[Phsstpok]

frequency of Hydrogen and a frequency shift? 1000 light years from the nearest star? Sounds like an interstellar craft, probably a Bussard Ramjet. You need to know the direction and duration of the frequency shift to know whether it's going away, passing at an angle or coming down our throats.

It could also be the deflector dish on a warp rider ship.

Most likely it's a hydrogen jet from an unseen black hole, but I like the other two prospects more (unless they're coming to seek revenge for us having broadcast My Mother The Car 35 years ago). You gotta think outside the box.

[grey_whiskers]

You wrote:

"unless they're coming to seek revenge for us having broadcast My Mother The Car 35 years ago). "

Humor columnist Dave Barry also considered something like this in a column long ago--he suggested, though, that
Carl Sagan's plaque would label us as galactic/intergalactic perverts ('the man on the plaque is clearly deranged. He's waving his hand as if to say "HA!
I'm as naked as a jaybird."')

He suggests the aliens LIKE our TV re-runs. :-)

[Physicist]

Sounds like an interstellar craft, probably a Bussard Ramjet.

The Pak fleet, headed here?