A new survey of our home galaxy, the Milky Way, combines the capabilities of the Very Large Array and the Effelsberg telescope in Germany to provide astronomers with valuable new insights into how stars much more massive than the Sun are formed.
From:
National Radio Astronomy Observatory
July 22, 2021 -- Astronomers using two
of the world's most powerful radio telescopes have made a detailed and
sensitive survey of a large segment of our home galaxy -- the Milky Way --
detecting previously unseen tracers of massive star formation, a process that
dominates galactic ecosystems. The scientists combined the capabilities of the
National Science Foundation's Karl G. Jansky Very Large Array (VLA) and the 100-meter
Effelsberg Telescope in Germany to produce high-quality data that will serve
researchers for years to come.
Stars with more than about ten times the
mass of our Sun are important components of the Galaxy and strongly affect
their surroundings. However, understanding how these massive stars are formed
has proved challenging for astronomers. In recent years, this problem has been
tackled by studying the Milky Way at a variety of wavelengths, including radio
and infrared. This new survey, called GLOSTAR (Global view of the Star
formation in the Milky Way), was designed to take advantage of the vastly
improved capabilities that an upgrade project completed in 2012 gave the VLA to
produce previously unobtainable data.
GLOSTAR has excited astronomers with new
data on the birth and death processes of massive stars, as well on the tenuous
material between the stars. The GLOSTAR team of researchers has published a
series of papers in the journal Astronomy & Astrophysics reporting
initial results of their work, including detailed studies of several individual
objects. Observations continue and more results will be published later.
The survey detected telltale tracers of
the early stages of massive star formation, including compact regions of
hydrogen gas ionized by the powerful radiation from young stars, and radio
emission from methanol (wood alcohol) molecules that can pinpoint the location
of very young stars still deeply shrouded by the clouds of gas and dust in
which they are forming.
The survey also found many new remnants
of supernova explosions -- the dramatic deaths of massive stars. Previous
studies had found fewer than a third of the expected number of supernova
remnants in the Milky Way. In the region it studied, GLOSTAR more than doubled
the number found using the VLA data alone, with more expected to appear in the
Effelsberg data.
"This is an important step to solve
this longstanding mystery of the missing supernova remnants," said Rohit
Dokara, a Ph.D student at the Max Planck Institute for Radioastronomy (MPIfR)
and lead author on a paper about the remnants.
The GLOSTAR team combined data from the
VLA and the Effelsberg telescope to obtain a complete view of the region they
studied. The multi-antenna VLA -- an interferometer -- combines the signals
from widely-separated antennas to make images with very high resolution that
show small details. However, such a system often cannot also detect large-scale
structures. The 100-meter-diameter Effelsberg telescope provided the data on
structures larger than those the VLA could detect, making the image complete.
"This clearly demonstrates that the
Effelberg telescope is still very crucial, even after 50 years of
operation," said Andreas Brunthaler of MPIfR, project leader and first
author of the survey's overview paper.
Visible light is strongly absorbed by
dust, which radio waves can readily penetrate. Radio telescopes are essential
to revealing the dust-shrouded regions in which young stars form.
The results from GLOSTAR, combined with
other radio and infrared surveys, "offers astronomers a nearly complete
census of massive star-forming clusters at various stages of formation, and
this will have lasting value for future studies," said team member William
Cotton, of the National Radio Astronomy Observatory (NRAO), who is an expert in
combining interferometer and single-telescope data.
"GLOSTAR is the first map of the
Galactic Plane at radio wavelengths that detects many of the important star
formation tracers at high spatial resolution. The detection of atomic and
molecular spectral lines is critical to determine the location of star
formation and to better understand the structure of the Galaxy," said Dana
Falser, also of NRAO.
The initiator of GLOSTAR, the MPIfR's
Karl Menten, added, "It's great to see the beautiful science resulting
from two of our favorite radio telescopes joining forces."
The National Radio Astronomy Observatory
is a facility of the National Science Foundation, operated under cooperative
agreement by Associated Universities, Inc.
https://www.sciencedaily.com/releases/2021/07/210722112844.htm
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