Type Ia Supernova

Type Ia supernova is the explosion of a white dwarf star in a binary star system. Material from a companion red giant star is dumped on the white dwarf until the smaller star reaches a precise mass limit. At that point the white dwarf can no longer support its own weight, and burns its nuclear fuel so suddenly that it explodes. These explosions always release roughly the
Type1a Supernova Binary System same amount of energy, and studies of relatively nearby type Ia supernovae have shown that they reach almost the same peak brightness in every case. Therefore it can be used as "standard candles" to determine their true distance. Figure 01 is a Type Ia supernova observed in 1994. It is the bright spot on the lower left at the fringe of the galaxy. Figure 02

Figure 01 Supernova Type Ia

Figure 02 Binary System [view large image]

shows such binary system before the explosion.

Accelerating Expansion Measurements from high-redshift supernovae are found to be about 20 per cent fainter than expected. Most astronomers interpret this as evidence for accelerating expansion of the Universe caused by an unknown "dark energy". Figure 03 the supernova observations (red dots) deviate slightly but significantly from the pattern for a deceleration expansion (blue line) that should occur if the universe is flat and has no cosmological constant. The measurements suggest that expansion is accelerating, perhaps because of a nonzero cosmological constant (red line).

Figure 03 Accelerating Expansion [view large image]