obrazell
April 27th, 2025, 08:39 AM
NGC 3166
Sex
R.A. 10h13m45.7s
Dec. +03°25'30" (2000)
Magnitude: 11.50 B
Size: 4.5' x 2.8'
Type S0(a)
This OOTW is the small galaxy group catalogued as LGG 192 in Sextans. The group contains
5 galaxies found in the NGC in NGC 3156, 3165, 3166, 3169 and the much fainter galaxy
UGC 5539. There are going to be a range of challenges when trying to observe this group as
NGC 3169 and 3166 are pretty bright galaxies and should be visible in telescopes of 20cm
aperture. NGC 3166 and NGC 3169 were discovered by William Herschel in December 1783,
whilst it was almost a year later that he discovered NGC 3156, possibly after he switched from
side view to front view with his telescopes to gain more light without having an extra reflection
from the secondary mirror. NGC 3165 is much fainter and was discovered in 1856 by Mitchell
using Lord Rosse’s 72” speculum metal mirror telescope at Birr. The main group containing the
NGC galaxies is quite tight and the whole lot should fit within the field of view of a medium
power (150x) hyperwide (100degree) eyepiece. NGC 3169 and 3166 appear to be a physical pair
and deep images show that the spiral arms of NGC 3169 appear distorted, in many ways I am
surprised this pair did not make either Arp’s catalogue or the VV catalogue. It is classified as
SA(s)a pec. NGC 3169 and NGC 3166 do appear to be strongly interacting from the distortions
in them.
5698
GALEX UV images suggest there is a lot of star formation going on in both NGC 3169
and 3165, and possibly in a circumnuclear ring in NGC 3166. NGC 3165 on the other hand
appears to be a dwarf spiral, possibly of the Magellanic type. NGC 3166 appears to have not
much happening at all, although Hubble images do show some dust lanes. NGC 3169 and 3166
are only about 160 thousand light years apart, if they are at the distance of about 60-65 million
light years. There does however seem to be some discrepancy in the separation with some
sources suggesting it may be as small as 50 thousand light years. In terms of size NGC 3169 is a
bit larger than our Milky Way at about 125 thousand light years across, although it is embedded in a halo
of star streams and patches that would be up to 235 thousand light years across. In comparison
NGC 3166 is about 85000 light years across. Over time the galaxies will merge. There is a superb
amateur image at https://apod.nasa.gov/apod/image/2303/NGC3169LRGBrevFinalcropCDK1000_27Feb2023_2048.jpg.
Hubble also snapped NGC 3169 – see https://www.sci.news/astronomy/hubble-spiral-galaxy-ngc-3169-07411.html#google_vignette.
NGC 3169 is also an active galactic nucleus of a form known as a LINER. This small group appears
to be a sub group of the larger Leo I group of galaxies, which itself is part of the Leo II group, also
known as the Leo cloud.
Visually I don’t expect NGC 3169 and 3166 to be much of a challenge, even for modest telescopes
in the 20cm class. NGC 3165 will be more of a challenge and I suspect that 30cm will be required to
find that. The faintest galaxy in the group, barring the UGC one, NGC 3165 I think may require 40cm+
to see as it was described as faint with the 72” and faint with a modern 17.5”. All four galaxies will fit
in a medium power field with a modern hyperwide eyepiece.
Sex
R.A. 10h13m45.7s
Dec. +03°25'30" (2000)
Magnitude: 11.50 B
Size: 4.5' x 2.8'
Type S0(a)
This OOTW is the small galaxy group catalogued as LGG 192 in Sextans. The group contains
5 galaxies found in the NGC in NGC 3156, 3165, 3166, 3169 and the much fainter galaxy
UGC 5539. There are going to be a range of challenges when trying to observe this group as
NGC 3169 and 3166 are pretty bright galaxies and should be visible in telescopes of 20cm
aperture. NGC 3166 and NGC 3169 were discovered by William Herschel in December 1783,
whilst it was almost a year later that he discovered NGC 3156, possibly after he switched from
side view to front view with his telescopes to gain more light without having an extra reflection
from the secondary mirror. NGC 3165 is much fainter and was discovered in 1856 by Mitchell
using Lord Rosse’s 72” speculum metal mirror telescope at Birr. The main group containing the
NGC galaxies is quite tight and the whole lot should fit within the field of view of a medium
power (150x) hyperwide (100degree) eyepiece. NGC 3169 and 3166 appear to be a physical pair
and deep images show that the spiral arms of NGC 3169 appear distorted, in many ways I am
surprised this pair did not make either Arp’s catalogue or the VV catalogue. It is classified as
SA(s)a pec. NGC 3169 and NGC 3166 do appear to be strongly interacting from the distortions
in them.
5698
GALEX UV images suggest there is a lot of star formation going on in both NGC 3169
and 3165, and possibly in a circumnuclear ring in NGC 3166. NGC 3165 on the other hand
appears to be a dwarf spiral, possibly of the Magellanic type. NGC 3166 appears to have not
much happening at all, although Hubble images do show some dust lanes. NGC 3169 and 3166
are only about 160 thousand light years apart, if they are at the distance of about 60-65 million
light years. There does however seem to be some discrepancy in the separation with some
sources suggesting it may be as small as 50 thousand light years. In terms of size NGC 3169 is a
bit larger than our Milky Way at about 125 thousand light years across, although it is embedded in a halo
of star streams and patches that would be up to 235 thousand light years across. In comparison
NGC 3166 is about 85000 light years across. Over time the galaxies will merge. There is a superb
amateur image at https://apod.nasa.gov/apod/image/2303/NGC3169LRGBrevFinalcropCDK1000_27Feb2023_2048.jpg.
Hubble also snapped NGC 3169 – see https://www.sci.news/astronomy/hubble-spiral-galaxy-ngc-3169-07411.html#google_vignette.
NGC 3169 is also an active galactic nucleus of a form known as a LINER. This small group appears
to be a sub group of the larger Leo I group of galaxies, which itself is part of the Leo II group, also
known as the Leo cloud.
Visually I don’t expect NGC 3169 and 3166 to be much of a challenge, even for modest telescopes
in the 20cm class. NGC 3165 will be more of a challenge and I suspect that 30cm will be required to
find that. The faintest galaxy in the group, barring the UGC one, NGC 3165 I think may require 40cm+
to see as it was described as faint with the 72” and faint with a modern 17.5”. All four galaxies will fit
in a medium power field with a modern hyperwide eyepiece.