Supernovas & Massive Gamma Ray Bursts
Δημοσιεύθηκε στις 11 Δεκ 2013
A look at real life "death stars"
that are far worse than the one in Star Wars such as supernovas that
unleash massive gamma-ray bursts (GRB) that could eradicate all life for
thousands of light years; a look at "WR104", a dying star 8000 light
years away that could point a GRB right at Earth, and "3C321", a "death
star galaxy" that could be a terrifying vision of what may befall the
Milky Way galaxy. Eta Carinae and Betelgeuse are given as examples of
stars that could have violent ends that are too close for comfort.
Gamma-ray
bursts (GRBs) are flashes of gamma rays associated with extremely
energetic explosions that have been observed in distant galaxies. They
are the brightest electromagnetic events known to occur in the universe.
Bursts can last from ten milliseconds to several minutes. The initial
burst is usually followed by a longer-lived "afterglow" emitted at
longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and
radio).
Most observed GRBs are believed to consist of a narrow
beam of intense radiation released during a supernova as a rapidly
rotating, high-mass star collapses to form a neutron star, quark star,
or black hole. A subclass of GRBs (the "short" bursts) appear to
originate from a different process. This may be the merger of binary
neutron stars. The cause of the precursor burst observed in some of
these short events may be due to the development of a resonance between
the crust and core of such stars as a result of the massive tidal forces
experienced in the seconds leading up to their collision, causing the
entire crust of the star to shatter.
The sources of most GRBs are
billions of light years away from Earth, implying that the explosions
are both extremely energetic (a typical burst releases as much energy in
a few seconds as the Sun will in its entire 10-billion-year lifetime)
and extremely rare (a few per galaxy per million years). All observed
GRBs have originated from outside the Milky Way galaxy, although a
related class of phenomena, soft gamma repeater flares, are associated
with magnetars within the Milky Way. It has been hypothesized that a
gamma-ray burst in the Milky Way, pointing directly towards the Earth,
could cause a mass extinction event.
GRBs were first detected in
1967 by the Vela satellites, a series of satellites designed to detect
covert nuclear weapons tests. Hundreds of theoretical models were
proposed to explain these bursts in the years following their discovery,
such as collisions between comets and neutron stars. Little information
was available to verify these models until the 1997 detection of the
first X-ray and optical afterglows and direct measurement of their
redshifts using optical spectroscopy, and thus their distances and
energy outputs. These discoveries, and subsequent studies of the
galaxies and supernovae associated with the bursts, clarified the
distance and luminosity of GRBs. These facts definitively placed them in
distant galaxies and also connected long GRBs with the explosion of
massive stars, the only possible source for the energy outputs observed.
WR
104 is a Wolf-Rayet star discovered in 1998, located 8,000 light years
from Earth. It is a binary star with a class OB companion. The stars
have an orbital period of 220 days and the interaction between their
stellar winds produce a spiral "pinwheel" outflow pattern over 200
astronomical units long. The spiral is composed of dust that would
normally be prevented from forming by WR 104's intense radiation were it
not for the star's companion. The region where the stellar wind from
the two massive stars interacts compresses the material enough for the
dust to form, and the rotation of the system causes the spiral-shaped
pattern.
Some optical measurements indicate that WR 104's
rotational axis is aligned within 16° of Earth. This could have
potential implications to the effects of WR 104's eventual hypernova,
since these explosions often produce jets from their rotational poles.
It is possible that WR 104 may even produce a gamma-ray burst, though it
is not possible to predict with certainty at this time. Newer
spectroscopic data suggest that WR 104's rotational axis is more likely
angled 30--40° from Earth.
that are far worse than the one in Star Wars such as supernovas that
unleash massive gamma-ray bursts (GRB) that could eradicate all life for
thousands of light years; a look at "WR104", a dying star 8000 light
years away that could point a GRB right at Earth, and "3C321", a "death
star galaxy" that could be a terrifying vision of what may befall the
Milky Way galaxy. Eta Carinae and Betelgeuse are given as examples of
stars that could have violent ends that are too close for comfort.
Gamma-ray
bursts (GRBs) are flashes of gamma rays associated with extremely
energetic explosions that have been observed in distant galaxies. They
are the brightest electromagnetic events known to occur in the universe.
Bursts can last from ten milliseconds to several minutes. The initial
burst is usually followed by a longer-lived "afterglow" emitted at
longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and
radio).
Most observed GRBs are believed to consist of a narrow
beam of intense radiation released during a supernova as a rapidly
rotating, high-mass star collapses to form a neutron star, quark star,
or black hole. A subclass of GRBs (the "short" bursts) appear to
originate from a different process. This may be the merger of binary
neutron stars. The cause of the precursor burst observed in some of
these short events may be due to the development of a resonance between
the crust and core of such stars as a result of the massive tidal forces
experienced in the seconds leading up to their collision, causing the
entire crust of the star to shatter.
The sources of most GRBs are
billions of light years away from Earth, implying that the explosions
are both extremely energetic (a typical burst releases as much energy in
a few seconds as the Sun will in its entire 10-billion-year lifetime)
and extremely rare (a few per galaxy per million years). All observed
GRBs have originated from outside the Milky Way galaxy, although a
related class of phenomena, soft gamma repeater flares, are associated
with magnetars within the Milky Way. It has been hypothesized that a
gamma-ray burst in the Milky Way, pointing directly towards the Earth,
could cause a mass extinction event.
GRBs were first detected in
1967 by the Vela satellites, a series of satellites designed to detect
covert nuclear weapons tests. Hundreds of theoretical models were
proposed to explain these bursts in the years following their discovery,
such as collisions between comets and neutron stars. Little information
was available to verify these models until the 1997 detection of the
first X-ray and optical afterglows and direct measurement of their
redshifts using optical spectroscopy, and thus their distances and
energy outputs. These discoveries, and subsequent studies of the
galaxies and supernovae associated with the bursts, clarified the
distance and luminosity of GRBs. These facts definitively placed them in
distant galaxies and also connected long GRBs with the explosion of
massive stars, the only possible source for the energy outputs observed.
WR
104 is a Wolf-Rayet star discovered in 1998, located 8,000 light years
from Earth. It is a binary star with a class OB companion. The stars
have an orbital period of 220 days and the interaction between their
stellar winds produce a spiral "pinwheel" outflow pattern over 200
astronomical units long. The spiral is composed of dust that would
normally be prevented from forming by WR 104's intense radiation were it
not for the star's companion. The region where the stellar wind from
the two massive stars interacts compresses the material enough for the
dust to form, and the rotation of the system causes the spiral-shaped
pattern.
Some optical measurements indicate that WR 104's
rotational axis is aligned within 16° of Earth. This could have
potential implications to the effects of WR 104's eventual hypernova,
since these explosions often produce jets from their rotational poles.
It is possible that WR 104 may even produce a gamma-ray burst, though it
is not possible to predict with certainty at this time. Newer
spectroscopic data suggest that WR 104's rotational axis is more likely
angled 30--40° from Earth.
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