Does the oid column have an implicit index on it?

This may sound like a stupid question, and i apologize if it is, but I
couldn't find the answer in any documentation.

Every table has a implicit column oid. Does this column have an index on it?
I assume not, and I am putting an index on it anyway.

The real problem is that I have a table like the following:

create table foo (
time timestamp DEFAULT CURRENT_TIMESTAMP,
...
)

I insert an row, and I want to get the timestamp of that row. So i do a
select on oid. I want an index. Does one already exist?

-rchit