Building upon its groundbreaking mission, WMAP has released its latest findings based on refined measurements from an additional two years of data. These results offer unparalleled insights into the universe's early stages and its ongoing evolution. The WMAP science team has conducted detailed studies on the temperature and polarization of the Cosmic Microwave Background (CMB), achieving remarkable accuracy and precision. Through these studies, WMAP has unveiled significant aspects of the universe's fundamental properties. WMAP has precisely determined the age of the universe, the density of atoms, and the density of non-atomic matter, among other crucial parameters. These advancements have transformed cosmology from speculative theory to a precision science. By capturing the "baby picture of the universe," WMAP has provided invaluable insights into the universe's infancy, mapping its afterglow when it was a mere 375,000 years old. These observations support the prevailing "big bang" framework of cosmology. WMAP's observations bolster the theory of inflation, suggesting a rapid expansion of the universe in its earliest moments. This expansion generated minute fluctuations that eventually led to the formation of galaxies. Confirming predictions of inflation theory, WMAP has observed fluctuations in density across the sky, following a bell curve pattern with equal numbers of hot and cold spots. Additionally, it has verified the slightly larger amplitude of variations in density on larger scales. WMAP's measurements have revealed the composition of the universe, with ordinary atoms comprising only 4.6%, while dark matter and dark energy constitute 24% and 71%, respectively. Launched on June 30, 2001, WMAP positioned itself near the "second Lagrange point" of the Earth-Sun system, approximately a million miles from Earth. Over the years, WMAP has meticulously scanned the heavens, providing crucial data for cosmological research. With its final release of results, WMAP concludes its remarkable mission, leaving a profound impact on our understanding of the cosmos.
The WMAP team has reported the first direct detection of pre-stellar helium, offering a crucial test of the predictions of the big bang model. By analyzing microwave patterns in the sky, WMAP, in conjunction with data from ACBAR and QUaD experiments, has discerned the presence of helium prior to the formation of the first stars. WMAP now provides 50% tighter limits on the standard model of cosmology, confirming its consistency with observations. Moreover, WMAP has detected a key signature of inflation, shedding light on the universe's early rapid expansion. The latest WMAP data offer significant insights into dark energy and the geometry of the universe. Combining WMAP with other data sources, researchers have constrained dark energy to be within 14% of the expected value for a cosmological constant, while the universe's geometry must be flat to within 1%. WMAP has placed new constraints on the number of neutrino-like species in the early universe, revealing an effective number of 4.34 ± 0.87, in contrast to the standard model's prediction of 3.04. With high significance, WMAP has detected temperature shifts induced by hot gas in galaxy clusters. These observations challenge previous X-ray observations and numerical simulations, suggesting a need for a more comprehensive understanding of gas physics in cluster regions. WMAP has visually demonstrated that the polarization pattern around hot and cold spots in the map aligns with predictions from the standard model, providing further validation of cosmological theories.
The 5-year data from WMAP reveals cosmic microwave temperature fluctuations across the entire sky. With an average temperature of 2.725 Kelvin, these fluctuations, represented as colors akin to a weather map, provide crucial insights into the universe's early conditions. WMAP meticulously measures the composition of the universe, offering snapshots of its evolution. The data indicate shifts in the relative constituents over time, with dark matter and atoms becoming less dense as the universe expands, while dark energy maintains its dominance. A visual representation illustrates the universe's evolution over 13.7 billion years. From the rapid expansion during inflation to the emergence of dark energy, WMAP provides a comprehensive timeline, illuminating key milestones in cosmic history. Analyzing temperature fluctuations across different angular sizes, WMAP unveils insights into the early universe's sound waves. The detection of harmonic overtones, particularly the third overtone, provides evidence for the presence and influence of neutrinos. The latest WMAP data herald three significant discoveries. Firstly, evidence of a cosmic neutrino background suggests a substantial role for neutrinos in the early universe, with their influence imprinted in the observed microwave patterns. Secondly, clear evidence of a drawn-out process in the creation of the cosmic fog by the first stars marks the end of the "dark ages." This revelation provides crucial insights into the universe's transition from a primordial state to one populated by stars. Lastly, tight constraints on the burst of expansion during inflation refine our understanding of the universe's earliest moments. By eliminating certain inflationary theories while bolstering others, WMAP's data offer valuable guidance for cosmological models, reshaping our perspective on the universe's formative stages. These findings revolutionize our understanding of the universe's infancy and development. WMAP's meticulous observations and precise measurements continue to shape cosmological research, paving the way for new insights into the cosmos. With each release of data, WMAP continues to illuminate the mysteries of the universe, solidifying its legacy as a cornerstone of modern astrophysics. Its contributions transcend scientific boundaries, inspiring generations of researchers to unravel the secrets of the cosmos. The WMAP mission is a collaborative effort involving institutions worldwide, including NASA's Goddard Space Flight Center, University of Texas at Austin, University of Oxford, and The Johns Hopkins University, among others.
In February 2003, WMAP unveiled results from its initial year of flight data, presenting crucial insights across 13 papers spanning 241 journal pages. These findings were readily accessible for scientific scrutiny and analysis. Thomson ISI recognized a WMAP paper as the "Hot Paper in Physics" for multiple months in 2004 and 2005, indicating significant and sustained interest in the research. Moreover, ISI listed two WMAP papers as the top-ranked among the 103 "Super Hot Papers," a rare achievement for space science within such esteemed company. Science Watch also underscored the impact of WMAP publications in its analysis, emphasizing the probe's exceptional contributions to cosmological understanding. Greg Davidson's 2003 science news metric report further highlighted WMAP's remarkable productivity and influence, particularly in elucidating aspects of the universe's structure, dark matter, and early galaxy formation. The 3-year data release expanded WMAP's dataset significantly, providing a richer resource for analysis and enabling enhanced error analyses and calibration techniques. The WMAP Observatory features an innovative back-to-back optical system facilitating differential sky measurements. Its design includes passive cooling elements and shields against strong microwave interference from celestial bodies. Proposed to NASA in 1995 and selected in April 1996 as a MIDEX mission under the Explorers Program, WMAP adopted an efficient spacecraft configuration with streamlined mission operations and data analysis strategies. Launched on June 30, 2001, aboard a Delta II rocket from the Cape Canaveral Air Force Base, WMAP completed its primary 2-year mission phase by September 2003. Subsequent mission extensions, endorsed by the 2002 and 2004 Astronomy and Physics Senior Review, extended WMAP's operations until September 2009. In February 2003, the WMAP Team released a comprehensive set of papers along with flight data from the initial year of observations, followed by the 3-year data release in March 2006, including full polarization data and detailed analyses of experimental procedures and outcomes.
NASA has unveiled groundbreaking insights into the early universe through the Wilkinson Microwave Anisotropy Probe (WMAP), capturing an unparalleled "baby picture" of cosmic evolution. Over a year-long observation of the entire sky, WMAP has delivered a high-resolution cosmic portrait, revealing the cosmic microwave background, the afterglow of the big bang. Dr. Charles L. Bennett, WMAP Principal Investigator at the Goddard Space Flight Center (GSFC), describes the data as a "gold mine," offering unprecedented accuracy in describing the universe. Surprisingly, the data indicates that the first generation of stars ignited just 200 million years after the big bang, earlier than previously thought. Moreover, WMAP precisely determines the age of the universe at 13.7 billion years with a remarkably small one percent margin of error. The findings reaffirm the validity of the big bang and inflation theories, outlining the universe's composition as 4 percent atoms, 23 percent dark matter, and 73 percent dark energy, shedding light on the enigmatic nature of dark energy, which acts as anti-gravity. Dr. Anne Kinney, NASA director for astronomy and physics, hails these revelations as a milestone in cosmology, marking a turning point in our understanding of the universe. The patterns observed in the cosmic microwave background, frozen in place 380,000 years after the big bang, provide invaluable insights into the universe's evolution. WMAP's observations align with predictions from various cosmic theories, solidifying its role as a cosmic detective. Named in honor of Princeton University's David Wilkinson, WMAP continues its mission from its distant orbit around the second Lagrange Point, promising further revelations into the early universe and the nature of dark energy.
Operating within its L2 orbit, WMAP diligently collects high-quality scientific data. The mission has generated the most detailed full-sky map of variations in the temperature of the cosmic microwave background radiation, providing a wealth of insights into the early universe. The mission background reveals a meticulously designed observatory featuring a back-to-back optical system for precise sky measurements, along with passive cooling elements and shielding mechanisms to protect against interference. Proposed to NASA in 1995 and selected in April 1996, WMAP was launched on June 30, 2001, from the Cape Canaveral Air Force Base aboard a Delta II rocket. Following its first full year of science observations at L2 in September 2002, the WMAP Team released a set of 13 papers detailing observations of the cosmic microwave background. WMAP completed its prime 2-year mission phase by September 2003, with subsequent mission extensions granted until September 2010. In March 2006 and 2008, the team released 3-year and 5-year data, respectively, providing deeper insights into the universe's composition and evolution. WMAP is notable for being the first mission to utilize an L2 orbit as its permanent observing station, leveraging the semi-stable region of gravity about four times further than the Moon. Each WMAP observation of the full sky spans a six-month period, with the spacecraft orbiting L2 in an oval pattern and requiring occasional station-keeping maneuvers to maintain position. The mission, scheduled for nine years at L2, has demonstrated excellent system functionality. Diagrams and animations depicting WMAP's journey to L2 offer further insight into the mission's trajectory and orbit pattern.
WMAP proposed to NASA in 1995 and approved for a definition study in 1996, followed by development approval in 1997. On June 30, 2001, WMAP was launched aboard a Delta II-7425-10 (no. 286) launch vehicle at 15:46:46 EDT. After a three-month journey, it arrived at L2 Lagrange Point on August 10, 2001, where it conducted its first full-sky observations in April 2002. Celebrating its first year of flight on July 1, 2002, WMAP completed its second full sky scan in August 2002. On February 11, 2003, the initial full-sky data was released, coinciding with the renaming of the MAP spacecraft to WMAP in honor of David T. Wilkinson. August 2003 saw WMAP completing its third full sky scan at L2, followed by its fourth in August 2004, marking three years of flawless operation. In March 2005, two of WMAP's first-year papers were listed as the most highly cited in space science. By August 2005, WMAP had completed four years at L2, maintaining impeccable performance. The second data release on March 16, 2006, focused on polarized signals and included calibration and error analyses. In March 2008, the third data release provided further insights into the universe's evolution. The fourth data release on January 26, 2010, unveiled seven-year results, including findings on polarization and dark energy. WMAP ceased science operations on August 19, 2010, with final data analysis and publication expected in two years. Finally, on October 28, 2010, WMAP received its last command, ending communications and transitioning to silent data collection orbiting the Sun beyond L2.
Constructed and tested at Goddard Space Flight Center in Greenbelt, MD, WMAP was transported to Cape Canaveral in the Spring of 2001 for integration and launch. The WMAP team devoted long days to resolving details and addressing issues, culminating in a nearly flawless, on-time launch at the end of June 2001. Preparation at Kennedy involved mounting WMAP to the third stage of the Delta rocket and lifting it into position for launch, with a protective fairing cover shielding it during the launch. In the official launch photo, WMAP is depicted rising from the launch tower as the Delta rocket flies east over the Atlantic Ocean. On June 30, 2001, at 3:46 p.m. EDT, WMAP embarked on its journey from Kennedy Space Center, ultimately reaching its destination at L2, as captured in a photograph taken by Ian Dell'Antonio using the KPNO 4m telescope.
Positioned at L2, WMAP completed its first full scan of the sky by April 1, 2002, marking a significant milestone in its mission. The completed orbital path at L2 showcases the spacecraft's journey over nine months at its observing station. A reunion of the WMAP development team commemorated the one-year anniversary of WMAP's launch and its successful year of flight. This celebration highlighted the dedication and achievements of the team in advancing our understanding of the universe.
WMAP's sun shield, a mere 4.5 meters wide, may seem invisible from 1.5 million kilometers away, but two scientists working on the ESA's Gaia space mission proved otherwise! Using a 2.2-meter telescope from a Chilean mountaintop, they successfully imaged WMAP's position. This experiment served as a feasibility test for Gaia's new tracking scheme. Gaia, stationed at L2 like WMAP, requires unprecedented positional accuracy, beyond conventional satellite tracking techniques. Thanks to WMAP, tracking Gaia from Earth with optical telescopes, achieving one-part-in-a-billion accuracy (absolute positioning to within 150 meters), now seems achievable. Gaia's mission is ambitious, aiming to map over a billion stars in our galaxy and beyond, measuring their positions, distances, space motions, and physical characteristics. With precision reaching millionths of a second of arc, Gaia will map the Milky Way in three dimensions, offering unparalleled insights into stellar distributions and distances. The composite image captured by the European Southern Observatory at La Silla, Chile, showcases WMAP's movement as a sequence of colored dots. This successful endeavor demonstrates the potential for precise celestial cartography and highlights WMAP's role in advancing astronomical capabilities.
The science and instrument papers authored by the WMAP team provide comprehensive coverage of the collected data and its analysis, as well as detailed discussions on mission design and instrument specifications. These papers are available on the Legacy Archive for Microwave Background Data Analysis (LAMBDA), an online archive maintained by NASA specifically for cosmic microwave radiation science data. For access to all WMAP technical papers, please visit: WMAP Technical Papers. Additionally, the latest observations have led to updates in cosmological parameters. For a list of these parameters based on the most recent observations, you can visit: Cosmological Parameters.