To avoid contaminating the gas but still bathe it in ultraviolet rays, the stars would need to lie in a massive protogalaxy
just 10,000 light-years or so away, or less than half the span between our solar system and the Milky Way's center.
The cluster, located roughly 10 billion light-years from Earth and seen as it was when the universe was less than four billion years old, contains within it a giant protogalaxy
- the Spiderweb Galaxy.
Rather, Shen's team suggests that the spinning disk of the protogalaxy
could have naturally generated a handlelike bar that then thickened on its own.
Before then, scientists thought all stars in a GC were created at about the same time in protogalaxy
The so-called protogalaxy
resides about 11 billion light-years from Earth.
What's more, this protogalaxy
is seen when it was about 2 million years old in a 600-million-year-old universe, and it contains only first-generation stars composed of the light elements synthesized in the Big Bang.
This object appears to fit every definition of a protogalaxy
," he and his colleagues will report in the May Astronomical Journal.
There's no way yet to be sure that it's a genuine protogalaxy
fragment rather than a bright star-forming region in a larger galaxy that remains mostly invisible.
For Irwin, the finding clinches his belief that the cloud is not a budding galaxy or protogalaxy
but just an unusually large gas envelope surrounding a slowly evolving, already-formed galaxy known as an irregular dwarf.
1 is a protogalaxy
becauseit contains a large amount of ionized hydrogen and comparatively few stars.