[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

[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

Astrophysics, abstract
astro-ph/0601375

From: Charles J. Lada [view email]

Date: Tue, 17 Jan 2006 20:56:12 GMT (44kb)

Stellar Multiplicity and the IMF: Most Stars Are Single Born

Authors: Charles J. Lada

Comments: Submitted to Astrophysical Journal Letters, 5 pages, 2 figures.

Complete paper can be also obtained at this http URL:

http://www.cfa.harvard.edu/~clada/pubs_html/binaries.html

In this short communication I compare recent findings suggesting a low binary star fraction for late type stars with knowledge concerning the forms of the stellar initial and present day mass functions for masses down to the hydrogen burning limit. This comparison indicates that most stellar systems formed in the galaxy are likely single and not binary as has been often asserted. Indeed, in the current epoch two-thirds of all main sequence stellar systems in the Galactic disk are composed of single stars. Some implications of this realization for understanding the star and planet formation process are briefly mentioned.

http://arxiv.org/abs/astro-ph/0601375

[ljk4-1]

General Relativity and Quantum Cosmology, abstract
gr-qc/9306035

From: Andrei Linde [view email]

Date: Tue, 29 Jun 1993 05:15:07 GMT (609kb)

Date (revised): Wed, 1 Feb 2006 20:20:32 GMT
Date (revised): Wed, 1 Feb 2006 21:03:31 GMT

From the Big Bang Theory to the Theory of a Stationary Universe

Authors: Andrei Linde, Dmitri Linde, Arthur Mezhlumian

Comments: No changes to the file, but original figures are included. They substantially help to understand this paper, as well as eternal inflation in general, and what is now called the "multiverse" and the "string theory landscape." High quality figures can be found at this http URL

Journal-ref: Phys.Rev. D49 (1994) 1783-1826

We consider chaotic inflation in the theories with the effective potentials phi^n and e^{\alpha\phi}. In such theories inflationary domains containing sufficiently large and homogeneous scalar field \phi permanently produce new inflationary domains of a similar type. We show that under certain conditions this process of the self-reproduction of the Universe can be described by a stationary distribution of probability, which means that the fraction of the physical volume of the Universe in a state with given properties (with given values of fields, with a given density of matter, etc.) does not depend on time, both at the stage of inflation and after it. This represents a strong deviation of inflationary cosmology from the standard Big Bang paradigm. We compare our approach with other approaches to quantum cosmology, and illustrate some of the general conclusions mentioned above with the results of a computer simulation of stochastic processes in the inflationary Universe.

http://arxiv.org/abs/gr-qc/9306035

[ljk4-1]

Milky Way's fastest pulsar is on its way out of the galaxy, astronomers find

http://www.news.cornell.edu/stories/Feb06/....pulsar.lg.html

Feb. 6, 2006

By Dave Finley and Lauren Gold

lg34@cornell.edu

The Milky Way's fastest observed pulsar is speeding out of the galaxy at more than 670 miles a second, propelled largely by a kick it received at its birth 2.5 million years ago.

Using the Very Long Baseline Array (VLBA), 10 radio telescopes spanning 5,000 miles from Hawaii to the U.S. Virgin Islands, James Cordes, professor of astronomy at Cornell University, his former student Shami Chatterjee, now of the Harvard-Smithsonian Center for Astrophysics, and colleagues studied the pulsar (a fast-spinning neutron star) B1508+55, about 7,700 light years from Earth. With the ultra-sharp radio vision of the continentwide VLBA, they precisely measured both the distance and the speed of the pulsar.

The team then plotted the star's motion backward to a birthplace among groups of giant stars in the constellation Cygnus, which contains stars so massive they inevitably explode as supernovae.

Commenting on the research, which was published last fall in Astrophysical Journal Letters, Chatterjee said, "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding. This discovery is very difficult for the latest models to explain." Chatterjee is also a Jansky fellow at the National Radio Astronomy Observatory (NRAO).

The VLBA measurements show the pulsar moving at nearly 1,100 kilometers (more than 670 miles) per second. At this speed, it could travel from London to New York in five seconds.

[ljk4-1]

Astrophysics, abstract
astro-ph/0602101

From: John F. Beacom [view email]

Date: Sun, 5 Feb 2006 21:21:31 GMT (51kb)

The Cosmic Stellar Birth and Death Rates

Authors: John F. Beacom (Ohio State University)

Comments: Accepted for publication in New Astronomy Reviews (invited talk at "Astronomy with Radioactivities V", Clemson Univ., Sept. 2005). 9 pages, 5 figures

The cosmic stellar birth rate can be measured by standard astronomical techniques. It can also be probed via the cosmic stellar death rate, though until recently, this was much less precise. However, recent results based on measured supernova rates, and importantly, also on the attendant diffuse fluxes of neutrinos and gamma rays, have become competitive, and a concordant history of stellar birth and death is emerging. The neutrino flux from all past core-collapse supernovae, while faint, is realistically within reach of detection in Super-Kamiokande, and a useful limit has already been set. I will discuss predictions for this flux, the prospects for neutrino detection, the implications for understanding core-collapse supernovae, and a new limit on the contribution of type-Ia supernovae to the diffuse gamma-ray background.

http://arxiv.org/abs/astro-ph/0602101

[ljk4-1]

Astrophysics, abstract
astro-ph/0602117

From: T. Padmanabhan [view email]

Date: Mon, 6 Feb 2006 13:49:38 GMT (909kb)

Advanced Topics in Cosmology: A Pedagogical Introduction

Authors: T. Padmanabhan

Comments: 40 pages; 6 figures; RevTex4; Extended version of Lecture Courses given at several places including X Special Courses at Observatorio Nacional, Rio de Janeiro, Brazil during 26-30 Sept, 2005. To appear in the Proceedings

These lecture notes provide a concise, rapid and pedagogical introduction to several advanced topics in contemporary cosmology. The discussion of thermal history of the universe, linear perturbation theory, theory of CMBR temperature anisotropies and the inflationary generation of perturbation are presented in a manner accessible to someone who has done a first course in cosmology. The discussion of dark energy is more research oriented and reflects the personal bias of the author.

Contents: (I) The cosmological paradigm and Friedmann model (II) Thermal history of the universe (III) Structure formation and linear perturbation theories (IV) Perturbations in dark matter and radiation (V) Transfer function for matter perturbations (VI) Temperature anisotropies of CMBR (VII) Generation of initial perturbations from inflation (VIII) The dark energy.

http://arxiv.org/abs/astro-ph/0602117

[ljk4-1]

Astrophysics, abstract
astro-ph/0602122

From: Adam J. Burgasser [view email]

Date: Mon, 6 Feb 2006 15:58:28 GMT (155kb)

Not Alone: Tracing the Origins of Very Low Mass Stars and Brown Dwarfs Through Multiplicity Studies

Authors: Adam J. Burgasser (MIT), I. Neill Reid (STScI), Nick Siegler (UA Steward), Laird Close (UA Steward), Peter Allen (Penn State), Patrick Lowrance (SSC), John Gizis (U Delaware)

Comments: 16 pages, 7 figures, contributed chapter for Planets and Protostars V meeting (October 2005); full table of VLM binaries can be obtained at this http URL

The properties of multiple stellar systems have long provided important empirical constraints for star formation theories, enabling (along with several other lines of evidence) a concrete, qualitative picture of the birth and early evolution of normal stars. At very low masses (VLM; M <~ 0.1 M_sun), down to and below the hydrogen burning minimum mass, our understanding of formation processes is not as clear, with several competing theories now under consideration. One means of testing these theories is through the empirical characterization of VLM multiple systems. Here, we review the results of various VLM multiplicity studies to date. These systems can be generally characterized as closely separated (93% have projected separations Delta < 20 AU) and near equal-mass (77% have M_2/M_1 >= 0.8) occurring infrequently (perhaps 10-30%). Both the frequency and maximum separation of stellar and brown dwarf binaries steadily decrease for lower system masses, suggesting that VLM binary formation and/or evolution may be a mass-dependent process. There is evidence for a fairly rapid decline in the number of loosely-bound systems below ~0.3 M_sun, corresponding to a factor of 10-20 increase in the minimum binding energy of VLM binaries as compared to more massive stellar binaries. This wide-separation ``desert'' is present among both field (~1-5 Gyr) and older (> 100 Myr) cluster systems, while the youngest (<~10 Myr) VLM binaries, particularly those in nearby, low-density star forming regions, appear to have somewhat different systemic properties. We compare these empirical trends to predictions laid out by current formation theories, and outline future observational studies needed to probe the full parameter space of the lowest mass multiple systems.

http://arxiv.org/abs/astro-ph/0602122

[ljk4-1]

Supernova in Spiral Galaxy Messier 100

Discovered is shared by Shoji Suzuki (Japan) and M. Migliardi of CROSS (Italy). A type Ia supernova found 1-2 weeks before maximum light. M100 is one of our more prolific galaxies when it comes to supernovae. This will be the fifth one observed in the 100+ years we have been looking. The last one was 1979C. We have a DSS Photometry reference image made by Odd Trondal. Icon generated from the CROSS color image. This supernova is in the Constellation Coma Berenices.

http://www.rochesterastronomy.org/sn2006/sn2006X.html

[ljk4-1]

SUCKED IN! OUR GALAXY EATS NEIGHBOUR (Space & Astronomy News, 14/2/06)

Astronomers have released new evidence to show that a region of stars in our
galaxy known as the Arcturus stream is the digested remains of what was once
a neighbouring galaxy.

http://www.abc.net.au/science/news/space/S...ish_1568599.htm

[ljk4-1]

STELLAR CHEMISTRY

- Rogue Pulsar Speeding Out Of The Galaxy

http://www.spacedaily.com/reports/Rogue_Pu...The_Galaxy.html

Charlottesville VA (SPX) Feb 15, 2006 - Astronomers have precisely calculated
the speed of the Milky Way's fastest observed pulsar: It is heading out of the
galaxy at more than 670 miles a second, propelled by an explosive kick it
received at birth some 2.5 million years ago.

- VLT Unveils Metal-Rich Distant Galaxy
http://www.spacedaily.com/reports/VLT_Unve...ant_Galaxy.html

- Astronomers Discover 'RRATS' In The Cosmos
http://www.spacedaily.com/reports/Astronom...The_Cosmos.html

- Galactic Center Found To Glow Unevenly
http://www.spacedaily.com/reports/Galactic...w_Unevenly.html