HD 5980 AB |
Home | X-Objects | Stars | Habitability | Life | |
Nazé
et al, 2002, U. Liege,
CXC,
NASA
Larger x-ray image.
The x-ray bright, HD 5980
star system lies next to
a hot gas cloud that spans
100 light-years (more at
CXC
and
Astronomy
Picture of the Day).
Intergalactic Region around the Supernova
In 1994, a star in the
Small
Magellanic Cloud (SMC or
NGC
292), brightened to
outshine everything else in nearby galaxy, which lies about
210,000 light-years away from the Milky Way. The SMC is a
small
irregular
galaxy and orbiting satellite of the Milky Way visible
to naked-eye observers from Earth's Southern Hemisphere,
slightly north of the globular cluster
47
Tucanae.
A neighbor of the closer,
Large
Magellanic Cloud
to which it may not be gravitationally bound
(Demers
and Irwin, 1993), the SMC is located in the eastern part
(, ICRS 2000.0) of Constellation
Tucana,
the Toucan -- . It is one of the most distant objects
that can be seen with the naked eye by Humans and so has
been known since pre-historic times.
The second brightest and largest of the
Milky Way's satellites at ,000 ly wide or more, the SMC has
around billion stars which eventually be torn apart and
integrated gravitationally into the Milky Way within a few
billion years (more image and information about
SMC,
galaxies
in general, and the
absorption
of satellite galaxies). Gravitational tides induced by the
much massive Milky Way have already distorted the SMC's original
shape by moving around its gas, dust, and stars, which may help to
foster stellar formation in nebulae like NGC 346 as the galaxy has
a preponderance of young, hot, blue stars indicating it has
undergone a recent period of star formation.
Photo by
David
Malin,
The HD 5980 system lies within the young NGC 346 star cluster
of the Small Magellanic Cloud.
Juan C. Forte and Sergio Cellone,
CASLEO
The NGC
346 cluster contains a lot of young, massive
stars. It contains about half of all the early type-O
stars in the SMC and is responsible for the ionization
of N66, the most luminous H-II region in the SMC
(Ye et al, 1991). (More discussion about observing NGC 346
from the
Astronomical
Society of New South Wales.)
HD 5980 A
The star is of uncertain spectral and luminosity
type. Once thought to be a Wolf-Rayet star (WN3-6)
(Niemela, 1997; and 1988),
it usually looks like a blue to blue-white supergiant
(O7-B1.5 I) but
erupted like a luminous blue variable in 1994 with
their association spectrum. While it is helium-rich,
(He/H= 0.43), it has not ejected all of its outer
hydrogen envelope as yet, and its evolutionary
characteristics suggests that core fusion has not
progressed to helium burning.
It is located 180,000 ly (59 kpc - Mathewson
et al, 1986) away in the Small
Magellanic Cloud's dusty nebula, NGC 346
(0:59:5.0-72:10:42.1, J2000; and ICRS 2000.0). Possibly born as a
120-Solar-mass
(Stothers
and Chin, 1993), low metallicity star, it have ejected
off enough mass to have only 40 to 62 times the mass
of Sol, sometimes swells from 48 to around 160 times
Sol's diameter (exceeding its binary orbital separation),
and around four million times its luminosity
Koenigsberger
et al, 1998). A useful catalogue
number for the progenitor star is: Sk -69 202. Useful
catalogue numbers and designations for the supernova are:
LMC SN, SN 1987A, and LMC 264.
Nazé
et al, 2002,
The eclipsing binary system lies HD 5980 lies within a
hot, heart-shaped cloud gas about 100 ly across. At
about eight million °C and bright in x-rays, the gas
cloud is probably the remnant of a supernova explosion
that occurred thousands of years ago (i.e., an expanding
hot shell of ejecta) or a nebula of ejecta associated
with a luminous blue variable such as Star A.
Moreover, its spatial proximity to the system suggests
that the remnant is related to the system. A compact,
x-ray bright object at the location of the system is
also found, that is somewhat less luminous than
Eta Carinae. If colliding
stellar winds from Stars A and B are not responsible
for producing the observed (as is found with
Eta Carinae which may also be
a binary star system), then the x-ray
brightness of the system may be from a compact object
orbiting as a third companion "C" --
e.g., a neutron star or black hole -- which also requires
the existence of a fourth companion "D" in a wider orbit.
(Nazé
et al, 2002).
Stars A and B have an
eccentric orbit (e= 0.28) with period
of 19.3 days that is inclined by more than 88 degress from
the perspective of an observer on Earth
Koenigsberger
et al, 1998).
HD 5980 B
Companion B is a Wolf-Rayet of a
spectral and luminosity type O7I (, J2000; and
ICRS 2000.0).
It may have around 18 to 30 times the mass of Sol, sometimes
times Sol's diameter,
and times its luminosity
Koenigsberger
et al, 1998).
© Anglo-Australian
Observatory
Larger image.
The Small Magellanic Cloud contains
an abundance of young hot blue stars
(more at
Astronomy
Picture of the Day
and
AAT).
(Permission being sought)
Larger image.
The HD 5980 star system
lies in NGC 346, a young
star cluster
(more).
CXC,
NASA
Larger x-ray image.
The x-ray bright, hot gas
cloud is either a supernova
remnant or the type of nebula
associated with the ejecta of
luminous blue variables (more
at
CXC
and
HEASARC).
Other Information
Up-to-date technical summaries on this star are available at: NASA's ADS Abstract Service for the Astrophysics Data System; and the SIMBAD Astronomical Database mirrored from CDS, which may require an account to access.
Tucana is a small constellation located around the South Pole. For more information about the stars and objects in this constellation and an illustration, go to Christine Kronberg's Tucana. For another illustration, see David Haworth's Tucana.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
© 2002 Sol Company. All Rights Reserved. |