Most sites should show up if you just enter their site name and tld. If they do not show up for that search or are outranked for it then the site is either very poorly optimized or penalized. So if it does not show up number 1 for that search then that would be a clear signal that it is not an authority site, but if it does show up it does not mean it is an authority site.
Google is on a quest to try and determine the quality of a site and how authoritative it is, and there are probably many different factors that go into determining that including: quality of links to site, number of citations for the site, quality and authority of writers on the site, etc.
So your question is a very good one, but I am afraid there is no simple process to determine what an authority site is. Of course some sites are easy to identify as authority such as cnn, bbc, nytimes, .gov sites, etc. All of these sites have in common lots of quality backlinks, lots of citations, highly recognized and esteemed journalists or editors, etc.
The best option is to install seomoz tool bar in mozilla or chrome. There is an option where it shows the domain authority and some other important options in the bottom. You can also check the backlinks of a specific page and their domain authority in www . opensiteexplorer . org.
I didn’t know this was so complicated. My question was about identifying a google authority site.
(upon searching the main url, the way google displays results…) Doesn’t the style of the "2 column linkset’ following the domain name and description identify a site as an authority site?