What Exactly Is a Galaxy?

sciencehabit writes "Surprising as it may sound, astronomers don't have an answer to this basic question. There's no agreement on when a collection of stars stops being a cluster and starts being something more. Now, in an echo of the recent wrangling over Pluto's status as a planet, a pair of astrophysicists from Australia and Germany want to start a debate on the issue — and they have even set up a Web site for people to cast their votes." While we're on the subject of galaxies, reader mvar pointed out that astronomers using data from Hubble have spotted what could be a new record holder for the most distant known galaxy, located roughly 13.2 billion light years from Earth.

Distant Galaxy Now even Further

[spiedrazer]

The interesteing thing not mentioned about the Distant Galaxy in the article. eventhough it's position 13.2 billion years ago was that far away from our current position, it is currently probably more like 45 billion light years away!

Re:Standard for astronomy.

[Tynin]

...such as the difference between a tropical storm or a hurricane.

Sorry, but this isn't so.

Tropical Storm = Distinct rotary circulation, constant wind speed ranges 39-73 miles per hour (34-63 knots).

Hurricane = Pronounced rotary circulation, constant wind speed of 74 miles per hours (64 knots) or more.

I'm guessing you don't live in an area that regularly gets hit by these storms, as I really though this was common knowledge. Nothing arbitrary about it, unless we are using different definitions of arbitrary. Source: NOAA [noaa.gov].