Credit: ESA/Hubble & NASA
This NASA/ESA Hubble Space Telescope picture shows NGC 5398, a barred spiral galaxy located about 55 million light-years away
The galaxy is famous for containing an especially extensive HII region, a large cloud composed of ionised hydrogen (or HII, pronounced “H-two”, with H being the chemical symbol for hydrogen and the “II” indicating that the atoms have lost an electron to become ionised).
NGC 5398’s cloud is named Tol 89 and sits at the lower left end of the
galaxy’s central “bar” of stars, a structure that cuts through the
galactic core and funnels material inwards to maintain the star
formation occurring there.
Tol 86 is conspicuous in being the only large massive star forming
complex in the entire galaxy, with an extension of roughly 5000 times
4000 light-years; it contains at least seven young and massive star clusters.
The two brightest clumps within Tol 89, which astronomers have named
simply “A” and “B”, appear to have undergone two bursts of star-forming
activity — “starbursts”
— roughly 4 million and less than 3 million years ago respectively. Tol
89-A is thought to contain a number of particularly bright and massive
stars known as Wolf-Rayet stars, which are known for their high temperatures and extreme stellar winds.
Source: ESA/Hubble/Potw
