[X] My Assistant

[Palomar]

***Image***

Article: A "new look" for our Milky Way Galaxy

Based on data from Spitzer. Wow, if that IS what our Milky Way Galaxy looks like...! Majestic, exquisite...incredible.

They're fairly certain our Galaxy contains a central bar which is 27,000 l/y long (7,000 l/y longer than previously believed). The bar seems primarily populated by "old and red stars" (red giants).

It also shows that the bar is oriented at about a 45-degree angle relative to a line joining the sun and the center of the galaxy.

Article discusses the methods/processes involved in building up such a "portrait."

With the help of NASA's Spitzer Space Telescope, astronomers have conducted the most comprehensive structural analysis of our galaxy and have found tantalizing new evidence that the Milky Way is much different from your ordinary spiral galaxy.

Yep, I'm biased...but honestly, if that IS what our MWG looks like I must say it's the most beautiful yet "seen." All those incredibly long swirling arms around that huge central bar.

[Palomar]

*If you're going to this nebula any time soon...

...you'd best bundle up really good. It's the coldest-known region in the observed distant universe: Just 1 degree above Absolute Zero. Yipes.

The boomerang shaped cloud appears to have been created by a high-speed wind of gas and dust blowing from an aging central star at speeds of over 300,000 miles per hour.

A different source said 600,000 mph. ?? Anyway, the rapid expansion of gas/dust from that wind is what caused the cooling.

Is called the Boomerang Nebula, is 5000 l/y distant "in" the constellation Centaurus.

It's also believed to be progressing towards a planetary nebula phase.

Here's an HST photo. The photography was accomplished earlier this year but the photo itself was only released yesterday:

A lovely "bow-tie"

[ljk4-1]

Paper: astro-ph/0601005

Date: Sat, 31 Dec 2005 18:50:46 GMT (980kb)

Title: Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium

Authors: M. K. Ryan Joung (1 and 2), Mordecai-Mark Mac Low (2 and 1) ((1)
Columbia University, (2) AMNH)

Comments: 15 pages, 11 figures, submitted to ApJ
\\
To study how supernova feedback structures the turbulent interstellar medium,
we construct 3D models of vertically stratified gas stirred by discrete
supernova explosions, including vertical gravitational field and parametrized
heating and cooling. The models reproduce many observed characteristics of the
Galaxy such as global circulation of gas (i.e., galactic fountain) and the
existence of cold dense clouds in the galactic disk. Global quantities of the
model such as warm and hot gas filling factors in the midplane, mass fraction
of thermally unstable gas, and the averaged vertical density profile are
compared directly with existing observations, and shown to be broadly
consistent. We find that energy injection occurs over a broad range of scales.
There is no single effective driving scale, unlike the usual assumption for
idealized models of incompressible turbulence. However, >90% of the total
kinetic energy is contained in wavelengths shortward of 200 pc. The shape of
the kinetic energy spectrum differs substantially from that of the velocity
power spectrum, which implies that the velocity structure varies with the gas
density. Velocity structure functions demonstrate that the phenomenological
theory proposed by Boldyrev is applicable to the medium. We show that it can be
misleading to predict physical properties such as the stellar initial mass
function based on numerical simulations that do not include self-gravity of the
gas. Even if all the gas in turbulently Jeans unstable regions in our
simulation is assumed to collapse and form stars in local freefall times, the
resulting total collapse rate is significantly lower than the value consistent
with the input supernova rate.

Supernova-driven turbulence inhibits star formation globally rather than triggering it.

\\ ( http://arXiv.org/abs/astro-ph/0601005 , 980kb)

[ljk4-1]

New comet on the Southern Hemisphere

Grzegorz Pojmanski, Warsaw University Astronomical Observatory reports:

Using the ASAS3V instrument of The All Sky Automated Survey
(telephoto lens 180/2.8, diameter 65mm + CCD + Johnsons V filter,
3 minute exposures, pixel size 14.8 arcsec, rms astrometric accuracy:
4 arcsec) ASAS has discovered an apparently cometary
object on images taken on January, 1, 2006.

Object cannot be located in MPC/CBAT pages.

Observations:

DATE UT HJD RA (2000) DEC V

29/12/2005 00:45:17 (Dec 29.032) 2453733.5285 21:50:29 -69:40.6 13.20
01/01/2006 01:03:11 (Jan 01.044) 2453736.5407 21:40:28 -68:36.5 12.46
04/01/2006 00:46:26 (Jan 04.033) 2453739.5290 21:31:33 -67:31.2 12.00
04/01/2006 00:53:46 (Jan 04.038) 2453739.5341 21:31:33 -67:31.1 11.99
05/01/2006 00:52:27 (Jan 05.037) 2453740.5332 21:28:45 -67:08.8 11.92

FWHM of the coma is 63 arcsec;
Diameter of the ASAS-detected coma (largest contour) is 2 arcmin.

Images of the comet can be inspected on the WWW following the links:

http://www.astrouw.edu.pl/~gp/asas/asas.html -> Alert Service Page -> Comets

or directly on new comet's page:

http://www.astrouw.edu.pl/~gp/asas/asas_c2006.html

Regards, Grzegorz Pojmanski

[ljk4-1]

Astrophysics, abstract
astro-ph/0601168

From: Andrew R. Liddle [view email]

Date: Mon, 9 Jan 2006 09:38:44 GMT (369kb)

The Cosmological Parameters 2005

Authors: Ofer Lahav, Andrew R Liddle

Comments: 26 pages TeX file. Article for The Review of Particle Physics 2006 (aka the Particle Data Book), published version at this http URL . This article supersedes astro-ph/0406681

Report-no: SUSSEX-AST/06-1

Journal-ref: S. Eidelman et al., Phys. Lett. B 592, 1 (2004) and 2005 partial update for the 2006 edition available at the PDG WWW pages at http://pdg.lbl.gov/

This is a review article for The Review of Particle Physics 2006 (aka the Particle Data Book). It forms a compact review of knowledge of the cosmological parameters as at the end of 2005. Topics included are Parametrizing the Universe; Extensions to the standard model; Probes; Bringing observations together; Outlook for the future.

http://arxiv.org/abs/astro-ph/0601168

[ljk4-1]

Paper: astro-ph/0601420

Date: Thu, 19 Jan 2006 10:07:28 GMT (10kb)

Title: Motion toward the Great Attractor from an ether-drift experiment

Authors: M. Consoli, E. Costanzo, V. Palmisano

Comments: 12 pages, plain Latex
\\
Since the end of 80's, the region of sky of galactic coordinates (l\sim
309^o, b\sim 18^o), corresponding to a declination \gamma\sim -44^o and right
ascension \alpha\sim 202^o, usually denoted as the "Great Attractor", is known
to control the overall galaxy flow in our local Universe. In this sense, this
direction might represent a natural candidate to characterize a hypothetical
Earth's "absolute motion". Our analysis of the extensive ether-drift
observations recently reported by an experimental group in Berlin provides
values of \alpha and \gamma that coincide almost exactly with those of the
Great Attractor and not with the values \gamma\sim -6^o and \alpha\sim 168^o
obtained from a dipole fit to the anisotropy of the CMB. This supports in a new
fashion the existence of a discrepancy between the observed motion of the Local
Group and the direction obtained from the CMB dipole.

\\ ( http://arXiv.org/abs/astro-ph/0601420 , 10kb)

Astrophysics, abstract
astro-ph/0407329

From: Ulrich Kirchner [view email]

Date (v1): Fri, 16 Jul 2004 08:06:41 GMT (37kb)
Date (revised v2): Thu, 19 Jan 2006 18:53:06 GMT (42kb)

Multiverses and Cosmology: Philosophical Issues

Authors: W. R. Stoeger, G. F. R. Ellis, U. Kirchner

Comments: 37 pages

The idea of a multiverse -- an ensemble of universes or universe domains -- has received increasing attention in cosmology, both as the outcome of the originating process that generated our own universe, and as an explanation for why our universe appears to be fine-tuned for life and consciousness. Here we carefully consider how multiverses should be defined, stressing the distinction between the collection of all possible universes, and ensembles of really existing universes, which are essential for an anthropic argument. We show that such realised multiverses are by no means unique, and in general require the existence of a well-defined and physically motivated distribution function on the space of all possible universes. Furthermore, a proper measure on these spaces is also needed, so that probabilities can be calculated. We then discuss several other major physical and philosophical problems which arise in the context of ensembles of universes, including the emergence and causal effectiveness of self-consciousness, realized infinities, and fine- tuning, or the apparent need for very special initial conditions for our universe -- whether they or generalized generic primordial conditions are more fundamental. Then we briefly summarise scenarios like chaotic inflation, which suggest how ensembles of universe domains may be generated, and point out that the regularities which must underlie any systematic description of truly disjoint multiverses must imply some kind of common generating mechanism. Finally, we discuss the issue of testability, which underlies the question of whether multiverse proposals are really scientific propositions.

http://arxiv.org/abs/astro-ph/0407329

[ljk4-1]

Physics, abstract
physics/0512263

From: Javier Casahorran [view email]

Date: Thu, 29 Dec 2005 10:02:23 GMT (13kb)

The Uniqueness of the World

Authors: Luis J. Boya

Comments: To appear in Foundations of Physics. First Emilio Santos Festschrift Issue. March, 2006

Subj-class: Popular Physics; General Physics

We follow some (wild) speculations on trying to understand the uniqueness of our physical world, from the field concept to F-Theory.

http://arxiv.org/abs/physics/0512263

[ljk4-1]

Astrophysics, abstract
astro-ph/0601580

From: Warren R. Brown [view email]

Date: Wed, 25 Jan 2006 23:52:32 GMT (119kb)

A Successful Targeted Search for Hypervelocity Stars

Authors: Warren R. Brown, Margaret J. Geller, Scott J.Kenyon, Michael J. Kurtz (Smithsonian Astrophysical Observatory)

Comments: 5 pages, submitted to ApJ Letters

Hypervelocity stars (HVSs) travel with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Following our discovery of the first HVS, we have undertaken a dedicated survey for more HVSs in the Galactic halo and present here the resulting discovery of two new HVSs: SDSS J091301.0+305120 and SDSS J091759.5+672238, traveling with Galactic rest-frame velocities at least +558+-12 and +638+-12 km/s, respectively.

Assuming the HVSs are B8 main sequence stars, they are at distances ~75 and ~55 kpc, respectively, and have travel times from the Galactic Center consistent with their lifetimes. The existence of two B8 HVSs in our 1900 deg^2 survey, combined with the Yu & Tremaine HVS rate estimates, is consistent with HVSs drawn from a standard initial mass function but inconsistent with HVS drawn from a truncated mass function like the one in the top-heavy Arches cluster. The travel times of the five currently known HVSs provide no evidence for a burst of HVSs from a major in-fall event at the Galactic Center in the last \~160 Myr.

http://arxiv.org/abs/astro-ph/0601580


Harvard-Smithsonian Center for Astrophysics
Press Release

Release No.: 06-10

For Immediate Release: Thursday, January 26, 2006

Note to editors: Images to accompany this release are online at

http://www.cfa.harvard.edu/press/pr0610image.html

Two Exiled Stars Are Leaving Our Galaxy Forever

Cambridge, MA - TV reality show contestants aren't the only ones under threat of exile. Astronomers using the MMT Observatory in Arizona have discovered two stars exiled from the Milky Way galaxy. Those stars are racing out of the Galaxy at speeds of more than 1 million miles per hour - so fast that they will never return.

"These stars literally are castaways," said Smithsonian astronomer Warren Brown (Harvard-Smithsonian Center for Astrophysics). "They have been thrown out of their home galaxy and set adrift in an ocean of intergalactic space."

Brown and his colleagues spotted the first stellar exile in 2005. European groups identified two more, one of which may have originated in a neighboring galaxy known as the Large Magellanic Cloud. The latest discovery brings the total number of known exiles to five.

"These stars form a new class of astronomical objects - exiled stars leaving the Galaxy," said Brown.

Astronomers suspect that about 1,000 exile stars exist within the Galaxy. By comparison, the Milky Way contains about 100,000,000,000 (100 billion) stars, making the search for exiles much more difficult than finding the proverbial "needle in a haystack." The Smithsonian team improved their odds by preselecting stars with locations and characteristics typical of known exiles. They sifted through dozens of candidates spread over an area of sky almost 8000 times larger than the full moon to spot their quarry.

http://www.cfa.harvard.edu/press/pr0610.html

[ljk4-1]

Scientists May Soon Have Evidence for Exotic Predictions of String Theory

http://www.spaceref.com/news/viewpr.html?pid=18850

"Researchers at Northeastern University and the University of California, Irvine
say that scientists might soon have evidence for extra dimensions and other exotic predictions of string theory.

Early results from a neutrino detector at the South Pole, called AMANDA, show
that ghostlike particles from space could serve as probes to a world beyond our familiar three dimensions, the research team says."

[ljk4-1]

SURPRISE! MOST STARS ARE SINGLE

Astronomers have known since the 1700s that a significant fraction of
stars belong to binary or multiple systems. But what is that fraction?
Given the observed fact that most solar-size and larger stars reside in
binaries, many astronomers have concluded that more than half of our
galaxy's stars belong to multiple-star systems.

But a new study shows that the conventional wisdom is almost certainly
wrong. The problem is that astronomers have neglected to consider our
galaxy's most common stellar denizens: red dwarfs. These low-mass,
low-luminosity stars make up more than 80 percent of all the stars in the
Milky Way....

http://SkyandTelescope.com/news/article_1669_1.asp