V445 Puppis
Encyclopedia
V445 Puppis was a nova
in the constellation
Puppis
. It was discovered by Kazuyoshi
Kanatsu of Matsue, Shimane
, Japan
, who recorded a peak magnitude of 8.6 on November 28, 2000. The nova was reported by Taichi Kato of Kyoto University
in the International Astronomical Union
circular 7552, issued on December 30, 2000. The location of this nova coincided with a magnitude 13.1 star that had been photographed in 1967. The proper motion
of this star was measured as -4.7 mas
/yr in right ascension
and +6.4 mas/yr in declination
, with a standard error of 4 mas/yr.
Examination of the optical spectrum of this nova showed absorption lines of calcium
(Ca I), sodium
(Na I) and singly ionized iron
(Fe II). The initial spectrum was deficient in hydrogen and did not match those typical of other nova types. The infrared
spectrum measured on January 31 showed a featureless continuum that decreased with increasing wavelength
. This is consistent with emission from heated dust and suggests that the star is a recurrent nova that has generated dust during prior outbursts. By 2004, the object had faded and the dust emission had disappeared.
The deficient level of hydrogen in this outburst, along with an enrichment of helium and carbon, and a higher level of ionization, suggested that it was the first observed instance of a helium nova. This is theorized to occur when a white dwarf
star predominantly accretes helium (rather than hydrogen) from an orbiting companion. When sufficient helium has accumulated along a shell on the surface of the white dwarf, a run-away thermonuclear explosion results in a nova outburst. Hence, V445 Puppis may belong to a binary star
system and be surrounded by an accretion disk of matter drawn from the companion star.
At present, the system is being obscured by an optically thick cloud of dust. A bi-polar outflow of material has been observed moving away from the system at a velocity of . Knots of material within this outflow are moving at velocities of up to . Based upon the expansion parallax
for this outflow, the system lies at a distance of .
The white dwarf in the V445 Puppis system has an estimated mass of more than 1.3 times the mass of the Sun
, and this mass is increasing because of recurring helium shell flashes from accreted material. As the mass of the white dwarf approaches the Chandrasekhar limit
of about 1.38 solar mass
es, it will likely explode as a Type Ia supernova
.
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...
in the constellation
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....
Puppis
Puppis
Puppis is a constellation in the southern sky. Its name is the Latin word for the poop deck of a ship, and Puppis represents the deck of the ship and its deckhouses...
. It was discovered by Kazuyoshi
Kanatsu of Matsue, Shimane
Matsue, Shimane
is the capital city of Shimane Prefecture in the Chūgoku region of Japan.As of August, 2011, the city has an estimated population of 207,000, following its most recent merging with Higashi-Izumo...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, who recorded a peak magnitude of 8.6 on November 28, 2000. The nova was reported by Taichi Kato of Kyoto University
Kyoto University
, or is a national university located in Kyoto, Japan. It is the second oldest Japanese university, and formerly one of Japan's Imperial Universities.- History :...
in the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
circular 7552, issued on December 30, 2000. The location of this nova coincided with a magnitude 13.1 star that had been photographed in 1967. The proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
of this star was measured as -4.7 mas
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
/yr in right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
and +6.4 mas/yr in declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
, with a standard error of 4 mas/yr.
Examination of the optical spectrum of this nova showed absorption lines of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
(Ca I), sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
(Na I) and singly ionized iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
(Fe II). The initial spectrum was deficient in hydrogen and did not match those typical of other nova types. The infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
spectrum measured on January 31 showed a featureless continuum that decreased with increasing wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
. This is consistent with emission from heated dust and suggests that the star is a recurrent nova that has generated dust during prior outbursts. By 2004, the object had faded and the dust emission had disappeared.
The deficient level of hydrogen in this outburst, along with an enrichment of helium and carbon, and a higher level of ionization, suggested that it was the first observed instance of a helium nova. This is theorized to occur when 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...
star predominantly accretes helium (rather than hydrogen) from an orbiting companion. When sufficient helium has accumulated along a shell on the surface of the white dwarf, a run-away thermonuclear explosion results in a nova outburst. Hence, V445 Puppis may belong to a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
system and be surrounded by an accretion disk of matter drawn from the companion star.
At present, the system is being obscured by an optically thick cloud of dust. A bi-polar outflow of material has been observed moving away from the system at a velocity of . Knots of material within this outflow are moving at velocities of up to . Based upon the expansion parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
for this outflow, the system lies at a distance of .
The white dwarf in the V445 Puppis system has an estimated mass of more than 1.3 times the mass of the Sun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
, and this mass is increasing because of recurring helium shell flashes from accreted material. As the mass of the white dwarf approaches the Chandrasekhar limit
Chandrasekhar limit
When a star starts running out of fuel, it usually cools off and collapses into one of three compact forms, depending on its total mass:* a White Dwarf, a big lump of Carbon and Oxygen atoms, almost like one huge molecule...
of about 1.38 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es, it will likely explode as a Type Ia supernova
Type Ia supernova
A Type Ia supernova is a sub-category of supernovae, which in turn are a sub-category of cataclysmic variable stars, that results from the violent explosion of a white dwarf star. A white dwarf is the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion...
.