An artist’s impression of some of the first stars in the early Universe. Five protostars are seen here forming in the centre of disks of gas.
Credit: Shantanu Basu, University of Western Ontario.
Click here for a full size image
The first stars in the Universe were born several hundred million years
after the Big Bang, ending a period known as the cosmological 'dark
ages' – when atoms of hydrogen and helium had formed, but nothing shone
in visible light. Now two Canadian researchers have calculated what
these objects were like: they find that the first stars could have
clustered together in phenomenally bright groups, with periods when they
were as luminous as 100 million Suns. Alexander DeSouza and Shantanu
Basu, both of the University of Western Ontario in Canada, publish their results in a paper in Monthly Notices of the Royal Astronomical Society.
The two scientists modelled how the luminosity of the stars would
have changed as they formed from the gravitational collapse of disks of
gas. The early evolution turns out to be chaotic, with clumps of
material forming and spiralling into the centre of the disks, creating
bursts of luminosity a hundred times brighter than average. These first
stars would have been at their brightest when they were 'protostars',
still forming and pulling in material.
In a small cluster of even 10 to 20 protostars, the ongoing bursts
would mean the cluster would spend large periods with enhanced
brightness. According to the simulation, every so often a cluster of 16
protostars could see its luminosity increase by a factor of up to 1000,
to an extraordinary 100 million times the brightness of the Sun.
The earliest stars lived very short lives and produced the first
heavy elements, like the carbon and oxygen that the chemistry of life
depends upon.
Light from these stars has travelled towards us for almost 13 billion
years, so to observers on Earth they look very faint and also have
their light stretched out into infrared wavelengths by the expansion of
the universe. This makes these stars very hard to observe, but the next
generation James Webb Space Telescope
(JWST) will survey the skies to look for them. Although the luminosity
of an individual first star is probably too faint for JWST to spot it,
the new work suggests that clusters of the first protostars could be
prominent beacons in the early universe.
Dr Basu commented: "Seeing the very first stars is a key science goal
for JWST and part of astronomers’ quest to track the history of the
cosmos. If we’re right, then in just a few years’ time, we could see
these enigmatic and dazzlingly bright objects as they came into being,
and lit up the universe around them."
Further information
The new work appears in A. L. DeSouza & S. Basu, "The Luminosity of Population III Star Clusters", Monthly Notices of the Royal Astronomical Society, vol. 450, pp. 295-304, 2015, published by Oxford University Press.
Science contact
Dr Shantanu BasuUniversity of Western Ontario
Canada
Tel: +1 519 661 2111 x86706
Mob: +1 519 520 7856
basu@uwo.ca
Media contact
Dr Robert MasseyRoyal Astronomical Society
Tel: +44 (0)20 7734 3307 x214
Mob: +44 (0)794 124 8035
rm@ras.org.uk
Notes for editors
The Royal Astronomical Society (RAS), founded in 1820, encourages and
promotes the study of astronomy, solar-system science, geophysics and
closely related branches of science. The RAS organizes scientific
meetings, publishes international research and review journals,
recognizes outstanding achievements by the award of medals and prizes,
maintains an extensive library, supports education through grants and
outreach activities and represents UK astronomy nationally and
internationally. Its more than 3800 members (Fellows), a third based
overseas, include scientific researchers in universities, observatories
and laboratories as well as historians of astronomy and others. Follow
the RAS on Twitter via @RoyalAstroSoc
Source: Royal Astronomical Society (RAS)
