APOD: Hidden Galaxy IC 342 (2013 Jul 18)

[APOD Robot]

Hidden Galaxy IC 342

Explanation: Similar in size to large, bright spiral galaxies in our neighborhood, IC 342 is a mere 10 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342's light is dimmed by intervening cosmic clouds, this deep telescopic image traces the galaxy's obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

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[conch (say konk)]

Just like Ole Galaxia Nostra--^MILKY WAY^ Bet it has millions of planets!

[Boomer12k]

Wonderful...a pretty galaxy...yellow core...pink star formation...dust lanes....great image!

Click on his name to go to the Sedona Stargazer Observatory. More wonderful images!

THANKS!!

:---[===] *

[Ann]

This is a nice picture, and IC 342 is an interesting galaxy.

Thanks to the fact that IC 342 is very reddened, coupled with the fact that this image has been color-balanced in such a way that only the very bluest stars look blue, we can easily discern the different populations that make up this galaxy. Since IC 342 is a substantial galaxy, similar in size to the Milky Way, we most definitely expect it to have a yellow bulge - and it does.

Photo: ESO

Interestingly, we can see that the inner arms of IC 342 are yellower than the outer arms. The same phenomenon can be seen in spiral galaxy NGC 1232 at left. There is a substantial population of old stars in the inner arms of both IC 342 and NGC 1232.

NGC 1232 has a large number of sharply defined, thin arms. Only large galaxies tend to be so elegantly shaped. NGC 1232 therefore looks larger or at least brighter than IC 342, and it is, too. According to my software, NGC 1232 is twice as bright as IC 342.

Click to view full size image

Photo: Bob Franke

NGC 6946 has more in common with IC 342 than NGC 1232 does. Like IC 342, NGC 6946 has rather broad arms. The arms are typically made of intermediate-aged stars of spectral classes A and F, and therefore they are muted in color rather than bright blue. Red emission nebulae stand out in both galaxies, and small blue patches of very hot blue stars can also be discerned. Interestingly, NGC 6946 is dust-reddened just like IC 342 and is seen through a veil of Milky Way dust, although the dust is thinner than the dust in front of IC 342. Very interestingly, NGC 6946 and IC 342 appear to be about equally bright, similar to the Milky Way.

But NGC 6946 clearly has more star formation than IC 342. There is so much star formation in NGC 6946 and so many supernovae that the entire galaxy is distorted. IC 342, by contrast, appears to be undisturbed by any internal turmoil.

Click to view full size image

Photo: Leonardo Orazi

In some ways, IC 342 is similar to M74. M74 is quite undisturbed, like IC 342. It is also similar in brightness to IC 342. But M74 is more elegantly shaped than IC 342, and it may or may not be intrinsically bluer.

Ann

[Ann]

Boomer12k wrote:
Click on his name to go to the Sedona Stargazer Observatory. More wonderful images!

Absolutely! Check out more wonderful images by Stephen Leshin!

Ann

[rghoeing@buffalo.edu]

Thank you for uncovering this hidden gem!

[neufer]

Click to view full size image

Photo: Leonardo Orazi

In some ways, IC 342 is similar to M74. M74 is quite undisturbed, like IC 342. It is also similar in brightness to IC 342. But M74 is more elegantly shaped than IC 342, and it may or may not be intrinsically bluer.

[b][color=#BF6000]A golden spiral is a logarithmic spiral whose growth factor is φ, the golden ratio. That is, a golden spiral gets wider (or further from its origin) by a factor of φ for every quarter turn it makes. (The constant angle Φ ~ 72.96762º)[/color][/b]

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Barring the Bar these seem to be logarithmic spirals
whose growth factor is ~1.5 < φ.

That is, a tighter spiral than golden that gets wider by a factor of ~1.5 for every quarter turn it makes.
(The constant angle Φ ~ 75.5º)

[Night eyes]

Thank you all, APOD, etc. for all your wonderful information. Viewing this photo takes me back to the library where a book discovery showed pictures of galaxies and the wonders of the universe opened. WOW, a beauty pic!!!!!!!

[deathfleer]

That galaxy, its black core must be spinning anticlockwise, am I right.

[FLPhotoCatcher]

A bit off topic, but I couldn't help but notice that the satellite galaxy in the first picture Ann posted (NGC 1232) looks very much like the Large Magellanic Cloud.

[Ann]

A bit off topic, but I couldn't help but notice that the satellite galaxy in the first picture Ann posted (NGC 1232) looks very much like the Large Magellanic Cloud.

I agree that the satellite galaxy, NGC 1232A, looks quite a bit like the Large Magellanic Cloud. The galaxy is strongly barred, just like LMG, and it has a lot of "blue fluff" flying around the bar. You can see NGC 1232A better
NGC 1232A used to cause astronomers a lot of headache, because its recession velocity appeared to be much larger than the recession velocity of NGC 1232 itself. This would imply that the satellite galaxy wasn't a satellite galaxy at all, but a distant background galaxy. Of course there are several problems with this scenario. NGC 1232A is extremely similar in apparent color to NGC 1232 proper, and its "blue clumps" are almost exactly the same size as the blue clumps of the larger galaxy. Also NGC 1232 is located almost exactly at the end point of a long spiral arm of NGC 1232, suggesting that NGC 1232A had somehow been "torn off" its parent galaxy.

We may compare the appearance of NGC 1232 and NGC 1232A with the appearance of NGC 1309 and a striking but unnamed barred galaxy apparently located close to it. We can see, at a glance, that the strikingly barred blue galaxy to the upper left of NGC 1309 is a background galaxy. First of all, NGC 1309 itself has a lot of star formation and broad thick arms, which suggests that NGC 1309 isn't a very large galaxy. According to my software, NGC 1309 is about equally luminous as the Milky Way, whereas NGC 1232, with its long thin arms, is more than twice as luminous as our own galaxy.

But the barred blue galaxy to the upper left of NGC 1309 has a shape similar to NGC 7479. NGC 7479 is more than twice as luminous as the Milky Way, according to my software. To me, that strongly suggests that the barred galaxy seen in the same field of view as NGC 1309 is big, too, and definitely bigger than NGC 1309 itself. Also the "blue clumps" of the barred galaxy next to NGC 1309 are generally smaller than the blue clumps of NGC 1309. At high magnification, the smaller galaxy looks coarser than NGC 1309. Conclusion: the blue barred galaxy to the upper left of NGC 1309 is a background object, not a satellite galaxy.

But NGC 1232A shows every sign of being a satellite galaxy of NGC 1232. And when I checked my software today, the recession velocity of NGC 1232A is now thought to be very similar to the recession velocity of 1232 itself. Problem solved!

Ann