By jmbrill

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In some cases, the dwarf may siphon material from its companion. This ultimately triggers a runaway reaction that detonates the thief once it reaches a specific point where it has gained so much mass that it becomes unstable. Astronomers have also found evidence supporting another scenario, involving two white dwarfs that spiral toward each other until they merge. If their combined mass is high enough that it leads to instability, they, too, may produce a type Ia supernova.

These explosions peak at a similar, known intrinsic brightness, making type Ia supernovae so-called standard candles – objects or events that emit a specific amount of light, allowing scientists to find their distance with a straightforward formula. Because of this, astronomers can determine how far away the supernovae are by simply measuring how bright they appear.

Astronomers will also use Roman to study the light of these supernovae to find out how quickly they appear to be moving away from us. By comparing how fast they’re receding at different distances, scientists will trace cosmic expansion over time. This will help us understand whether and how dark energy has changed throughout the history of the universe.

Previous type Ia supernova surveys have concentrated on the relatively nearby universe, largely due to instrument limitations. Roman’s infrared vision, gigantic field of view, and exquisite sensitivity will dramatically extend the search, pulling the cosmic curtains far enough aside to allow astronomers to spot thousands of distant type Ia supernovae.

Roman will study dark energy’s influence in detail over more than half of the universe’s history, when it was between about 4 and 12 billion years old. Exploring this relatively unprobed region will help scientists add crucial pieces to the dark energy puzzle.

Video Credit:
NGSVS

https://science.nasa.gov/mission/roman-space-telescope/type-ia-supernovae/

Type Ia Supernovae

Roman will use type Ia supernovae to measure cosmic distances, which will help us understand how the universe has expanded over time.

* Video Credit:
NASA Goddard's Scientific Visualization Studio

Roman will see thousands of exploding stars called supernovae across vast stretches of time and space. Using these observations, astronomers aim to shine a light on several cosmic mysteries – primarily dark energy. Roman will use type Ia supernovae to measure cosmic distances, which will help us understand how the universe has expanded over time.

Roman’s supernova survey will help clear up clashing measurements of how fast the universe is currently expanding, and even provide a new way to probe the distribution of dark matter, which is detectable only through its gravitational effects. One of the mission’s primary science goals involves using supernovae to help pin down the nature of dark energy – the unexplained cosmic pressure that’s speeding up the expansion of the universe.

Roman will use multiple methods to investigate dark energy. One involves surveying the sky for a special type of exploding star, called a type Ia supernova.

Many supernovae occur when massive stars run out of fuel, rapidly collapse under their own weight, and then explode because of strong shock waves that propel out of their interiors. These supernovae occur about once every 50 years in our Milky Way galaxy. But evidence shows that type Ia supernovae originate from some binary star systems that contain at least one white dwarf – the small, hot core remnant of a Sun-like star. Type Ia supernovae are much rarer, happening roughly once every 500 years in the Milky Way.
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https://science.nasa.gov/mission/roman-space-telescope/type-ia-supernovae/

@grobi

"Type Ia supernovae are used as standard candles to establish the distance scale of the universe."

#quotes
#supernova
#APOD

2025 July 31

Supernova 2025rbs in NGC 7331
* Image Credit: Ben Godson (University of Warwick)
https://warwick.ac.uk/fac/sci/physics/research/astro/people/bengodson/

Explanation:
A long time ago in a galaxy 50 million light-years away, a star exploded. Light from that supernova was first detected by telescopes on planet Earth on July 14th though, and the extragalactic transient is now known to astronomers as supernova 2025rbs. Presently the brightest supernova in planet Earth's sky, 2025rbs is a Type Ia supernova, likely caused by the thermonuclear detonation of a white dwarf star that accreted material from a companion in a binary star system. Type Ia supernovae are used as standard candles to establish the distance scale of the universe. The host galaxy of 2025rbs is NGC 7331. Itself a bright spiral galaxy in the northern constellation Pegasus, NGC 7331 is often touted as an analog to our own Milky Way.
https://goto-observatory.org/bright-supernova-2025rbs-discovered-by-goto/
https://www.wis-tns.org/object/2025rbs
https://rochesterastronomy.org/supernova.html

https://apod.nasa.gov/apod/ap250731.html

2018 April 19

NGC 7635: The Bubble Nebula
* Image Credit: NASA, ESA, Hubble Heritage Team -
https://www.nasa.gov/
https://www.spacetelescope.org/
https://heritage.stsci.edu/
* Reprocessing by Maksim Kakitsev
https://www.flickr.com/photos/wildespace/39512823160/

Explanation:
Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 7 light-year diameter bubble offers evidence of violent processes at work. Above and left of the Bubble's center is a hot, O-type star, several hundred thousand times more luminous and some 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula and associated cloud complex lie a mere 7,100 light-years away toward the boastful constellation Cassiopeia. This sharp, tantalizing view of the cosmic bubble is a composite of Hubble Space Telescope image data from 2016, reprocessed to present the nebula's intense narrowband emission in an approximate true color scheme.

https://apod.nasa.gov/apod/ap180419.html

2025 February 3
A starfield is shown with a large spherical nebula in the center. The nebula shows a great deal of internal structure.

Wolf-Rayet Star 124: Stellar Wind Machine
* Image Credit: Hubble Legacy Archive, NASA, ESA
https://hla.stsci.edu/
https://www.nasa.gov/
https://www.esa.int/
* Processing & License: Judy Schmidt
https://www.flickr.com/photos/geckzilla/

Explanation:
Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they are slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the featured image center, is thus creating the surrounding nebula known as M1-67, which spans six light years across. Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of the Arrow (Sagitta). The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts.

https://apod.nasa.gov/apod/ap250203.html

Type Ia supernova

From Wikipedia, the free encyclopedia

At the core of a planetary nebula, Henize 2-428, two white dwarf stars slightly under one solar mass each are expected to merge and create a Type Ia supernova destroying both in about 700 million years (artist's impression).

A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf.

Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses (M☉). Beyond this "critical mass", they reignite and in some cases trigger a supernova explosion; this critical mass is often referred to as the Chandrasekhar mass, but is marginally different from the absolute Chandrasekhar limit, where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, or merges with a second white dwarf, the general hypothesis is that a white dwarf's core will reach the ignition temperature for carbon fusion as it approaches the Chandrasekhar mass. Within a few seconds of initiation of nuclear fusion, a substantial fraction of the matter in the white dwarf undergoes a runaway reaction, releasing enough energy (1×1044 J) to unbind the star in a supernova explosion.

The Type Ia category of supernova produces a fairly consistent peak luminosity because of the fixed critical mass at which a white dwarf will explode. Their consistent peak luminosity allows these explosions to be used as standard candles to measure the distance to their host galaxies: the visual magnitude of a type Ia supernova, as observed from Earth, indicates its distance from Earth.
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Read more:
https://en.wikipedia.org/wiki/Type_Ia_supernova

10 Years ago ..

2016 February 9

The Rise and Fall of Supernova 2015F
* Video Credit & Copyright: Changsu Choi & Myungshin Im (Seoul National University)
https://physics.snu.ac.kr/en

Explanation:
Sit back and watch a star explode. The actual supernova occurred back when dinosaurs roamed the Earth, but images of the spectacular event began arriving last year. Supernova 2015F was discovered in nearby spiral galaxy NGC 2442 by Berto Monard in 2015 March and was unusually bright -- enough to be seen with only a small telescope. The pattern of brightness variation indicated a Type Ia supernova -- a type of stellar explosion that results when an Earth-size white dwarf gains so much mass that its core crosses the threshold of nuclear fusion, possibly caused by a lower mass white-dwarf companion spiraling into it. Finding and tracking Type Ia supernovae are particularly important because their intrinsic brightness can be calibrated, making their apparent brightness a good measure of their distance -- and hence useful toward calibrating the distance scale of the entire universe. The featured video tracked the stellar disruption from before explosion images arrived, as it brightened, and for several months as the fission-powered supernova glow faded. The remnants of SN2015F are now too dim to see without a large telescope. Just yesterday, however, the night sky lit up once again, this time with an even brighter supernova in an even closer galaxy: Centaurus A.

https://apod.nasa.gov/apod/random_apod.html

How Stars Explode:
Four Ways to Make a Supernova

What makes a star go boom? By understanding supernovae – stellar explosions – scientists can unlock mysteries that are key to what we are made of and the fate of our universe.

https://exoplanets.nasa.gov/news/1493/kepler-beyond-planets-finding-exploding-stars/

CREDIT
Jet Propulsion Laboratory