Scattered jewels in the core of a cluster

By Phil Plait | March 18, 2011 7:00 am

I love all the Hubble images of nebulae and galaxies, but sometimes you need a palate cleanser, an image clean and simple. Like one, say, full of the stars of NGC 288:

[Click to englobularclusternate.]

NGC 288 is a globular cluster, which are usually tightly-packed spheres of stars. NGC 288, though, is looser, with stars dispersed more throughout. This image from Hubble actually resolves the stars even in the core, where they tend to overlap in denser clusters. From 30,000 light years away — half the diameter of our galaxy! — this is a pretty decent feat.

The image is not exactly true color: blue is blue, but orange starlight is shown as green here, red represents near infrared light, and what you see here as orange is actually from the reddish glow of hydrogen. Confused? Yeah, sometimes astronomers color things oddly to make some characteristics clearer. In this case, the colors represent different mass stars. Medium mass red giants look yellow in the picture, and blue stars are more massive. The fainter stars are ones that are still happily fusing hydrogen into helium like the Sun does. However, those stars are much lower mass than the Sun, and have longer life spans.

And there’s more: If you look carefully, you can see fuzzy orange objects poking through the stars. Those are distant background galaxies! They’re probably hundreds of millions of light years away.

We think most globular clusters like NGC 288 form their stars all at once, making them really nice laboratories for studying how stars grow old and die. Since we can be pretty sure the stars are all the same age, it’s one less thing we have to worry about when trying to understand them! Simplification can be nice… in science and in beauty.

Related posts:

A buzzing beehive and a dying star
It’s full of stars!
Alien clusters invade our galaxy!
Vampires and thrillseekers rejuvenate dead stars

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (36)

  1. Dave Bowman

    My God…it’s full of stars!

  2. Talori

    Connect the dots, la la lala

  3. Messier Tidy Upper

    Superluminous stars aplenty
    A cluster jammed to bursting
    So many Sun’s aglow with light
    Sending photons travelling to us
    Across the gulfs of space.

    I love this image. :-)

    @1. Dave Bowman : LOL. Very apt. :-)

  4. Jenna

    I want to see one of these fuzzy orange things… can someone point one out to me?

  5. Messier Tidy Upper

    @ ^ Jenna : look really closely. They don’t stand out but they are there.

    Hmm .. look along the right hand side scan about halfway down to where there’s a ^ triangle of stars – all with diffraction spikes (straight rays of light) – top = yellow/orangish white, left (tilted down to lefthand side like a sloping pyramid) = white & right vivid blue. There’s a faint orangish blob diagonally below & to the right of the blue star there. Plus another on the line between the blue and white stars there.

    Then further in there’s a mini-sickle / upside down question mark reminiscent of the front of Leo (at least for Southern hemispherers like me) with a faint fuzzier object a bit more orangish white near the start of the sickle / upside down-?’s curve.

    Or bottom left hand corner in line with the purplish diffraction spike for teh star that’s half off-screen there’s a straight white line which I suspect might possibly be an edge on spiral galaxy in the distant background. (Or maybe just an asteroid trail?)

    Does that help at all? Hope so. :-)

  6. Messier Tidy Upper

    @ 3.Jenna : Plus near the top half centre square /diamond (tilted somewhat again) of blue stars – with an extra blue star just out of line with them left and a row of three other blue stars making a symbolic curved bridge type asterism. ( if that’s the right word – mini-asterism? micro-asterism?) There’s two vivid blue stars next to each other with a really white star just above them on the left and the fuzzy orange galaxy suspect just on top rightwards of them. Alternatively for that same object there’s like an inverted (upside down) pyramid of blue stars with the left hand one being a binary with the object just in there.

    Plus a separate one – there’s like an igloo /tent in the lower half of the photo. Soem of the stars yellow orange (brighter) most of the stars blue. Sort of like an oval clock with the big hand (three blue stars around same brightness from central brighter yellow-orange haloed white one pointing at about five m,inutes totwelve and the shorter hand composed of a greenish white star nearer the “clock centre” star and one fainter blue star pointing at the 2 o’clock position. Really fiant small object just next to that smaller 2 o’clock hand.

    Or just imagine you’re playing ‘Where’s Wally’ (you call him Waldo in the States right?) and scan around looking real close! 😉

    Not sure if these directions are working for you – hope they help. :-)

  7. Sion

    Needs paragraphs scrolling away in perspective.

  8. Joseph
  9. Keith Bowden

    When I clicked to englobularclusternate, we had a brown out. Very eerie! The majesty of the universe overwhelmed everything! :)

    The sun and you and me and all the stars that we can see
    Are moving at a million miles a day

  10. Messier Tidy Upper

    CORRECTION – because I was typing half asleep :


    Plus a separate one – there’s like an “igloo /tent” asterism in the central lower half of the photo. Some of the stars making it up are yellow orange (brighter+), most of the stars in it are blue. It looks – sort of – like an rather oval clock with the big hand (three blue stars of around the same brightness) coming out vertically but slightly diagonally left from central brighter yellow-orange haloed white star pointing at about five minutes or less to twelve with the top of the “semi-clock” being a pair of brighter yellow-white+ stars. There’s also a shorter hand composed of a greenish white star nearer the “clock centre” star and one fainter blue star pointing at the 2 o’clock position. There’s a “mini-horsehoe” asterism – the open end facing down and slightly right – immediately below that greenish-white star. A really, faint, small object sits just next to that smaller “2 o’clock hand” seeming almost like it is coming from the blue star at the top of that imaginary “clock hand.” Magnify it in the larger image – click on the main picture to get to it – and it seems like a possible barred spiral galaxy. :-)


    This is one of these images where the more closely you look the more you’ll see. :-)

    @7. Sion : Needs paragraphs scrolling away in perspective.

    Ohh-kkkayyy . That was cryptic. Care to elaborate, please? 😉

    Hope that’s made things clearer & been helpful. :-)


    + These yellow stars make an inverted pie-shaped triangle of sorts – albeit there’s four of them two in the (top-left) tip giving a bent over / bitten off effect.

  11. Mapnut

    Wait, Phil, you said the stars probably all formed about the same time, but the blue ones are massive, and the smaller ones are long-lived? Aren’t massive stars short-lived? Is the whole cluster then fairly young? I thought globular clusters were mostly old stars. Are the blue ones not really that massive?

  12. Jamie

    @10.MTU re @7.Sion:
    Think Star Wars….

  13. Messier Tidy Upper

    @ ^ Mapnut : False colour image remember.

    EDIT : Hang on, the BA did write “blue is blue” So, hmm… interesting.

    Not sure what spectral class these blue stars are but suspect they’re NOT O-B or even A but maybe F-G types?

    Also there are the odd blue stragglers that form later than the rest via stellar mergers to consider.

    Plus the lower metallicity – assuming it is low metallicity in this Glob – could be making these stars low metal sub-dwarfs which have somewhat different characteristics to the higher metallicity stars we’re used to.

    Eg. Compare RR Lyrae “cluster variables” usuallyfound in oler regions such as globular clusters with the “Classical Cepheid variables” as found in the disk & spiral arms. Population I versus Pop’n II star types.

    Please can you elaborate on that though Phil – it is rather curious.

  14. Don

    One question about forming all at the same time, that I wanted to confirm. I see that sentence all the time in popular descriptions of clusters and star forming regions. I just was wondering if my presumption that all at the same time means within several million years. Because in several star forming including an earlier picture for a few days ago that BA posted there are supernova remnants. Which means a star has formed and died while new stars are still forming. Since, even the most massive stars live a couple million years that would mean there is up to several million years of age difference. So, I presume what astronomers mean is they are the same age within a few percentage or less depending on the estimated overall age as that couple million year difference starts to become insignificant.

  15. JMW

    @8 Joseph

    …or he can continue to be a paid propaganda tool of the oil industry…

  16. Thameron

    Brightly cold and very old
    Rubies beyond price
    Diamonds beyond measure
    And sapphires all comprise
    The bounty of this treasure

  17. Joseph G

    Meh, my images always disappear.
    Did my image posting privileges get revoked because I posted that one picture of a “black hole with brown dwarf”?
    I was pretty drunk, and I promise it’ll never, ever happen again 😀

  18. Joseph G

    @JMW: More likely, he’s trying to keep a lid on the crazy. You may not like his politics, but when people go too far into loonyland, he calls them on it. For instance, when other right-wing commentators were getting birther-fever, he was dismissing the whole idea as silliness. When Ann Coulter tells you that reactor meltdowns aren’t a problem because “some” radiation is good for you, it doesn’t take oil company money to tell her to STFU.

    Incidentally, there’s some pretty convincing evidence for the hypothesis of radiation hormesis, but again, dosage is everything. People who don’t know what a “therapeutic index” is shouldn’t be telling people to expose themselves to anything dangerous (be it herbs, minerals, or ionizing radiation).

  19. Jenna

    @Tidy Upper
    Thank you so much! Your descriptions were so vivid that I found them all!

  20. Matt B.

    When did the Milky Way shrink to only 60,000 c-yrs wide? Last I heard it was somewhere between 100,000 and 150,000, which would make 30,000 c-yr somewhere between 0.2 and 0.3 of our galaxy’s diameter, not 0.5.

  21. Vex

    I was never very good at Where’s Waldo, so the descriptions are very helpful!

    Whew, the large image is almost enough to make me dizzy – so many stars!

  22. Someone You Know

    @ Matt B.

    Maybe Phil meant radius rather than diameter. That would make the diameter of the galaxy 120,000 light-years, which fits nicely in your range.

  23. Brian Too

    @Someone You Know,

    I don’t think I know you.

    (Head explodes in an infinite improbability vortex).

  24. Messier Tidy Upper

    @20. Jenna : My pleasure. Excellent! :-)

    @12. Jamie : Hmmm … still not quite getting it although I am now hearing it in Yoda’s voice! 😉

    @16. Thameron : Nice . I like that one. :-)

    Please, Bad Astronomer, can you tell us which spectral types – and luminosity classes – each star colour corresponds to in this image? Are the blue stars type B, type F, type G, or what?

    Was I right earlier thinking these stars are all metal poor sub-dwarfs or am I mistaken about that?

  25. Mohammad Neyaz Hasan

    wow that looks awesome, cannot imagine how much unknown beauty is hidden in the universe.

  26. Messier Tidy Upper

    @13 : PS. Links for reference / explaination :



    for an odd youthful globular named for a type of fish. (Okay,not really! 😉 )

  27. Messier Tidy Upper

    28. Joseph G & #15. JMW & #19.Joseph G. :

    @ Phil – OFF TOPIC Look Phil! O’Reilly can be skeptical too!

    Actually, many on the Right Wing of politics think Bill O’Reilly is too pro-Obama & almost too centrist in his approach – see :



    That is the view of many right wing folks anyhow whether folks agree with it or not.

    Personally, I know of O’ Reilly only by reputation from what others have posted about him – haven’t seen his show or enough of him to be able to judge fairly for myself. Although his Moon comments noted in the “Bill O’Reilly: tidal bore” post by the BA here (posted
    January 31st, 2011 11:09 AM) were pretty stupid.

    OTOH, Bill O’Reilly came over as fairly reasonable in one interview I did see of him on ‘Letterman’ (TV Late Show there with) and on some of his other Youtube videos so, again, too little to tell. His views on astronomy are clearly bad but them his views on politics which is more his field of expertise may be more factually based, perhaps?

  28. Messier Tidy Upper

    Aaaaarrrrgggghhhh! Last link there (# 26- awiting moderation) isn’t working – my apologies. :-(

    Take II :

    Hopefully that’ll work now.

    Otherwise search : Ken Croswell articles + Whiting 1 /globular clusters.

    BTW. Totally off topic, but anyone else following the Cricket World Cup might like to know Australia is now 132 for 4 versus Pakistan in the 33rd over . Fortunately, Mike Hussey is batting! :-)

  29. chris j.

    since it’s so sparse near the center, has anyone taken follow-up images to track the movements of the core stars? or for that matter, focused on the exact center to see if there’s anything acting like a black hole there?

  30. Joseph G

    @MTU: Er, I think that “politics” and “factual” don’t really belong in the same sentence 😀

    In any case, he’s certainly opinionated, he just doesn’t go in for unverifiable fringe ideas (that is, conspiracy theories).
    Maybe that’s why I can’t seem to stop having some fondness for the guy despite disagreeing with a bunch of his views, or his religious blind spot. He sorta reminds me of my dad, I think :)
    (My dad’s also somewhat conservative and can be grouchy, but he’s intelligent and a skeptic all the same)

  31. Joseph G

    Just curious, regarding blue stragglers, and the hypothesis that they’re lower mass stars that have collided: has anyone ever observed a stellar collision? Would there be some characteristic spectra or light curve or something that would give such a thing away?

  32. Messier Tidy Upper

    @ ^ Joseph G. : Such stellar collisions and mergers are incredibly rare guiven how vats space is. I can’t rule it out but I very much doubt we’ve ever witnesssed a stellar collision directly.

    We have however seen stars in various stages of merging –

    1. Extremely close spectroscopic binaries such as Spica (Alpha Virginis) and Sheliak. (Beta Lyrae)

    2. Contact Binaries where the stars are actually touching and starting to fuse together.

    & finally

    3. Single very rapidly rotating stars – FK Comae Berenices variables.

    Ken Croswell had a good article on this “Dance of the Double Sun” about ER Vulpeculae – two sunlike stars that will one day merge into one Sirius-like star – in the July 1993 issue of Astronomy magazine if you can somehow find a copy of that.

    @31. Joseph G :

    @MTU: Er, I think that “politics” and “factual” don’t really belong in the same sentence.

    Very true. :-)

  33. Messier Tidy Upper

    See :

    for more on Sheliak (Beta Lyrae) one of the stars mentioned above and archetypal very close binary system via Kaler’s superb website.

    See :

    for contact binaries via Wikipedia and see :

    for the blue straggler entry on Wikipedia. :-)

  34. Messier Tidy Upper

    @32. Joseph G :

    Just curious, regarding blue stragglers, and the hypothesis that they’re lower mass stars that have collided: has anyone ever observed a stellar collision?

    Hey, guess what I just stumbled upon online? This :

    Purely by rather awesome co-incidence about five minutes ago! 😀

  35. Someone You Know

    @Brian Too:

    But maybe you know me without thinking you know me.


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