Ultra Compact Dwarf Galaxies once crowded with stars

Article written: 12 Feb , 2009
Updated: 24 Dec , 2015
by

Astronomers think they’ve found a way to explain why Ultra Compact Dwarf Galaxies, oddball creations from the early universe, contain so much more mass than their luminosity would explain.

Pavel Kroupa, an astronomer at the University of Bonn in Germany, led a research team that’s proposing the unexplained density may actually be a relic of stars that were once packed together a million times more closely than in the solar neighbourhood. The new paper appears in the Monthly Notices of the Royal Astronomical Society.

UCDs were discovered in 1999. At about 60 light years across, they are less than 1/1000th the diameter of the Milky Way — but much more dense. Astronomers have proposed they formed billions of years ago from collisions between normal galaxies. Until now, exotic dark matter has been suggested to explain the ‘missing mass.’

The authors of the new study think that at one time, each UCD had an incredibly high density of stars, with perhaps 1 million in each cubic light year of space, compared with the 1 that we see in the region of space around the Sun. These stars would have been close enough to merge from time to time, creating many much more massive stars in their place. The more massive stars would consume hydrogen rapidly, before ending their lives in violent supernova explosions, leaving either superdense neutron stars or black holes as their remains. 

In today’s UCDs, the authors think, the previously unexplained mass comprises these dark remnants, largely invisible to Earth-based telescopes.

“Billions of years ago, UCDs must have been extraordinary,” study co-author Joerg Dabringhausen, also of the University of Bonn, said in a press release. “To have such a vast number of stars packed closely together is quite unlike anything we see today. An observer on a (hypothetical) planet inside a UCD would have seen a night sky as bright as day on Earth.”

PHOTO CAPTION: Background image taken by Michael Hilker of the University of Bonn using the 2.5-metre Du Pont telescope, part of the Las Campanas Observatory in Chile. The two boxes show close-ups of two UCD galaxies in the Hilker image. These images were made using the Hubble Space Telescope by a team led by Michael Drinkwater, at the University of Queensland.

Source: Royal Astronomical Society


19 Responses

  1. Jorge says

    Fascinating. I very much doubt that with such star densities there would be any planets around to enjoy the view, though…

  2. robbi says

    If there is enough protection against radiation from such energy from close-packed stellar-objects, I would love to venture there, whether virual or in reality,-perhaps there’s a few
    ‘rocks’ to stop at ,rest on and enjoy the sky scenery before continuing on out…what a view!!!……….

  3. Timmy says

    Today’s mainstream astronomers have neither the knowledge to understand nor the courage to realize that cosmic objects with that kind of density and power are likely not natural in origin.

    But I can see how something that big and powerful created by a mind to match would frighten your typical talking monkey with car keys.

  4. robbi says

    Timmy- I believe such density and power does exists, but don’t last long- it will probably disperse and be more liken to a dense globular cluster which is still far more dense with stars then what we have in our ‘neighborhood’ which I am glad of. I remember about 25 or so years ago, astronomers thought there was a star with about 3K times the mass of the Sun in the Large Magellan galaxy- I believe30 Doradus or a R__( I forgot name lol), with further advanced ‘scopes, there was found to be many super massive stars in a relatively small area, about 3 light years diameter, a few dozen had masses 50x-100x, a few slightly over 100, but there was hundreds of 8-50x mass of the Sun. I doubt any lifeform cans even get a foothold in such an environment, and this area in an astronomic way of thinking of short ages , will appear like
    an area of firecrackers going off as these massive stars have such short lifespans..

  5. Keith A says

    LOL @ timmy

    Neither “knowledge nor courage”, eh? Hmmm…checked any mirrirs lately?

  6. Ken says

    hahaah Timmy! What a fool, you made me burst out laughing.

    yes Timmy, because you don’t understand something and/or can’t conceive of the possibilities within the natural world, we must invoke causes that are not natural instead of trying to actually understand them right?

    Makes it all so simple for you right? … just hop around each day in blissful ignorance … this is amazing! therefore it can’t be natural! … and move on with your day.

    What do you learn from that attitude? … nothing at all.

  7. Uwe says

    You may laugh at Timmy, but he is right about one thing – we ARE just talking monkeys with car keys!

  8. fred houpt says

    Methinks that yet again mainstream astronomers are barking like mad dogs against a tree that befuddles them because they keep on calling it a tree.

    Halton Arp would probably tell you that the two objects are more probably ejected highly condensed core material that were “popped” out of the centres of the galaxies and although they might not have fully formed larger baby galaxies around them, they non the less were formed as ejections from the larger parent galaxies. A closer reading of Arp will put to rest the unnecessary invention of fiction-science, when in fact he already has posited much more accurate explanations for Quasar like objects.

  9. Timmy says

    Keith A. spouted:

    Neither “knowledge nor courage”, eh? Hmmm…checked any mirrirs lately?

    Maybe I will take you a bit more seriously when you learn how to spell the word mirror.

    And yes, I am just so closed minded because I try to think outside the box.

    I keep forgetting you talking monkeys wouldn’t know what an advanced culture looks or acts like anyway.

  10. Zibit says

    Its a trap.

  11. robbi says

    Timmy=I am not closed minded, I also think outside the box for phenomena like why comet Holmes acted as it did as solar wind alone could not have caused such a brighening at such distances. I think very much outside the box,most of the time, the findings will get most phenomena back into conventional findings, however, I’m always thinking about other types of other strange objects in our Universe still not answered by conventional thinking..

  12. Alex Jones says

    @robbi and @Ken

    Please, do yourself and others here a favour: Don’t feed the troll.

  13. Vanamonde says

    Whoa. Asimov wrote of a world with three suns that only had a night once every few years. Clarke wrote that my namesake enjoyed the many coloured shadows on the world of Seven Suns.

    But a constant skyful of suns? And some that merge? Probably not a pleasant place for carbon-based life that depends on liquid water to function and DNA that can last long enough to replicate truth without a lot of radiation rewritting it at random.

    And if this solves that nasty “dark matter” issue, that would be WAY COOL!

  14. Vanamonde says

    Always good advice there, Mr. Jones!!!!

  15. RUF says

    I like the idea of “poped-out” galactic cores. Could these explain Dark matter?

  16. fred houpt says

    RUF: read Halton Arp and you’ll have all your answers. Here is a good starting point:http://www.electric-cosmos.org/arp.htm

    and here is a link to buy his book

    http://www.amazon.com/Seeing-Red-Redshifts-Cosmology-Academic/dp/0968368905/ref=sr_1_1?ie=UTF8&s=books&qid=1234880203&sr=8-1

  17. Timmy says

    I was not trolling and Robbi, I know you are not close-minded. Too bad these others are too dense to see past their little self-made boxes and had to prove my point.

    I am sure that when some day we do discover something artificial in space made by non-humans, these same chuckleheads will be the first ones trying to claim they knew it was alien all along.

  18. araç sorgulama says

    I am just so closed minded because I try to think outside the box.

  19. jason says

    Ya know all this is extremely funny. You get these religous fanatics that all say they are so open minded and they think outside the box. Timmy you sir dont even know what the hell the box is to be thinking inside or outside of it. Anyone that may think that something like a star would be created by something other than natural means is just ludacris. and the guy misspelled mirror cause it was a freakin typo but I guess because you are so out of the box that you could not quite see that huh or you just wanted to to make an ass out of someone only befouling yourself. Sir take a minute to think next time before you type. The replies here are meant to be of a intelligent nature made for debate and to provoke thought not senselessness as your post has done. Thank you and have a nice day.

    end of line

Comments are closed.