Astronomers unveil a distant
protogalaxy connected to the cosmic web.
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.
We started with a mass of primordial gas in a spherical region representing a
protogalaxy or halo.
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 halos.
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.
Over the last 25 years astronomers have produced a number of papers with the catchy title "The Origin of the Hubble Sequence." Proposed determinants of a galaxy's Hubble type include the galaxy's total mass; the mass of its bulge; its angular momentum; the angular momentum of its dark-matter halo; the collapse rate of the protogalactic gas cloud that formed the galaxy; and the
protogalaxy's "cooling time."