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Vassar Prof Part of a Team of Astronomers Whose Discovery Sheds Light on Early Universe

Vassar Professor of Astronomy Debra Elmegreen was part of a team of scientists who have found sources of energy that help explain the workings of the early universe.

Professor of Astronomy on the Maria Mitchell Chair Debra Elmegreen

The team, led by Indian astronomer Kanak Saha, used a telescope recently launched by the Indian Space Research Organization to detect high-energy photons from a small galaxy 9.3 billion light years from Earth. The photons split atoms aparta process called reionization. Astronomers have been searching for sources that reionized the early universe.

Elmegreen, Professor of Astronomy on the Maria Mitchell Chair, and her husband, Bruce Elmegreen, an astronomer at IBM, were asked to join the team because of their previous work in studying distant early galaxies, Debra Elmegreen said.

The initial discovery was made during the team’s observations of a small galaxy in 2016, shortly after the launch of the AstroSat Ultra Violet Imaging Telescope. Elmegreen explained that such ultraviolet photons cannot be viewed from earth because the light is absorbed by the atmosphereand indeed, most ultraviolet photons are absorbed by gas in a galaxy or between galaxies.

She said everyone on the team of astronomers was enthusiastic about their findings almost immediately but could not publish news of their discovery until they had meticulously checked their work. “Right away, there was excitement that we had a detection that seemed to come from a distant galaxy,” Elmegreen said. “Then it took a long time for us to make sure we weren’t getting these photons from another source. The ‘aha moment’ was immediate but the grunge work of checking for errors was a slow but necessary process.”

The discovery sheds light on star formation in the early universe, Elmegreen explained. The Big Bang, which happened about 14 billion years ago, produced protons and electrons, but they could not combine as atoms until the universe cooled about 300,000 years later. Sometime after that, as stars and small galaxies formed, the universe became reionized when photons emitted by these clusters of stars split atoms apart again.

We don't know exactly how long the reionization period took, nor the sources of the stars,” Elmegreen said. “We know the stars formed in galaxies, which were much less massive early on than today’s galaxies. My team’s discovery involved the detection of these energetic photons that escaped from a tiny clumpy galaxy in a period of timein my galaxy’s case, about 4 billion years after the Big Bang, where such detections had not previously been made, so they provide a clue as to the nature of the photon emitters.”