of a thin shell around the star. The underlying white dwarf remains intact, and as new hydrogen builds up, the process may repeat in a few years to tens of thousands of years.

8 thoughts on “Naked-Eye Nova in Centaurus

  1. Anthony BarreiroAnthony Barreiro

    I would think that the 15th magnitude star was the companion star whose gas accreted onto the white dwarf that went nova. Or could it have been the white dwarf itself?

  2. Navneeth

    There are large swaths of the Northern hemisphere where this object would easily be visible even from within a moderately large city, the light pollution being the only hindrance.

  3. Alan MacRobert

    > There are large swaths of the Northern hemisphere
    > where this object would easily be visible

    Not when it’s still this close to the Sun before dawn. This is not the time of year when you can see Alpha and Beta Cen in a dark sky from as far north as is possible.

  4. D.ousley

    I rose a little earlier today at about 15:30UTC on the 8th December (3:30am 9/12/2013 local AEST) and had a look in the field near Beta Centauri using the photometric chart on this web site. Even without the use of 10 x 50 binoculars there was a strange 4.5 to 5th magnitude star that looked out of place near Beta Centauri. In 10 x 50 binoculars I would estimate the nova to be about 4.7 to 4.8 magnitude visually. The low angle to the south east may have reduced its naked eye visibility to about just above 5th magnitude. It had a very slight pinkish to yellow tinge colour to it, I felt in comparison to almost white of Beta Centauri in the same field in the binoculars. At about 4:00am the commencement of the approaching twilight starts to fade out the fainter stars as the sky starts to brighten. It was very lucky that the usual stratocumulus cloud at this time of year, that drifts in of the Coral sea was absent this morning.

  5. Paul Vondra

    Its preliminary designation is PNV J13544700-5909080? Do you think the astro-gods of the IAU would be offended if we mere mortals referred to it as "Nova Centauri 2013"?

  6. clifford wright

    Finally got a clear enough sky for binocular and naked eye observation last night (NZ time). Centaurus is very low at this time of year but the nova was perfectly clear to the naked eye and brilliant in 7×35 Pentax binoculars. I concur with the earlier colour estimates. If possible I will have a look with the 200mm reflector tonight fo better colour estimates. It was certainly much brighter than mag 4, I guesstimate about 3.5.

  7. clifford wright

    Have made several binocular observations since early December and had noted a drop down to around mag 5 a few days ago.
    Surprised to see in back up to around 3.5 tonight (27 dec).
    Not well placed even at 36 South as Centaurus is very low to the South at present. However there are definitely quite a lot of unexpected brightness changes with this nova.

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