APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

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APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by APOD Robot » Fri Dec 26, 2014 5:10 am

Image Cetus Duo M77 and NGC 1055

Explanation: At the top right, large spiral galaxy NGC 1055 joins spiral Messier 77 in this sharp cosmic view toward the aquatic constellation Cetus. The narrowed, dusty appearance of edge-on spiral NGC 1055 contrasts nicely with the face-on view of M77's bright nucleus and spiral arms. Both over 100,000 light-years across, the pair are dominant members of a small galaxy group about 60 million light-years away. At that estimated distance, M77 is one of the most remote objects in Charles Messier's catalog and is separated from fellow island universe NGC 1055 by at least 500,000 light-years. The field of view is about the size of the full Moon on the sky and includes colorful foreground Milky Way stars (with diffraction spikes) along with more distant background galaxies.

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Ann » Fri Dec 26, 2014 6:10 am

The great thing about this picture is that it shows us the proximity of M77 and NGC 1055 in the sky. Are they a real pair? Are they interacting? Their radial velocities are different - compare the data from Simbad database for M77 and NGC 1055. But because they are certainly so relatively close to us, at about the same distance as the Virgo Cluster, their individual proper motion is large compared with their cosmic redshift, and their redshift can't reliably be used to infer the distance to them. They do look like a pair, even though I can't spot any tidal tails or any other obvious signs of interaction. But they are basically the same size, and the apparent distance between them seems quite typical for galaxies that are gravitationally bound to each other.

Both are quite dusty. Both are almost two magnitudes brighter in far infrared than in blue light, and this is indicative of a lot of dust. Dust is often associated with star formation or even with starbursts, which produce a lot of dust. There is no sign of any starburst in either of these galaxies, but an interesting possibility is that they may have undergone starbursts in the moderately recent past due to their interactions. If they have undergone recent starbursts, the hot bright stars have burned out, but the dust they left behind still remains. Of course, in the case of M77, the supermassive black hole in the center may also produce a lot of dust.

The colors of this picture are mostly pale. Certainly the galaxies look pale. The colors of galaxies are always pale, because they are made up of a mixture of stars of many colors. Even so there are color gradients and color differences in most spiral galaxies, and we can see them particularly well if the galaxy is oriented face on, like M77. But the paleness of today's APOD is not wrong, because it underscores the typical muted hues of galaxies.

It is quite startling to see a few very colorful stars in the image. The very blue star is HD 16835 of spectral class F0. It is very much bluer than the Sun, but not nearly as blue as Vega, for example. The yellow-looking star relatively close to M77 is SAO 130073 of spectral class M0, and it is very much more yellow-orange than the Sun.

I'm not sure of the orientation of this picture. In my software, MGC 1055 is located north to northwest of M77 (that is, it is located to the upper right of M77). The blue star near NGC 1055 is located to the left (east) of the more colorless bright star near the same galaxy. The yellowish star near M77 is located to the left (east) of the galaxy in my software.

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Boomer12k » Fri Dec 26, 2014 8:32 am

Wikipedia has them at: M77 around 47 Mly...and NGC1055 around 52 Mly. But maybe the separation is too great for interaction....there could be streams between them, from when they were possibly a tad closer??? There might be a seeming, 500,000 ly distance in the visible view of the photo...but 5 MILLION ly in actual distance between them...so it can be a deceptive view...because the Angle is not taken into consideration.

Any way...very nice shot, and showing the relationship of these galaxies.

Merry Xmas...and on to a Happy New Year!!! :D

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by rwlott » Fri Dec 26, 2014 2:34 pm

I followed the listed link to the April 2010 APOD of NGC 1055 but found that I had to rotate it approximately 80 degrees to the right and then flip it horizontally to make it match the perspective of today's photo. Differences in rotation I can understand, but what accounts for the reversal of the image? Is this a common occurrence?

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by geckzilla » Fri Dec 26, 2014 2:44 pm

rwlott wrote:I followed the listed link to the April 2010 APOD of NGC 1055 but found that I had to rotate it approximately 80 degrees to the right and then flip it horizontally to make it match the perspective of today's photo. Differences in rotation I can understand, but what accounts for the reversal of the image? Is this a common occurrence?
I think mirroring is generally frowned upon but it happens with strangely high frequency. I think it happens by accident sometimes and other times photographers do it because it looks better to them.
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Ron-Astro Pharmacist » Fri Dec 26, 2014 9:45 pm

I received one great present yesterday that would be good for many others who do not already know the night sky well : a celestial globe. Many of the nighttime objects are already imprinted on the inner clear plastic dome but the outside is smooth for use with an appropriate marker to add the other nighttime gems. With the APOD supplying the ammo, I aim to cover it with additional targets for future outside viewing pleasure. Today's two will be a good start. I hope it will really clear my brain where these dusty devils live in the heavens above. Thanks Wife!!
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Jack_Decker63 » Fri Dec 26, 2014 10:37 pm

They're at right angles to each other. How did that or could that happen with them being relatively so close to each other.

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by BDanielMayfield » Sat Dec 27, 2014 1:31 am

Jack_Decker63 wrote:They're at right angles to each other. How did that or could that happen with them being relatively so close to each other.
This orientation is no more unlikely than any other Jack. Conservation of angular momentum of randomly infalling gas and the effects of gravity as galaxies orbit around should be able to produce all kinds of angle combinations.
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by chanio » Sat Dec 27, 2014 3:22 am

I think mirroring is generally frowned upon but it happens with strangely high frequency. I think it happens by accident sometimes and other times photographers do it because it looks better to them.
:idea: Isn't it possible that they are both the same gallaxy? :oops:
Wouldn't it be wonderful? :roll:
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by ta152h0 » Sat Dec 27, 2014 4:50 am

So all the light sources at the face on galaxy arrive here about the same time and all the light coming from the edge on galaxy arrives about 100000 light years apart from the nearest to the farthest source ?
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Chris Peterson » Sat Dec 27, 2014 5:28 am

ta152h0 wrote:So all the light sources at the face on galaxy arrive here about the same time and all the light coming from the edge on galaxy arrives about 100000 light years apart from the nearest to the farthest source ?
100,000 years difference, not light years. Not that this delay is enough to change the appearance of the galaxy significantly from our perspective, given that it probably has a rotation period on the order of 100 million years. Also, the galaxy itself blocks our view of any real structure.
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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by Ann » Sat Dec 27, 2014 5:37 am

Jack_Decker63 wrote:They're at right angles to each other. How did that or could that happen with them being relatively so close to each other.
NGC 5426 and NGC 5427 are even closer to each other. They are not at right angles to each other, but they are definitely differently orientated.

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Re: APOD: Cetus Duo M77 and NGC 1055 (2014 Dec 26)

Post by starsurfer » Sat Dec 27, 2014 3:00 pm

Tidal features associated with NGC 1055 have been reported in the following scientific papers:
http://www.cosmotography.com/images/dmd ... stream.pdf
http://www.aanda.org/articles/aa/full_h ... 1/F18.html

This image by Ken Crawford shows them pretty well. He also has a nice collection of galaxy images with tidal features.

The deep AAO image archive also includes many images of galaxies with faint outer tidal features.