This week's Hurricane Sandy got us thinking about spirals. Most of us have seen images of hurricanes from above – either photos from airplanes or radar taken with satellites.
There are many spiral shapes throughout nature (see the recent Here, There & Everywhere blog post at http://hte.si.edu/blog/?p=87). The most common spiral shape that Chandra or any other telescope looks at is the spiral galaxy. These galaxies – that consist of a flat, rotating disk of stars, gas, and dust in a spiral pattern – are the most common type in the Universe. Thanks to studies of how spiral galaxies behaved, astronomers decades ago found evidence for the existence of dark matter: http://chandra.harvard.edu/xray_astro/dark_matter/index2.html
Perhaps one of the most compelling reasons to study these galaxies is that our very own galaxy, the Milky Way, is a spiral. We cannot get a very good look at our galactic home as a whole because we are embedded within it. Therefore, examining similar other spirals gives us important information.
Over the years, Chandra has observed many spiral galaxies. For example, the views of M101, aka "the Pinwheel" galaxy, gives us a spectacular face-on view of a spiral: http://www.chandra.harvard.edu/photo/2012/m101/ Studies of our sister galaxy, Andromeda, with Chandra have given us a better understanding of the populations of objects – including black holes -- that lie within the centers of spiral galaxies: http://www.chandra.harvard.edu/photo/2010/type1a/ and http://chandra.harvard.edu/photo/2006/m31/ And the longest view of a spiral galaxy in X-rays has given us insight into how stars go supernova within them: http://chandra.harvard.edu/photo/2012/m83sn/
From hurricanes to galaxies, spiral structures are certainly important. While we normally focus on news of spirals of the galactic kind, our thoughts are with everyone who was affected by this week's terrestrial version.
-Megan Watzke, CXC