These images, taken with NASA's Hubble Space Telescope, reveal fresh star birth in the ancient elliptical galaxy NGC 4150, located about 44 million light-years away.
The images combine observations taken in visible and near-ultraviolet light with Hubble's Wide Field Camera 3. Ultraviolet light traces the glow of young stars.
In the large-scale image, NGC 4150 looks very much like a typical elliptical galaxy. The dark strands of dust in the center, however, provide tentative evidence of a recent galaxy merger. The inset image shows a magnified view of the chaotic activity inside the galaxy's core. Those regions within about 650 light-years of the center that are not obscured by dust appear bright in near-ultraviolet light (shown here in blue). The blue areas indicate a flurry of recent star birth. The stellar breeding ground is about 1,300 light-years across. The stars in this area are less than a billion years old. By comparison, most of the stars in the galaxy are about 10 billion years old. These young stars most likely formed during an encounter with a smaller galaxy that was about one-twentieth the mass of NGC 4150.
The Hubble observations bolster the emerging view that ancient elliptical galaxies like NGC 4150 harbor a significant amount of recent, merger-driven star formation.
The images were taken Oct. 30 and Nov. 9, 2009.
NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore), R. O'Connell (University of Virginia, Charlottesville), and the WFC3 Scientific Oversight Committee