Astronomers spot faint plumes extending from first known spiral galaxy

Astronomers have recently observed faint plumes extending from first known spiral galaxy M51a, also called the "Whirlpool Galaxy."

The image also provided new details of the linear northwest plume, which itself is nearly 120,000 light-years long, and reveals a lack of stars in a portion of the southeast tail.

M51a is the first known spiral galaxy, identified and sketched by William Parsons, the Earl of Rosse, in 1845. The whirlpool and its small companion, M51b, are in the hunting dogs constellation, Canes Venatici, about 31 million light years away.

The team aimed the telescope at M51 on moonless nights and exposed its digital camera to the light from the galaxy at 20-minute intervals, recalibrating in between. For a total of 10 hours, light was filtered to reveal younger stars. For another 10 hours, light was filtered to reveal older stars. These 10-hour images were merged to create the 20-hour final image.

Aaron Watkins, a PhD student in the department of astronomy at Case Western Reserve, said that the astronomers are now devising other ways to look at M51, particularly to gather more detail from the faint plumes and the northwest plume was bright enough that it might be a good candidate for further study using the Hubble telescope.

The research is published in Astrophysical Journal Letters.