PDA

View Full Version : Discussion: New Map of Debris Around the ...



Fraser
2003-Sep-24, 04:28 PM
SUMMARY: A new survey of the stars surrounding the Milky Way has produced a detailed map of how streams of stars and debris are being added to our galaxy. Researchers from the University of Virginia used data from the 2MASS sky survey to map out the Sagittarius galaxy which wraps around the Milky Way in a long stream of stars. They were able to distinguish between galaxies because a certain class of stars, called M giants, are much more common in Sagittarius - when they tuned their search to just look for these stars, Sagittarius "popped into view".


Comments or questions about this story? Feel free to share your thoughts.

SCHNECK
2003-Sep-27, 10:20 AM
B)

Tammann has obtained the Coma Velocity of 7157 +-73 km/s relative to the cosmic microwave backgroung and 1179 +- 17km/s for the Virgo cluster velocity relative to the microwave background.(The Extragalactic Distance Scale by Sidney van den Bergh )


NATIONAL RESEARCH COUNCIL
Vol. 2, Part 3, May, 1921, Number 11, pp 171-217.

***THE SCALE OF THE UNIVERSE
PART I: BY HARLOW SHAPLEY
Mount Wilson Observatory, Carnegie Institution of Washington
PART II: BY HEBER D. CURTIS
Director, Allegheny Observatory

CONTENTS Part I
Evolution of the idea of galactic size
Surveying the solar neighborhood
On the distances of globular clusters
The dimensions and arrangement of the galactic system

Part II
Dimensions and structure of the galaxy
Evidence furnished by the magnitude of stars
The spirals as external galaxies





***The Scale of the Universe
Great Debate in 1996

In April 1920, Harlow Shapley and Heber D. Curtis first debated The Scale of the Universe in the main auditorium of Smithsonian's Natural History Museum in Washington, DC. In April 1996, Sidney van den Bergh and Gustav A. Tammann again debated "The Scale of the Universe" in the same auditorium. The 1996 debate centered on the recent controversies surrounding the determinations of Hubble's constant - the expansion rate of the Universe. This single number, named for astronomer Edwin Hubble, parametrizes the size and age of our Universe. Interpreting recent observational results from space borne and ground based telescopes, two large camps emerged backing different values of Hubble's constant. At the 1996 Scale of the Universe debate, champions for each camp outlined their arguments.

Debate Proceedings: Six published papers from the 1996 debate which appeared in the 1996 December Publications of the Astronomical Society of the Pacific. Included are the two introductory talks, an opening by the organizers, and a closing by the moderator.
The Scale of the Universe Debate in 1996 by Bonnell, Nemiroff & Goldstein
The Scale of the Universe: A Curtain-Raiser in Four Acts and Four Morals by Owen Gingerich
H_0: The Incredible Shrinking Constant, 1925-1975 by Virginia Trimble
The Hubble Constant: A Discourse by Gustav A. Tammann
The Extragalactic Distance Scale by Sidney van den Bergh
Is H_0 Well Defined? by John N. Bahcall


About the 1996 Debate: Background information about the 1996 is given below.
The Program distributed at the 1996 Scale of the Universe Debate. The program includes an introduction, the schedule of events, and a brief profile of all the program participants.
Images from the debate.
Comments about the debate. Comments from people who attended.

Historical Background: In addition to Trimble's and Gingerich's historical introductions listed above, below find papers published involving Edwin Hubble and his role in the determination of the constant that bears his name:
A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae published in 1929 by Edwin Hubble
The Large Radial Velocity of N.G.C. 7619 by M. L. Humason
Edwin Hubble 1889-1953 an obituary by Allan Sandage
Edwin Powell Hubble, Biographical Memoirs by N. U. Mayall


Scientific Background: Below find links and lists intended for students, educators, and the generally inquisitive.
Edwin Hubble Discovers the Universe an Astronomy Picture of the Day about Edwin Hubble
M100 and the Expanding Universe an APOD about the modern quest to determine Hubble's constant. Follow the links to find out more.
Hubble at the 100-inch Hooker Telescope from Mount Wilson Observatories On-Line Archives


Return to Great Debates in Astronomy Page

Guest_SCHNECK
2003-Sep-27, 10:45 AM
IUGG 2003 Leadings Atmosphere Evolution

The synchronous rotation of the Moon around the Earth is caused by an unsymetrical
distribution of mass in the Moon.Interaction on the Moon slows the Earth
rotation about two milliseconds per century.The dust oscuration,the plasma that
filled the early universe during its first years was opaque to electromagnetic
radiations.The solar system rotates every two hundred forty million years in the
Milky Way at hundreds kilometers per second relative to the
Microwave Background Radiation.Actually,atomic clocks on board GPS satellites
are stable within one second in thirty two thousands kilometers at speed of ligth
as the effect of the Earth'spassage on plasma or a postulate aether(beginning of the century).
Since the Cretaceous-Tertiary boundary sixty five million years ago,the error on the position of
the Earth in space around the sun is more than one earth diameter.Oceans,atmospheres
and continents where in place by 4.3 billion years on Earth.
The study of the evolution of the partial pressure
of atmospheric oxygen over phanerozoic time supports the hypothesis of high
atmospheric content during the Carboniferous.The fluctuations in primary fluid
inclusions in marine halites are in phase with oscillations in sea floor
spreading rates,volcanism and global sea level.Laser cooled clock Parcs are going to be
installed on the ISS,where gravity is weaker than at Earth's surface,in late 2005
and would keep time within one second every 300 million years,apparently nearer
to the accretion time of matter.Earth athmosphere and Milky Way speed seem more at the new clocks atomic times.GPS are
operational since fifty years in a pre-evolving Milky Way.

Ref:Penzias and Wilson.On the Electrodynamics of moving bodies.J.Van
Oman and T.L.Grove.T.Hiroi.USGS.NASA.