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Object of the Week October 15th, 2023 - NGC 7727
NGC 7727
ARP 222
Aquarius
RA: 23h 39m 53.5s
DEC: -12° 17’ 38”
Size: 4.7’ x 3.5’
Mag: 10.6
Class: SAB(s)a pec
(I’m filling in this week for Paul as he and Deb travel with the Lowrey’s for yesterday’s annular eclipse)
Approximately 1 billion years ago, two spiral galaxies close enough to be gravitationally bound to one another began the slow arduous process of merging together. Today, we see the continuation of this process as the wispy, peculiar galaxy NGC7727. Unfortunately, with an estimated 1 billion years to go before its completion, we won’t get to see the final product of their merger.
NGC 7727 was discovered by Sir William Herschel in 1785 using his 18.7” f/13 speculum mirrored telescope. Upon its entry into the NGC/IC in 1885, John Dreyer described NGC 7727 as “pretty bright, pretty large, irregularly round, much brighter in the middle”. Neither Herschel nor Dreyer make mention of the faint, wispy arms first annotated by Robert Burnham Jr. in his infamous trio Burnham’s Celestial Handbook. In Vol. 1 on page 171, Burnham makes mention of the arms as ”…faint outer arms extending to 5’.” And finally, in 1966, Halton Arp designates NGC7727 as Arp 222 in his catalog of Peculiar Galaxies owing in part to the pairs “amorphous arms”.
NGC 7727 is the home to two supermassive blackholes – one from each colliding galaxy. In 2021, a team of astronomers using ESO’s Very Large Telescope (VLT) imaged and collected data on the blackholes themselves and determined that they were approximately 154 million and 6.3 million solar masses respectively. Lying approximately 1600 light-years apart from one another, the two are destined to collide with one another in about 250 million years. When this happens, the impending collision will undoubtedly send out gravitational waves similar to the ones recently detected by our own LIGO. Furthermore, the team determined that NGC7727 now holds the record as the closest pair of supermassive blackholes to us located a mere 89 million light-years away. The previous recordholder, UGC 4211 in Cancer, lies 500 million light-years distant.
Visually, NGC 7727 sits within a circlet of stars (think Pisces) and is visible as a faint, non-descript faint glow in telescopes as small as 5”. To have any hopes of seeing the “amorphous arms”, the observer must really use larger aperture with dark, steady skies. In scopes north of about 15” to 18”, the core will appear as a brighter glow with the galaxy as a whole appearing larger and elongated. In the neighborhood of 20 to 25” scopes, the brighter of the two arms reveals itself as it extends itself off to the east. The core, though very small, appears quite bright. Wider field of views will provide you with a nice view as NGC 7727 pairs nicely with its ~12th magnitude neighbor NGC7724 off to the northwest.
Although a bit of a challenge, NGC 7727 makes for a great OOTW. It offers a few of the attributes we look for when selecting an object. It’s visually appealing, albeit in larger telescopes, and it offers a wonderful mental exercise when contemplating what’s going on. Here we have 2 galaxies that began their cosmic dance more than a billion years ago and will continue to do so, for another billion. And now, we know there are two supermassive blackholes that one day will collide and morph into one monster more than 250 million years into the future! And all of this happening in our, relatively speaking of course, cosmic backyard at only 89MLy. Amazing.
So if you manage to get out this dark moon period, please give NGC 7727 a chance. Hopefully you’ll be impressed with all that this cosmic trainwreck has to offer. Both visually and mentally.
And as always, give it a go and let us know!
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