Sukanya Chakrabarti, Ph.D., an assistant professor of physics for the Charles E. Schmidt College of Science at Florida Atlantic University, has developed a mathematical method called "tidal analysis" to find satellite, or dwarf, galaxies by analyzing the ripples in the hydrogen gas distribution in large spiral galaxies in outer space.

Chakrabarti, who specializes in the study of astrophysics, black holes and galaxies, used this method to predict that a dwarf galaxy sat on the opposite side of the Milky Way from Earth earlier this year. This dwarf galaxy has been unseen to date because it is "dark" and obscured by the intervening gas and dust in the galaxy's disc.

"The tidal analysis approach has broad implications for many fields of physics and astronomy," said Chakrabarti. "Current cosmological theories predict a far higher number of dwarf galaxies that have actually been observed so far. Tidal analysis may help solve this mystery, bringing us one step closer to the indirect detection of dark matter and understanding galaxy evolution driven by satellite impacts."

Chakrabarti brought her expertise to a research group for a study titled, "The Sagittarius Dwarf Impact as an Architect of Spirality and Outer Rings in the Milky Way Galaxy," which was recently published in the renowned British research journal Nature.

The study was conducted along with principal investigator Chris W. Purcell, from the department of physics at the University of Pittsburgh; and James S. Bullock, Erik J. Tollerud and Miguel Rocha, from the Center for Cosmology within the department of physics at the University of California, Irvine.

According to the study, it has been known that the Sagittarius dwarf galaxy, which is dominated by dark matter and has an invisible, massive dark halo, has collided with the Milky Way. Until now, most astronomical research has focused on the effects the collision had on the Sagittarius dwarf galaxy itself.

In the study, Chakrabarti and her colleagues explored what effects, if any, the repeated collisions of the Sagittarius dwarf galaxy had on the larger Milky Way. Through analysis of data from telescopes and detailed simulations, the team found that the Sagittarius dwarf galaxy has collided with the Milky Way twice over the past 1.8 billion years.

These impacts sent streams of stars bulging out one side, which were then gradually tugged inward by the Milky Way's gravity to form its spiral arms. The study indicates that Sagittarius will rotate around once again for a third impact, but not for another 10 million years or so.

To read "The Sagittarius Dwarf Impact as an Architect of Spirality and Outer Rings in the Milky Way Galaxy," visit http://dx.doi.org/10.1038/nature10417. Chakrabarti joined FAU in 2011 from the University of California Berkeley, where she was a President's Fellow and theoretical astronomer. Prior to her time at UC Berkeley, she was a National Science Foundation Fellow at Harvard.

"Sukanya is a wonderful example of the truly brilliant young faculty we are attracting to our university," said Gary W. Perry, Ph.D., dean of the College of Science at FAU. "We are very excited about the research she is doing in our physics department."

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