By Josephine Wolff
Data transmissions by the Wilkinson Microwave Anisotropy Probe (WMAP) provide multiple insights into the formation of the universe and its infancy, said several University researchers who were involved in designing and launching the satellite. The probe’s mission is led by a partnership between NASA and the University, in collaboration with scientists at several other institutions.
The data allowed researchers to calculate a more precise estimate of the age of the universe, now thought to be 13.7 billion years old, with only a 120 million year margin of error, said physics professor Lyman Page, one of the team’s lead researchers. Page added that the satellite has also helped scientists determine what actual processes were going on when the universe was less than a billionth of a billionth of a second old.
“We can start to probe those earliest times with a new degree of confidence,” he said.
The pictures transmitted by the probe have also helped the researchers make important discoveries about the formation of the first stars.
“Currently the WMAP data is pretty much the only way to gain information as to when the universe was ionized by the first generation of stars,” said Eiichiro Komatsu, an astronomy professor at the University of Texas-Austin who worked on the WMAP project from 2001 to 2003, when he was a postdoctoral fellow at Princeton.
The data showed that the first stars must have formed during the first 500 million years after the Big Bang, astrophysics professor David Spergel ’82 said.
This discovery will have important implications for the James Webb Space Telescope, scheduled to be launched in 2013 by NASA, Komatsu said.
“One of [the Webb Telescope’s] prime science goals is to see the sources of ... the first generation of stars directly,” Komatsu said. “It is important to know when a significant fraction of these sources were around, so that we know where to look using this telescope.”
Discovering dark matter
The WMAP transmissions also provide the first evidence for the existence of the mysterious dark matter astrophysicists have long suspected composes much of the universe.
“[WMAP data] implies that atoms make up only 5% of the universe,” Spergel said in an e-mail. “The next roughly 20% is made up of ‘dark matter,’ most likely a new class of subatomic particles that interact[s] only extremely weakly with normal matter. The remaining 75% is made up of ‘dark energy’ associated with empty space.”
Many scientists have suspected that dark matter exists, specifically particles called neutrinos, but its existence was never before confirmed by evidence, said Charles Bennett, WMAP’s principal investigator and a physics and astronomy professor at Johns Hopkins.
“Dark matter has never been detected directly in the laboratory; we’ve only inferred its existence from astronomical observations,” said Gary Hinshaw, an astrophysicist with the NASA Goddard Space Flight Center. “Neutrinos have been detected, but not this kind. These are produced shortly after the Big Bang.”
The cosmic neutrino background that the probe shows is only a small fraction of the total dark matter in the universe, Hinshaw added.
“[The neutrino background] has always been assumed to be there ... [The] challenge was to actually see it in the data,” Komatsu said. “Particle physicists are detecting neutrinos on the ground, but those neutrinos are from the atmosphere, sun, or nuclear reactors. The energy of the cosmic neutrino background is at least a million times smaller than their neutrinos, which means that it is extremely difficult to detect them ... with the current technology.” Though the WMAP has helped clarify questions about dark matter, dark energy remains an unknown and unexpected quantity that the WMAP may help explain in the future, Bennett said.
