Selections from 2016: Hidden Galaxies Found Behind the Milky Way

Editor’s note: In these last two weeks of 2016, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded papers published in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.

The Parkes H I Zone of Avoidance Survey

Published February 2016


Main takeaway:

883 galaxies have been discovered within a few hundred million light-years of us, hiding behind the Milky Way. The galaxies were found by a team led by Lister Staveley-Smith (International Center for Radio Astronomy Research, University of Western Australia) using the 64-m Parkes radio telescope in Australia.

Zone of Avoidance galaxies

Distribution of the galaxies discovered in the Zone of Avoidance. Radial distance is measured by the recessional velocities of the galaxies. [Staveley-Smith et al. 2016]

Why it’s interesting:

These new galaxies were discovered in what’s known as the “Zone of Avoidance”, a gap that extends roughly 5° above and 5° below the galactic plane. The Zone of Avoidance has been excluded from many past surveys because the stars and dust of the Milky Way prevent us from being able to identify background galaxies in this region.  But the Parkes radio telescope — equipped with an innovative new receiver — was able to peer through the foreground of the Milky Way to detect the hidden galaxies behind it.

What this could teach us:

The discovery of hundreds of new galaxies may help explain the gravitational anomaly known as the Great Attractor region, a diffuse concentration of mass roughly 250 million light-years away that is pulling the Milky Way and hundreds of thousands of other galaxies toward it.


L. Staveley-Smith et al 2016 AJ 151 52. doi:10.3847/0004-6256/151/3/52