NGC 3521 is popularly known as the Bubble Galaxy. It is an intermediate spiral galaxy. It is located approximately 35 million light-years away in the constellation Leo. The galaxy earns its nickname from the gigantic, very faint bubble-like shells and tidal remnants that surround it.
Astronomers believe these shells are tidal debris. They consist of streams of stars and gas. These materials were torn from smaller satellite galaxies. NGC 3521 absorbed them in the distant past. These outer structures are very faint and typically only appear in deep, long-exposure astrophotography. In smaller backyard telescopes, the galaxy often appears as a simple glowing object. It is rounded in shape. This appearance also contributes to the “bubble” moniker.
I photographed this galaxy from my driveway here in Burke County, NC. I used APT for session management and automation. Over two nights, I gathered 105 3 minute exposures. I used a GSO RC8 telescope at 1625mm fl paired with a ZWO ASI071MC Pro cooled to 14f. These ride a Skywatcher EQ6r Pro Equatorial mount. The subframes are manually calibrated, debayered, aligned, integrated, and processed in PixInsight 1.9.3.
