An international research team led by scientists at the University
of British Columbia today announced a more reliable estimate
that verifies the age of the universe at 13-14 billion years.
Prof. Harvey Richer of UBC’s Physics and Astronomy Dept.,
the study’s principal investigator, discussed the group’s
research at a Space Science Update held today at NASA headquarters
in Washington, D.C.
"The remarkable thing is that our estimate of the age
of the universe, based on burned-out stars, agrees very well
with the estimate based on the measured expansion rate. The
two methods are absolutely unrelated to each other yet they
give the same result – it’s amazing," Richer says.
Previous research setting the age of the universe at 13 to
14 billion years was based on the rate of expansion of space,
but the universe’s birth date is such a fundamental quantity
that astronomers have long sought other age-dating techniques
to cross-check their conclusions.
Using NASA’s Hubble Space Telescope, Richer’s group uncovered
the oldest burned-out stars in the Milky Way – in a globular
star cluster 6,000 light years away in the constellation Scorpius.
These extremely dim and old "clockwork stars" give
a completely independent reading on the age of the universe.
Hubble photographed the ancient star cluster for a total
of eight days between January and April 2001. The data from
the 246 images were painstakingly analyzed at UBC by Richer
and UBC postdoctoral student James Brewer over a 12-month
period to yield the age estimate. The software for this analysis
was written by group member Dr. Peter Stetson of the Herzberg
Institute of Astrophysics (NRC) in Victoria.
"We measured the brightness and temperatures of white
dwarf stars – the burned-out remnants of the earliest stars
which formed in our galaxy. These stars are wonderful cosmic
clocks because they get cooler and fainter in a very predictable
way. We measured the faintest, coldest stars in the cluster
and used that data to analyze their age," Richer says.
Richer’s group reached the estimate of 13-14 billion years
by determining that the ancient white dwarf stars photographed
by Hubble are 12 to 13 billion years old. Earlier observations
show the first stars formed less than one billion years after
the universe’s birth in the Big Bang, so finding the age of
the oldest stars puts astronomers well within reach of calculating
the absolute age of the universe.
"This new observation short-circuits getting to the
age question, and offers a completely independent way of pinning
down that age," Richer says.
This approach has been recognized as more reliable than age-dating
the oldest stars still burning by nuclear fusion, which relies
on complex models and calculations about how a star burns
its nuclear fuel and ages.
"Everything we know about the universe depends on the
age we assign it, and because of this work and the expansion
research, we have a good idea of that age," Richer says.
The group’s work was supported by two of Canada’s most prestigious
granting agencies – Natural Sciences and Engineering Research
Council of Canada grants and a Canada Council Killam Fellowship
to Richer. The results of the study are to be published in
the Astrophysical Journal Letters this year.
In the fall, the collaboration will be submitting a proposal
for further research with Hubble to study another star cluster
with different characteristics in order to confirm their results.
Biography – Harvey B. Richer
Prof. Harvey Richer was born in Montreal, Quebec. He studied
at McGill University and obtained his doctorate in physics
and astronomy from the University of Rochester. His doctoral
program supervisor, Dr. Stewart Sharpless, was one of the
first astronomers to recognize that we live in a spiral galaxy.
Sharpless also mapped out the distribution of ionized gas
clouds by using a tiny wide-field camera.
Richer has been at the University of British Columbia since
the early 1970s. For the past two years, he has been the Gemini
Scientist for Canada. This year he was awarded a Canada Council
Killam Fellowship that allows him to work full time on his
research.
His research is largely focused on stellar astronomy and
on what resolved systems of stars can tell us about dark matter,
the age of the universe, the dynamical evolution of stellar
systems, and the formation of galaxies. To investigate these
diverse subjects, he observes a wide range of objects, including
nearby stars, open and globular star clusters, and the resolved
components of our neighbouring galaxies. To accomplish his
research goals, he uses a variety of telescopes, particularly
the Canada-France-Hawaii Telescope and the Hubble Space Telescope.
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