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View Full Version : Object Of The Week September 29, 2019 - NGC 7469 and Arp 298



wvreeven
October 4th, 2019, 12:02 PM
NGC 7469, Arp 298

Seyfert 1 galaxy

Constellation: Pegasus

RA: 23 03 15.674
DEC: +08 52 25.28

Visual magnitude: 12.34
Dimensions: 1.38' x 1.15'

NGC 7469 is an annular Seyfert 1 galaxy and, together with IC 5283, forms Arp 298. Some background on Seyfert galaxies can be found in an earlier OOTW article of mine (http://www.deepskyforum.com/showthread.php?1137-Object-Of-The-Week-March-10-2018-NGC-3147) and also Halton Arp and his catalog were discussed on this forum before (sorry for not being able to find a link to this discussion).

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Hubble Space Telescope image of the Arp 298 system

NGC 7469 was discovered by William Herschel on November 12, 1784. In 1943 this galaxy was one of the six listed by Carl Seyfert to have broad emission lines in their nucleus. Because of the AGN nature of the nucleus, several studies have found variability in optical emission but also UV and X-ray. Apart from that, this galaxy has a striking circumnuclear starburst ring. This ring, together with the Seyfert nucleus, made this galaxy one of the key targets for studying their relation. Finally, the interaction with IC 5283 probably is the cause of the starburst activity in NGC 7469 and the tidal tail of IC 5283.

Visually NGC 7469 is not very difficult due to the relatively bright nucleus but the galaxy contains several details that are much harder to see. The smallest aperture reported at DeepSkyLog (http://deepskylog.org) is 8” or 20 cm but due to the compactness of the galaxy and its relatively high brightness I'd expect it to be visible in 6” or 15 cm telescopes and possibly a bit smaller.

My own notes with my 20” telescope from an SQM 21.0 sky read:

“At 320x I see a bright center with a faint star on one side. Around the center I see an oval and I think I sometimes see two dark spots indicating that the oval actually is a ring. No sign of the outer ring. At higher magnifications the faint star becomes better visible but I don't see the dark spots anymore.”

Interestingly I do not mention IC 5283 which probably means that I didn't know of the Arp nature of the duo at the time of my observation. I will revisit this pair from a darker location some time (hopefully) soon.

As always,

"Give it a go and let us know!
Good luck and great viewing!"

Ivan Maly
October 4th, 2019, 11:46 PM
I have this from 2012 (D = 16 in, Pentax oculars, m21.7/sq arcsec site, elev. 700 m):

"NGC 7469 (H III.230, not in the Herschel 400) is immediately visible and elongated at 45x. At 225x, the elongation is less conspicuous and the halo seems diminished. Bright starlike nucleus. Diffuse and similarly elongated IC 5283 nearby. ~100 Mly. The pair is Arp 298. At 225x, when the IC becomes visible, the two galaxies are almost the same size. There is no concentration in the IC. Thin moon crescent (~2 days before new) on the opposite horizon just clearing the trees."

Clearly there is much more to see there. Tonight's run however is off due to the latest forecast update, and this is probably it for this dark of the moon.

Uwe Glahn
October 12th, 2019, 07:09 AM
Wonderful pair Wouter. Especially the fainter IC galaxy shows some structure because of their dark bands inside.

sketch: 27", 419x-586x, NELM 7m0+, Seeing IV
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