A Double-Scoop of Super Spiral Galaxies in Boötes
Scott Harrington
On the last night of the Texas Star Party (thus May 16th), I drove up with Brent Archinal to visit and hopefully do a little observing with Jimi Lowrey, Steve Gottlieb, Howard Banich, and Akarsh Simha. The night turned out to be a poor one, but even a poor one out in West Texas with a 48-inch still beats a great one back home! We ended up not looking at a lot of objects on any of our lists because of high, thin clouds covering certain parts of the sky, but here are two standouts:
Steve Gottlieb’s pick was LEDA 1713491, but became better known as OGC 1546 for its inclusion in Patrick Ogle’s 2019 Galaxy Catalog of the Most Optically Luminous Galaxies (with a redshift under ~3 billion light-years). To encourage us to vote “yes”, Steve mentioned that it was a face-on “super spiral” galaxy 2 billion light-years away that was currently high overhead in Boötes. Who could resist that!?
Jimi dutifully found it and cranked it up to 697x using a 7mm Takahashi eyepiece. Lying less than 1’ SE of a magnitude +14.8 star, I saw a glow no more than 15” across that contained a faint core at its center. The galaxy spans over 200,000 light-years and in survey images has a remarkably high surface brightness thanks to a large central region and enhanced star-formation in its outer arms.
After observing Steve’s pick of OGC 1546 high up in Boötes, I suggest another super spiral galaxy still in the same constellation. Carrying the designation IC 4479, it was discovered by Stéphane Javelle using the 30-inch f/23 refractor at the Nice Observatory in France. Jimi queued it up and I excitedly scrambled up to the top of the ladder with my chart in hand to take a look after he put “mo power” on it!
At a distance of 650 million light-years, IC 4479 still spans an impressive 81”, yielding a true diameter of 250,000 light-years. But what is even more impressive is that a few short sections of this face-on spiral’s arms are exploding with star formation. I wanted to see if I could claim the feat of having seen the arms of a spiral galaxy two-thirds of a billion light-years away…and I wasn’t disappointed!
With 697x, I could easily make out the galaxy as a 1’-wide disk surrounding a much brighter yet nonstellar core. On the SSE edge of the disk was a short, distinct bar 10”-long while I my eye kept catching sight of an even fainter and shorter (4”) bar on the complete opposite side of the galaxy’s disk. To the SW and well beyond the galaxy’s disk was the edge-on spiral galaxy LEDA 214309. It lies at approximately the same distance as IC 4479 and displayed a dull, 15”-long glow of even surface brightness that got a little wider at the middle.
