Negative WISE W1 image of the newly found cluster Camargo 438 and 439. The cluster is about 16,000 light years away, so the image is about 24 light years across. The black dots in the image are individual stars. Credit: D. Camargo/NASA/WISE
Brazilian astronomers have made a remarkable discovery: a cluster of stars forming on the very edge of the Galaxy. The team, led by Denilso Camargo of the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, publish their results in the journal Monthly Notices of the Royal Astronomical Society.
The Milky Way,
the Galaxy we live in, has a barred spiral shape, with arms of stars,
gas and dust winding out from a central bar. Viewed from the side, the
Galaxy would appear relatively flat, with most of the material in a disc
and the central regions.
Stars form inside massive and dense clumps of gas in so-called giant molecular clouds
(GMCs) that are mainly located in the inner part of the galactic disc.
With many clumps in a single GMC, most (if not all) stars are born
together in clusters.
Denilso’s team looked at data from NASA’s orbiting Wide-Field Infrared Survey Explorer
(WISE) observatory. They not only found GMCs thousands of light years
above and below the galactic disc, but that one of them unexpectedly
contained two clusters of stars. This is the first time astronomers have
found stars being born in such a remote location.
The new clusters, named Camargo 438 and 439, are within the molecular
cloud HRK 81.4-77.8. This cloud is thought to be about 2 million years
old and is around 16000 light years beneath the galactic disk, an
enormous distance away from the usual regions of star formation, in the
direction of the constellation of Cetus.
Denilso believes there are two possible explanations. In the first
case, the 'chimney model', violent events such as supernova explosions
eject dust and gas out of the galactic disk. The material then falls
back, in the process merging to form GMCs.
The other idea is that the interaction between our Galaxy and its satellites, the Magellanic Clouds, may have disturbed gas that falls into the Galaxy, again leading to the creation of GMCs and stars.
Denilso commented: "Our work shows that the space around the Galaxy
is a lot less empty that we thought. The new clusters of stars are truly
exotic. In a few million years, any inhabitants of planets around the
stars will have a grand view of the outside of the Milky Way, something
no human being will probably ever experience.
"Now we want to understand how the ingredients for making stars made
it to such a distant spot. We need more data and some serious work on
computer models to try to answer this question."
The chimney model would need several hundred massive stars to have
exploded as supernovae over several generations, creating a 'superwind'
that threw HRK 81.4-77.8 into its present position. Over millions of
years, the bubbles created by the explosions may then themselves
compress material, forming more stars and fuelling the ejection of
material in a 'galactic fountain', where the dust and gas eventually
rains back on to the disk.
Media contact
Robert MasseyRoyal Astronomical Society
Tel: +44 (0)20 7734 3307 x214
Mob: +44 (0)794 124 8035
rm@ras.org.uk
Science contact
Denilso CamargoFederal University of Rio Grande do Sul
Porto Alegre
Brazil
Tel: +55 51 3308-6513
denilso.camargo@ufrgs.br
Images and captions
- Negative WISE W1 image of the newly found cluster Camargo 438. The cluster is about 16,000 light years away, so the image is about 24 light years across. The black dots in the image are individual stars. Credit: D. Camargo/NASA/WISE
- Another negative WISE W1 image of the newly found cluster Camargo 439. The clusters is about 16,000 light years away, so the image is about 24 light years across. The black dots in the image are individual stars. Credit: D. Camargo/NASA/WISE
- A negative WISE W3 image of dust emission centred on Camargo 438. Some of the stars in these clusters may be hidden by dust. Credit: D. Camargo/NASA/WISE
- An artist's impression of the Milky Way that shows how it might appear from a planet orbiting a star in one of the newly discovered clusters. Credit: NASA/JPL-Caltech/ESO/R. Hurt
Further information
The research was carried out by Dr Denilso Camargo, Dr Eduardo Bica,
Dr Charles Bonatto and Gustavo Bonatto (MSc Gustavo SALERNO), of the
Federal University of Rio Grande do Sul and Colégio Militar de Porto
Alegre - Exército Brasileiro.
It appears in the paper D. Camargo et al., "Discovery of two embedded clusters with WISE in the high Galactic latitude cloud HRK 81.4-77.8", Monthly Notices of the Royal Astronomical Society, vol. 448, pp. 1930-1936, 2015, published by Oxford University Press.
Notes for editors
The Royal Astronomical Society (RAS), founded in 1820, encourages and
promotes the study of astronomy, solar-system science, geophysics and
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