Starship Asterisk*

by geckzilla » Sat Oct 30, 2010 2:36 pm

Ahhh this is a great Halloween themed APOD. I was hoping for something other than the witch head again and glad she got a much deserved break!

orin stepanek» Sat Oct 30, 2010 wrote:

geckzilla» Sat Oct 30, 2010 2:36 pm wrote:
Ahhh this is a great Halloween themed APOD.
I was hoping for something other than the witch head again and glad she got a much deserved break!

Aah; but Halloween is Sunday. We could get her (the Witch) yet.

neufer wrote: Surprisingly, the ubiquitous witch's head & witch's broom nebulae
have only shown up ONCE in a 'Halloween themed' APOD: in 2008.

The info about the staggered and reluctant acceptance of the current calendar was fascinating

robolt wrote:
How far apart are the molecules of the gases that form the image?
If we had a cubic foot of the stuff, are the individual gases in a concentration we could detect?

http://en.wikipedia.org/wiki/Bok_globule wrote:
<<Bok globules or Thackeray's Globules are dark clouds of dense dust and gas in which star formation sometimes takes place. Bok globules are found within H II regions, and typically have a mass of about 2 to 50 solar masses (i.e., up to 1×10³² kg) contained within a region about a light year or so across (about 4.5 × 10⁴⁷ m³). They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) of silicate dust.>>

http://en.wikipedia.org/wiki/Vacuum wrote:

• Vacuum __________________ Pressure (Torr)
  ------------------------------------------------------------
  Low vacuum _______________ 760 to 25
  Medium vacuum ____________ 25 to 1×10⁻³
  High vacuum _____________ 1×10⁻³ to 1×10⁻⁹
  Ultra high vacuum _________ 1×10⁻⁹ to 1×10⁻¹²
  Extremely high vacuum _______ <1×10⁻¹²
  Bok globules _____________ 6×10⁻¹⁶ to 15×10⁻¹⁵ (at room temperature)

------------------------------------------------------------------------------------------------------------------------
# Low vacuum, also called rough vacuum or coarse vacuum, is vacuum that can be achieved or measured with rudimentary equipment such as a vacuum cleaner and a liquid column manometer.

# Medium vacuum is vacuum that can be achieved with a single pump, but the pressure is too low to measure with a liquid or mechanical manometer. It can be measured with a McLeod gauge, thermal gauge or a capacitive gauge.

# High vacuum is vacuum where the MFP of residual gases is longer than the size of the chamber or of the object under test. High vacuum usually requires multi-stage pumping and ion gauge measurement. Some texts differentiate between high vacuum and very high vacuum.

# Ultra high vacuum requires baking the chamber to remove trace gases, and other special procedures. British and German standards define ultra high vacuum as pressures below 10⁻⁶ Pa (~10⁻⁸ Torr).

http://en.wikipedia.org/wiki/Wake_Shield_Facility wrote:

Deployment of the WSF using the Space Shuttle robotic arm. Night period STS-60 photo

---

<<Wake Shield Facility is an experimental science platform that was placed in low-earth orbit by the Space Shuttle. It is a 3.7 meter (12 ft) diameter, free-flying stainless steel disk. The WSF is deployed in the wake of the Space Shuttle at an orbital altitude of over 300 kilometers (186 mi), within the thermosphere, where the atmosphere is exceedingly tenuous. The forward edge of the WSF disk redirects atmospheric and other particles around the sides, leaving an "ultra-vacuum" in its wake. The resulting vacuum is used to study epitaxial film growth. Pre-flight calculations suggested that the pressure on the wake side could be decreased by some 6 orders of magnitude over the ambient (10⁻⁸ Torr) pressure in low earth orbit. Analysis of the pressure and temperature data gathered from the two flights concluded that the decrease was some 2 orders of magnitude or 4 orders of magnitude less than expected (i.e., from 10⁻¹⁰ to 10⁻¹² Torr).

Ann wrote: