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News and Articles on PASS Vol. 9:
How Big Is The Universe
Online Articles
- 1 November 2007. Diverse
Galaxies Lithograph.
Image from the Hubble Space
Telescope shows the diversity of galaxies
in the universe. In addition to many elliptical
and spiral galaxies, the image contains a
few small irregular galaxies, and red, yellow,
and blue foreground stars. An inquiry-based
classroom activity accompanies the lithograph
- both can be downloaded as PDF files from
the Website.
- 11 March 2007. Out
There, By RICHARD PANEK,
NY Times. Research by Saul Perlmutter, George
Smoot (2006 Nobel Prize in Physics), and other
groups over the last few years have started
to destroy the general belief by astronomers
that a simple model of the universe could explain
most of the phenomena observed by astronomers.
According to the latest observations, 96% of
the mass of the universe is missing.
- 18 April 2006. Update
from Wilkinson Microwave Anisotropy Probe (WMAP) The
satellite gathered data during three years
of continuous observations of remnant afterglow
light -- cosmic background radiation that lingers,
much cooled, from the universe's energetic
beginnings 13.7 billion years ago. WMAP data
reveals that its contents include 4% atoms,
the building blocks of stars and planets. Dark
matter comprises 22% of the universe. This
matter, different from atoms, does not emit
or absorb light. It has only been detected
indirectly by its gravity. 74% of the Universe,
is composed of "dark energy", that
acts as a sort of an anti-gravity. This energy,
distinct from dark matter, is responsible for
the present-day acceleration of the universal
expansion.
- 30 October 2002. Astronomers
have discovered an ancient star near the
center of our galaxy that may shed light
on the universeÍs
composition shortly after it was blasted into
existence by the Big Bang. http://www.msnbc.com/news/828187.asp
- 4 August 2001. By JAMES GLANZ, Exploring
Cosmic Darkness, Scientists See Signs
of Dawn -- discovery... amounts
to a sighting of the first dawn in the
cosmos as starlight and other radiation
began to pervade the heavens... made by
scientists with the Sloan Digital Sky Survey,
an ambitious effort to map large swaths
of the universe and catalog some 200 million
celestial objects.
- May-June 2001. T. Joseph W. Lazio, Razor-Sharp
Radio Astronomy. Mercury Magazine.
pp. 34-40. By constructing virtual telescopes
the size of continents (and larger) radio
astronomers are obtaining spectacular
high resolution results.
- 21 April 2001. FARTHEST SUPERNOVA EVER SEEN
SHEDS LIGHT ON DARK UNIVERSEftp://ftp.hq.nasa.gov/pub/pao/pressrel/2001/01-058.txt
-- NASA Release: 01-58
- 20 August 2000. How
Hipparchos data affects parallax measured
distances (Dome-L posting)
- 27 April 2000. Firming Up the Case for
a Flat Cosmos-- BOOMERanG,
a balloon-borne telescope mapped the microwave
sky while circling Antarctica. Andrew Lange
(Caltech) and Paolo de Bernardis (University
of Rome La Sapienza, Italy) unveiled BOOMERanG's
map of the far-southern microwave sky which
shows minuscule variations in brightness
(and hence temperature) of the all-pervasive
microwave background, amounting to only
a few hundredths of a percent.
 Similar
variations were revealed by the
COBE satellite in the early 1990s, but COBE
had very coarse vision, and couldnÕt
resolve sky patches any smaller than about
7 degrees wide, the size the Big Dipper's
bowl. BOOMERanG, by contrast, mapped details
as small as a sixth of a degree of arc, or
one-third the diameter of the full Moon. (From
Sky & Telescope)
- March 2000. Sally Stephens, Hubble Warrior --
Wendy Freedman rests in the eye of the storm
of the great Hubble constant debate. (Astronomy
Magazine, pages 52-59.)
- 17 December 1998. Accelerating
Universe -- Accompanying
Image (sn1998bu)
- 8 October 1998. Hubble Deep Field Image -- http://oposite.stsci.edu/pubinfo/pr/1998/32/index.html --
galaxies could be over 12 billion light-years
away (depending on cosmological models) Æ making
them the farthest objects ever seen.
Hardcopy Articles
- Measuring the Astronomical Unit
by Katherine Bracher. Mercury Magazine, Jan 2005. Excerpt:
Fundamental to our estimates of the size of
the Solar System is knowing how far away Earth
is from the Sun. Last June's transit of Venus
across the face of the Sun ... reminded many
people of earlier expeditions t.... In 1761,
1769, 1874 and 1882 astronomers traveled to
remote parts of the globe to take measurements
of this rare phenomenon ... to measure the
length of the Astronomical Unit or AU (the
mean distance of Earth from the Sun). In ...
January 1965, Brian G. Marsden described various
techniques for determining this quantity...[In]
the 3rd century BCE ...Aristarchus's idea was "to measure the angle between the sun and the moon
when the latter appeared to be exactly half illuminated... [he]
determined the angle to be 87', implying that the sun was 19
times more distant than the moon." ...One method for finding
distances is to observe an object's parallax. ...One could in
principle observe the Sun from different places on Earth, and
use this method. But we cannot observe the Sun against a background
of stars because it is too bright. Edmond Halley ... suggested...
that this could be done "from observations of transits
of Venus across the face of the sun."... measuring the
position of Venus against the Sun from different terrestrial
locations, .... in both the 1761 and 1769 transits, expeditions
went to places like northern Canada, Siberia, St. Helena in
the south Atlantic, and to Tahiti ... But the accuracy of determining
the exact moment of beginning or end of the event was too poor
to yield a good result. This was largely because of the illusion
called the "black drop" effect, where "Venus
appeared to attach itself to the sun by a long
filament.... Marsden attributed this effect
to the atmosphere of Venus. But later astronomers
observed transits of Mercury, which has no
atmosphere, and saw the same thing. It is now
explained as an effect of blurring caused by
a combination of the telescope and Earth's
atmosphere. Astronomers then sought other nearby
objects for which a parallax might be measurable,
and by the 19th century several asteroids had
been used in this way. In 1898 the asteroid
Eros ... yielded a value for the AU of 149,670,000
km (plus or minus 20,000 km.) This was the
best value until the advent of modern radar
techniques. ... radio waves could be bounced
off Venus; the length of time for the pulse
to go and come back would yield the distance
to Venus...Results from ...experiments in the
early 1960s gave the AU as 149,598,000 km,
plus or minus about 300 km. Currently the NASA
website gives a value of 149,597,870.691 km.
- The Universe as Seen by WMAP by John G. Cramer
Alternate View Column Published in the October-2003 issue of
Analog Science Fiction & Fact Magazine; This column is about
the beginning of a new era of what is being called precision
cosmology. It used to be a joke in the physics community that
astrophysicists put the error bars in the exponent. In other
words, they used numbers so poorly determined that they were
unknown by several orders of magnitude. ... the Wilkinson Microwave
Anisotropy Probe (WMAP) satellite, a joint initiative of Princeton
University and NASA's Goddard Spaceflight Center, in its first
year of operation has nailed down most of the constants of our
universe to an accuracy of a few percent.
- Hirshfeld, Alan W., The Race to Measure the Cosmos,
Sky & Telescope magazine, November, 2001, p. 39.
Books
- Hirshfeld, Alan W., Parallax: The Race to Measure the Cosmos, W.H. Freeman and Co., 2001.
- Webb, Stephen, Measuring the Universe: the Cosmological Distance Ladder, Springer-Verlag, 1999 -- How astronomers figured out how far away the planets, stars, and galaxies are. Aimed at undergraduates.
Web Sites
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