Credit: X-ray: NASA/CXC/SAO; IR/Optical: NASA/ESA/HST; UV: NASA/ESA/STScI/Catholic Univ of America; Image Processing: NASA/CXC/SAO/J. Major, and K. Arcand
Growing Big Stars without Metals
Scientists believe that the first stars to form in the Universe were much more massive than our Sun, tens to hundreds of times more massive. Part of the reason these dinosaur stars grew so large is due to the scarcity of "metals", (i.e. elements with more than 2 protons in their atomic nucleus) in the early Universe. Metals are needed to form complex molecules and dust, and molecules and dust play a vital role in cooling the gas clouds out of which stars form, and this cooling is neccesary in order for smaller, less massive stars to form. So studying massive young clusters of stars is an important way to understand all the cosmic implications of how dense interstellar clouds turn themselves into stars. And, since young massive stars possess strong winds (driven by their enormous output of radiation) when these winds collide with surrounding gas or dust, or nearby stars, or other stellar winds, these collisions produce hot gas at temperatures of millions of degrees, hot enough to produce X-ray emission. So studying the X-ray emission from young massive star-forming clouds helps our understanding of the star formation process. The image above shows a star cluster called NGC 346, located in the Small Magellanic Cloud, one of the Milky Way's satellite galaxies. The image is a composite of ultraviolet and optical emission from the hot stars (in blue), along with infrared emission from the cold dust in brown. The image includes, in purple, a Chandra X-ray Observatory image of point-like X-ray emission from some of the stars in NGC 346, along with broader diffuse X-ray emitting gas from a supernova remnant near the cluster and from the powerful collisions of the young stars' stellar winds. Since the Small Magellenic Cloud has only about one tenth the abundance of complex elements compared to the Milky Way, it provides an important test of star formation in the type of low-metallicity environments common in the early Universe.
Published: February 23, 2026
<
HEA Dictionary ● Archive
● Search HEAPOW
● Other Languages
● HEAPOW on Facebook
● Download all Images
● Education ● HEAD
>
Each week the HEASARC
brings you new, exciting and beautiful images from X-ray and Gamma ray
astronomy. Check back each week and be sure to check out the HEAPOW archive!
Page Author: Dr. Michael F. Corcoran
Last modified Monday, 23-Feb-2026 13:47:26 EST