Astronomers catch a star's explosion early in a nearby galaxy, one of the closest of its kind since 2011

A white dwarf star blew itself apart in a nearby galaxy, and astronomers caught it early enough to watch it brighten toward its peak, expected Nov. 18 to 23, NSF NOIRLab said in a Nov. 12 release.  The supernova, named SN 2026ahvu, is one of the nearest of its kind found since 2011.  It is too far south to be seen well from San Jose.

What exploded

A white dwarf is the dense, burned-out core left when a star like the Sun dies.  This one was pulling gas from a close companion star until it detonated in a runaway nuclear blast, the kind astronomers call a Type Ia supernova.  Nothing is left of the white dwarf afterward.

It sits in NGC 1433, a spiral galaxy with a bar of stars across its middle, about 50 million light-years away; the release notes published distances vary.  That is about 290 million trillion miles.  The light now arriving left about 50 million years ago.

How it was found

ATLAS, the Asteroid Terrestrial-impact Last Alert System, recorded it on Nov. 2. A separate team using the Keck II telescope in Hawaii took its spectrum, the colors of its light, on Nov. 3 and confirmed it was a young Type Ia supernova, the release says. In days it brightened about 25-fold, from magnitude 17 to 13.5.

What magnitudes mean

Astronomers rate brightness in magnitudes, a scale that runs backward: the bigger the number, the fainter the object. Each step of 1 is about 2.5 times dimmer, and a difference of 5 is exactly 100 times, according to the International Astronomical Union's astronomy glossary. The bright star Vega is set at zero; Sirius, the brightest star at night, is about minus 1.5; the full Moon is about minus 12.7. In very dark skies, people with excellent vision can see stars down to about magnitude 6. Binoculars reach about magnitude 10, and an 8-inch backyard telescope about 14, according to Australia's national science agency, CSIRO.

How fast a supernova rises and fades

A Type Ia supernova usually takes about 17 days to climb from the moment of the explosion to its peak, though some take as few as 13 days and others 23, according to a study of 105 well-observed explosions from the Sloan Digital Sky Survey, published in The Astrophysical Journal in 2010. That fits this one: it was spotted Nov. 2, and its peak is expected 16 to 21 days later.

At its peak, a Type Ia supernova shines about 5 billion times brighter than the Sun, NASA says, and a supernova can briefly outshine its entire galaxy. Before the explosion, the white dwarf was far too faint to see at this distance.

Then it fades quickly. For the first three to four weeks after the peak, a Type Ia supernova dims by about 0.09 magnitude a day, according to Swinburne University of Technology's COSMOS astronomy encyclopedia. That works out, by our arithmetic, to roughly five to 10 times fainter a month after the peak. After that, the fading slows to about 0.015 magnitude a day, as the glow from decaying radioactive cobalt made in the blast takes over. If SN 2026ahvu follows that pattern, it would be around magnitude 12.5 to 14.5 a month after its peak, by our arithmetic, near the limit of an 8-inch telescope.

Why astronomers care

All Type Ia supernovae reach nearly the same true brightness, so how bright one looks tells astronomers how far away it is.  Measurements of distant ones led to the discovery that the universe's expansion is speeding up, work that earned Saul Perlmutter of Lawrence Berkeley National Laboratory and UC Berkeley a share of the 2011 Nobel Prize in physics.  Astronomers still don't fully know what kind of companion feeds these white dwarfs or exactly how they ignite, and the first days after an explosion hold clues that fade fast.

The picture and the telescopes

The photo, taken by the 8.1-meter (26.6-foot) Gemini South telescope, shows the supernova as the bright blue-white dot to the right of and slightly below the galaxy's core.  Gemini South sits 8,980 feet up on Cerro Pachón in Chile and saw first light in 2000.  NOIRLab also imaged the galaxy with DECam, a 570-megapixel camera that started work in 2012 on the 4-meter (13-foot) Víctor M. Blanco Telescope, 7,240 feet up at nearby Cerro Tololo; its older survey pictures show the galaxy before the blast.  NOIRLab's pages do not list the telescopes' costs.  NOIRLab is coordinating more observations and inviting other observatories to join.

Can you see it?

Not easily from here.  From San Jose, the galaxy climbs only about 5 degrees above the southern horizon around midnight, about half a fist held at arm's length, by our calculation, where haze, hills and city glow block the view.  Even at its predicted peak of magnitude 10.5 to 12.1, the supernova would be roughly 60 to 275 times too faint for the naked eye, so it needs a telescope.  Observers in the Southern Hemisphere have the real view.

Source:  NSF NOIRLab, "NSF NOIRLab-operated Facilities Capture Brightening Nearby Supernova" (noirlab2628, Nov. 12, 2026) and image noirlab2628a; NOIRLab pages for Gemini South, the Blanco Telescope and DECam; Nobel Prize, 2011 physics press release; Hayden et al., "The Rise and Fall of Type Ia Supernova Light Curves in the SDSS-II Supernova Survey", The Astrophysical Journal, 2010; Swinburne University of Technology, COSMOS: Type Ia supernova light curves; NASA, Hubble Spies Swirling Spiral and Space Place: What is a supernova?; International Astronomical Union Office of Astronomy for Education, glossary: apparent magnitude; CSIRO Australia Telescope National Facility, The Magnitude Scale.  The distance in miles, the brightening factor, the galaxy's height above San Jose's horizon the naked-eye comparison, the days from discovery to peak and the month-after-peak fading estimates are the Daily News's own arithmetic.  Drafted by AI for San Jose.