Wilkinson Microwave Wilkinson Microwave Anisotropy ProbeAnisotropy Probe

AST 403Jimmy Jones

WMAP:WMAP:

WMAP:WMAP:

Cosmic Cosmic Microwave Microwave Background Background Radiation Radiation

(CMB)(CMB)

CMBCMB• 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 DiscoveryCMB 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

COBECOBE• Cosmic Background

Explorer• Launched November

1989• Designed to measure

cosmic background radiation

• Possessed three instruments:– DIRBE – infrared– DMR – microwave– FIRAS – spectrum

analysis

COBE DataCOBE Data

• 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

Red areas .0002 degrees Red areas .0002 degrees warmer than black areaswarmer than black areas

Milky WayMilky Way

Why Study CMBs?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?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

WMAPWMAP

Microwave Microwave Anisotropy Probe:Anisotropy Probe:

The MissionThe Mission

Satellite TimelineSatellite 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 ComponentsSatellite 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 Measurement Error ControlControl

• 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 AcquisitionData Acquisition

WMAPWMAP

DataData

Universes’ ‘Baby Universes’ ‘Baby Picture’Picture’

Universes’ FingerprintUniverses’ Fingerprint

• Universes’ baby picture provides unique ‘fingerprint’ that can be analyzed to determine characteristics of the universe, past and present

Composition of Composition of UniverseUniverse

• 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?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 IIHow II

Variations due to Variations due to gravity?gravity?

Dark Matter?Dark Matter?

Variations due to Variations due to sound waves? sound waves?

Atoms?Atoms?

Shape of the UniverseShape 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 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 DataMore Data

• The universe is 13.7 billion ± 200 million years old

• The Hubble constant is 70 (km/sec)/Mpc, +2.4/-3.2

ReferencesReferences

• 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.html

Missions

• Results– http://www.cnn.com/2003/TECH/space/02/11/cosmic.p

ortrait/

• COBE– http://lambda.gsfc.nasa.gov/product/cobe/