A mutual acquaintance pointed me to this discussion. I see Dean (Hines) has already commented – but just to clarify a few points…

1. “Some of the most fun I had was working on protoplanetary disks”…”I worked with Glenn in particular on several very cool protoplanetary disks”. Indeed it was (fun) an they are “cool” (but not thermally, of course), but for clarity the circumstellar dust structure around HD 61005 is unequivocally NOT a protplanetary disk. It is a debris disk — interacting with the local interstellar medium. The distinction (between protoplanetary and [evolved] debris disks is very important, as the material around HD 61005 is not like interstellar grains or those around gas-rich (young) T Tauri stars, but result from collisions of planetesimals in orbit around the star.

2. “the part labeled ‘coronographic hole’ is where a small piece of metal block out the light from the star”. Well, no. STIS (the Space Telescope Imaging Spectrograph; Phil’s favorite HST instrument) does (or did, since it is now in slumber) use a “small piece of metal” (a “occulting wedge”) in a re-imaged focal plane to suppress central starlight. The “Moth” images we took are with HST’s NICMOS (the Near Infrared Camera and Multi-Object Spectrometer) coronagraph (a true Lyot coronagraph also with a pupil plane mask to control diffracted light), and literally has a hole in a first image plane mirror where the central starlight passes through and is not reflected “downstream”. That NICMOS internal mirror is at the f/24 focus of HST’s secondary mirror. And the central starlight falls into it so it is not scattered downstream before coronagraphic suppression of diffractive light in the pupil. Bottom line, it is a hole, not a piece of metal (FYI – physically the hole in the mirror is 165 microns in diameter). Oh, and coronagraph is with an “A” as in “corona”, both an “o”.

As Jeffersonian asks… projected onto the sky, the “hole” (region onbscured) is 0.3 arcseconds in radius. At the distance of HD 61005 that is about 10 Astronomical units – so we do not actually see the inner 10 AU of the dust structure. That is the size of the black region at the “head” of the moth. Procyan asks about the “discrete black blobules” — those are just noise in the image – don’t read anything astrophysical into that (again discussed in the context of residual image artifacts in our paper).
Cheers,

Glenn Schneider
NICMOS Project Instrument Scientist
Astronomer, Steward Observatory University oif arizona
http://nicmosis.as.arizona.edu:8000

Working with Glen, did he subject you to his bad puns? I remember being in a van with him after driving from Baltimore to Florida to see the shuttle launch for the first Hubble servicing mission in Dec. 1993. He came up with some real groaners.

Cool image!

To answer the comment Barton made about Rob, it’s just the way that Wordpress (BA’s blog software) works. When someone links to an article in their own blog, those comments are auto-generated and posted. They are called “trackbacks.” When it comes to bandwidth, the bytes the generate is probably less than a few square centimeters of the
photos of “anatomy and physiology lessons” that proliferate on the ‘Net like so many weeds.

Is it visible with binoculaers or unaided eyesight & where?

Anyone know?

Minor~est of nitpicks but isn’t Neptune’s orbit much more circular and less elliptical than shown with the image?