A series of astronomers from the University of New South Wales (UNSW) have recently published their findings on the formation of diffuse clouds within the interstellar medium. These astronomers are attempting to “map” galactic cloud formations, representing sources of new stars, with the belief it could reveal more information regarding their cosmic cycle.
According to Professor Michael Burton, who works for UNSW’s School of Physics, and was the research team’s lead, a huge mystery within the field of galactic astronomy centers around the means by which “… giant, diffuse clouds form in the interstellar medium.” Burton then goes on to suggest that this poorly understood mechanism has a role in the cosmic life and death of star formations.
The team, who recently published a journal in the Publications of the Astronomical Society of Australia, claim to be mapping out the location and dynamics of some of the galaxy’s galactic clouds, many of which can extend for up to 100 light years across.
The research was conducted using the Mopra Observatory, a 22-meter radio telescope, which is located in Coonabarabran of New South Wales, Australia, and operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), a national government body responsible for coordinating numerous research initiatives.
The Mopra Observatory managed to survive a recent bushfire in January this year, which destroyed the neighboring accommodation wing, workshops and offices. Luckily, the main telescope control room was left untouched, as it was protected by brickwork.
The Mopra Observatory is designed to map the dispersal and dynamics of carbon monoxide within a 40 degree sector of the Galactic Plane, and aims to collate and interpret findings alongside a number of other astronomical research facilities.
In astronomy, the interstellar medium refers to a range of matter that is present between star systems of a particular galaxy, constituting various gases, cosmic rays and dust. The interstellar medium consists of different phases, and is dependent upon temperature pressures, as well as the interference of magnetic fields, and the density of the matter contained within.
Within the interstellar medium, molecular gas clouds make up a tiny fraction of the overall volume (less than one percent), but remains the most dense part of the medium.
The means by which giant molecular gas clouds are created has long been speculated over. These so-called “stellar nurseries,” which regularly churn out nascent stars, are primarily composed of hydrogen gas; comparatively, most other types of interstellar gas clouds contain ionized gases.
Carbon Monoxide Studies
The researchers utilized the Mopra Observatory to perform carbon monoxide surveys of the Milky Way. When investigating interstellar gas clouds, hydrogen is notoriously difficult to detect using infrared and radio observations. Instead, carbon monoxide can generate a picture of how much hydrogen gas is present, since the carbon monoxide luminosity to hydrogen mass ratio is thought to remain fixed.
Professor Burton explains that carbon monoxide, a silent killer to human beings, is one of the most abundant molecules in space:
“… in space, it is the second most abundant molecule and the easiest to see. One of the largest unresolved mysteries in galactic astronomy is how these giant, diffuse clouds form in the interstellar medium. This process plays a key role in the cosmic cycle of birth and death of stars.”
These carbon monoxide maps have recently demonstrated that molecular gas clouds form principally within the spiral arms, forming and dissociating over a period of 10 million years.
One of the theories of giant molecular cloud formation involves the gravitational collapse of a cluster of small clouds. Coalescence of these smaller gas clouds is also referred to as the coagulation process, where the smaller, agglomerated clouds merge to form a single, massive cloud formation. On the other hand, an opposing “aggregation” process has also been cogitated over, whereby many smaller clouds collide with one another to form “clumps” of distinct clouds.
Dark Galactic Clouds
In addition, the international team is also involved in searching for “dark” galactic clouds. Dark galactic clouds lack the common tracers typically identified in either atomic or fully-formed molecular clouds, which are primarily comprised of hydrogen and carbon monoxide, respectively.
However, “dark” gas can be observed through analysis of the emission of neutral and uniformly-ionized carbon. It is also conjectured that dark gas may emit gamma rays, resulting from the interaction of cosmic ray particles with the nuclei of gases contained within the interstellar medium.
To understand more about dark gas clouds, they are harnessing the power of telescopes in both Chile and the Antarctica.
According to professor Burton, these latest surveys might provide information pertaining to the “distribution and movement of gas clouds in our galaxy.”
It is thought that, under the circumstances these dark clouds are found, they could explain the manifestation of gamma rays, whose source has remained an astronomical mystery for a so many years. Burton indicates that the source of 30 percent of gamma rays remains unidentified, a finding that he hopes his team’s research efforts will shed some light upon.
Although a lot of work is yet to be conducted to truly reveal the inner dynamics of galactic clouds, the researcher’s attempts to map these cosmological enigmas are looking very promising. Hopefully, soon we will gain a better appreciation for a small part of the cosmic cycle of our stars, as well as the stellar nurseries that produce them.
By: James Fenner