The Wilkinson Microwave Anisotropy Probe

WMAP
Completed Microwave Map of the Universe
Image Credit: NASA

Scientists announced this week that the mission of the Wilkinson Microwave Anisotropy Probe (WMAP) has been completed. The last set of observations were downloaded on 20 August 2010, and researchers are compiling the final results. The satellite was placed in a permanent parking orbit around the sun on 8 September 2010.

WMAP was launched on 30 June 2001 and placed into an orbit around SEL-2, the second Sun-Earth Lagrange point. SEL-2 lies 1,500,000 kilometers beyond the Earth on a line from the Sun to the Earth. WMAP was the first spacecraft to occupy this location. SEL-2 is extremely cold, shaded from the Sun’s activity by the Earth’s shadow and ideal as an astronomical location in space. In 2009, the Herschel Space Observatory and Planck space observatory took up residence at SEL-2. They will be joined in 2014 or 2015 by the James Webb Space Telescope.

First detected in 1964, the cosmic microwave background (CMB) radiation (television “snow” – before cable), is the remnants of the extremely hot radiation from the big-bang, now cooled to almost absolute zero after 13.73 billions years of the expansion of the universe. It is a pattern frozen in place when the cosmos was only 380,000 years old.

WMAP COBE was the successor to NASA’s Cosmic Background Explorer (COBE), which was launched on 18 November 1989 and produced the first map of the microwave radiation. Note the great increase in resolution between the COBE map at the right, and the WMAP result above.

The Planck observatory is currently making high resolution measurements of both the total intensity and polarization of the primordial CMB anisotropies that were first observed by COBE and WMAP.

The observations made by WMAP are the most accurate to date and have allowed scientists to rule out several “inflation” models about what happened in the first trillionths of a second during the birth of the cosmos, while supplying support for several other models:

  • The age of the universe is 13.73 billion years old to within 1% (0.12 billion years)
  • Ordinary matter (atoms) makes up only 4.6% of the universe (to within 0.1%)
  • Dark matter (not made up of atoms) makes up 23.3% (to within 1.3%)
  • Dark energy makes up 72.1% of the universe (to within 1.5%)

Dark energy is the force driving the galaxies in the universe apart at an ever increasing rate. At some point in the future, inhabitants of the Milky Way will not be able to see any other objects in the sky. These entities will conclude that they are at the center of the universe, and will have no information about the big bang and the creation of the cosmos as we know it today.

The Astronomy and Astrophysics Decadal Survey – 2012 to 2021

by Dave Fischer

The National Research Council has released Its sixth decadal survey of astronomy and astrophysics. The plan focuses on three science objectives:

  • The exploration of the origins of the universe
  • The search for habitable planets outside our solar system
  • The use of astronomical observations to investigate fundamental physics.

The report addresses large, medium, and small activities in these fields. It surveys the existing facilities and the new facilities that would be needed, both ground based and space based. It looks at the known science objectives and where new discoveries might be made. And it looks at the promise of the proposals and the risks associated with each.

The large scale space-based projects are:

  • 1. Wide Field InfraRed Survey Telescope (WFIRST)
  • 2. Explorer Program Augmentation
  • 3. Laser Interferometer Space Antenna (LISA)
  • 4. International X-ray Observatory (IXO)

WFIRST, the near infrared wide-field telescope, is intended to explore Dark Energy and Exoplanet statistics as well as support guest survey investigations.

The Explorer Program is ongoing and funds rapid, targeted projects that deliver a high science return. Past projects include WMAP, Swift, GALEX and WISE.

LISA will exploit the new field of astronomy using long wavelength gravitational radiation measured by three spacecraft 5 million kilometers apart.

IXO is a large area, high spectral resolution x-ray observatory to explore hottest regions in the universe, including clusters of galaxies, the intergalactic medium, and black hole accretion disks.

The medium scale space-based projects are:

  • 1. New Worlds Technology Development Program
  • 2. Inflation Technology Development Program

The New Worlds technology development program is a research program to obtain preliminary observations in order to study nearby habitable planets. Included is technology development in order to make an informed decision in the second half of this decade on a flagship mission.

The Inflation Technology development program will use ground based microwave background telescopes to examine “B-mode polarization.” This is a sensitive signature of processes thought to have occurred during the earliest moments of the universe. If a signal is seen, then a space-based mission with at least ten times greater sensitivity is warranted and associated technology development would be needed.

There are four large scale ground-based projects recommended, and prioritized as follows:

  • 1. Large Synoptic Survey Telescope (LSST)
  • 2. Mid-Scale Innovations Program
  • 3. Giant Segmented Mirror Telescope (GSMT)
  • 4. Atmospheric Cerenkov Telescope Array (ACTA)

The LSST project would address research such as dark energy using gravitational lensing, dark matter, Near-Earth Kuiper-belt objects, the Solar neighborhood, and transient phenomena such as gamma-ray bursts, variable stars, and supernova.

The mid-scale program would fund annual proposals to compete for funding, of which around 7 proposals would be chosen during the decade.

The Giant Segmented Mirror Telescope project suggests that NSF chose one of the two current 30 meter telescope projects (The Giant Magellan Telescope in Chile or the Thirty Meter Telescope in Hawaii) and invest in a quarter share in order to provide access for the entire US community.

The report proposes that the team responsible for the proposed US Advanced Gamma-ray Imaging System (AGIS) collaborate as a minor partner with the European Cherenkov Telescope Array (CTA).

There is one medium scale ground-based program that was recommended by the NRC Decadal Survey:

  • 1. Cerro Chajnantor Atacama Telescope (CCAT)

This 25 meter wide-field sub-millimeter telescope would work in conjunction with the Atacama Large Millimeter Array (ALMA) in Chile.

The small scale investment recommendations are:

  • Target work-force development (TSIP, Sub-orbital, AAG, ATP)
  • Address changing role of computation and theory (TCN)
  • Support current/upcoming facilities (Gemini, Lab Astro, TCN)
  • Develop technology for the future (NSF ATI, NASA Tech. Dev.)

Other documentation:

NASA press release

Preliminary Report

NRC committee reports.

Town Hall Slides (pdf).