Credit: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech
A Tax of Metal Poor Stars
How does chemistry affect stellar evolution? This is an important question, since the chemical abundance of the early Universe was far different (and far simpler) than it is now. The young Universe, and stars which formed therein, where mostly made of hydrogen and helium, while stars in the present epoch, on the whole, contain small but significant amounts of more complex elements (known to astronomers as "metals"). Estimating (or "taxing" to our Latin colleagues) the amount of X-ray emission from young, metal poor stars is one way astronomers try to assess the effects of "metallicity" on the properties of young stars. X-ray emission act as a tracer of stellar activity and helps identify young, active stars. Fortunately for us, we have a relatively nearby laboratory, the Small Magellanic Cloud, (a companion galaxy to our Milky Way) in which the stars have very low abundance of elements heavier than helium. The stunning composite image above, of a region of young stars in the SMC known as NGC 602, combines optical, infrared and X-ray images to reveal stellar activity properties in this young region. The X-ray image, in particular, shows a diffuse glow from NGC 602, which is believed to arise from the combined X-ray activity of many faint, young, solar mass-type stars. Evidently, young solar-type stars with low metallicity can behave in the same outrageous fashion as their more metal rich cousins.
Published: April 15, 2013
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