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Supernova type codes, as summarised in the table above, are taxonomic: the type number is based on the light observed from the supernova, not necessarily its cause. For example, type Ia supernovae are produced by runaway fusion ignited on degenerate white dwarf progenitors, while the spectrally similar type Ib/c are produced from massive stripped progenitor stars by core collapse.

A small number of type Ia supernovae exhibit unusual features, such as non-standard luminosity or broadened light curves, and these are typically categorized by referring to the earliest example showing similar features. For example, the sub-luminous SN 2008ha is often referred to as SN 2002cx-like or class Ia-2002cx. [63] Let's look at the more exciting Type II first. For a star to explode as a Type II supernova, it must be several times more massive than the sun (estimates run from eight to 15 solar masses). Like the sun, it will eventually run out of hydrogen and then helium fuel at its core. However, it will have enough mass and pressure to fuse carbon. When a star explodes, it shoots out elements and debris into space that span millions of miles and eventually condense to create new stars or celestial bodies. Most of the elements we find here on Earthlikely had their origins in the core of a star These elementsmove on to form new stars, planets and every cosmic entity existing in the universe. (Photo Credit: Pixabay)

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Imagine that you’re an astronomer in the early years of the 17th century. The telescope hasn’t yet been invented, so you scan the night sky only with the unaided eye. Then one day you see a remarkable sight: A bright new star appears, and for the next few weeks it outshines even the planet Venus. It’s so bright it can even be seen in broad daylight. It lingers in the sky for many months, gradually dimming over time. So the resultant light from this explosion has been traveling through space for 21 million years before it finally reached our planet last week. A supernova is the explosion of a massive star. There are many different types of supernovae, but they can be broadly separated into two main types: thermonuclear runaway or core-collapse. This first type happens in binary star systems where at least one star is a white dwarf, and they're typically called Type Ia SNe. The second type happens when stars with masses greater than 8 times the mass of our sun collapse in on themselves and explode. There are many different subtypes of each of these SNe, each classified by the elements seen in their spectra. What happens after a supernova? Toward the end of the 20th century, astronomers increasingly turned to computer-controlled telescopes and CCDs for hunting supernovae. While such systems are popular with amateurs, there are also professional installations such as the Katzman Automatic Imaging Telescope. [43] The Supernova Early Warning System (SNEWS) project uses a network of neutrino detectors to give early warning of a supernova in the Milky Way galaxy. [44] [45] Neutrinos are particles that are produced in great quantities by a supernova, and they are not significantly absorbed by the interstellar gas and dust of the galactic disk. [46] "A star set to explode", the SBW1 nebula surrounds a massive blue supergiant in the Carina Nebula. Ultra-stripped supernovae occur when the exploding star has been stripped (almost) all the way to the metal core, via mass transfer in a close binary. [128] [129] As a result, very little material is ejected from the exploding star (c. 0.1 M ☉). In the most extreme cases, ultra-stripped supernovae can occur in naked metal cores, barely above the Chandrasekhar mass limit. SN 2005ek [130] might be the first observational example of an ultra-stripped supernova, giving rise to a relatively dim and fast decaying light curve. The nature of ultra-stripped supernovae can be both iron core-collapse and electron capture supernovae, depending on the mass of the collapsing core. Ultra-stripped supernovae are believed to be associated with the second supernova explosion in a binary system, producing for example a tight double neutron star system. [131] [132]

The first type of supernova is associated with binary star systems. Binary stars are two stars that orbit the same point, or center of mass. When one of the stars—a white dwarf(a highly dense star not much bigger than our sun)—steals matter from its companion star as it orbits the axis, it begins to accumulate enormous amounts of matter. This causes the star to eventually explode, resulting in a supernova. Supernova of a binary star(Photo Credit: Wikimedia Commons) A white dwarf star may accumulate sufficient material from a stellar companion to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it. There are three avenues by which this detonation is theorised to happen: stable accretion of material from a companion, the collision of two white dwarfs, or accretion that causes ignition in a shell that then ignites the core. The dominant mechanism by which type Ia supernovae are produced remains unclear. [74] Despite this uncertainty in how type Ia supernovae are produced, type Ia supernovae have very uniform properties and are useful standard candles over intergalactic distances. Some calibrations are required to compensate for the gradual change in properties or different frequencies of abnormal luminosity supernovae at high redshift, and for small variations in brightness identified by light curve shape or spectrum. [75] [76] Normal Type Ia [ edit ] Supernovae have shown scientists that we live in an expanding universe (by observing the redshift), one that is growing at an ever-increasing rate. Astronomers have concluded that supernovae play a vital role in distributing the elements produced in their cores throughout the universe. a. Type Ib supernovae are the more common and result from Wolf–Rayet stars of type WC which still have helium in their atmospheres. For a narrow range of masses, stars evolve further before reaching core collapse to become WO stars with very little helium remaining, and these are the progenitors of type Ic supernovae. [124]The last supernova directly observed in the Milky Way was Kepler's Supernova in 1604, appearing not long after Tycho's Supernova in 1572, both of which were visible to the naked eye. The remnants of more recent supernovae have been found, and observations of supernovae in other galaxies suggest they occur in the Milky Way on average about three times every century. A supernova in the Milky Way would almost certainly be observable through modern astronomical telescopes. The most recent naked-eye supernova was SN 1987A, which was the explosion of a blue supergiant star in the Large Magellanic Cloud, a satellite of the Milky Way.

A 1414 text cites a 1055 report: since "the baleful star appeared, a full year has passed and until now its brilliance has not faded". [14] Historical supernovae in the local group A sufficiently large and hot stellar core may generate gamma-rays energetic enough to initiate photodisintegration directly, which will cause a complete collapse of the core. In type II-L the plateau is absent because the progenitor had relatively little hydrogen left in its atmosphere, sufficient to appear in the spectrum but insufficient to produce a noticeable plateau in the light output. In type IIb supernovae the hydrogen atmosphere of the progenitor is so depleted (thought to be due to tidal stripping by a companion star) that the light curve is closer to a type I supernova and the hydrogen even disappears from the spectrum after several weeks. [62] A version of the periodic table indicating the origins – including stellar nucleosynthesis of the elements. (Photo Credit: Cmglee/Wikimedia Commons) There are several means by which a supernova of this type can form, but they share a common underlying mechanism. If a carbon- oxygen white dwarf accreted enough matter to reach the Chandrasekhar limit of about 1.44 solar masses [77] (for a non-rotating star), it would no longer be able to support the bulk of its mass through electron degeneracy pressure [78] [79] and would begin to collapse. However, the current view is that this limit is not normally attained; increasing temperature and density inside the core ignite carbon fusion as the star approaches the limit (to within about 1%) [80] before collapse is initiated. [77] In contrast, for a core primarily composed of oxygen, neon and magnesium, the collapsing white dwarf will typically form a neutron star. In this case, only a fraction of the star's mass will be ejected during the collapse. [79] The blue spot at the centre of the red ring is an isolated neutron star in the Small Magellanic Cloud.Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a white dwarf, or the sudden gravitational collapse of a massive star's core. One specific type of supernova originates from exploding white dwarfs, like type Ia, but contains hydrogen lines in their spectra, possibly because the white dwarf is surrounded by an envelope of hydrogen-rich circumstellar material. These supernovae have been dubbed type Ia/IIn, type Ian, type IIa and type IIan. [97] A supernova is a star that has reached the end of its life and has exploded. The light from a supernova can be seen from billions of light years away and is so bright that it can outshine an entire galaxy. Supernovae are important because they help create new elements and distribute them throughout the universe. Next, gradually heavier elements build up at the center, and the star forms onion-like layers of material, with elements becoming lighter toward the outside of the star. Once the star's core surpasses a certain mass (called the Chandrasekhar limit), it begins to implode. For this reason, these Type-II supernovae are also known as core-collapse supernovae. We were sent a video in which I could clearly see our daughter unconscious in the car with the Palestinians and them driving around the Gaza Strip.” How are relatives getting information?