When I visit http://area51.stackexchange.com/proposals/51/astronomy it tells me:
The Astronomy site didn't have enough activity during the beta. It has been closed, and its content has been merged into Physics. You can download the data dump of all questions here.
and separately in the sidebar:
This site has been Closed
This proposal didn't have enough activity during the beta. It was closed 5 years ago.
but I'm pretty sure the site still exists.
Is this just a glitch, or am I misunderstanding the message?