Hubble spies young stars in ancient galaxy's core

These images, taken with the NASA/ESA 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 centre, 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 centre 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 30 October and 9 November 2009.