by Andrew Moseman
December 01, 2010
A study by Yale astronomer Pieter van Dokkum just took the estimated number of stars in the
universe - 100,000,000,000,000,000,000,000 (1022), or 100 sextillion - and
And you thought nothing good ever happens on Wednesdays...
study in the journal Nature (A
Substantial Population of Low-Mass Stars in Luminous Elliptical
Galaxies) focuses on
red dwarfs, a class of small, cool
They're so small and cool, in fact, that up to now
astronomers haven't been able to spot them in galaxies outside our
That's a serious holdup when you're trying to account for all
the stars there are.
As a consequence, when estimating how
much of a galaxy's mass stars account for - important to
understanding a galaxy's life history - astronomers basically had to
assume that the relative abundance of red-dwarf stars found in the
Milky Way held true throughout the universe for every galaxy type
and at every epoch of the universe's evolution, Dr. van Dokkum says.
"We always knew that was sort of a stretch, but it was the only
thing we had. Until you see evidence to the contrary you kind of go
with that assumption," he says.
But van Dokkum's team, using the Keck
Observatory in Hawaii, surveyed eight elliptical
galaxies nearby (between about 50 and 300 million light years
away) for these dim stars.
Their spectrometer could catch the
collective signature of these faraway red dwarfs and estimate how
many of them the neighbor galaxies harbor.
In the Milky Way there
are about 100 red dwarfs for every one star like the sun, but in
these galaxies that number may be more like 1,000 to one.
Elliptical galaxies are some of the
largest galaxies in the universe. The largest of these galaxies were
thought to hold more than 1 trillion stars (compared with the 400
billion stars in our Milky Way).
The new finding suggests there may
be five to 10 times as many stars inside
elliptical galaxies than previously thought, which would triple
the total number of known stars in the universe, researchers said.
While van Dokkum's Nature paper
was released to the public today, it's been raising a more private
For the past month, astronomers have
been buzzing about van Dokkum's findings, and many aren't too happy
about it, said astronomer Richard Ellis of the California Institute
Van Dokkum's paper challenges the assumption of,
more orderly universe" and gives credence to "the idea that the
universe is more complicated than we think," Ellis said.
Ellis said it is too early to tell if van Dokkum
is right or wrong, but it is shaking up the field "like a cat among
Van Dokkum agreed, saying,
"Frankly, it's a big pain."
And besides tripling the number of stars
in the universe (isn't that enough???) and infuriating some
astronomers, van Dokkum's find has some serious secondary
More stars, of course, means the opportunity for
planets, and many recently found
exoplanets orbit red dwarfs.
Furthermore, the plethora of red dwarfs
could explain a
dark matter mystery:
Elliptical galaxies posed a problem: The
motions of the stars they contained implied that they had more mass
than one would get by adding the mass of the normal matter
astronomers observed to the expected amount of dark matter in the
Some suggested that ellipticals somehow had extra dark
matter associated with them. Instead, the newly detected red dwarfs
could account for the difference, van Dokkum says.