15Apr2013

A Long Awaited View Into The Small Magellanic Cloud.

In this composite image the Chandra data is shown in purple, optical data from Hubble is shown in red, green and blue and infrared data from Spitzer is shown in red. Credit: Chandra

Southern Hemisphere observers are very familiar with the sight of one of the Milky Way‘s closest neighbors – the Small Magellanic Cloud (SMC). It’s an amazing sky sight.This dwarf galaxy is so bright that it’s readily apparent to the unaided eye and a vision to behold through optical equipment. Because it is so close and bright, the SMC is the perfect place to study phenomena that happen in other galaxies besides our own. 

One of the most recent studies taken on by Chandra X-Ray Observatory has been the x-ray emission detection of young stars with masses similar to our Sun. While we can find these types of stars in our own galaxy, we can further our understanding of stellar formation even more by validating observations outside the Milky Way. These new low-mass star observations taken by Chandra occur in an area known as the “Wing” of the SMC. In this composite image of the Wing the Chandra data is shown in purple, optical data from the Hubble Space Telescope is shown in red, green and blue and infrared data from the Spitzer Space Telescope is shown in red.

What the study helps to reveal is metallicity – and the “Wing” is known to have fewer metals than most parts of the Milky Way. Astronomers are looking for all elements heavier than hydrogen and helium – ones with more than two protons in the atom’s nucleus. When combined, these properties make the Wing the perfect laboratory to examine the life cycle of stars and the gas housed in-between them. Dwarf irregular galaxies like the SMC are known to have these properties and the same conditions may have been common in the early Universe.

English: Artist's conception of the spiral str...

English: Artist’s conception of the spiral structure of the Milky Way with two major stellar arms and a central bar. “Using infrared images from NASA’s Spitzer Space Telescope, scientists have discovered that the Milky Way’s elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms.” (Photo credit: Wikipedia)

In examining the Wing, the most prominent area of star formation happens in a small region cataloged as NGC 602 – home of at least three star clusters. Of these, NGC 602a is almost identical in age, mass and size to another famous star formation area – the Orion Nebula. Researchers have taken great care to examine young stars, those that are only a few million years old, to see if they have different properties when formed in low metallicity environments like those that exist in NGC 602a.

With Chandra’s help, astronomers have pinpointed extended x-ray emissions from two of its most densely populated regions. According to the Chandra team: “The extended X-ray cloud likely comes from the population of young, low-mass stars in the cluster, which have previously been picked out by infrared and optical surveys, using Spitzer and Hubble respectively.

This emission is not likely to be hot gas blown away by massive stars, because the low metal content of stars in NGC 602a implies that these stars should have weak winds. The failure to detect X-ray emission from the most massive star in NGC 602a supports this conclusion, because X-ray emission is an indicator of the strength of winds from massive stars. No individual low-mass stars are detected, but the overlapping emission from several thousand stars is bright enough to be observed.”

So what’s happening here? If Chandra is correct, young, metal-poor stars like those in NGC 602a are emitting x-rays much like those with higher metal content. The authors of the paper venture that if the x-ray properties are similar – yet environmentally different – then the same conditions must also exist in similar galaxies. This also means that related properties, such as the formation and evolution of circumstellar disks and proto-planetary disks, must also be similar. The x-ray emission also factors in the magnetic activity of the youthful stars and this correlates to how their magnetic dynamo operates – showing us the magnetic fields which involve stellar rotation speeds and convection properties.

Not only is this new image beautiful to look at, but the combination of infrared, optical and x-ray data gives us a look outside our Galaxy at objects which could be at an even younger state of stellar evolution. These “young stellar objects” could be only a few thousand years old… locked in the embrace of pillars of gas and dust… very similar to the “Pillars of Creation” found in the Eagle Nebula!

And waiting in the wings…

Original Story Source: Chandra Observatory News Release. Submitted by Tammy Plotner for “Dave Reneke’s World of Space and Astronomy News”.

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