“We were excited to see
this disklike structure because it may be evidence for a WolfRayet Star
forming from a binary interaction. There are very few examples in the galaxy of
this process in action because this phase is shortlived, perhaps lasting only
a hundred thousand years, while the timescale over which a resulting disk is
visible could be only ten thousand years or less”
Study
leader Dr. Jon Mauerhan of the University of California, Berkeley whose team
observed NaSt1 using the Hubble Space Telescope
NASA (National Aeronautical
Space Administration) Hubble Space Telescope is still full of surprises.
NASA (National
Aeronautical Space Administration) is celebrating the 25th
Anniversary of the Hubble Space Telescope as reported in the article “Celebrate
With NASA as Agency Commemorates Hubble Space Telescope’s 25th Anniversary”,
published April 16, 2015, NASA.
Even at 25, the Hubble
Space Telescope is still making discoveries that make us question the origin of
some of the strangest anomalies in the Universe as noted in the article “The
Hubble Space Telescope: A 25th Anniversary Photo Celebration”, published
April 20, 2015 07:15am ET By Space.com Staff , Space.
One of these anomalies
is the Star NaSt1, otherwise nicknamed Nasty 1, as reported in the article “Hubble
observes oneofakind Star nicknamed 'Nasty'”, published May 21, 2015 by
Ray Villard, Physorg. This stellar anomaly is
shedding new insight into the formation of WolfRayet Stars, all thanks to
the Hubble Space Telescope.
This new insight is
based on the work of a team led by Dr. Jon Mauerhan and his fellow
astronomers at the University of California, Berkeley. Their
work is currently published in the Monthly Notices of the Royal Astronomical
Society since Thursday May 21st 2015.
So what makes this
Nasty 1 Star so exciting? It may provide insights into the formation of one of
the most enigmatic objects in the universe, that being the
WolfRayet Stars.
NaSt1 the Wolf-Rayet Star – Origins of Nebulae
may be a Future Past
Discovered by
Jason Nassau and Charles Stephenson back in 1963, NaSt1, located
some 3000 Light Years from Earth, gets its name from the concatenation of the
first letters of the surnames of the co-discoverers.
They identified it as a
WolfRayet Star, a type of Star that tends to be much larger than our Sun
but with a very short lifespan. Wolf–Rayet stars have an abundance of Helium,
Nitrogen, Carbon, Silicon and Oxygen, all of which are unsuitable for Nuclear
Fusion and indicate a star that has spend most of its Hydrogen.
This is based on the
missing spectra from Spectroscopy analysis of the emission from these heavenly
bodies, the telltale sign that the star is a Wolf-Rayet star!.
Because of its massive
size, its life is short lived, dying as it supposedly runs out of hydrogen,
causing the outer layers of hydrogen to be ejected, leaving behind the
shimmering embers of its helium rich core.
Until now scientists
have not been sure how these exotic WolfRayet Stars, particularly what
causes it to lose so much mass in the first place. This is where studying the
Nasty 1, as it’s remarkably similar to another possible WolfRayet Star
called Eta Carinae.
NaSt1 has two (2) gas
jets emanating from opposite sides of the Star, like a pulsar only not rotating
at all. Instead, inspection by the Hubble Space Telescope team at the University
of California revealed nebulae of gas in a disc shape nearly 2 trillion miles
wide. This is completely different from most WolfRayet Stars, which makes it
rather interesting to study.
So how did that
particular WolfRayet Star end up with such a huge nebulae so quickly?
Maybe the Star had a dancing partner!
University of California’s NaSt1 Star – How a
WolfRayet Stars forms from Binary Star Private Nebulae Dancer
The Team from the
University of California knew that typically, a WolfRayet Star were once
super-massive Stars, which are usually unstable and fast-burning, deplete their
Hydrogen close to their central core.
But rather than collapse
under the weight or its outer core and rebound outward, causing a Super Nova, it
begins to eject its outer layer via a series of violent eruptions from within
the Star. These eruptions create jets of charged particles, called a stellar
wind, that stream outwards from the center of the Star, carrying away the outer
layers as it streams outwards.
However, Direct-mass ejection
as this is called, cannot sufficiently explain the presence of the huge and
widely dispersed 1 trillion mile wide nebulae surrounding NaSt1 or the number
of WolfRayet Stars that have already been confirmed. Thus a more
plausible theory has been proposed that accounts for this particular anomaly as
well as a suspected 70% of all other WolfRayet Stars.
The new model, which
the Team from the University of California has formulated, suggests that the Star
once hands a binary partner. As it began to transition toward becoming a Wold-Rayet
Star in the usual manner, this other companion Star began to feed on the
ejected outer layers of NaSt1.
These outer layers, now
very loosely bound, would be pulled apart from the Star by its binary partner
in a Gravitational stripping process similar to stripping off the outer layers
of an onion.
Co-author of the NaSt1
paper Dr. Nathan Smith of the University of Arizona in Tucson, supports this
hypothesis, quote: “We're finding that it is hard to form all the WolfRayet
stars we observe by the traditional wind mechanism, because mass loss isn't as
strong as we used to think. Mass exchange in binary systems seems to be vital
to account for WolfRayet stars and the supernovae they make, and catching
binary stars in this shortlived phase will help us understand this process”.
The result is that the
binary partner begins to get bigger while NaSt1 gets smaller, rapidly stripped
off its outer more loosely-bound hydrogen layers until only the naked Helium core
is left. In so doing, it becomes a WolfRayet Star and many Astronomers
agree that this hypothesis is a more likely explanation for the prevalence of
this type of Star.
Like a baby eating too
much food at once, the companion Binary Star doesn’t eat everything that it
strips from its dying companion. Instead, that excess hydrogen gas may linger about
the two Stars and Start swirling outwards, encircling them both in thick hazy
nebulae.
Observations using the
Hubble Telescope as well as from previous observations indicate that the gas in
the outer part of the nebulae is moving at a rate of
22,000 miles per hour. This is a lot slower than the gas in the
nebulae swirling about Eta Carinae, another Wolf-Rayet Candidate. .
It’s nebula gas cloud
is clocking speeds n the thousands of miles per hour, suggesting a less violent
event created the nebula for NaSt1 and thus making the binary companion theory
more plausible.
There may be another
star orbiting NaSt1, a binary companion that making the surrounding environment
nasty with remnant from stripping away its outer core.
NaSt1 feeding a Binary Baby Star – Figure Skater
draws her arms inwards in X-Ray-ted Lambada
Through observations
made by Dr. Mauerhan at the University of California and colleagues at the
University of Arizona using the Magellan telescope at Las Campanas Observatory
in Chile, they've come to realize that a recently formed large pocket of dust
and gas may be obscuring the light of the binary Stars within the nebulae.
This large pocket of
dust and gas is still hot after thousands of years, suggesting that it was
formed recently, possibly while Humans were on Earth. Dr. Jon Mauerhan believes
that Nasty 1 is a WolfRayet star in sheep's clothing, quote: “That's what we
think is happening in Nasty 1. We think there is a WolfRayet star buried
inside the nebula, and we think the nebula is being created by this
masstransfer process. So this type of sloppy stellar cannibalism actually
makes Nasty 1 a rather fitting nickname”.
This large pocket of
dust and gas is obscuring our view of the two (2) Stars locked in their dance
to the death, with the stellar winds mixing things up a bit, leaving the dust
and gas shaken but not stirred.
Thus the clumps and
knots in the nebulae disc and the gaps in-between may be due to the sporadic
changes in the stellar wind. These observations provides more evidence of a
companion Star's gravitational tug and thus suggesting that the mechanism of
the formation of the WolfRayet Star NaSt1.
Realizing that they
needed a clearer picture of what is going on inside of the gaseous envelope,
the Team from the University of California had enlisted the help of NASA's
Chandra X-ray Observatory.
Scorching hot plasma
jets, the same pair observed coming from both ends of the NaSt1, seem to be
colliding with plasma jets from the companion Star. As the gas stripped from
NaSt1 begins to swirl around the companion Star, it accelerates, creating
friction between itself and the surface of the companion Star.
Like a figure skater
pulling in her hands, the gas coming closer accelerates the rate of spin of the
swirling gas and thus the friction between the gas and the Star causes a gas to
rebound off the surface. This rebounding of gas createws shock-waves on the
surface of NaSt1 and is also accompanied by bursts of radiation in the X-Ray
spectrum.
Dr. Jon Mauerhan is
clearly excited about what the future holds as it relates to this chance of
observing this rare event, quote: “What evolutionary path the star will take is
uncertain, but it will definitely not be boring. Nasty 1 could evolve into
another Eta Carinaetype system. To make that transformation, the massgaining
companion star could experience a giant eruption because of some instability
related to the acquiring of matter from the newly formed WolfRayet”.
The super-nova even,
interestingly, is still on the cards.
So too is a merger with
the companion star, if it is massive enough, to quote Dr. Mauerhan: “Or, the
WolfRayet could explode as a supernova. A stellar merger is another potential
outcome, depending on the orbital evolution of the system. The future could be
full of all kinds of exotic possibilities depending on whether it blows up or
how long the mass transfer occurs, and how long it lives after the mass
transfer ceases”.
This observation is
consistent with other known Wolf-Rayet Stars. As NaSt1 runs out of gas, the
disk will dissipate, hopefully providing astronomers with a view of the binary
dancers in their death like embrace sometime in the future.
Here’s the link:
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