Astronomers using the NASA/ESA Hubble Space Telescope have captured a stunning image of the globular cluster Terzan 12, a vast, tightly bound collection of stars in the constellation of Sagittarius.
Globular clusters are stable, densely packed collections of hundreds of thousands or even millions of stars, gravitationally bound into a single structure about 100-200 light-years across. The word globulus, from which these clusters take their name, is Latin for small sphere.
They are among the oldest known objects in the Universe and are relics of the first epochs of galaxy formation.
Our own Milky Way Galaxy hosts at least 150 globular clusters and a few more are likely to exist hidden behind the Galaxy’s thick disk.
“Globular clusters are not uncommon in the Milky Way,” Hubble astronomers said.
“Around 150 are known, mostly in its outer halo, and Hubble has revolutionized their study since its launch in 1990.”
“However, examining clusters like Terzan 12, highly obscured by interstellar dust, is complicated by the resulting reddening of the light.”
“When starlight passes through an interstellar cloud it can be absorbed and scattered by particles of dust,” they said.
“The strength of this scattering depends on the wavelength of the light, with shorter wavelengths being scattered and absorbed more strongly.”
“This means that the blue wavelengths of light from stars are less likely to make it through a cloud, making background stars appear redder than they actually are.”
“We refer to the color change caused by the scattering and absorption of starlight as reddening, and it is responsible for the vibrant range of colors in the new image of Terzan 12.”
“Relatively unobscured stars shine brightly in white and blue, whereas creeping tendrils of gas and dust blanket other large portions of Terzan 12, giving stars a sinister red hue.”
“The more dust that lies along our line of sight to the cluster, the more the light of the stars is…
Read the full article here