Astronomers using ESO’s Very Large Telescope have taken a picture of DG121, a HII region located in the constellation of Puppis.
This image, taken with ESO’s Very Large Telescope, shows the HII region DG121, which is also known as RCW 7, GAL 232.62+01.00, and IRAS 07299-1651. The brightest star in DG121, seen near the center in the picture, is HD 60068. Image credit: ESO.
HII regions, a type of emission nebulae, are created when young, massive stars ionize nearby clouds of interstellar gas with high-energy ultraviolet (UV) radiation.
These objects are composed primarily of hydrogen, hence the name (astronomers use the term HII to refer to ionized hydrogen, HI for neutral hydrogen).
They have temperatures of around 10,000 K and range in size from one to several hundreds of light-years.
They are often associated with giant molecular clouds, and appear clumpy and filamentary, sometimes showing intricate shapes.
Spiral and irregular galaxies contain many HII regions, while elliptical galaxies are almost devoid of them.
In spiral galaxies, they are concentrated in the spiral arms, while in irregular galaxies they are distributed chaotically.
“HII regions are created when young, massive stars release enough UV energy to ionize the surrounding gas clouds,” ESO astronomers said.
“These regions tend to have irregular structures and lack sharp boundaries, giving them their hazy, yet photogenic, appearance.”
The researchers observed the HII region DG121 with the FORS 2 (FOcal Reducer and low dispersion Spectrograph 2) instrument on ESO’s Very Large Telescope at Paranal Observatory in Chile.
They used four optical filters to sample various wavelengths.
“FORS 2 is what we call the ‘Swiss army knife of instruments at Paranal,’ because of its ability to study many different astronomical objects in many different ways,” the scientists said.
