Sakurai's Object
Encyclopedia
Sakurai's Object in the constellation
of Sagittarius
, an object discovered to behave as a "slow nova
" by Yukio Sakurai, a Japanese amateur astronomer, in 1996. It is believed to have been an asymptotic giant branch
star
that has undergone a final helium flash
relieving it from its atmosphere to become a white dwarf
.
Sakurai's Object is largely believed to be a red giant star
that was previously a white dwarf. The Very Late Thermal Pulse (VLTP) occurred during the white dwarf phase and swelled it up to giant size (due to the thermal pulse). These types of objects, of which only a handful have been observed, become hydrogen deficient and enriched in Helium and other metals. It is then expected that these
will end up as a DB, or helium rich, white dwarf after retracing its evolution track from the "born-again" giant phase back to the white dwarf cooling track. Other observed "born-again" objects include V605 Aquilae
and FG Sagittae
.
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Sagittarius
Sagittarius (constellation)
Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...
, an object discovered to behave as a "slow nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
" by Yukio Sakurai, a Japanese amateur astronomer, in 1996. It is believed to have been an asymptotic giant branch
Asymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
that has undergone a final helium flash
Helium flash
A helium flash is the runaway fusion of helium in the core of low mass stars of less than about 2.25 solar masses and greater than about 0.5 solar mass, or on the surface of an accreting white dwarf star. They may also occur in the outer layers of larger stars in shell flashes...
relieving it from its atmosphere to become a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
.
Sakurai's Object is largely believed to be a red giant star
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
that was previously a white dwarf. The Very Late Thermal Pulse (VLTP) occurred during the white dwarf phase and swelled it up to giant size (due to the thermal pulse). These types of objects, of which only a handful have been observed, become hydrogen deficient and enriched in Helium and other metals. It is then expected that these
will end up as a DB, or helium rich, white dwarf after retracing its evolution track from the "born-again" giant phase back to the white dwarf cooling track. Other observed "born-again" objects include V605 Aquilae
V605 Aquilae
V605 Aquilae, in the constellation Aquila, is the variable central star of the planetary nebula Abell 58, exhibiting features similar to R Coronae Borealis variable stars , but also peculiar brightenings since 1919. Its spectrum exhibit the characteristic hydrogen deficiency and other features...
and FG Sagittae
FG Sagittae
FG Sagittae, in the constellation Sagitta, is a supergiant star in the constellation Sagitta at a distance of 8000 light-years. When first noted in 1943, it was noticed to be a variable star, and its spectrum was registered as of B4Ieq in 1955. Since then it has expanded and reddened to G in...
.