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This 'Star' is older than the Universe itself


For more than 100 years, astronomers have observed a curious star located about 190 light
years away from Earth, in the constellation Libra. It travels quickly across the sky at 1.3 million
kilometers per hour. But more interestingly, HD 140283 - or Methuselah as it is commonly
known - is also one of the oldest known stars in the universe.



This is a backyard view of the sky surrounding the ancient
Methuselah star, cataloged as HD 140283. Image released March 7, 2013.
(Image credit: A. Fujii and Z. Levay (STScI))


In 2000, scientists sought to date the star using observations from the European Space
Agency's (ESA) Hipparcos satellite, which estimated an age of 16 billion years. This
information was quite mind-boggling and also very disconcerting. As astronomer Howard
Bond of Pennsylvania State University has pointed out, the age of the universe - determined
from observations of the cosmic microwave background - is 13.8 billion years old. "It was a
serious discrepancy," he said.

The expected age of the star raised a major problem. How could a star be older than the
universe? Or, conversely, how could the universe be younger? It was certainly clear that
Methuselah was old because it was poor in metal and is predominantly made of hydrogen
and helium and contains very little iron. Its composition means that the star must have
appeared before iron became common in the universe. But more than two billion years older
than its environment? This is certainly not possible.

Bond and his colleagues decided to find out whether that initial figure of 16 billion was
accurate or not. They analyzed 11 sets of observations that were recorded between 2003 and
2011 by the Hubble Space Telescope's Fine Orientation Sensors, which record the positions,
distances and energy production of the stars. When acquiring new and more accurate
information, a better age estimate could be determined.

"One of the uncertainties with the age of HD 140283 was the precise distance from the star,"
Bond told All About Space magazine. “It was important to get this right because we can better
determine its luminosity and, from that age - the brighter the luminosity, the younger the star.
We were looking for the parallax effect, which meant that we were seeing the star every six
months in addition to looking for the change in position due to Earth's orbital movement,
which finally indicates the distance ”, he concluded.

Bond and his colleagues estimated the age of HD 140283 to be 14.46 billion years - a
significant reduction from the previous 16 billion. That was still, however, more than the age
of the universe itself, but scientists put an 800 million year old uncertainty rate, which Bond
said made the age of the star compatible with the age of the universe, even if it wasn't totally
perfect.

Other improvements made the HD 140283's age drop a little more. A 2014 follow-up study
updated the star's age to 14.27 billion years.

“The conclusion was that the age is about 14 billion years and, again, if we include all sources
of uncertainty - both in observational measurements and in theoretical modeling - the error is
about 700 or 800 million years, so there is no conflict, because 13.8 billion years are within
the star's 'margin of error', concluded Bond. [ LiveScience ]

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