APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

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APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby APOD Robot » Wed Jul 12, 2017 4:07 am

Image Messier 63: The Sunflower Galaxy

Explanation: A bright spiral galaxy of the northern sky, Messier 63 is about 25 million light-years distant in the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across. That's about the size of our own Milky Way Galaxy. Known by the popular moniker, The Sunflower Galaxy, M63 sports a bright yellowish core in this sharp composite image from space- and ground-based telescopes. Its sweeping blue spiral arms are streaked with cosmic dust lanes and dotted with pink star forming regions. A dominant member of a known galaxy group, M63 has faint, extended features that are likely star streams from tidally disrupted satellite galaxies. M63 shines across the electromagnetic spectrum and is thought to have undergone bursts of intense star formation.

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Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby Boomer12k » Wed Jul 12, 2017 5:49 am

Merger after merger... and not quite settled yet...

Me sad, Ugh... telescope no work...hide in cave.
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Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby Ann » Wed Jul 12, 2017 7:51 am

M63. Photo: Ruben Kier.
Andromeda galaxy. Stock image.



















I've always thought that M63 looks kind of small. Just compare it with the appearance of the Andromeda galaxy. Of course, Andromeda is big, really big.

But according to my software, Guide, M63 is kind of big. Its luminosity is said to be 1.9 times that of the Milky Way.

M63 in infrared light, showing its dust in red.
Photo: NASA/JPL-Caltech/Spitzer Space Telescope.
M104, the Sombrero Galaxy, in visible and infrared light.
Credit: R. Kennicutt (Steward Obs.) et al., SSC, JPL, Caltech, NASA
















M63 is a dusty galaxy. The Spitzer Space Telescope infrared picture of M63 shows its dust in red. Compare the amount of dust in M63 with the amount in dust in M14, the Sombrero Galaxy. Admittedly the two images weren't taken in the same way and are not directly comparable - but they are comparable enough, if you ask me.

Let's return to the size of M63. Today's APOD shows huge, faint, extended features of the galaxy. These extended features are very nicely spiral-shaped, so I don't see why they shouldn't be considered to be spiral arms. I haven't been able to find a small version of today's APOD, so I can't post it here, but do go back to the APOD and look at it.

APOD Robot wrote:
Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across. That's about the size of our own Milky Way Galaxy.


If M63 is nearly 100,000 light-years across, does that include the outer, extended, faint spiral arms? Or are we just talking about the bright inner disk?

Because if the bright inner disk is 100,000 light-years across, how big is M63 if we include the faint outer features?

M94. Photo: Leonardo Orazi.
M63 is fairly isolated in the sky. The only galaxy that I can spot relatively nearby in the sky is M94. The respective recessional velocities of M63 and M94 are relatively similar, although M63 does recede a bit faster. My software, Guide, says that the distance to M63 is 29 million light-years, while the distance to M94 is 23 million light-years. That's not a big difference. However, the picture of M94 was the APOD of May 26, 2015, and APOD Robot wrote:

M94, pictured here spans about 30,000 light years, lies about 15 million light years away(...)


What a difference! M94 is only 15 light-years away, and it is only 30,000 light-years across - and that is really tiny for a spiral galaxy! (Particularly since M94 also has extended outer features, as you can see from Leonardo Orazi's picture.) But M63 is 25 million light-years away and 100,000 light-years across! Surely that large size must include the outer features of M63?

Ann
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RocketRon

Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby RocketRon » Wed Jul 12, 2017 11:41 am

viewtopic.php?t=21076


APOD Robot wrote:in the loyal constellation


"loyal" ???

In what sense is that word used ?

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Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby Ann » Wed Jul 12, 2017 11:52 am

RocketRon wrote:http://asterisk.apod.com/viewtopic.php?t=21076


APOD Robot wrote:in the loyal constellation


"loyal" ???

In what sense is that word used ?


M63 is in the constellation Canes Venatici, the hunting dogs. The "loyal" thing is a joke.

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Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby Case » Wed Jul 12, 2017 12:27 pm

Ann wrote:If M63 is nearly 100,000 light-years across, does that include the outer, extended, faint spiral arms? Or are we just talking about the bright inner disk? Because if the bright inner disk is 100,000 light-years across, how big is M63 if we include the faint outer features?
M63 is fairly isolated in the sky. The only galaxy that I can spot relatively nearby in the sky is M94. The respective recessional velocities of M63 and M94 are relatively similar, although M63 does recede a bit faster. My software, Guide, says that the distance to M63 is 29 million light-years, while the distance to M94 is 23 million light-years. That's not a big difference. However, the picture of M94 was the APOD of May 26, 2015, and APOD Robot wrote: M94, pictured here spans about 30,000 light years, lies about 15 million light years away(...)
What a difference! M94 is only 15 light-years away, and it is only 30,000 light-years across - and that is really tiny for a spiral galaxy! (Particularly since M94 also has extended outer features, as you can see from Leonardo Orazi's picture.) But M63 is 25 million light-years away and 100,000 light-years across! Surely that large size must include the outer features of M63?

Image
Taking the distances from Wikipedia, 27 Mly and 16 Mly, and scaling the two images to the same scale, we may get a better comparison side by side. The problems seems to be what one defines as the edge of a galaxy, where the star density fades out at the outer rim. The scale is from base images in SDSS, on which the prettier images were overlaid. From the base images we know what 10 arcmins is in the image, and that can be translated to a width at the presumed distance. From that, the width in pixels can be reconstructed for 100,000 ly in one image and 30,000 ly in the other.

gendler

Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby gendler » Wed Jul 12, 2017 12:32 pm

Regarding M63's outer faint structure....these are not faint spiral arms but rather stellar streams left in the wake of an interaction with a passing dwarf galaxy in the remote past. See Jay GaBany's seminal image and explanation. http://www.cosmotography.com/images/small_ngc5055.html

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Postby neufer » Wed Jul 12, 2017 2:31 pm

Ann wrote:
RocketRon wrote:
APOD Robot wrote:
in the loyal constellation

"loyal" ??? In what sense is that word used ?

M63 is in the constellation Canes Venatici, the hunting dogs. The "loyal" thing is a joke.
https://en.wikipedia.org/wiki/Canes_Venatici wrote:
<<The stars of Canes Venatici are not bright. In classical times, they were listed by Ptolemy as unfigured stars below the constellation Ursa Major in his star catalogue.

In medieval times, the identification of these stars with the dogs of Boötes (literally, "ox-driver"; from βοῦς bous “cow”) arose through a mistranslation. Some of Boötes's stars were traditionally described as representing the club (Greek, Κολλοροβος) of Boötes. When the Greek astronomer Ptolemy's Almagest was translated from Greek to Arabic, the translator Hunayn ibn Ishaq did not know the Greek word and rendered it as the nearest-looking Arabic word, writing العصا ذات الكلاب in ordinary unvowelled Arabic text "al-`aşā dhāt al-kullāb", which means "the spearshaft having a hook". When the Arabic text was later translated into Latin, the translator Gerard of Cremona mistook the Arabic word كلاب for kilāb (the plural of كلب kalb), meaning "dogs", writing hastile habens canes ("spearshaft having dogs"). In 1533, the German astronomer Peter Apian depicted Boötes as having two dogs with him.

These spurious dogs floated about the astronomical literature until Hevelius decided to specify their presence in the sky by making them a separate constellation in 1687. Hevelius chose the name Asterion (from the Greek 'αστέριον, meaning the "little star", the diminutive of 'αστηρ the "star", or adjective meaning "starry") for the northern dog and Chara (from the Greek χαρά, meaning "joy") for the southern dog, as Canes Venatici, the Hunting Dogs, in his star atlas. In his star catalogue, the Czech astronomer Bečvář assigned the names Asterion to β CVn and Chara to α CVn.>>
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Re: APOD: Messier 63: The Sunflower Galaxy (2017 Jul 12)

Postby Ann » Wed Jul 12, 2017 8:29 pm

Case wrote:
Ann wrote:If M63 is nearly 100,000 light-years across, does that include the outer, extended, faint spiral arms? Or are we just talking about the bright inner disk? Because if the bright inner disk is 100,000 light-years across, how big is M63 if we include the faint outer features?
M63 is fairly isolated in the sky. The only galaxy that I can spot relatively nearby in the sky is M94. The respective recessional velocities of M63 and M94 are relatively similar, although M63 does recede a bit faster. My software, Guide, says that the distance to M63 is 29 million light-years, while the distance to M94 is 23 million light-years. That's not a big difference. However, the picture of M94 was the APOD of May 26, 2015, and APOD Robot wrote: M94, pictured here spans about 30,000 light years, lies about 15 million light years away(...)
What a difference! M94 is only 15 light-years away, and it is only 30,000 light-years across - and that is really tiny for a spiral galaxy! (Particularly since M94 also has extended outer features, as you can see from Leonardo Orazi's picture.) But M63 is 25 million light-years away and 100,000 light-years across! Surely that large size must include the outer features of M63?

Image
Taking the distances from Wikipedia, 27 Mly and 16 Mly, and scaling the two images to the same scale, we may get a better comparison side by side. The problems seems to be what one defines as the edge of a galaxy, where the star density fades out at the outer rim. The scale is from base images in SDSS, on which the prettier images were overlaid. From the base images we know what 10 arcmins is in the image, and that can be translated to a width at the presumed distance. From that, the width in pixels can be reconstructed for 100,000 ly in one image and 30,000 ly in the other.


Thanks a lot, Case! So M63 isn't 100,000 light-years across unless we count the outer features, and M94 is indeed more than 30,000 light-years across if we count the outer features - and why shouldn't we?

The two galaxies really look like they are more or less the same size, some 50,000 to 60,000 light-years across.

Ann
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