Wednesday, August 20, 2014

Leo Galaxy Cluster aka Abell 1367: Part 3 quasars and cosomology

Caught a number of background quasars in the field of Abell 1367.

quasars (quasi-stellar radio sources)
look like faint blue stars
but they have *very* high red-shifts
which made them somewhat of a mystery

turns out they are actually extremely distant galaxies
with black holes that are actively feeding on matter
generating massive amounts of light.
though light cannot escape the black holes,
energy is generated just outside the event horizon
by massive gravitational stresses and friction acting on the incoming material.

the most distant quasar in the image
(blue dot just below the S in QSO lower left)
has a red shift (Z) of 3.36: 

recall that the redshift of the galaxy cluster 330 million light years distant was 2.3% or .023
the QSO's red shift is 3.36 or 336%!

so how far away is it?
well here's where things get *relatively* slippery
the universe is expanding
it's taken light a really long time to reach us from this object
do we want to know how far away it is now or how far away it was when the light left the galaxy?
when it left the galaxy, our planet, solar system and sun didn't exist.
now, due to the expansion of the universe, the galaxy is moving away from us faster than the speed of light
it's current distance can never be observed

dirty cosmology trick:
nothing can move through space faster than the speed of light
but the universe itself can expand faster than the speed of light
(my head hurts)

the commonly used figure is
light travel time
which is neither where it is now, nor where it was when it emitted the light
but a measure of how long it took the photons to reach us

it gets even worse:
redshift versus distance is not linear for large distances
so in order to calculate the distance
theoretical models with various parameters including the shape of the universe!
have to be used
best estimates for the parameters change over time

...so by one of the more commonly used estimates*, this one is
11.8 billion light years away
the big bang happened 13.7 billion years ago
the universe was a lot smaller place when light left this object

here's another small crop from the center of the image
including the Ha emitting galaxy from last time
with 3 quasars (distance in billions of light years):



interesting cosmological explanations (laymen's terms):

life the universe and everything
(be sure to mouse over the answer)

Ned Wright's FAQ on cosmology and the big bang

*Ned Wright's Cosmology Calculator

Saturday, August 16, 2014

Leo Galaxy Cluster aka Abell 1367: Part 2 Red Shift

when distances get very large, astronomers measure the "red shift" of light to determine distances:
more distant objects are moving away more rapidly due to the expansion of the universe
and therefore the light from these objects is shifted further to longer wavelengths (more red) by the Doppler effect*

this was part of Hubble's big thing,
took two very cool discoveries:
1 certain fuzzy patches had shockingly large redshifts suggesting they are "island universes" (galaxies) much further away than we had imagined.
2 a special type of variable star has a period proportional to it's absolute brightness, which means they can be used to measure distances with reasonable accuracy by comparing the measured brightness to the absolute brightness.

Hubble combined these discoveries, plotting distance to galaxies versus red shift
 and found more distant galaxies were moving away more rapidly
 proving the expansion of the universe

Abell 1367 has a redshift of 2.2%
this means that hydrogen alpha emissions at 656 nm will be shifted to 700 nm
completely out of the range of my narrow band Ha filter (5 nm centered at 656)
fortunately, i have an SII filter centered at 672 nm with a 12nm band width
allowing me to catch redshifted hydrogen emissions with a filter designed for sulfur
which is a cool trick, part of why i picked the cluster

though subtle, i caught one galaxy that definitely shows enhanced Ha emissions:

The upper right tail of this edge-on spiral galaxy (UGC 6697) is clearly blue (due to active young star formation) in standard images
but has a red patch in the middle of the blue with the SII (Ha) enhanced images
and possibly a more subtle red area around the bright core
due to hydrogen emissions in a large nebula (often found in star forming regions)
or active galactic nucleus = black hole feasting on stars emitting high energy photons as it rips apart matter

there were two much more subtle regions
the upper arm of the small spiral galaxy NGC 3861b:




and the red smile in this faint irregular galaxy KUG 1140+202A:
:-)



*technically not the Doppler effect in this context

Wednesday, August 13, 2014

Leo Galaxy Cluster aka Abell 1367: Part 1 Deep Sky

factoid: Abell 1367 has more galaxies brighter than mag 14 than any other galaxy cluster

the term "deep sky objects" is used by amateur astronomers to denote
objects other than solar system objects and individual stars.
as some may have notice, all of my images since moving have involved objects in our solar system,
most sol itself.  the most distant object being saturn at approximately 8 million miles or 11 a.u. or 1 light hour

at 330 million light years, Abell 1367 goes to the other extreme.
to put things in perspective, the closest star is 4 light years away
the pleiades are 375 light years (ly) away
orion nebula 1500 ly
crab nebula 6000 ly
the black hole at the center of the milky way 27,000 ly
the andromeda galaxy 2 million ly
M51, the whirl pool galaxy 15 million ly
the virgo galaxy cluster 50 million ly

link to full size


most of the dots in this field are not stars, but galaxies each containing billions of stars.
here's an annotated version with galaxies circled
the large circle outlines the galaxy cluster itself which is a bit bigger than my field of view
objects circled with an arrow pointing away are high proper motion stars
more about QSO's later

link to full size annotated


details:
FS102 OLV @ 618.8 mm, 2.15”/px, IDAS LPR filter/astronomiks 12nm SII filter, SX H9/H9C camera
Luminance 120x5 min, RGB 25x20 min, SII 24x20 min
4/24-5/5/2014 Newport Beach, CA

needless to say it took a lot of work to pull the galaxies out of the light pollution in the image