This object is a dim 14.3 magnitude disturbed spiral galaxy located almost a half billion light years away in the constellation of Serpens at a declination of +17 degrees. This galaxy spans 1 arc-minutes in our apparent view, which corresponds to an actual diameter of 140,000 light years.

I have imaged many objects but this is the first time that I have seen a galaxy that contains a green color. I see a distinct green oval ring around the bright core. Faint shades of pink are also seen. At first I thought it was an artifact of some sort, but then I researched and found many articles which discusses the extensive gas structure of this galaxy. The gas is primarily doubly ionized Oxygen but also H-alpha. It turns out that this green feature is a rare type of astronomical object called a quasar ionization echo.

The OIII signal appears green in the image instead of its normal teal color due to cosmological redshift. Because of this redshift, our OIII filters are not able to capture the signal.

The Hubble site does the best job of describing this quasar-initiated phenomenon:

“A quasar beam has caused once-invisible filaments in deep space to glow through a process called photoionisation. Oxygen, helium, nitrogen, sulphur and neon in the filaments absorb light from the quasar and slowly re-emit it over many thousands of years. Their unmistakable emerald hue is caused by ionised oxygen, which glows green. These ghostly structures are so far from the galaxy’s heart that it would have taken light from the quasar tens of thousands of years to reach them and light them up. So, although the quasars themselves have turned off, the green clouds will continue to glow for much longer before they too fade.

Not only are the green filaments far from the centers of their host galaxies, they are also immense in size, spanning tens of thousands of light-years. They are thought to be long tails of gas formed during a past merger. The first object of this type was found in 2007 by Dutch schoolteacher Hanny van Arkel in the online Galaxy Zoo project (in galaxy IC 2497). This bizarre feature was dubbed Hanny’s Voorwerp (Dutch for Hanny’s object).”

A team of researchers has found a total of twenty galaxies with voorwerpjes.  My voorwerp galaxy collection is here.