A WISE view of a small neighbor

By Phil Plait | January 4, 2011 7:00 am

What shall be the first astronomical object to grace this blog in 2011*? With a whole sky to choose from, why not use an old friend, but seen in a surprisingly new way? So I present to you the nearby Triangulum Galaxy, M33, as seen by the orbiting far-infrared telescope WISE:

Yeah, that’ll do! Click to galactinate.

M33 is familiar to pretty much any serious amateur astronomer north of the Equator. It’s not that far in the sky from its bigger buddy M31, the Andromeda Galaxy, and in fact isn’t terribly far in space either; Andromeda is about 2.5 million light years away, while M33 is about 3 million. M33 is a spiral galaxy as well, and one of the closest to us.

Andromeda is probably the most well-known galaxy in the sky. So why is M33 so less famous? Mostly because it’s smaller; Andromeda and the Milky Way are roughly the same size (so close, in fact, that astronomers have been arguing for decades over which is the beefier of the two, and the title has swapped back and forth many times), but M33 is only half our size. Also, it’s more face-on to us, spreading its light out, making it actually a somewhat tough object to see. I’ve seen it in binoculars from dark sites, but it’s only marginally brighter than the sky background.

In the WISE image, blue and cyan are from infrared light at 3.4 and 4.6 microns (roughly 5 and 6.5 times the reddest light your eye can see). That comes mostly from stars. Green and red are IR at 12 and 22 microns, much farther in the infrared, and comes from cooler material like interstellar dust, which is opaque to visible light.


Here’s a shot of M33 in visible light. It looks a bit different than in the IR, doesn’t it? The core is bright in visible, but basically gone in the infrared. That’s a clear sign that stars aren’t being born there; they create a lot of dust when they form, and that lights up in the IR.

Interestingly, the overall shape of the galaxy in both images is similar. You can trace the spiral arms easily in both, and the WISE image gives you a pretty clear view of where stars are forming. Those bright spots in the the IR shot look like stars, but are pinkish in the visible image, which marks them as gigantic gas clouds where lots and lots of stars are being made — the pink is from the presence of vast quantities of heated hydrogen gas, which shines brightly in red.

See that really bright red-tinged white blob in the WISE picture on the left, smack dab on a spiral arm? That’s one of my favorite objects in the sky, called NGC 604. Doesn’t look like much, does it? That’s because WISE, while a great observatory, actually sports a rather small mirror: just 40 cm (16 inches) across. It was designed to survey the whole sky, and not see small objects in high resolution. However, we have bigger telescopes like, say, Hubble with its 2.4 meter (8 foot) mirror:

Boom! Yeah, now you can see why I love this object; it’s beautiful, intricate, and amazing. NGC 604 is a vast star-forming factory well over 1500 light years across, much bigger even than our own Orion Nebula (which itself is pretty dang big). NGC 604 is so big and bright that were it located as close as Orion, it would be second only to the Moon as brightest object in our night sky!

One other thing about the WISE picture: it’s pretty big. At about 1.5° on a side, over 11 full Moons could fit in this shot! It would take Hubble weeks to take a picture covering that much sky. I’ll note that WISE has to use a cryogen — frozen hydrogen! — to keep its instruments cold, but the coolant ran out in October. Still, it can take images in the shorter two of the four wavelengths of infrared, so it’s still up there scanning the sky. I was surprised to learn that WISE discovered more than 33,000 asteroids, over 100 of which pass near the Earth! That’s phenomenal.

I don’t know how many more beautiful pictures we’ll see from WISE, but I’m glad it’s still up there doing science and keeping its cold eye open for more potentially threatening asteroids. The more, the better.

Image Credit: WISE: NASA/JPL-Caltech/WISE Team. Visible M33: T.A.Rector (NRAO/AUI/NSF and NOAO/AURA/NSF) and M.Hanna (NOAO/AURA/NSF). NGC 604: NASA and The Hubble Heritage Team (AURA/STScI).



* Not counting the Sun, which I posted yesterday but is 1) an old picture, and b) was not the primary reason for that post.


Related posts:

- A Swiftly UV galaxy
- Galaxy on edge
- Unwind with some spirals
- The first spectacular views of the sky from WISE


CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (16)

  1. Well, I just got a new set of eyepeices for my Celestron, so I think I may have to use this as my first galaxy of 2011 to look at! :) Thanks for the inspiriation!

  2. Messier Tidy Upper

    What shall be the first astronomical object to grace this blog in 2011? With a whole sky to choose from, why not use an old friend, but seen in a surprisingly new way? So I present to you the nearby Triangulum Galaxy, M33

    Good choice! I like it. :-)

    Andromeda is probably the most well-known galaxy in the sky.

    [Pedantic] Not the Milky Way? Or the Magellanic Clouds? If counting the latter, do we count them as collectively one or consider the LMC & SMC separately? [/pedant] ;-)

    I don’t know how many more beautiful pictures we’ll see from WISE, …

    Hopefully plenty more!

    but I’m glad it’s still up there doing science …

    Me too. I love this mission – and I hope it finds a few brown dwarfs incl. maybe one that’s closer than Proxima Centauri perhaps. Any idea on how that search has gone & when we might hear of that yet?

    .. and keeping its cold eye open for more potentially threatening asteroids. The more, the better.

    The more *potentially threatening asteroids* the better!?! Really? :-o

    Good for your book sales perhaps BA, but a bit scary for the rest of us & hazardous to Humanity’s & our planet’s health methinks! ;-)

  3. Messier Tidy Upper

    See :

    http://en.wikipedia.org/wiki/Messier_33

    For more info on M33 also known as the Triangulum galaxy and sometimes the Pinwheel galaxy a moniker it shares with M 101.

    &

    http://stars.astro.illinois.edu/sow/tri-t.html

    For Kaler’s constellation photo-map of Triangulum showing M33 roughly midway betwixt Mirach (Beta Andromedae) and Mothallah. (Alpha Triangulae – see : http://stars.astro.illinois.edu/sow/mothallah.html )

    See that really bright red-tinged white blob in the WISE picture on the left, smack dab on a spiral arm? That’s one of my favorite objects in the sky, called NGC 604.

    I see quite a few red tinged white blobs and several spiral arms. Please could you specify that a bit more? An image with an arrow pointing to it would be really wonderful!

  4. Jamey

    @Messier – Actually, I’d say he’s right. I think more people know of Andromeda than the LMC and GMC. And few really think that much of the Milky Way.

  5. Messier Tidy Upper

    @ ^ Jamey : Could be the case, yeah. Of course, the Magellanic Clouds are a lot more familiar in my hemisphere & part of the globe.

    Only real way is find out is to do a (global?) survey of what non-astronomers can recognise / know about in the skies the results of which may be rather depressing. Hopefully not though but ..

    few really think that much of the Milky Way.

    But, but, its all our homes! Plus pretty impressive in its own right being the second largest in the Local Group too! ;-)

  6. Jon Hanford

    A stunning image image by Rogelio Andreo shows both M 31 and M 33 (at decent resolution) in the same field, centered on the star Mirach (beta Andromedae): http://deepskycolors.com/pics/astro/2010/09/mb_2010-08.9_M31_M33_DWF.jpg

    Look closely at Mirach to find the nearly hidden image of the galaxy NGC 404 (to the left). A very beautiful comparison of two well known galaxies (and galactic cirrus to boot!).

    More detail on this image (in the galaxies section, duh) and his many other astroimages here: http://blog.deepskycolors.com/

  7. andy

    NGC 604 is so big and bright that were it located as close as Orion, it would be second only to the Moon as brightest object in our night sky!

    On the other hand it would presumably be quite an extended source, therefore the actual surface brightness would presumably not be nearly so impressive.

  8. James Harmer

    “hazardous to Humanity’s & our planet’s health methinks!”
    Er, Messier, those asteroids are still out there whether they’re discovered or not. Ignorance is not bliss when one unexpectedly impacts at several Km per second.
    Forewarned is forearmed after all.
    Have a look at http://en.wikipedia.org/wiki/Tunguska_event for eyewitness accounts of the last big one. And remember that Tunguska was actually minor as these things go ….

  9. Sam H

    “I’ll note that WISE has to use a cryogen — frozen hydrogen! — to keep its instruments cold, but the coolant ran out in October.”

    What the dang? Spitzer was launched in 2003 with coolant that lasted fully six years – and it’s a heck of a lot bigger than WISE. Sure, a telescope is not defunct after it’s coolant runs out, but it’s less viable for some types of imaging – Why couldn’t the ESA pack a few more pounds of liquid H2 to create a durable investment?

    Probably a launch vehicle issue…as usual (insert roll of eyes, I dunno the smiley for that :) )

  10. Messier Tidy Upper

    @8. James Harmer : You misunderstand me – I’m saying & hoping those potentially asteroids aren’t there in the first place NOT that WISE (or any other space or ground based observatory misses them if they *are* there! ;-)

    If the Potentially Hazardous Near Earth Asteroids are there then let’s find them ASAP, but I’d rather there were fewer of them than more of them in existence.

    Of course, the population of PHNEA’s varies over time as asteroids fall into and occassionally get ejected out of the inner solar system or disappear via impacting Mars, Earth, Venus and Mercury so constant vigiliance is required.

    @ Sam H. (above) : insert roll of eyes, I dunno the smiley for that.

    : roll : without the spaces gives you the eye-rolling (smiley) emoticon here. :-)

  11. Matt B.

    “What shall be the first astronomical object to grace this blog in 2011*?”

    Aw, you ruined it by not hiding the picture behind the cut. You can’t ask someone to guess and not give them sufficient time to guess. [/Sheldon Cooper]

    Frozen hydrogen? I wasn’t aware anyone had managed to make hydrogen solid. Am I wrong?

  12. Messier Tidy Upper

    @ ^ Matt B. : Well Jupiter has metallic hydrogen in its core & I think we’ve successfully created that and also got down to within a whisker of absolute zero in a lab somewhere (although I could be mistaken) so, yeah, ‘frozen hydrogen’ works for me.

    I do agree a “guess what” with the image hidden and then revealed by clicking for more info or on a box to reveal would have been neater still. ;-)

  13. Aah, the Triangulum galaxy! I still have fond memories from the time back when I visited there. A great place where many adventures await. People over there are also very friendly.

  14. Biff

    Spitzer observed down to longer wavelengths than WISE so would need to be cooled more to be sensitive to that part of the spectrum, requiring liquid He. WISE could get away with liquid H2 which presumably made it all a bit cheaper.

    Not sure if H2 is intrinsically less long lasting than He, or whether it was down to the quantities used and quality of the cryostat ??

    afaik hydrogen remains liquid down to absolute zero and needs pressure to solidify,

  15. don gisselbeck

    M33 was an easy naked eye object from Top Hut on Mt Kenya in Sept 1981.

  16. andy

    afaik hydrogen remains liquid down to absolute zero and needs pressure to solidify,

    Melting point of hydrogen is about 14 K under standard pressure. Now helium on the other hand…

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »