(Ron Baalke) wrote in message ...
The Keck Interferometer observations revealed a gap of 18
million miles between DG Tau and its orbiting dust disc.

Whoops, just a few minutes ago I posted a query about the distance to
DG Tauri. Then I dug a little further, and mostly answered my own
question.

A PDF file containing a preprint of the DG Tau research paper is on
the Keck web site. Thanks to the folks at Keck for easy access to
this resource. I'll remember to look next time. The paper claims a
distance of 140 parsecs, and references some earlier studies. I have
to wonder what method was used to estimate the distance, given that DG
Tau is that far away and, being a T Tauri object, also quite dim.
Parallax doesn't look likely.

But, if we take that distance at face value, the folks at Keck
measured an 18-million mile object (the dust gap near the star) at a
distance of 140 parsecs. Holy smoke. I compute an angular resolution
of 1.4 milliarcseconds -- for a ground-based instrument. If we were
looking at our own Sun from ten light years away, its disk would
clearly be resolvable. Way to go!

--
John J. Ladasky Jr., Ph.D.
Department of Biology
Johns Hopkins University
Baltimore MD 21218
USA
Earth