Hub of beauty

By Phil Plait | November 10, 2009 11:03 am

When Galileo first turned his telescope to the sky, almost exactly 400 years ago, he could not possibly have known what he was starting.

Today, four centuries later, we’ve come a long, long way. To celebrate the anniversary of Galileo’s telescopic revolution, NASA’s Great Observatories — Hubble, Spitzer, and Chandra — have released a jaw-dropping mosaic of the very heart of the Milky Way galaxy. Behold!

hst_spitzer_chandra_mw

[Oh yes, you want to click to embiggen that-- what I show here is a very compressed version. Or you can go here for a massive copy. You can also get wallpaper versions here.]

This image is nothing less than a heroic effort of astronomical artistry. It’s a chunk of the sky 38 x 14 arcminutes across, or about half the size of the full Moon, and it’s aimed right into the core of our galaxy. See the bright spot just to the right of the center? Buried in there behind light years of dust and gas is the monster of the Milky Way, a black hole with four million times the mass of the Sun. But even that is dwarfed by the 400 billion solar mass heft of the entire galaxy.

hst_spitzer_chandra_mw2There is so much going on in this image it’s hard to know where to start. But first… the Hubble images are in the near-infrared, with a wavelength a little more than twice what the eye can see (1.87 microns for those playing at home). That’s represented in the image as yellow. Spitzer contributed observations in four infrared wavelengths (3.6, 4.5, 5.8, and 8.0 microns), and those are depicted in red. Chandra sees X-rays which are normally written as units of energy, but to remain consistent with the other two images, they were at wavelengths of 0.0005, 0.00025, and 0.00016 microns, and are shown in blue.

What does all this mean? Different objects emit light at different characteristic wavelengths. Warm dust, for example, emits strongly in the infrared. Stars and warm gas emit visible and near-infrared light. Violently heated gas, affected by huge magnetic fields or shocked by colossal collisions glows in X-rays. So this image is a polychromatic view of the crowded downtown region of a bustling city: our galaxy.

You might want to look at an annotated version of this image so you can get your bearings. It’s worth it!

The huge arches of gas on the left are actually the edges of gigantic molecular clouds (dense nebulae where stars are born), lit up by the torrential blast of light from a clutch of massive stars nearby. This clot of stars, called the Arches Cluster due to the arcs it excites, can be seen as a small spot glowing blue just to the left of center in the picture. Don’t be deceived by its diminutive appearance: the Arches cluster has thousands of superstars in it, each dwarfing our Sun, and each capable of sleeting out vast amounts of radiation that lights up the gas surrounding it. Were this cluster much closer than its 25,000+ light year distance, it would blaze in our sky like a beacon. Replace the Sun in our solar system with just one of those stars, and the Earth would be fried beyond the capability of any life to survive. You might as well try living in the flame of an arc-welder.

hst_spitzer_chandra_mwann

Below and just to the left of the Arches is a clumpier, more twisted arc of gas called the Sickle. That’s a giant cavity being carved out of dense gas by the Quintuplet cluster, the pinkish glow in its center. It’s another nursery of stars like the Arches cluster, which is also blasting out light and stellar winds which eat away at the gas enveloping it. The Pistol Star resides there, perhaps one of the most massive stars in the Milky Way.

And there’s more! The blue glow on the left is from an X-ray binary called 1E1743.1-2834, what is probably a massive star being orbited by either a neutron star or a black hole. Matter is being stripped from the star and piling up outside the collapsed companion, where it gets heated up to millions of degrees and emits X-rays.

Supernovae remnants dot the image, as do stars, filaments of gas, clouds of dust, and more. This picture is an astronomer’s dream, a map of everything someone might want to visit with a starship — as long as the shields are at full strength. This image is also a map of violence, turbulence, and unrest… a typical scene, so we think, of any normal spiral galaxy like ours. And our Galaxy’s center is considered quiet by astronomers! Some are far worse.

But this is home for us. It’s a place of unimaginable fury but also astonishing beauty… and we see it now as we do because we have dared to examine the world around us, to use tools we invent to peer closer, to magnify the tiny, to extend our eyes into realms we once didn’t even know existed. And every time we do — every single time — we find more questions, more puzzles, more things to examine.

And we find art. Galileo wasn’t the first to turn his telescope to the sky, nor was he the first to record what he saw. But he was the one who made everyone see what he did, and for that, all these years later, he is owed a debt of gratitude.

CATEGORIZED UNDER: Astronomy, NASA, Pretty pictures

Comments (46)

  1. New desktop! :D

    That is just stunning beyond words, yet somehow you do find them!

  2. Cool.

    Now, take a series of these images over the course of several years, and see what else we can learn. (Like they did with the stars orbiting the galaxy’s center.)

    Larian, check NASA’s APOD site in a few days. Images like these usually end up there a few days after Phil posts them here.

  3. I know Ken. :) I just like giving credit to Dr. Plait (mancrush and all).

  4. Stephen P

    Just bought a new 22-inch monitor a few days ago, and was looking around for a new desktop. I thought it probably wouldn’t take you long …

  5. TMb

    Wow. Wow wow wow.

    I love how you can see the X-ray gas filling in the cavities in the dust. And how the near-IR emission rims what you see in the IRAC bands. It’s amazing how much more complete a picture you get than from looking at any one wavelength individually.

  6. FC

    At that resolution a picture every few years would likely remain the same unless a supernova occurred suddenly.

  7. DrFlimmer

    My desktop looks rather coloured, now ;) My previous picture was an all-sky-map… rather dark compared to this one.

    To say in one word, what this is:

    beautiful, magnificent, extraordinary, unbelievable, astonishing, breath-taking, overwhelming

    Just great! Like your description, Phil!

  8. Mooselet

    Wow… just wow.

  9. tripencrypt

    Sweet! And by sweet I mean totally cool ;)

  10. coolstar

    Gotta say i’m pretty underwhelmed (more so because of all the pre-release hype): aesthetically, this doesn’t really compare to lots of other images I’ve seen from the Great Observatories, or lots of ground-based images by amateurs. (and we have the 6×3 foot mural of this too, also underwhelming.). NASA’s PR department, even after decades, still just doesn’t quite get it.

  11. navyboyct99

    This is brilliant, I love it

  12. I know I am being tangential kinda here. But this has been bothering me for quite a while now:

    We are located towards the outer edges of (one of the arms of) Milky Way here, right? And when we look towards the center of the galaxy, we see the bright center of the galaxy somewhat obscured by enormous dust clouds, right? So we cannot observe what is beyond Milky Way in that part of the sky. And strong radio sources within our galaxy hinder exploration of that region with radio telescopes as well. So, we will not figure out what is there in that region for at least next few millenia until we revolve around the center of the galaxy enough to bring that region to our view. I mean, there may be one or more nearby galaxies (even within local group) and we don’t know it, right?

    Or am I being a simpleton, here?

  13. Chris A.

    @coolstar (14):
    Although I find this image very pretty, I can see your point. After the first “Great Observatories Multi-Spectral Release” earlier this year (of M101), I found myself wondering why they decided to compress the wavelength information in each image down to a single color (in this case, Chandra seems to have gotten blue and purple, however). In effect, each of the Great Observatories’ data became monochromatic. Why not assign a _band_ of color within the visible spectrum to each? I would have thought that that would make a much prettier picture.

  14. Len

    Nice.

    How would this image look in the visible spectrum, or would you see much of anything?

    Oh, in the annotated image it gives a scale bar showing 50 light years. How does this apply to this image which has objects at depth, its confusing me more than anything :)

  15. gaiainc

    I showed my MA. She said, “Wow! Pretty!”. ‘Nuff said.

  16. I'd rather be fishin'

    I just replaced the desktop of Saturn with this one. “WOW!!!” just doesn’t seem to do the photo and the science justice.

  17. csneil

    Phil, I love the pics you post… but it’s your boundless enthusiasm for the beauty of the universe that keeps me coming back to your blog. You’re awesome. Thank you for sharing your joy with us!

  18. Spectroscope

    Superb. Beyond superlatives. Wow. :-D

    This is a snapshot of our Galaxy’s core 25,000 years ago for that’s about how long it takes light (& other forms of electromagnetic radiation) to travel from there to our eyes here on Earth.

    I wonder what its like now & whether the gas has shifted and any of the stars blown up?

  19. Spectroscope

    There’s also the Peony nebula star and Eta Carinae to consider on the list of our Galaxy’s most massive, super-luminous and galactic “heavyweight” stars. See : http://en.wikipedia.org/wiki/Peony_nebula_star for more.

    (Pretty sure Wikipedia is fairly good and reliable here.)

    @ 16. mastmaker Says:

    I know I am being tangential kinda here. But this has been bothering me for quite a while now:

    We are located towards the outer edges of (one of the arms of) Milky Way here, right? And when we look towards the center of the galaxy, we see the bright center of the galaxy somewhat obscured by enormous dust clouds, right? So we cannot observe what is beyond Milky Way in that part of the sky. And strong radio sources within our galaxy hinder exploration of that region with radio telescopes as well. So, we will not figure out what is there in that region for at least next few millenia until we revolve around the center of the galaxy enough to bring that region to our view. I mean, there may be one or more nearby galaxies (even within local group) and we don’t know it, right? Or am I being a simpleton, here?

    No, you are not being a “simpleton” at all – good questions and comments there. I’ll run thro’ them quickly as I understand them:

    We are located towards the outer edges of (one of the arms of) Milky Way here, right?

    Yep. About two thirds of the way out from the centre or 25-30,000 light years~ish in the Orion spur if memory serves. (Exact figures may vary from source to source, I think.)

    And when we look towards the center of the galaxy, we see the bright center of the galaxy somewhat obscured by enormous dust clouds, right? So we cannot observe what is beyond Milky Way in that part of the sky. And strong radio sources within our galaxy hinder exploration of that region with radio telescopes as well. So, we will not figure out what is there in that region for at least next few millenia until we revolve around the center of the galaxy enough to bring that region to our view.

    Yes, the heart of the Milky Way is, indeed, obscured by dust at some wavelengths – esp. visible and radio. UV, X & Gamma rays can pass right through – I think but might be wrong there.

    I mean, there may be one or more nearby galaxies (even within local group) and we don’t know it, right?

    Yes but we are finding more and more of these hidden dwarfs all the time. The Saggitarius dwarf elliptical* was detected even despite the obstacles along with a number of others** and I think we’ll probably still find more.

    * See http://en.wikipedia.org/wiki/Sagittarius_Dwarf_Elliptical_Galaxy

    ** For example, the Canis Major dwarf galaxy see : http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy

    @ 14 Coolstar :

    Gotta say i’m pretty underwhelmed (more so because of all the pre-release hype): aesthetically, this doesn’t really compare to lots of other images . NASA’s PR department, even after decades, still just doesn’t quite get it.

    I disagree with you on both counts there. You’re really not impressed with this panorama? Well, whatever floats your boat, mate but it sure impresses me. I find your comment there a bit sad really & I’m not sure I get whatever point it is you think you’re making with it.

  20. ausduck

    I am overcome by teh awesome!
    I love the colours from the different wavelengths. And Phil: thank you for your enthusiasm, not only by sharing the images but also the enthusiasm in which your explanations are imparted.

    I has a new desktop background :)

  21. Nigel Depledge
  22. Nigel Depledge

    Chris A (17) said:

    Why not assign a _band_ of color within the visible spectrum to each? I would have thought that that would make a much prettier picture.

    Because that is more likely to obscure detail than to illuminate it.

    Let me explain:

    Our visual system operates with only three peaks of wavelength-sensitivity. These wavelengths correspond to the colours we call red, green and blue, but in fact red and green are much closer to one another in wavelength than either is to blue. Where a photon has a wavelength that is between the peaks, it activates both photoreceptor types (actually, a single photon cannot activate your colour-sensitive cone cells, which is why we lose colour vision at low light levels, but consider a stream of photons instead) and we perceive an intermediate colour. This is the rain’s way of interpreting that mixed signal.

    However, if you have a stream of photons that are monochromatic and between the red and green peaks of sensitivity, we perceive that as yellow, but we also perceive as yellow a light stream that has an equal mixture of red and green photons (by which I mean photons with wavelengths that correspond to our perception of the colours red and green). This effect is how TV and computer screens generate a many-coloured picture out of just three colours.

    Now, back to the NASA pic.

    Because the three types of spectrum have each been assigned a single colour, we can see additional detail where those colours mix and produce (for instance) yellow or white light (or, more specifically, a mixture that we perceive as yellow or white). This mixing stands out from the image.

    Now, if each waveband had been assigned a portion of a continuum of light, we would not be able to pick out areas that are bright in both the far- and near- IR, or areas where X-ray sources are mixing it with dust clouds. These mixtures would either appear too close to one end of one of the two contributing wavebands, or they would appear to us as a colour that is plentiful elsewhere already. It would be harder for us to interpret the image.

    D’you see?

    Now, why did they choose blue, red and yellowy-orange instead of blue, red and green? Probably to represent as best they could the actual wavelengths involved. The red is the far-IR; yellowy-orange is the near-IR; and blue (being the shortest visible wavelength and slightly closer to actual X-rays than any other visible wavelength) is X-rays.

  23. Oscar Ferro

    “the flame of an arc-welder”

    I have to admit that it sounds better than “the arc of an arc-welder”.

  24. Moochie
  25. @24 Spectroscope:

    Thanks for the information.

  26. bubba

    there is no bright spot right of center.

  27. gss_000

    I can’t believe no one has mentioned that NASA has donated this images to about 150 schools and planetariums. This event is more than just an awesome picture, it’s about getting the next generation involved in STEM (science, technology, engineering, math) fields.

  28. Melusine

    I second what csneil said. Enthusiastic writing does the image justice.

    Incredible how we’ve gone from Galileo to Hubble, et al. (Yes, they seem like people-machines.) Can you imagine what Galileo would say? Probably the same kind of excitement he must have had then…everything is relative to the times.

  29. This is some real cool astronomy info.

    It’s stuff like this which makes me unable to fathom some people who are so earth-centric that they fight over religious differences and don’t believe in the benefits of space exploits.

    There is so much more to life than just fighting, shopping for the latest Ipod and not caring who you screw on your way up the corporate ladder.

    Reminds me of a famous quote from Katherine Hepburn that went along the lines of “Human nature is the one thing we are put on this Earth to rise above.”

  30. Charon

    Truly awesome image.

    “Galileo wasn’t the first to turn his telescope to the sky, nor was he the first to record what he saw.”

    I’m curious what your reference for this is. I dabble in teaching the history of science, and have a particular fondness for Galileo. Conventional wisdom is that he was indeed the first to create a telescope that was good enough for astronomical research, and the first to use one in that way. It was less than a year between the invention of the telescope and when he began his observations for Sidereus Nuncius (and less than a year after that it was published). He had contacts close to the original telescopes to feed him info, and most educated people of the time though the whole telescope thing was nonsense until they saw one (persistent myths of such things had been around for thousands of years).

  31. Azorus

    Is there a way perhaps to tell which objects are closer in the foreground on this? maybe by picking up the intensity of the light perhaps. It’s a great map I just wonder what a lot of these little dots around some of these stars are.

  32. Azorus

    I think i figured the answer to my question out. I think they are solar systems.

  33. Nigel Depledge

    Azorus (39) said:

    Is there a way perhaps to tell which objects are closer in the foreground on this? maybe by picking up the intensity of the light perhaps.

    While we can measure the intensity of the light from each object, that does not allow us to tease apart distance and intrinsic brightness. We know that stars vary over a huge range of light outputs. But most of the brightest naked-eye stars are quite a distance away (hundreds of light years in most cases, IIUC).

    Measuring distance is a real challenge in astronomy.

    The closest objects can be directly triangulated using their parallax shift (apparent change in position against the background of more distant stars over the course of the year as Earth moves from one side of the sun to the other). Some stars give us clues, because we can infer their intrinsic brightness from other properties (look up Cepheid variables on Wikipedia).

    There are several techniques used, and the uncertainties get larger with larger distances, but we are able now to infer a measurement of distance for the most distant galaxies based on their red-shift (recession velocity).

  34. Damon

    Before I even clicked the link I knew I had a new desktop background.

  35. Eva

    I love how much we don’t know yet. Makes me happy. :)

  36. lincolnd

    a super-massive star possibly being orbited by a black hole? just tying to imagine that, and imagine what it would mean. space/time-wise and even beyond that. anyway, this is possibly the most beautiful thing i’ve ever seen.

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