Ultra-Dense Galaxies In the Early Universe

Science Daily is reporting on the characterization of a population of ancient galaxies, formed less than 3 billion years after the Big Bang, that are as massive as some modern galaxies but are only 1/20 the size. Each of the 9 compact galaxies found is less than 5,000 light-years across, and could fit comfortably inside the Milky Way's central hub (if you moved the supermassive black hole out first). The stars in these galaxies were 1/2 to 1 billion years old when observed and at least one generation of massive stars had already exploded as supernovae.

Comments

A science fiction reference

[Anonymous Coward]

Poul Anderson's Tau Zero makes the suggestion that interstellar contacts between races are more likely in the beginning of the universe than towards the end, simply because all matter will spread so far apart and there won't be enough fuel to move around.

Gene Wolfe's Book of the New Sun also conjectures a future where galaxies move so far apart that the steersmen of ships cannot locate their destinations by sight and must rely on old charts.

Just out of curiosity - how far away are they?

[mmell]

Or - to put it more bluntly - how long ago did they look like that?

If they're over thirteen million light-years distant, they might represent a tantalizing glimpse into the physics of galaxy formation shortly after the Big Bang - the presence of heavier-than-helium elements indicates that at least one round of (superheavy) star formation/destruction has taken place, but they could still be relatively good examples of galactic physics in the (then neonatal) Universe.

Probably won't matter much

[Moraelin]

The thing is, the rate of new star formation is decreasing over time.

While technically there still is plenty of hydrogen left, the quantity of _free_ hydrogen (available for a new star) is becoming gradually more rare. More and more is locked inside old dead stars. Even a supernova doesn't eject all the matter in the star. A red giant only sheds the outer layer, or to put it other wise, does about as much to recycle the star as shedding does to recycle your dog ;)

So basically if we're talking 100 billion years in the future -- which was the last number I heard for a universe where nothing is visible outside the galaxy -- there may be a rather extreme shortage of stars like the sun, and of civilizations trying to make contact with each other.

Imprecision Annoys

[SWestrup]

Am I the only one annoyed by such an imprecise expression as "1/20th the size". One doesn't know from reading it if this is 1/20th the linear dimensions, or 1/20th the volume. (Turns out its the former, which makes it 1/8000th the volume, which is far more interesting.)