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Claumetria Jones
ED 498/R. Holden
February 22, 2010
A Stellar Swan-Song
The life cycle of a star is a moderately long process. The time period in which a star
evolves is very long. For instance the sun, which happens to be one of the largest stars in the
universe, was born more than 4.5 billion years ago, and is said to only be halfway through its life
cycle. A study has indicated that some phases of the solar development of a star are at an
extremely rapid aging process.
Asplund (2005) suggests that the faster cases of the solar
development are known as the rebirth of a giant star. This article will discuss the life of one very
important star, Sakurai’s Object and the converse that surrounds it.
There are only three stars that have been observed while in the act of a fast stellar
evolution, F.G. Sagittac, V605 Aquilae, and Sakurai’s Object (V4334 Sar). In February of 1996
Yukio Sakurai, a Japanese amateur astronomer, was looking for comets when he noticed an
object in the constellation Sagittarius. At first, Yukio Sakurai reported the object to be a nova,
but a closer look at its size revealed that it was a giant star that had been born again. It has been
reported that only after 10 years of its first growth encounter, Sakurai’s Object has started to heat
up again.
Since the appearance of Sakurai’s Object, many astronomers have studied it
progression. Studies show that since its 1996 discovery, Sakurai’s Object’s stellar surface has
cooled from approximately 8000K to approximately 6000K, while its chemical composition,
hydrogen, and lithium levels have changed remarkably. The changes in Sakurai’s Object’s
makeup is said to be the results of the revival of nuclear burning in a white dwarf (Asplund,
2005).
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Toward the end of a star’s life, it become a so-called asymptotic giant branch (AGB) star,
because a mass containing 1 to 8 solar masses enlarges to a giant dimensions. Asplund (2005)
found that the nuclear energy of a star is produced interchange by helium and hydrogen burning
in shells around its stellar core. In various cases, stars can momentarily avoid fading to stellar
oblivion.
Because of an increase in the temperature in its stellar interior, a final helium
explosion may occur when a star has long left the ABG phase. The born-again phase of a star’s
life cycle can last anywhere from 10 to 1000 years before the star goes back to the white dwarf
regime.
Because of the dimness of the star, the evidence presented by Hajduk e al. that Sakurai’s
Object has started to heat up again is indirect (Asplund, 2005). The observation conducted by
scientists and astronomers suggest that there is a new area inside the old planetary nebula, which
requires a stellar surface temperature of greater than 20, 000K, which is much bigger than those
observed in 1996. The evolution Sakurai’s Object has been faster than suggested by the previous
stellar replica of the born-again giant events. The calculations presented for Sakurai’s Object
resulted in a reduction by a rapid nuclear burning.
The life of Sakurai’s Object is extremely interesting and complicated. The star will
continuously change as it ages. Because of the unprecedented process of Sakurai’s Object
evolution over the last ten years, its future evolution will be studied closely. Sakurai’s Object
will continue to heat up causing it to become visible again inside the new planetary nebula. The
final process will ultimately be revealed to scientists and astronomers universally.
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Reference:
Asplund, M. (2005). A Stellar Swan-Song. Science, 308(5719), 210-211. Retrieved from
Academic Search Complete database.