Gorgeous galaxies celebrate Hubble's 21st birthday

By Phil Plait | April 20, 2011 10:00 am

Happy 21st birthday, Hubble Space Telescope!

On this day, April 20, 1990, On April 24th, 1990, the Space Shuttle Discovery roared into space, carrying HST into orbit and into history. In honor of this anniversary, astronomers have released a new image of the interacting galaxies Arp 273, and it’s a beaut:

[Click to galactinate, or grab the cosmic4000 x 4000 pixel version — and trust me, you want the bigger versions!]

Years ago, astronomer Halton Arp observed and cataloged a large number of oddly-shaped galaxies, and we now know these galaxies are interacting gravitationally, and some are colliding. These two galaxies, UGC 1810 (top) and UGC 1813 (bottom) are just such a pair. Collectively called Arp 273, they are in the early stages of a collision.

Most spiral galaxies are pretty close to being symmetric and circular, but UGC 1810 is offset and weird. That one arm is thick and sweeps out much farther than the others, making the nucleus of the galaxy decidedly off-center. The string of blue clumps on the top of the galaxy is a sign of furious star formation; massive, hot, blue stars are the culprit, and don’t live long, meaning they were born relatively recently. UGC 1813 is distorted as well, with its arms twisted oddly and gas flung every which-way.

These two galaxies probably passed very close to each other in the past few million years. The gravity of each galaxy distorted the other, drawing the arms out, slamming gas clouds into each other. Also, the nuclei of both galaxies are unusual: the smaller galaxy’s core is very luminous in the infrared, indicating strong star formation obscured by dust, and the bigger galaxy’s core is giving off light indicating copious amounts of ionized gas. This is another sign of collision. The gravitational disturbance of this cosmic train wreck has funneled gas into the cores of both galaxies; in the case of the smaller one it has triggered a burst of star formation, and in the bigger one the gas has flowed around the massive black hole at its core, heating up and giving off light (although recent observations of other galaxies have cast some doubt on this idea of collision-fed black holes).

While both galaxies are distorted, they still have retained their overall spiral/disk shapes, which indicates this is still early on in their cosmic dance. If they’re bound to each other gravitationally the interactions will continue, and most likely will end with the two galaxies merging to become one larger galaxy. It’s a common occurrence in the Universe, and our own galaxy may have grown to its large size this way too.

Whatever the ultimate fate of these two galaxies, to us, sitting here 300 million light years away from them, they’re gorgeous. And it reminds me that while Hubble has done an amazing amount of science over the past 2+ decades, I still think that one of its most important contributions has been to figuratively open the eyes of the public to the beauty and majesty of the cosmos. It’s probably the one telescope people can identify by name, and the images it has sent down from orbit have been stunning.

I think astronomy is undergoing a renaissance in popular culture, and if that’s so, it’s due in very large part to Hubble.

Happy birthday, Hubble, and may you have many more.

Related posts:

Collision of past and present
The beauty of cosmic collisions
Awesome Antennae
Felicia Day collides galaxies!

CATEGORIZED UNDER: Astronomy, Pretty pictures, Top Post

Comments (35)

  1. Brian Schlosser

    Wow… 21 years! And to think that at first it was “the only space telescope to be equipped with a white cane and dark glasses”, as Dave Barry quipped…

    In my opinion, the Hubble is the single most important piece of post-Apollo space exploration done by NASA.

    And since it’s now legal, lets all have a toast!

  2. Keith Bowden

    “I think astronomy is undergoing a renaissance in popular culture, and if that’s so, it’s due in very large part to Hubble.” Aided and abetted by one Philip Plait.

    In the upper right extended arm of UGC 1810, there is a white/red area among the young star factories. It looks like an itty bitty spiral bar galaxy (much, much farther away), but it also kind of looks like it’s part of UGC 1810. What is it?

  3. I think today would be a good day to invent a Hubble Based drink of some sort…

    151 Rum (to make you blind at first?)
    OJ (Launched from the Cape, FL)
    Grenadine (Red Shift)
    Vodka (OJ and Vodka is a screwdriver signifying all the repairs)

    Anyone else have ideas?

  4. Jerry

    I think you might have jumped the gun on that. Launch date looks like it was April 24. Sorry, HST, no crazy bar runs until Sunday :)

  5. AJKamper

    I was wondering about that galaxy-looking thing too. I’d presume it’s a background galaxy, but it’s the same color as UGC 1810, which implies to me it’s not redshifted by additional distance.

  6. DrBB

    @2 Keith Bowden

    I was just trying to figure out how to describe that feature and ask the same question. “Itty bitty spiral bar galaxy” is exactly what it looked like to me too. In the higher res version it looks more like a single source illuminating gas around it, distinctly within UGC 1810 at least to my eye. So Phil, you’re the guy who knows, right? To quote a very long ago Steve Martin SNL skit… What in the heck IS that thang?

  7. Jerry- Launch was April 20, deployment was April 24.

  8. Ian

    Can you cite that Phil? Wiki and NASA say launch was the 24th and deployment was the 25th.


  9. VJBinCT

    Back in 1968, I was a grad student doing observations using the 120 inch at Lick Observatory with my boss, and Werner von Braun shows up to get an idea of what big telescopes were about, having the Hubble in mind. It was so foggy, we couldn’t open the dome that night, so we just talked about the lunar program, and I still have his sketches showing the paths, and translunar injection and all that. We figured that the project I had spent a year on (adding up multiple exposures of molecular absorption spectra–on photographic plates– in clouds against bright OB stars to increase S/N) could be done in 30 minutes with a 24-inch telescope with a ‘modern’ detector on the far side of the moon. Quite a night. Later we heard from the kitchen staff that they were afraid NASA would take their precious telescope and launch it into orbit.

    A few years before, as a college student, I worked summers at Perkin-Elmer, and got to see the Stratoscope telescope in its little ‘hanger’ building back of the employee parking lot. That was the ancestral instrument to the Hubble, and impressive in its day.

  10. Dagnappit! That’s so odd: over the years, for some reason, the date April 20 has been stuck in my head for the launch. I’ve made this mistake before and it’s vexing – it doesn’t help they released this image today instead of Sunday coming up. :) Anyway, yes, I was wrong and corrected the text. Grrr.

  11. Wayne on the Plains

    Don’t worry, one thing we love about this blog is that you admit your mistakes and correct them. It’s still a great picture and a great telescope, whichever day it launched on.

  12. Mark Hall

    I do believe I have found a new wallpaper.

  13. Jason Dick

    It’s really too bad that Halton Arp went from the realm of good scientist to crackpot. I really do wonder just how that happens.

    Tremendously beautiful image, though!

  14. Skrim

    What are those 3 large twinkles in the image? One inside the galaxy’s arms, one just outside, and one in the middle of nowhere?

    Would those be novae/supernovae, or stars in our galaxy in the far far foreground?

  15. @Skrim,

    Those are foreground images. You can tell by the large “spikes” around the light source.

  16. Ooh! Man, that’s a good image.

  17. Joel

    I was wondering about the mini-Galaxy type thing at about 2 o’clock on UGC 1810 too. Before I scrolled down to see the full photo, my first thought was that this was a picture of UGC 1810 interacting with a dwarf Galaxy.

    Second question, what’s the little blue blob right down in the bottom left of the picture? It’s vaguely crescent shaped, so I shall think of it as the Blue Banana. Is it a background Galaxy (which seems unlikely if it’s that blue), or a star forming region from one of the Galaxies here that’s separated from the main body somehow? Or something else?

  18. Jamey

    @19 – Joel: I was looking at the same thing, and to *me*, it looks like there might be some bow shock on the right side! There’s a similar object, but much smaller and fainter, over on the lower right side of the image (I snagged the 4K x 4K pixel image to look at). There’s also what looks to be some galaxies seen edge-on, but with a bright nucleus *way* off center, and some other things that makes me wonder if there’s not some gravitational lensing taking place. Really – a fascinating image way deep in!

  19. Monkey

    Start the movement – the Global Museum of Science Art (just finished the Science Friday podcast talking about art/science meeting, so its on my mind!)

    The Hubble room
    The (fill in your satellite of choice) room
    The artists renditions of *actual* astronomical features/events room
    The electron microscopy room

    A massive building, each room itself massive with towering walls. Grand space for a grand exhibit

    These pictures dont belong on a computer, they belong as 5mx5m wall hangings. or bigger…grander…students get in free, families get in free, adults get in free, children get in free, … !

    I know, I know….dreams and pipes….these are just so stunning that it is a shame they are confined to the common monitor for a few moments of glory. Imagine this in stained glass, the size of a wall?

    ok…must go work…

  20. J. Rich

    First: I love merging galaxies and would love HST images of all of these systems in the local universe (pretty please?). Happy Birthday HST indeed!

    I just have a little science quibble about one sentence from your entire post: it’s not clear that you can build spiral galaxies that look like the Milky Way with major mergers. I was bothering someone who does cosmological simulations of merging galaxies about this question just last week: I wanted to know if you can have a major merger in the past history of a local spiral and if so, how long ago would it have to be?

    Aside from the definition of major (talking to this person, anything with mass ratio less than 1:5 was assumed) the basic answer I got was that major mergers cause a serious disruption in the evolution of the parent systems and that it’s difficult to create a z=0 spiral disk from a galaxy (galaxies) that has undergone a major merger event in the past-though if it’s long enough ago (the paper I link below says z>2 for instance) you could get a modern disk, but it would have a much larger bulge than expected.

    an example study might be e.g. http://adsabs.harvard.edu/abs/2011ApJ…729…16K (and references therein :-)

    Gobbling up little galaxies on the other hand… that doesn’t seem to be a problem. So basically I wrote a bunch of sentences about 1/2 a sentence from your post… but it was for science!

  21. DrBB

    @21 Monkey

    I live in an artists’ building near Harvard and one of the residents, an astrophysicist associated with Harvard Smithsonian, has had some of his astronomical images hung in our gallery shows. As I remarked when posting this link on my Facebook page: “Awe is the natural medium of the universe.”

  22. DrBB

    @22 J. Rich: “So basically I wrote a bunch of sentences about 1/2 a sentence from your post… but it was for science!”

    And it was darned interesting. Great question and a great answer–thanks for posting it.

    Now if Phil would just weigh in with an answer on that mini-galaxy thingy….

  23. RwFlynn

    @3. Larian LeQuella

    Hehe, that’d be a fitting first drink for Hubble.

  24. Joel

    The more I look at it (on a massive great screen, too) the more I’m convinced that the funny mini galaxy thing is just a background galaxy viewed through the arm of the closer one. I’m still more intrigued by the blue banana.

  25. Alli

    Me & Hub share the same birthday – April 24 (albeit different years). And, we both wear glasses!

    Now if only I had the same views out my window *sigh*

  26. Messier Tidy Upper

    Wow! Superluminous picture – great choice of galaxies. I don’t like this – I <3 *love* <3 this! :-)

    @15. Skrim : Would those be novae/supernovae, or stars in our galaxy in the far far foreground?

    Foreground stars in our Milky Way – as #16. Larian LeQuella ha salos pointed out.

    Supernovae are exceedingly rare events (& novae only somewhat less so) even in starburst galaxies and if one was present, I’m pretty sure the imaging team and the BA would have noted the fact. Nice thought though! :-)

  27. Messier Tidy Upper

    @ Skrim (still – I always seem to remember other stuff to add later.)

    It’s possibnly worth recalling here that the last nearby supernova was the one in the Large Magellanic Cloud in 1987. Our own Milky Way hasn’t had a supernovae for a very long time – like centuries – or at least not that we’ve seen.

    There’s more brilliant images available here :


    for y’all. :-)

  28. Messier Tidy Upper

    See also :


    Which notes :

    Although no supernova has been observed in the Milky Way since 1604, supernovae remnants indicate on average the event occurs about once every 50 years in the Milky Way.





    From this blog where the BA observes that :

    “.. in a typical galaxy, you get roughly one supernova per century. It depends on a lot of things, but hey– close enough. Some galaxies are underachievers (we haven’t seen one on our own Galaxy since the 1600s!), and others are brown-nosers, blowing stars up left and right. Meet NGC 1316. [Where 4 supernovae went over in 30 years – two in just the one year of 2006 – ed.]

    For more supernova frequency~wise. :-)


    “…about 40 supernovae are exploding somewhere in the [entire] universe every second. However, light from most of these events won’t reach Earth for billions of years, if ever.”
    – Page 73, “Ask Astro” column in ‘Astronomy‘ magazine October 2008.

    [Brackets] and emphasis added.

  29. Czy jesteśmy w stanie ogarnąć to co się tam dzieje ?
    Naszym trójwymiarowym umysłem ? z dodatkiem religii i niewiedzy …. pozdrawiam wszystkich ciekawych … jest co oglądać .

  30. Jon Hanford

    #2 Keith Bowden asks:

    “In the upper right extended arm of UGC 1810, there is a white/red area among the young star factories. It looks like an itty bitty spiral bar galaxy (much, much farther away), but it also kind of looks like it’s part of UGC 1810. What is it?”

    The ESA press release notes “[a] possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in colour) on one side, to clumpy and extremely blue on the other. The fairly regular spacing of the blue star-forming knots fits with what is seen in the spiral arms of other galaxies and can be predicted from the known instabilities in the gas contained within the arm.”

    There is little published literature on Arp 273 and I could find no mention of this possible 3rd galaxy projected onto UGC 1810. Followup on the nature of this object is needed. Seems it could indeed be a possible small disk galaxy involved with the Arp 273 system. I think the same could be said for the two Blue Compact Dwarf galaxies located to the left of UGC 1810 and UGC 1813 respectively. The bright blue clusters in these dwarf galaxies appear similar in appearance to clusters in Arp 273, possibly indicative of their membership in this system.

    Although not mentioned by Phil, the PR notes that Arp 273 may be a recently formed ring galaxy:

    “The large, outer arm appears partially as a ring, a feature that is seen when interacting galaxies actually pass through one another. This suggests that the smaller companion actually dived deeply, but off-centre, through UGC 1810. The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and coming back out the other side. How these two spiral patterns connect is still not precisely known.”

    Arp 273 has been listed as a possible ring galaxy in several lists of such objects and bears some resemblance to other “off-center” collisional ring galaxies. AM 1724-662, the Lindsay-Shapley Ring(AM o644-741) and NGC 7714-15(Arp 284) are somewhat similar in appearance to Arp 273.

  31. Messier Tidy Upper

    See also this :


    great animation zooming in.

    Happy Birthday Hubble! 8)

    (Same link as posting on the new actual birthday thread comment #7 [‘awaiting moderation’], hope that’s okay, if not then my apologies & please let me know. Uncertain of the right “netiquette” here. Figuring this applies equally well & is appropriate for both threads.)


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