May 2, 2013
Danish Telescope Captures Breathtaking Image Of Star-Forming Region
John P. Millis, Ph.D. for redOrbit.com - Your Universe Online
Located relatively nearby, a mere 5000 light-years from Earth, NGC 6559 is found in the constellation of Sagittarius (The Archer). The nebula is only a few light years across, a stark contrast to its more well-known neighbor, the Lagoon Nebula, which stretches more than 100-light years in diameter.
NGC 6559 is dominated by hydrogen gas, the basic building block of stars. When regions of the nebula are disturbed, the gas can begin to clump together. Gravity then takes over and begins drawing in more and more hydrogen. Eventually the temperature at the center of the forming object will approach 10 million kelvin, sufficient to drive nuclear fusion in the core. Through this process hydrogen nuclei will begin fusing into helium, establishing hydrostatic equilibrium as the outward radiation pressure balances the inward gravitational force. At this point, a star is formed.
As the stars inject energy into the surrounding nebula, the gas becomes ionized as the electrons are stripped from their atoms. The consequence is the release of energy, which appears as red light, giving NGC 6559 its signature glow. This type of system defines what we know as an emission nebula, since the gas itself is radiating energy into outer space.
In contrast, a nearby region of the nebula, seen in the right hand portion of the above image, is dominated more by particles of dust, made of heavier elements, such as carbon, iron or silicon. Here, the light from the stars interacts with the dust particles through a process known as Rayleigh scattering, according to an ESO release.
While the process will occur from the various wavelengths of light emitted by the surrounding stars, the more energetic blue light scatters more easily, giving the region, known as a reflection nebula, its signature hue. This is the same process, incidentally, that gives rise to our blue sky during the day time.
The above image was captured by the Danish observatory known as the Faint Object Spectrograph and Camera (DFOSC) on the 1.54-metre Telescope at La Silla in Chile.