Has Hubble Snapped a Young Galaxy in Today's Universe?
This NASA Hubble Space Telescope photo reveals a ragged collection of stars and gas clouds inside a recently formed galaxy in our own cosmic backyard, just 39 million light-years away.
The mystery is that the galaxy, called DDO 68, should have started making stars billions of years ago as most galaxies do. Therefore, it's a "later bloomer" among the nearby galaxy population.
Astronomers usually have to peer very far into the universe to see back in time to when galaxies were born. At those early times, these infant galaxies appear small and fuzzy because they are over 10 billion light-years away. Their light is just reaching us now after crossing the universe for billions of years.
DDO 68 is a unique and ideal candidate for observing a newly formed galaxy close-up. Astronomers believe DDO 68 is relatively youthful based on its structure, appearance, and composition.
DDO 68 appears to be very low in heavier elements, which is unusual for galaxies today. Our Sun, for example, is a second-generation or third-generation star made up of elements heavier than hydrogen and helium. Elements like carbon, nitrogen, and oxygen were processed through nucleosynthesis in the cores of first-generation stars and then recycled into subsequent generations.
Because the stars in DDO 68 are deficient in heavier elements, they must have formed only about 1 billion years ago. The late birth may have been triggered by the collision of two clouds of hydrogen gas.
Hubble observations are now being analyzed to confirm whether or not there are any older stars in DDO 68. If there are, this would disprove the hypothesis that the galaxy is entirely made up of young stars. If not, it would confirm the unique nature of DDO 68.
The image is composed of exposures in visible and infrared light taken with Hubble's Advanced Camera for Surveys.
Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Acknowledgment: A. Aloisi (STScI)