FLASHBACK: One
year ago today, on Oct. 24, 2007, Comet 17P/Holmes shocked astronomers
when it suddenly exploded, brightening a million-fold to naked-eye
visibility. Within three days of the blast, the comet was bigger
than Jupiter, and within three weeks it was larger than the sun
itself. Spanish photographers Vicent Peris and José Luis Lamadrid
recorded this view on Nov. 1, 2007, using little more than a 7-inch
telescope:

What happened to Comet Holmes? Just-released observations by NASA's Spitzer Space Telescope define the mass and velocity of
the explosion: "The energy of the blast was about 10¹⁴ joules and the total mass was of order 10¹⁰ kg,"
says Bill Reach of Caltech. In other words, Holmes exploded like
24 kilotons of TNT and ejected 10 million metric tons of dust and
gas into space. These numbers fit a model favored by Reach in which
a cavern of ice some hundred meters beneath the comet's crust changed
phase, from amorphous to crystalline, releasing in transition enough
heat to cause Holmes to blow its top.
Holmes has exploded twice in recorded history--in 1892 and 2007.
Two caverns down, how many to go? No one knows. Browse the gallery
for a preview of what the next blast might look like:
www.spaceweather.com
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Amazing Comet Holmes  

Astronomy Picture of the Day NASA
https://antwrp.gsfc.nasa.gov/apod/astropix.html
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Hoag’s Object glares balefully 
			across the light-years. Credit: Hubble Heritage

Oct 24, 2008
Is Hoag’s Object a Dense Plasma Focus?

What force swept away the stars and formed this 120,000
light-year-wide ring in space? This could be one of electrical
energy’s protean forms.

Thunderbolts Picture of the Day
https://thunderbolts.info/tpod/00current.htm

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Where Have All the Gamma Ray Bursts Gone?

Astronomers are confused.
As if gamma-ray bursts (GRBs) weren't mysterious enough, there's
something else to add to the bag of confusion. GRB events are missing
from the furthermost reaches of the Universe. Right around the time
when there should be a lot of GRBs, during the "star forming epoch"
(when stars were just beginning to evolve after the Big Bang), there
appears to be none. Zero. There's no ancient flashes of
massive star death to be found. What's more, there doesn't appear to be
any afterglow from previous gamma-ray bursts either.
So what's going on? Were there no GRB events before 12.8 billion
years ago? Possibly… although there might be another answer. They are out there but we just can't see them
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Life Will be Hard for Colonists - Kaguya Can't Find Water on the Moon

It's been a long-held belief that the Moon is hiding significant quantities of water ice, safe from the Sun's
ablative effects inside shady craters. One such crater is called
Shackleton at the lunar South Pole and previous Moon missions have
indicated it might hold a large reservoir of ice for all the water
needs of future Moon colonists. Alas, the Japanese lunar mission Kaguya (or the Selenological and Engineering Explorer - "SELENE") has taken a
peek into the crater to find… nothing. At least, it hasn't spotted any
significant quantities of surface ice. So where does this leave future
lunar colonies?
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Asteroseismology: Observing Stars Vibrate with CoRoT

Observing
a stars brightness pulsate may reveal its internal structure say
researchers using the Convection Rotation and Planetary Transits
(CoRoT) observatory. The highly sensitive orbital telescope can detect tiny variations in a distant star's brightness, leading
astronomers into a new field of stellar seismology called
"asteroseismology." Seismology is more commonly used by scientists on Earth to see how waves travel through the terrestrial crust, thereby
revealing the structure of the material below us. Even solar physicists
use the method of helioseismology to understand the interior
of our Sun by observing its wobble. Now, by observing the slight
changes in stellar brightness, it is possible to remotely probe deep
into the inner workings of a distant star…
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Dark Knight Ahead - B33 by Gordon Haynes

If you live in the northern hemisphere, I'm sure you've very much
noticed the daylight hours have become much shorter - but have you
noticed the return of the winter stars during the early morning hours?
If you're up before dawn the constellation of Orion sits high in the sky and with it brings promises of "Dark Knight Ahead"
In this beautiful h-alpha image of B33 and NGC2024 taken by Gordon Haynes,
we're getting a preview of one of the most sought after dark nebulae in
the heavens - the "Horsehead". The long tongue of nebulosity which
makes it visible is IC 434, first discovered photographically by Edward
Pickering in 1889. But it wasn't until January 25, 1900 that Isaac
Roberts picked up the dark notch on a photo he'd made and E.E. Barnard
visually recognized it around 1910.
The ever-vigilant, and visually astute Barnard made his first publication of the "dark knight" in Dark Regions in the Sky Suggesting an Obscuration of Light - Astrophysical Journal, Vol. 38, pages 496-501. In 1919, he officially cataloged it as B33 in On the Dark Markings of the Sky - with a Catalogue of 181 Such Objects where it remains to this day as an astronomical favorite. What makes
this 1,600 light year distant dark globule of dust and non-luminous gas
so important? Well, a recent study done using the h-alpha wavelength
and the 2.34 m Vainu Bappu Telescope were done to test fractal structure. Ten sample readings of the box
dimension of this image were taken using a fractal analysis software,
giving an average value of 1.6965725. The sample dimensions were found
to be different from the topological dimension of one. Importantly, the
box dimension of B 33 was not found to be significantly different from
that of the Julia set (box dimension 1.679594) with c = -0.745429 +
0.113008i. This provides compelling evidence to show that the structure
of the Horsehead nebula is not only fractal, but also that its geometry
can be described by the Julia function f(z) = z2 + c, where both z and
c are complex numbers.
While that's cool, I wanted to go even deeper. I checked into SCUBA
and this is what I found from the works of D. Ward-Thompson (et al):
"We present observations taken with SCUBA on the JCMT of the
Horsehead Nebula in Orion (B33), at wavelengths of 450 and 850 \mum. We
see bright emission from that part of the cloud associated with the
photon-dominated region (PDR) at the `top' of the horse's head, which
we label B33-SMM1. We characterise the physical parameters of the
extended dust responsible for this emission, and find that B33-SMM1
contains a more dense core than was previously suspected. We compare
the SCUBA data with data from the Infrared Space Observatory (ISO) and
find that the emission at 6.75-\mum is offset towards the west,
indicating that the mid-infrared emission is tracing the PDR while the
submillimetre emission comes from the molecular cloud core behind the
PDR. We calculate the virial balance of this core and find that it is
not gravitationally bound but is being confined by the external
pressure from the HII region IC434, and that it will either be
destroyed by the ionising radiation, or else may undergo triggered star
formation. Furthermore we find evidence for a lozenge-shaped clump in
the `throat' of the horse, which is not seen in emission at shorter
wavelengths. We label this source B33-SMM2 and find that it is brighter
at submillimetre wavelengths than B33-SMM1. SMM2 is seen in absorption
in the 6.75-\mum ISO data, from which we obtain an independent estimate
of the column density in excellent agreement with that calculated from
the submillimetre emission. We calculate the stability of this core
against collapse and find that it is in approximate gravitational
virial equilibrium. This is consistent with it being a pre-existing
core in B33, possibly pre-stellar in nature, but that it may also
eventually undergo collapse under the effects of the HII region."
So it's a chance thing… It just happens to look like a cosmic chess
piece. But this is one chess piece that has the odds stacked in its
favor for starbirth. This shapely cloud of H2 molecules may have a
density within its internal clumps that could reach up to 105 H2 per
cubic centimeters or more and have their own internal magnetic field
which will provides support against their own gravity. Deep inside, the
dust blocks out the stellar ultraviolet radiation, getting darker and
colder - just like our northern hemisphere nights. Near the center, the
carbon changes and the chemistry becomes exotic - stars begin to form
in a process very similar to condensation. The pressure appears to be
building inside B33…
And tomorrow's "Dark Knight" will be lit by new stars.
Many thanks to AORAIA member Gordon Haynes for the fine photograph!
https://www.universetoday.com/2008/10/23/dark-knight-ahead-b33-by-gordon-haynes/#more-19958