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Object Of The Week December 10, 2017: NGC 1084
NGC 1084, MCG -1-8-7, PGC 10464
SAc, Galaxy in group of galaxies
Constellation: Eridanus
RA: 02 45 59.9
DE: -07 34 43
Mag: 10.73
Size: 3'.1 x 2'.0
The winter sky of course is dominated by the Milky Way, but we are still in astronomical autumn. This means that constellations like Cetus and Eridanus, which contain loads of bright and structured galaxies, are visible right after astronomical dusk ends until almost midnight.
One of these bright and structured galaxies is NGC 1084, right at the border of Cetus and Eridanus but within the borders of Eridanus. It was discovered by William Herschel on 10 January 1785. The Vaucouleurs galaxy type SAc tells us that this galaxy has a small core with not too tightly wound spiral arms and no bar. In fact, this galaxy has multiple arms which are not too well defined.
An image taken from SDSS:
Attachment 2832
and from Hubble:
Attachment 2833
Over the past 50 years, 5 supernovae have been seen in NGC 1084! The galaxy is known for its chaotic star formation which is not confined to the spiral arms. However, it is not classified as a starburst galaxy since star formation has taken place in only small bursts over the part 40 million years. The cause of this star formation is thought to be a merger with a gas rich dwarf.
Several faint galaxies lie to the south south east of NGC 1084, being LEDA 1016283 (m=18.0), LEDA 1015643 (m=16.6) and LEDA 1015393 (m=18.0). These three galaxies, and a few more, are visible in the SDSS image. Make sure to check those out when you observe this galaxy and your telescope is big enough.
However, that is not why Simbad classifies this galaxy as a "galaxy in a group of galaxies". According to Wikipedia the galaxy belongs to a group with NGC 988, NGC 991, NGC 1022, NGC 1035, NGC 1042, NGC 1047, NGC 1052 and NGC 1110. And this group again is associated with the M77 group.
My observation of this galaxy was done on September 20, 2015, and reads
At 320x I see a very impressive galaxy. I see a large oval smudge with a faint stellar nucleus. The galaxy is speckled and motted as if spiral arms are about to pop into view. On one side the edge of the galaxy is dented. I'll revisit this galaxy under even darker skies.
As always,
"Give it a go and let us know!
Good luck and great viewing!"
