Object of The Week April 16, 2023-UGC 5829 The Spider Galaxy

[Jimi Lowrey]

UGC 5829 AKA Spider Galaxy
VV 794
Leo Minor
RA 10 42 42
DEC +34 27 11
TYPE Dwarf IRR
MAG 13.4V ?
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UGC 5829 is a large low surface galaxy that also has the name of “Spider Galaxy”. I first learned about this object in the late 90’s. I have never known who named this galaxy the spider galaxy but seeing that it has a VV catalog number I would not be surprised if that is who gave it its name . Vorontsov Velyaminov gave many nick names to galaxies in his catalog. If any one knows who named it the “Spider Galaxy”I would really like to know.
UGC 5829
5098

The first time I observed the Spider with my old 25” reflector in the early 2000’s I was shocked at how LSB this galaxy was and also it was hard to get my mind around what was going on with it it looked like a bomb had gone off in it. The big question in my mind even to this day is what happened to this galaxy? It is fairly close at 40MLY but it is not evident as to what has disturbed this galaxy. In the annotate image below by the late Rick Johnson he remarked that the SDSS had marked a bright spot as a galaxy. He like me is suspicious that the knot is a separate galaxy and not a star forming region. I would be interested in your thoughts on this.
Rick Johnson Image
5099

I think more research on the Spider would be in order I would really like to understand what forces are at work to disrupt this large galaxy like this.

Give It A Go
Good Luck And great Viewing

[Clear Skies]

Boris Vorontsov-Vel'yaminov was indeed the one to coin the nickname "Spider":

5100

https://articles.adsabs.harvard.edu/pdf/1977A%26AS...28....1V - page 41 & page 108 for the plates.

Some aperture required to bring out the detail in this happy mess. In my 14" in February 2019 I was able to only make out a NE-SW elongated glow that, without use of averted vision, was at the limit of visibility.

5101 5102 5103

Click here (https://clearskies.eu/csog/downloads/dsfootw2023#16) to download the guide.

[Jimi Lowrey]

Thanks for the information to clear up who named it the Spider. I had a hunch it was VV.

[Steve Gottlieb]

When I first came across the nickname I assumed VV thought the extensions looked like a spider's legs. But that's not the reason. He later explained


"In blue light the patchy main part is bright and is surrounded on one side by a network of short, disordered filaments resembling a torn cobweb (whence the name "The Spider")"

So, perhaps he should have called the galaxy the "Spider's Web"!

I copied this quote from a short paper he published in 1980 ("The Nature of the Peculiar Object VV 794 (https://articles.adsabs.harvard.edu//full/1980SvAL....6..109V/0000109.000.html)") using the Soviet 6-meter telescope. Although the poorly reproduced photograph on the second page shows south down, you can tell it's actually rotated. He concluded the North-South "bar" consisted a number of bright blue HII knots with no evidence of an interacting companion.

VV's summary: "Photographic and spectroscopic observation of the object VV 794 (MCG 6-24-6, "The Spider") with the 6-meter telescope show that the northern, brightest feature of this exceptionally complicated system consists of group of compact H II region, but the H-alpha and H-beta lines in this feature extends outside the HII zones. While there appears to be no evidence for two interacting galaxies, the object also bears very little resemblance to ordinary SB galaxies."

He concluded by calling it a "ruined SB spiral", but didn't speculate on the cause.

[Steve Gottlieb]

I noticed that Igor Karachentsev, who was involved in the late 1970's study, has a preprint last month titled "Distances to 10 nearby galaxies observed with the Hubble space telescope (https://arxiv.org/pdf/2303.05787.pdf)". The distance is given as 8.95 Mpc = 29 million l.y. (TRGB method).

He mentions "UGC 5829, an irregular (Im) galaxy with a very peculiar structure that has gotten the name “spider”. More than half the baryon mass of the galaxy belongs to the gaseous component, which evidently triggers numerous sources of star formation in it...The nearest relatively massive galaxy NGC 3432 with VLocal Group = 578 km/s and D = 9.14 Mpc (Anand et al 2021) is at a projection distance of 3.0° or 470 kpc [1.5 million l.y.]. UGC 5829 is a distinct example of how a distorted peculiar galactic structure can be created, not by an external perturbation, but by strictly internal properties of a galaxy."

[Keith Rivich]

I looked at this galaxy about 10 years ago at TSP. In my 25" I noted that it "was kinda of H shaped of very low SB. Had to sweep the area a few times to see. More resembles a diffuse planetary nebula"