In
the constellation Libra about 190 light years away from our planet, reside one
of the most mysterious objects in our galaxy, the impossible star which appears
to be older than the universe itself.
This
Methuselah star, cataloged as HD 140283, is a metal poor sub-giant star,
neither on the main sequence nor a red giant, has been known to astronomers for
more than 100 years as a high-velocity star — it cruises across the sky at a
relatively rapid clip.
Artistic illustration of HD 140283 a subgiant red star ©ex-astris1701 — DeviantArt
HD
140283 moves through our galactic neighborhood at astonishing speed of 800,000
mph (1.3 million km/h) relative to our solar system; with such speed, its cover
the width of the full moon in the sky every 1,500 years or so. This high rate
of motion is evidence that the star is just passing through our region of space
thus it will eventually rocket back out to our galaxy’s halo — the region of
space where the Milky Way’s oldest stars reside.
The
Methuselah star catch our attention back in 2000 when a team of scientists
calculate its age and got a shocking result, the stars appeared to be 16
billion years old, which is more than two billion years older than the
universe.
With this star map, you can find it ©A. Fujii and Z. Levay (STScI)
This
is an absurdity, obviously somebody’s got something wrong here, and it’s almost
certainly the age of Methuselah star, not our supposed age of the Universe,
which is measured to be 13.78 ± 0.037 billion years old. But here’s a surprise!
In
2014, A team of astronomers using NASA’s Hubble Space Telescope refine the
distance to HD 140283 and estimated its age: Methuselah star could be as old as
(14.5 ± 0.8) billion years, that, barely, gets the star into the realm of being
possible — it still older than the universe, which is a dilemma for
cosmologists.
We
have found that this is the oldest known star with a well-determined age,
said
Howard Bond.
Maybe
the cosmology is wrong, stellar physics is wrong, or the star’s distance is
wrong. So we set out to refine the distance.
So,
the question is what did we do wrong? Well, there are still many things that we
do not know about star formation and their aging process and everyone is
confident that HD 140283 is not, in fact, older than the Universe.
But
what we are pretty sure, the Methuselah star is one of the elder statesmen of
the universe. Considering the uncertainty of 800 million years, the star could
be as young as 13.6 billion years, which is within the age of the universe.
The extreme age of this star is nonetheless
fascinating and can tell us many interesting things: it is likely that HD
140283 formed when the universe was less than 170 million years old and it’s a
second generation star.
The
first stars in the universe were the so called population III stars, stars believed
to have formed from the primordial “molecular” clouds, 100 million years after
the Big Bang.
These
stars were super-giant stars — 100 to 1,000 times more massive than the Sun,
hot and bright, exploding as supernovae after only about 2 million years. Population
III stars produced and dispersed the first heavy elements, paving the way for
the eventual formation of pop II stars.
Methuselah
must have been of the second generation of stars, and its age being so close to
the birth of the Universe indicates that the space between the formation of the
first and second generations of stars was only a few tens of millions of years.
explained
scientists.
Is Methuselah Star the oldest star in the universe?
Well,
we don’t know but after six months (2014) when the media told us about HD
140283, the “Methuselah Star”, Australian scientists announced the discovery of
SMSS J031300.36-670839.3, an easy name to catch, a star at a distance of 6000
light years from Earth, with an age of approximately 13.6 billion years, the
oldest star ever seen in the Universe.
This
latest discovery, of SMSS J031300.36-670839.3, may be the oldest star we know
in the universe, but given the uncertainties involved, maybe it isn’t, nobody
knows for certain.
At
this moment, HD 140283 is one of the oldest known stars in the Universe, and
while that’s not quite as impressive as being older than the Universe, it’s
still a pretty cool superlative.
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