Are world's astronomers united?

[aphh]

In a purely speculative scenario, a giant asteroid approaches earth on a collision course. An astronomer in one country detects it first.

Does he inform his country's government first or does he inform other astronomers of the world first?

 

[MeteorWayne]

It gets rep[orted to the Minor Planet Center first, which is the clearinghouse for all astronomical observations of moving objects.
http://www.cfa.harvard.edu/iau/mpc.html

 

[SpaceTas]

After the initial report there is a further protocol which includes checking information and calculations and then issuing an alert via UN/COSPAR (I think) if the probability of a strike is high enough.

there was a recent example where a small asteroid was detected tracked and predicted to strike the earth. The hit happened and the it was atmospheric entry was tracked and the meteorite recovered. All in the space of a few days. So the system works well.

 

[MeteorWayne]

That was 2008 TC3, and the time from discovery to impact was 19 hours. The information was distrubuted wide enough that 570 observations were made of the object during the 18 hours it was visible before it entered the earths shadow.