APOD: M74: The Perfect Spiral (2011 Apr 06)

[APOD Robot]

M74: The Perfect Spiral

Explanation: If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe of about 100 billion stars, 32 million light-years away toward the constellation Pisces, M74 presents a gorgeous face-on view. Classified as an Sc galaxy, the grand design of M74's graceful spiral arms are traced by bright blue star clusters and dark cosmic dust lanes. The above image covers half the width of the full Moon and was obtained using 19 hours of exposure on the 1.23-meter telescope at Calar Alto Observatory in the Sierra de Los Filabres mountain range in Spain. Spanning about 30,000 light-years across the face of M74, it includes exposures recording emission from hydrogen atoms, highlighting the reddish glow of the galaxy's large star-forming regions.

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[Ann]

M74 is an extremely lovely spiral galaxy, and this is an extremely lovely picture.

I guess you could almost say that M74 is the flawless "ideal" of a galaxy, the "perfection" of this ideal, manifested in the real world.



This man agrees... I think....

Ann

[mexhunter]

Extraordinary image.
Congratulations to the team who performed: Vicent, José Luis, Steve, Ivette, Oriol, and Juan.
It's a perfect spiral and a perfect team.
Many Greetings
César

[neufer]

I guess you could almost say that M74 is the flawless "ideal" of a galaxy, the "perfection" of this ideal, manifested in the real world.



This man agrees... I think....

Or perhaps this one:

Archimedes(?)

---

[neufer]

[attachment=0]M74_3.6_5.8_8.0_microns_spitzer.jpg[/attachment]

<<Messier 74 (also known as NGC 628) is a face-on spiral galaxy in the constellation Pisces. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a Grand Design Spiral Galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. However, the relatively large angular size of the galaxy and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves.

M74 was discovered by Pierre Méchain in 1780. Méchain then communicated his discovery to Charles Messier, who listed the galaxy in his catalog.

Messier 74 is located 1.5° east-northeast of Eta Piscium. This galaxy has the second lowest surface brightness of all the Messier objects. (M101 has the lowest.) It may be very difficult to see unless the sky is dark and clear, and it may be difficult to see in locations affected by light pollution. This galaxy may be best viewed under low magnification; when highly magnified, the diffuse emission becomes more extended and appears too faint to be seen by many people. Additionally, M74 may be more easily seen when using averted vision when the eyes are fully dark adapted.

Two supernovae have been identified in M74: SN 2002ap and SN 2003gd.

SN 2002ap has attracted considerable attention because it is one of the few Type Ic supernovae (or hypernovae) observed within 10 Mpc in recent years. This supernovae has been used to test theories on the origins of similar Type Ic supernovae at higher distances[10] and theories on the connection between supernovae and gamma ray bursts.[11]

SN 2003gd is a Type II-P supernova. Type II supernovae have known luminosities, so they can be used to accurately measure distances. The distance measured to M74 using SN 2003gd is 9.6 ± 2.8 Mpc, or 31 ± 9 million ly. For comparison, distances measured using the brightest supergiants are 7.7 ± 1.7 Mpc and 9.6 ± 2.2 Mpc. Ben E. K. Sugerman found a "light echo" - a reflection of supernova explosion that appeared after the explosion itself - associated with SN 2003gd. This is one of the few supernovae in which such a reflection has been found. This reflection appears to be from dust in a sheet-like cloud that lies in front of the supernova, and it can be used to determine the composition of the interstellar dust.

M74 is the brightest member of the M74 Group, a group of 5-7 galaxies that also includes the peculiar spiral galaxy NGC 660 and a few irregular galaxies.

On March 22, 2005, it was announced that the Chandra X-ray Observatory had observed an ultraluminous X-ray source (ULX) in M74, radiating more X-ray power than a neutron star in periodic intervals of around two hours. It has an estimated mass of around 10,000 Suns. This is an indicator of an intermediate-mass black hole. This would be a rather uncommon class of black holes, somewhere in between in size of stellar black holes and the massive black holes theorized to reside in the center of many galaxies. Because of this, they are believed to form not from single supernovae, but possibly from a number of lesser stellar black holes in a star cluster. The X-ray source is identified as CXOU J013651.1+154547.>>

[ddale51]

I had no idea there were any galaxies that large relative to the size of the full moon. It's "bigger" than Andromeda, isn't it?

Thanks for including the relative size information. As I've mentioned before, the relative size info on astronomical objects is greatly helpful and I would LOVE to see it included on all such pictures.

[Ann]

I had no idea there were any galaxies that large relative to the size of the full moon. It's "bigger" than Andromeda, isn't it?

Thanks for including the relative size information. As I've mentioned before, the relative size info on astronomical objects is greatly helpful and I would LOVE to see it included on all such pictures.

Andromeda looks much bigger in the sky than M74 for two reasons. It is intrinsically bigger than M74, and it is much closer.

Check out this APOD of the relative size in the sky of the Moon and M31: http://apod.nasa.gov/apod/ap061228.html

The picture, in a smaller version, is here:



Ann

[Ann]

To return to M74, what makes it so graceful is not only its face-on orientation, but also that its two major arms are so regular, that the red HII regions mostly follow the arms, and that the irregularity in the arm above the center in today's APOD doesn't affect the overall shape of the galaxy, but is a local phenomenon. Another thing that adds to the grace of M74 is that its center is so small, and that the elegant spiral structure dominates the galaxy so completely.

Two things should be noted in the Spitzer infrared image of the galaxy that neufer included in its post. First that the importance of the two major arms is played down in the infrared, and the galaxy looks more like a multi-armed spiral than a grand design elegant two-armed spiral. Second, that the blue color in the infrared image, which represents starlight, is hardly seen at all outside the very small galactic bulge of M74. Doesn't this galaxy have stars outside its bulge? Of course it does, and we can see those stars clearly in optical images. But stars that are blue, hot and not very large don't show up in infrared images of galaxies.

Ann

[deathbed rider]

magnificient, but the earthlings cant get there to comb the galaxy for friends,

[MrDon]

I'm not a scientist, just someone who likes APOD and the bits of knowledge i can gain there...so please excuse a very elementary question.

I assume all spiral galaxies don't spiral in the same direction. I understand some are "edge-on" to us, but if Earth was on the other side of M74 it would appear to spiral counter clockwise instead of clockwise.

So like water down a drain on earth which spirals different in Northern or Southern Hemisphere, does the spiral tell Astronomers where this galaxy is in relationship to center of universe?
That is, the galaxies between us and center of universe go one way, and the ones between Earth and outer edge of universe go the other way?

Or is there no correlation and some just go one way and some the other? If so, any theories on why that would be? thanks!

[rstevenson]

I assume all spiral galaxies don't spiral in the same direction.

That's correct.

So like water down a drain on earth which spirals different in Northern or Southern Hemisphere, does the spiral tell Astronomers where this galaxy is in relationship to center of universe?
That is, the galaxies between us and center of universe go one way, and the ones between Earth and outer edge of universe go the other way?

That's not.

The direction of rotation of galaxies is determined by the local (a very big local in the case of galaxies) movement of the gas that formed the galaxy and everything in it originally, and by the effect of various galaxy collisions over the ages since they began to form. There is no center of the universe for us to be closer to or further from in relation to any particular galaxy. How any particular galaxy appears to us is simply coincidental.

Rob

[bystander]

The direction a galaxy is rotating depends entirely on which side you see it from. A galaxy that appears to rotate clockwise would appear to rotate counter-clockwise if you saw it from the other side. For more on the subject see: http://asterisk.apod.com/viewtopic.php?f=8&t=14572 and http://asterisk.apod.com/viewtopic.php?f=30&t=22248

[Brian Sandilands]

Has anyone else printed the Hubble images at home? I downloaded the large image (455 mb tif) of the Pinwheel galaxy and then printed it out in 18" x 12" sections. I now have a 6 feet by 4 feet image on my wall in exquisite detail. Cost was $50!