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 universe's 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) 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.
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