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| Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula.
Image Credit:
NASA, ESA, and the Hubble SM4 ERO Team
|
Eta Carinae is a
binary star system present at the distance of 7500 light years from the sun
which have two massive stars. The smaller one is having mass equal to 30 solar
masses and it’s one million times brighter than our sun. The bigger one is
nearly 90 times massive than our sun and in 5 million times brighter. The both
massive star revolve around Each other. Both stars eject large amount of
ionized gases into the space which is also called stellar wind. The both stars
are surrounded by dense gases and nebula which makes their observation difficult.
The orbit of secondary
star is highly elliptical that is not usually seen. The smaller star comes
closer to bigger star in every 5.5 years, at this time the stars are at their
closest distance which is also called periastron. The periastron is not more
than the distance between the planet Mars and Sun. During periastron, the solar
winds of both stars collide with each other and create amazing structures which
are still mysterious to astronomers.
The stellar winds
produced by both stars are not same. The stellar wind of primary star consists
of thick gases and produced at the rate of 1.6 million km/h and the secondary
star produces stellar wind of lesser density and having mass lesser by 100 times
but with the speed 6 times that of primary.
When the stars are at
the farthest distance from each other the stellar wind from both star undergo
head on collision and produces large cavity towards the side of smaller star
just like bow shock. But when they reach periastron, the smaller star carves
out cavity in the denser gases of primary star. You can understand this by viewing
video released by NASA’s Goddard space flight center. They have simulated a 3D
model of the Eta Carinae showing this amazing activity and structures which projects
outward.
The astronomers are continuously
observing the behaviour of star from 1990s. The star shows unique behaviour
during periastron. The recent periastron happened in 2014 and totally 4
periastron have been observed carefully. The X ray emission decreases during
the periastron and regains its natural level after periastron. But each time
the pattern is slightly different from previous which shows some structural
changes.
The stars are near
their end of life and will explode either as supernova or hypernova. As the
stars are very massive, the supernova will be very powerful and they will end
up into the black hole. The effect of supernova on Earth and its life is a great
concern. Some astronomers have said that the supernova produces Gamma Ray
Bursts which have ability to deplete ozone layer. The depletion of ozone layer
will lead to exposer to UV radiation from the sun and acid rain.
Many astronomers
believe that the distance between star and Earth is very large and we need not
to worry about. As an estimate, the normal distance of supernova should be less
than 26 light year from Earth to destroy half of its ozone layer but as this
supernova is 7500 light years away from us we need not to worry. The atmosphere
and magnetosphere of Earth will protect us from radiations. But the satellite
and other communication system may get affected due to high level of radiation.
The astronauts in the space will also be at risk.
The technical details
of the above points can be obtained from the following reference. The video is
also released by NASA Goddard Space Flight Center which shows their current
model of Eta Carinae.
Reference: