Paul Alsing
September 15th, 2019, 09:20 PM
Object of the Week - ARP 93, COLLIDING GALAXIES NGC 7284 & 7285 in AQUARIUS
R.A.: 22h28m38.0s: Dec.: -24°50'27" (2000)
Size: 2.4'x 1.5'
Magnitude: 11.90 (V); SB 22.5 Mag/arcsec²
Morphology; SB0^0(s) pec (for NGC 7284) SB(rs)a pec (for NGC 7285) - as per NED
Apologies for the late post… I had mistakenly loaded this week into my calendar rather than last week, but Jimi noticed my omission and alerted me, my thanks to Jimi.
Arp 93 is a pair of colliding galaxies in Aquarius, discovered by William Herschel on October 26th, 1785. However, as Dreyer wrote, NGC 7284 is "considerably faint, considerably small, a little extended, mottled but not resolved, double star involved". So, Herschel initially thought of NGC 7284 as a binuclear nebula, supposing the nuclei to be two stars. Later, a note was added to the second Index Catalog indicating "Delete 'double star involved' “. This pair of galaxies are receding at about the same rate, and are both therefore about 210 million light-years distant. Each galaxy has approximately the same diameter as our own Milky Way, roughly 150,000 light-years, so considering that this pair only extends 2.4 arc-minutes across our sky, you just know that Arp 93 is not particularly nearby. Someone observing the Milky Way from a planet in this system might see our galaxy about the same as we see them, but without the 2 cores :)
Since I live in the San Diego, Ca. area, Apr 93 rises only about 33° above my southern horizon at culmination, so it is never going to be any kind of showpiece from here, but nevertheless I was able to discern both galaxy cores and the surrounding halo of nebulosity. Even though it is a small object, it is fairly bright and elongated a little bit. Here is a photo, from the Carnagie-Irvine Galaxy Survey…
3635
Note that NGC 7285 shows a long tidal tail extending about twice the galaxy’s diameter, down to the SSE.
I’m going to go check the rest of my calendar to make sure that there are no other errors there :(
As always, give it a go and let us know.
R.A.: 22h28m38.0s: Dec.: -24°50'27" (2000)
Size: 2.4'x 1.5'
Magnitude: 11.90 (V); SB 22.5 Mag/arcsec²
Morphology; SB0^0(s) pec (for NGC 7284) SB(rs)a pec (for NGC 7285) - as per NED
Apologies for the late post… I had mistakenly loaded this week into my calendar rather than last week, but Jimi noticed my omission and alerted me, my thanks to Jimi.
Arp 93 is a pair of colliding galaxies in Aquarius, discovered by William Herschel on October 26th, 1785. However, as Dreyer wrote, NGC 7284 is "considerably faint, considerably small, a little extended, mottled but not resolved, double star involved". So, Herschel initially thought of NGC 7284 as a binuclear nebula, supposing the nuclei to be two stars. Later, a note was added to the second Index Catalog indicating "Delete 'double star involved' “. This pair of galaxies are receding at about the same rate, and are both therefore about 210 million light-years distant. Each galaxy has approximately the same diameter as our own Milky Way, roughly 150,000 light-years, so considering that this pair only extends 2.4 arc-minutes across our sky, you just know that Arp 93 is not particularly nearby. Someone observing the Milky Way from a planet in this system might see our galaxy about the same as we see them, but without the 2 cores :)
Since I live in the San Diego, Ca. area, Apr 93 rises only about 33° above my southern horizon at culmination, so it is never going to be any kind of showpiece from here, but nevertheless I was able to discern both galaxy cores and the surrounding halo of nebulosity. Even though it is a small object, it is fairly bright and elongated a little bit. Here is a photo, from the Carnagie-Irvine Galaxy Survey…
3635
Note that NGC 7285 shows a long tidal tail extending about twice the galaxy’s diameter, down to the SSE.
I’m going to go check the rest of my calendar to make sure that there are no other errors there :(
As always, give it a go and let us know.