This image of Cep OB 3b
was created by combining the light from four separate observations
taken through different filters on the 0.9 meter telescope at Kitt Peak.
The brightest yellow star near the center of the image is a foreground
star, lying between us and the young cluster. The other bright stars
are the massive young stars of the cluster that are heating the gas and
dust in the cloud and blowing out cavities. Image processing was done by
Dr. Travis Rector.
WIYN 0.9-meter
Exterior of the WIYN 0.9-meter telescope on Kitt Peak, near Tucson, Arizona.
Watching starbirth isn’t easy: tens of millions of years are needed
to form a star like our Sun. Much like archeologists who reconstruct
ancient cities from shards of debris strewn over time, astronomers must
reconstruct the birth process of stars indirectly, by observing stars in
different stages of the process and inferring the changes that take
place. Studies show that half of the common stars, including our Sun,
formed in massive clusters, rich with young stars, from which they
eventually escape. As part of his PhD thesis work, Thomas Allen,
University of Toledo, has been observing such a region where stars are
forming.
Named Cep OB3b, this cluster is located in the northern constellation
of Cepheus, and is similar in some ways to the famous cluster found in
the Orion Nebula. But unlike the Orion Nebula, there is relatively
little dust and gas obscuring our view of Cep OB3b. Its massive, hot
stars have blown out cavities in the gaseous cloud with their intense
ultraviolet radiation which mercilessly destroys everything in its path.
Cep OB3b may show us what the Orion Nebular Cluster will look like in
the future.
In a recently published paper, Allen and an international team of
astronomers from seven different Universities and Institutes (University
of Toledo, University of Massachusetts, Amherst, University of
Rochester, University of Exeter, Keele University, Harvard-Smithsonian
Center for Astrophysics and Space Telescope Science Institute) have
found that the total number of young stars in the cluster is as high as
3000. Infrared observations of the stars from the NASA Spitzer satellite
show about 1000 stars that are surrounded by disks of gas and dust from
which solar systems may form. As the stars age, the disks disappear as
the dust and gas get converted into planets or are dispersed into space.
As Allen says, “By studying nearby massive young clusters like Cep
OB3b, we can gain a greater understanding of the environments out of
which planets form.”
These observations pointed to a new mystery. Although the stars in
Cep OB3b are thought to be about three million years old, in some parts
of the cluster most of the stars had lost their disks, suggesting that
the stars in those parts were older. This suggests that the cluster is
surrounded by older stars, potential relics of previous clusters that
have since expanded and dispersed. To search for evidence for these
relic clusters, Allen used the Mosaic camera on the 0.9 meter telescope
at Kitt Peak National Observatory to observe wide field images of
CepOB3b. (See figure) These images show hot gas and its interaction with
the stars and permit the team to study a curious cavity in the gas for
evidence of older, yet still juvenile, stars that have lost their disks
of gas and dust. With these data, the team is searching for the previous
generations of star formation in the region surrounding Cep OB3b, and
piecing together the history of star formation in this magnificent
region. When finished, this may tell us how previous generations may
have influenced the current generation of stars and planets forming in
Cep OB3b.
The picture accompanying this release was created by combining
individual images observed through four different filters: blue, visual
(cyan), near infrared (orange) and an emission line of hydrogen (red).
Image processing was done by Dr. Travis Rector. The brightest yellow
star near the center of the image is a foreground star, lying between us
and the young cluster. The other bright stars are the massive young
stars of the cluster that are heating the gas and dust in the cloud and
blowing out cavities. Surrounding these massive cluster stars are
thousands of smaller young stars that may be in the process of forming
planetary systems.
Over the decades the telescopes at Kitt Peak National Observatory
have been used to probe many questions of star formation. Some 40 years
ago the same 0.9 meter telescope was used to study this cluster, but
back then the camera attached to the telescope made use of far less
sensitive photographic plates. Modern CCDs, familiar to everyone with a
cell phone camera, have enabled astronomers to tease out the mysteries
of how stars form with far more precision.
Kitt Peak National Observatory is located on the Tohono O’odham
Nation in Arizona. Dr. Ofelia Zepeda, a member of the Tohono O’odham
Nation, has written a poem entitled Hu’u ‘at Ma:Si / Birth of a Star. Originally written in the O’odham language, a translation of the first few lines begins:
They have seen the place where stars are born
They are embryonic.
Hydrogen gas, microscopic dust, silica, carbon,
Ultraviolet radiation, evaporation and erosion in space.
On the journey, and somewhere along the way they stopped and saw,
They saw the place where stars are born
Kitt Peak National Observatory is a division of the National Optical
Astronomy Observatory (NOAO), which is operated by Association of
Universities for Research in Astronomy Inc. (AURA) under a cooperative
agreement with the National Science Foundation.
