Kamuela, Hawaii – Star clusters with properties not seen before have been discovered by an international team of astrophysicists, led by Swinburne University of Technology’s Professor Duncan Forbes.
Using data from the Hubble Space Telescope and the W. M. Keck
Observatory in Hawaii, the researchers found several star clusters with
sizes and masses that were previously not known to exist.
“Old, compact star clusters, such as globular clusters, are well
known to amateur astronomers,” Professor Forbes said. “Although globular
star clusters were first discovered in 1665, it has taken more than 340
years to fully appreciate all the different types of star clusters that
are made in the Universe.”
The researchers confirmed the existence of a number of different star
clusters, overturning the idea that star clusters only come in certain
types.
“We now know that star clusters have a rather continuous range of
size and mass without any gaps in their properties,” Professor Forbes
said. “Our discovery was made possible by using the Hubble Space
Telescope to measure the sizes of the star clusters and long exposures
on the Deep Extragalactic Imaging Multi-Object Spectrograph fitted to
the Keck II telescope to obtain distances and confirm their status.”
Professor Jean Brodie, a team member from the University of California,
said.
They also measured the color of the star clusters, finding the lower
mass ones to be red and the higher mass ones to be blue in color,
suggesting differences in their chemical composition.
“No single model for the formation of these star clusters can
currently reproduce the diversity of structural properties we have
observed for old star clusters,” Professor Forbes said. “Our
observations present a challenge to researchers aiming to reproduce star
clusters in computer simulations.”
The research team included Vincenzo Pota and Christopher Usher
(Swinburne University of Technology), Jay Strader (Michigan State
University), Aaron Romanowsky (San Jose State University), Jean Brodie
and Jacob Arnold (University of California), and Lee Spitler (Macquarie
University).
The paper has
been accepted for publication in the Monthly Notices of the Royal
Astronomical Society, published by Oxford University Press.
The Keck II telescope’s DEIMOS instrument is capable of gathering
spectra from 130 galaxies or more in a single exposure. In “Mega Mask”
mode, DEIMOS can take spectra of more than 1,200 objects at once, using a
special narrow-band filter.
The W. M. Keck Observatory operates the largest, most scientifically
productive telescopes on Earth. The two, 10-meter optical/infrared
telescopes on the summit of Mauna Kea on the Island of Hawaii feature a
suite of advanced instruments including imagers, multi-object
spectrographs, high-resolution spectrographs, integral-field
spectroscopy and a world-leading laser guide star adaptive optics
system. The Observatory is a private 501(c) 3 non-profit organization
and a scientific partnership of the California Institute of Technology,
the University of California and NASA.
