August
2, 2006 meeting minutes:
-----------------------
7:02
PM Steve Layman introduced Rémy Indebetouw.
Why
would one want to study star formation? Images like the Tarantula is enough, I
just want to know what's going on. There's a mass of stars forming there, but
you might want a bigger picture than that.
Gravity
and Fusion energy from stars are chiefly responsible for galactic evolution. We
have a good handle on gravity, but Fusion energy is another thing. This is the
energy input from stars. If you want to know how the universe evolved, you gotta study this.
Radiation
pressure is part of the clearing out of a gas cloud, depending on star mass. An
accretion disk forms as material in the cloud falls into the star.
There
are 3 classes of star formation:
Class
0 = infant - deeply imbedded in cloud, infalling gas,
polar jets form, 10 to 4th years here.
Class
1 = child - accretion disk builds and infall
continues, polar jets build. 10 to the 5th power years here.
Class
2 = adolescent phase - accretion disk continues infall
is over. 10 to the 6th years spent here. You have to mask out the star to see
the remnant disk.
The
catalyst for cloud collapse is gravity, but internal turbulence makes this
tricky, slows it down (we think).
We
don't really know at this time what the initial conditions are. There are a
number of outstanding questions in star formation.
The
infrared wavelengths are where you look to study star formation. In these
frequencies you can easily tell class 0 from 1 and 2.
Infrared
lets you see heat, the constellation Orion is a dramatic demonstration of the
difference you see when you shift into the IR.
The
Spitzer telescope is the premier instrument for IR imaging today.
Spitzer
has a number of isntruments:
IRAC
= short, 3.5, 4.5, 6 & 8 uM
MIPS
= midrange, 24 micron
IRS =
3-35 uM spectrograph
Galactic
Legacy IR MidPlane Survey Extraordinaire (GLIMPSE) is
what I was working on starting in 2001.
Radiative
transfer models of protostars are needed. By modeling
the stars we can get an idea what is happening. Comparing the models to the
data is where you find out if you're on the right track.
The
debate today is the initial conditions of a gas cloud, because an incredibly
tiny modification to these conditions makes a huge change to the outcome.
Lively discussions have enlivened astronomical meetings to say the least!
Triggered
star formation is when a Supernova compresses a cloud of gas and makes star
formation start up. The "Pillars of Creation" in the Eagle Nebula is
a classic example of this kind of formation. Once the collapse begins, then
local gravity takes over. The supernova gets things going, but then gravity
does its trick at the standard speed, it's not particularly faster than
non-triggered formation.
The
IR measurements of the embedded sources in the Eagle lend themselves to IR
studies which have determined their masses & luminosities, for instance.
Infrared
Dark Clouds (IRDCs) are so dense that even in the IR
you can't see into them, so you have NRAO's ALMA
array coming on line soon to probe these frequencies to enable study of these
objects.
The
question here is: Are they really making stars? and
the answer is "Yes!" There is much to be learned about the chemistry
and physical conditions in the clouds.
ALMA
will have up to 64 dishes in the Atacama desert of Chile, and will be the premier instrument for
studies in these long wavelengths. Buildings have been built and the dishes
will start soon to arrive.
Spitzer
has another year or 2 or cryogen life to go before it dies. Then will come a
period of study of the data.
At
7:54 PM Steve took the floor.
New
members, Leo Lombardi, Ted & Jean Treiber &
Chester
58
members
$ 1,345.74 in the treasury.
August
observing is the Bear Mtn retreat. Aug 25-27
Group night Aug 11th. We're covering the Public night this Friday.
Sept
- show & tell from members
Nov -
John Turchi - Dob
conversion project
I
have contacted (for Dec meeting)
- Alwyn Wooten - ALMA project scientist
-
Adrienne Juett - Grad student
-
Ricardo Schiavon - Grad student
Any club
members with ideas, please contact Steve Layman.
Brunch
at Bear Mtn will be $12 and will be delicious.
Group
potluck for dinner!
The
10 minute topic would have been the VAAS website, but the internet isn't
working... But it'll be a good thing for us to do en masse!
The
door prize tonight is a moon observer's guide. Heidi Winter drew Snowdon Hall was the winner. Mike Gorman has the scope
fired up and we observe after the meeting!
See
you all at Bear Mtn!
8:10
PM and the meeting closed.