Transcript Pluto: - Rice University

WMAP:
Wilkinson Microwave
Anisotropy Probe
AST 403
Jimmy Jones
WMAP:
Cosmic Microwave
Background Radiation
(CMB)
CMB
• Big Bang predicts early
universe was very hot –
photons produced
• As universe expands,
the gas within cools and
photons lose energy
• Implies universe should
be filled with radiation
left over from Big Bang CMB
CMB Discovery
• Initially predicted by
George Gamow in
1948 and by Ralph
Alpher and Robert
Herman in 1950
• Inadvertently
observed by Arno
Penzias and Robert
Wilson in 1965
COBE
• Cosmic Background
Explorer
• Launched November
1989
• Designed to measure
cosmic background
radiation
• Possessed three
instruments:
– DIRBE – infrared
– DMR – microwave
– FIRAS – spectrum analysis
COBE Data
Milky Way
Red areas .0002 degrees
warmer than black areas
• COBE helped to
determine average
temperature of CMB
as 2.725 kelvins
• This temperature is
very uniform
• However, COBE was
able to detect slight
variations
Why Study CMBs?
• CMBs provide
information on the
universe as early as
400,000 years after Big
Bang
• (as opposed to studying
visible light sources in
the million year range)
• Studying fluctuations
can provide insight into
origin of galaxies and
measure the basic
parameters of the Big
Bang theory.
How?
• The Big Bang can account for background
radiation and the formation of light elements
but not galaxies
• One theory is:
– Large objects potentially grew out of small
fluctuations in the background radiation
– Areas of greater density expand slower allowing
for build up of even greater densities
– Further study of these anomalies can help to
prove the validity of this theory
WMAP
Microwave Anisotropy
Probe:
The Mission
Satellite Timeline
• Launched June 30,
2001
• Completed prime 2
years of mission
operations September
2003
• Extensions granted to
September 2009
• Orbits in L2 with back
to Sun and Earth
Satellite Components
• Uses differential
microwave radiometers
that measure
temperature differences
between two points on
the sky.
• To facilitate rejection of
foreground signals from
our own Galaxy, WMAP
uses five separate
frequency bands from
22 to 90 GHz.
Measurement Error Control
• Sensitivity better than 20 microkelvins per 0.3
degree square pixel
• Measures temp. differences rather than absolute
temp (implies most spurious signals will cancel)
• Spins and precesses like a top allowing an observing
pattern that covers 30% of sky during each 1 hour
precession.
• Five frequency bands (as compared to COBE’s three)
• The L2 Lagrange point offers exceptionally stable
environment and unobstructed view of deep space.
Data Acquisition
WMAP
Data
Universes’ ‘Baby Picture’
Universes’ Fingerprint
• Universes’ baby picture provides unique
‘fingerprint’ that can be analyzed to
determine characteristics of the
universe, past and present
Composition of Universe
• Although the data is
still be analyzed a
wealth of
information has
already been
discovered
• Based on analysis a
composition of the
primordial universe
has been proposed
How?
• WMAP measured temperature
fluctuations in term of their ‘angular
fluctuation spectrum’.
• Graphing this data produced features
generated by the various physical
processes that produce different
amounts of energy (temperature) at the
different angular scales.
How II
Variations due to
gravity?
Variations due to
sound waves?
Dark Matter?
Atoms?
Shape of the Universe
• The vertical peaks and
angular scale in the previous
graph provide information to
the density as well
• If the density is greater than
the critical density a closed
universe is produced
• If the density is less than the
critical density an open
universe is produced
• If the density is equal to the
critical density a flat
universe is produce
• Findings of the WMAP
mission appear consistent
with a flat universe
geometry
Rapid Inflation
• Measures of the fluctuations on the angular
scale seem to support the theory that the
universe underwent a period of extremely
rapid (exponential) expansion
More Data
• The universe is 13.7 billion ± 200
million years old
• The Hubble constant is 70
(km/sec)/Mpc, +2.4/-3.2
References
• General Information
– http://map.gsfc.nasa.gov/m_mm.html
– http://en.wikipedia.org/wiki/WMAP
• CMB
– http://www.astro.ubc.ca/people/scott/faq_basic.htmlMissions
• Results
– http://www.cnn.com/2003/TECH/space/02/11/cosmic.portrait/
• COBE
– http://lambda.gsfc.nasa.gov/product/cobe/