Starship Asterisk*

The Hydrogen Clouds of M33

Explanation: Gorgeous spiral galaxy M33 seems to have more than its fair share of glowing hydrogen gas. A prominent member of the local group of galaxies, M33 is also known as the Triangulum Galaxy and lies about 3 million light-years distant. The galaxy's inner 30,000 light-years or so are shown in this telescopic portrait that enhances its reddish ionized hydrogen clouds or HII regions. Sprawling along loose spiral arms that wind toward the core, M33's giant HII regions are some of the largest known stellar nurseries, sites of the formation of short-lived but very massive stars. Intense ultraviolet radiation from the luminous, massive stars ionizes the surrounding hydrogen gas and ultimately produces the characteristic red glow. To enhance this image, broadband data was used to produce a color view of the galaxy and combined with narrowband data recorded through a hydrogen-alpha filter. That filter transmits the light of the strongest visible hydrogen emission line.

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This is the second time in less than a month that we see a picture of M33. I like it! The September 17 APOD was an ordinary RGB image, whereas today's picture enhances the Ha emission of this starforming galaxy.

In a way the September 17 picture is a little bit "truer" when it comes to the galaxy's overall appearance, but today's APOD highlights the Ha emission that is certainly there in M33. Besides, all these pink splotches against a mostly blue background make for a really pretty picture!

Ann

Awesome... I wonder what they name THEIR nebula.....

:---[===] *

Amazing image! As well as Ha, a lot of the nebulae have OIII.

Ann wrote:This is the second time in less than a month that we see a picture of M33. I like it! [url=http://apod.nasa.gov/apod/ap160917.html]
Ann

Hmmm ... if it had been in the same calendar month, I suppose it would be a "blue APOD"?

M33 is a friendly little neighbor of our Galaxy, and is very small in comparison with our nice big Galaxy. Small, but trim and neat. I always like looking at it! I wonder if there is anyone in M33 looking at US?

heehaw wrote:
M33 is a friendly little neighbor of our Galaxy, and is very small in comparison with our nice big Galaxy. Small, but trim and neat. I always like looking at it! I wonder if there is anyone in M33 looking at US?

heehaw wrote: M33 is a friendly little neighbor of our Galaxy, and is very small in comparison with our nice big Galaxy. Small, but trim and neat. I always like looking at it! I wonder if there is anyone in M33 looking at US?

neufer wrote:M('31) dir. Fritz Lang

I guess that's appropriate, as the movie ends with the line:
"One has to keep closer watch over the children ... All of you."

At the vast distance to the Triangulum Galaxy there will presumably be no noticeable visual change in a view from Earth for a very long time. According to information in Danilo Pivato's website the image is a remake of one taken "2008.08.31 (L) - 2009.08.21 (Ha)" so a more recent view will therefore likely be the same, but I do still wonder if there has been any change?

PS. It's a lovely image .

Many thanks to everyone who appreciated the pictures of M33!
Best regards,

Danilo Pivato
http://www.danilopivato.com

DavidLeodis wrote:At the vast distance to the Triangulum Galaxy there will presumably be no noticeable visual change in a view from Earth for a very long time. According to information in Danilo Pivato's website the image is a remake of one taken "2008.08.31 (L) - 2009.08.21 (Ha)" so a more recent view will therefore likely be the same, but I do still wonder if there has been any change?

We can do a little back-of-the-envelope analysis. The resolution of the original data here appears to be about 0.6 arcsec/pix. It's quite possible to determine the center of a star to about a tenth of a pixel. Let's say to around 0.1 arcsec. Taking the galaxy to be 2.5 million ly away, and its contents having a typical orbital speed of 200 km/s, we might just detect gross structural change in a pair of images taken 2000 years apart.

Of course, there might be some fine structure- stellar jets, a supernova remnant, an ejected star- going fast enough to observe over a much shorter period. But I imagine we're still talking many years.

Chris Peterson wrote:

DavidLeodis wrote:At the vast distance to the Triangulum Galaxy there will presumably be no noticeable visual change in a view from Earth for a very long time. According to information in Danilo Pivato's website the image is a remake of one taken "2008.08.31 (L) - 2009.08.21 (Ha)" so a more recent view will therefore likely be the same, but I do still wonder if there has been any change?

We can do a little back-of-the-envelope analysis. The resolution of the original data here appears to be about 0.6 arcsec/pix. It's quite possible to determine the center of a star to about a tenth of a pixel. Let's say to around 0.1 arcsec. Taking the galaxy to be 2.5 million ly away, and its contents having a typical orbital speed of 200 km/s, we might just detect gross structural change in a pair of images taken 2000 years apart.

Of course, there might be some fine structure- stellar jets, a supernova remnant, an ejected star- going fast enough to observe over a much shorter period. But I imagine we're still talking many years.

Thanks Chris for your help and interesting information .