Starship Asterisk*

Facing NGC 6946

Explanation: From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 20 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation Cepheus. In this sharp telescopic portrait, from the core outward the galaxy's colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century ten confirmed supernovae, the death explosions of massive stars, were discovered in NGC 6946. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy.

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I like today's APOD but I dislike the fact that the picture is so large that I have to post it as an attachment!


At first I didn't recognize NGC 6946 in the APOD, partly because north is not up in the image, which is conventional.


The positions of two past supernova explosions are shown in the Kitt Peak National Observatory image. All ten of the recent supernova explosions are shown in this picture (and now I have to post my second attachment):


My favorite picture of NGC 6946 is actually an infrared one by Hubble:


Beautiful, isn't it?

My own favorite aspect of NGC 6946 is the fantastic super star cluster that it contains. You can see it at upper right n the infrared Hubble image I just posted. Okay, I'll do my third attachment now, why not?

Yu.N.Efremov et al. wrote about the super star cluster in NGC 6946:

The characteristics of ionized and HI gas in the peculiar star/cluster complex in NGC 6946, obtained with the 6-m telescope (BTA) SAO RAS, the Gemini North telescope, and the Westerbork Synthesis Radio Telescope (WSRT), are presented. The complex is unusual as hosting a super star cluster, the most massive known in an apparently non-interacting giant galaxy.

Impressive, NGC 6946! So it is larger than R136 in the Large Magellanic Cloud, then? Or is the LMC defined as interacting (with both the SMC and the Milky Way)? Also the LMC is not a giant galaxy, certainly.


R136, you'e got nothing on the super star cluster in NGC 6946 (maybe?)!


Anyway. The caption said that NGC 6946 is in Cepheus. Well, I don't think so!


Because unless my software is very wrong, NGC 6946 is straddling the border of Cepheus and Cygnus!

Ann

Exciting galaxy! Both a Seyfert and a starburst type, a record number of supernovas, this thing is alive!
I'll add this image from the Gemini Observatory, star births seem to be occurring nearly everywhere you look! (but what causes such activity?)

Ann wrote: ↑Fri Jul 26, 2024 6:02 am Anyway. The caption said that NGC 6946 is in Cepheus. Well, I don't think so!

Because unless my software is very wrong, NGC 6946 is straddling the border of Cepheus and Cygnus!

While the extended galaxy does indeed straddle Cepheus and Cygnus, its photometric center, which is what defines its recognized ICRS coordinates, actually lies in Cygnus. That is the constellation it lies in following conventional nomenclature.

Christian G. wrote: ↑Fri Jul 26, 2024 12:43 pm Exciting galaxy! Both a Seyfert and a starburst type, a record number of supernovas, this thing is alive!
I'll add this image from the Gemini Observatory, star births seem to be occurring nearly everywhere you look!

Click to view full size image

(but what causes such activity?)

What causes such activity?

Good question! What causes the ridiculous activity in isolated galaxy NGC 1313?


NGC 1313 is bursting with star formation in a very weird space dog shape!

Ann

Ah yes, the Catherine Wheel galaxy!

https://www.shutterstock.com/video/clip ... isplay-4th

There does seem to be something interestingly unique about spirals.