The Milky Way Supernova You've Never Heard Of

Every year astronomers see hundreds of supernovae erupt in other galaxies, but from such great distances these stellar explosions look only like bright dots. Researchers therefore prize the few supernovae that past observers witnessed in the Milky Way, where telescopes can scrutinize the wreckage. Since the year A.D. 1000, skywatchers have seen five of our galaxy's stars die in brilliant explosions. Now a new distance determination to the most mysterious of these is yielding new insight into its nature.

Astronomers discover new kind of supernova

This artist's conception shows the suspected progenitor of a new kind of supernova called Type Iax. Material from a hot, blue helium star at right is funneling toward a carbon/oxygen white dwarf star at left, which is embedded in an accretion disk. In many cases the white dwarf survives the subsequent explosion. Credit: Christine Pulliam (CfA)

(Phys.org)—Supernovae were always thought to occur in two main varieties. But a team of astronomers including Carnegie's Wendy Freedman, Mark Phillips and Eric Persson is reporting the discovery of a new type of supernova called Type Iax.

Farthest Supernova Yet Marked Death of Very Massive Star

Astronomers are reaching ever further back in time, seeking events from the earliest days of the universe. Now, the discovery of the farthest (and thus oldest) supernova ever seen is raising hopes that astronomers will soon detect the explosive deaths of the first stars to form after the universe's birth. These stars forged the first heavy elements, which helped create smaller and longer-lived stars like our own sun.

The earliest stars looked different from modern stars. The big bang produced only three light elements—hydrogen, helium, and a little lithium—but today, stars form in gas clouds that also contain heavier elements such as carbon and oxygen. These elements radiate away enough energy to eventually cool the clouds. When the clouds cool, they fragment into smaller clumps that collapse to spawn a plethora of mostly small stars.

'White Widow' Scenario for Birth of Type Ia Supernovae

J. Craig Wheeler has studied the exploding stars called supernovae for more than four decades. Now he has a new idea on the identity of the "parents" of one of the most important types of supernovae -- the Type Ia, those used as "standard candles" in cosmology studies that led to the discovery of dark energy, the mysterious force causing the universe's expansion to speed up.

Wheeler lays out his case for supernova parentage in the current issue of The Astrophysical Journal. He explains why he thinks the parents of Type Ia could be a binary star made up of white dwarf star (the burnt-out remnant of a Sun-like star) and a particular type of small star called an "M dwarf."

O novă scoate la iveală o gaură neagră

Satelitul NASA Swift a detectat recent un val crescut de raze X de înaltă energie provenind de la o sursă apropiată de centrul Căii Lactee. Explozia, un fenomen rar - o novă de raze X, a anunţat prezenţa unei găuri negre de masă stelară, anterior necunoscută.

"Novele de raze X strălucitoare sunt foarte rare, evenimente a căror observare poate fi un eveniment unic în viaţa unei misiuni NASA; acesta este primul astfel de eveniment astronomic detectat de Swift", a afirmat Neil Gehrels, principalul investigator al misiunii în cadrul Goddard Space Flight Center din Greenbelt, aparţinând NASA. "Acest fenomen este într-adevăr ceva ce aşteptăm de mult."

Cosmology: Out of the darkness

The 62nd Lindau Nobel Laureate Meeting opened with a talk by Brian Schmidt, who shared the 2011 physics prize for the shocking revelation that the Universe is expanding at an accelerating rate. Fifteen years after Schmidt's initial discovery, the 'dark energy' invoked to explain this cosmic acceleration is still a mystery.

It is the most sobering fact in physics. Everything that has ever been observed, from elementary particles to clusters of galaxies hundreds of millions of light years across, makes up just 4% of the Universe. The remaining 96% is currently missing: dubbed dark matter (23% of the Universe) and dark energy (73%), their existence is inferred by the effect they have on ordinary matter, but their natures are unknown.

No Star Left Behind: Fruitless Search for Supernova Survivor Hints at Unexpected Origins

A type Ia supernova is perhaps the ultimate combination of insult and injury—a star steals material from a companion star, reaches critical mass, becomes unstable, and then unleashes a nuclear blast powerful enough to decimate or destroy its already diminished victim.

The culprit in these cases is clear: type Ia supernovae arise from the cataclysmic explosions of small, dense stars known as white dwarfs. But the victim's identity is clouded, limiting the precision of cosmological distance estimates that rely on these luminous beacons as markers. Traditionally, scientists believed that with the victims were sunlike main-sequence stars or swollen giant stars. But recent studies have pointed to a major role for a lesser known mechanism—pairings of two white dwarfs in which one cannibalizes its orbital companion before exploding as a supernova.

Metrologie des supernovae de type Ia pour la cosmologie

Spiral Galaxy Photo Sheds New Light on Recent Star Explosion

A new, extremely deep photo of the site of a supernova explosion that was observed in 1957 has revealed X-rays emanating from the source.

The photo, taken by NASA's Chandra X-Ray space telescope, is the first to spot X-ray light coming from the remains of the dead star that sparked the explosion, and indicates that the supernova likely transformed the star into a pulsar.

Pulsars are super-dense, fast-rotating objects that have been compressed so tightly they are composed only of neutrons.

Moartea și moștenirea stelelor

Ultima fază a ciclului de viaţă al unei stele poate fi tumultuos.

Stelele cu mase mari se dilată sau chiar explodează. De obicei, tot ce rămâne în urma unei stele disipate sunt corpuri ceresti bizare.

Atunci când rezerva de hidrogen din centrul unei stele se epuizează, minimul de energie rezultată duce la scăderea presiunii interne. Miezul stelei se contractă sub propria forţă gravitaţională şi devine mai cald. Dacă nucleul este suficient de fierbinte, heliul se transformă în carbon şi oxigen şi, pentru o vreme, continuă să producă energie.