The area around dwarf galaxy DDO 68 (ground-based image)
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Videos
Panning across DDO 68
Hubble snaps what looks like a young galaxy in the local Universe
Astronomers usually have to peer very far into the distance to see back in time, and view the Universe as it was when it was young. This new NASA/ESA Hubble Space Telescope image of galaxy DDO 68, otherwise known as UGC 5340, was thought to offer an exception. This ragged collection of stars and gas clouds looks at first glance like a recently-formed galaxy in our own cosmic neighbourhood. But, is it really as young as it looks?
Astronomers have studied galactic evolution for decades, gradually
improving our knowledge of how galaxies have changed over cosmic
history. The NASA/ESA Hubble Space Telescope has played a big part in
this, allowing astronomers to see further into the distance, and hence
further back in time, than any telescope before it — capturing light
that has taken billions of years to reach us.
Looking further into the very distant past to observe younger and
younger galaxies is very valuable, but it is not without its
problems for astronomers. All newly-born galaxies lie very far away from
us and appear very small and faint in the images. On the contrary, all
the galaxies near to us appear to be old ones.
DDO 68, captured here by the NASA/ESA Hubble Space Telescope, was one
of the best candidates so far discovered for a newly-formed galaxy in
our cosmic neighbourhood. The galaxy lies around 39 million light-years
away from us; although this distance may seem huge, it is in fact
roughly 50 times closer than the usual distances to such galaxies, which
are on the order of several billions of light years.
By studying galaxies of various ages, astronomers have found that
those early in their lives are fundamentally different from those that
are older. DDO 68 looks to be relatively youthful based on its
structure, appearance, and composition. However, without more detailed
modelling astronomers cannot be sure and they think it may be older than
it lets on.
Elderly galaxies tend to be larger thanks to collisions and mergers
with other galaxies that have bulked them out, and are populated with a
variety of different types of stars — including old, young, large, and
small ones. Their chemical makeup is different too. Newly-formed
galaxies have a similar composition to the primordial matter created in
the Big Bang (hydrogen, helium and a little lithium), while older
galaxies are enriched with heavier elements forged in stellar furnaces
over multiple generations of stars.
DDO 68 is the best representation yet of a primordial galaxy in the
local Universe as it appears at first glance to be very low in heavier
elements — whose presence would be a sign of the existence of previous
generations of stars.
Hubble observations were carried out in order to study the properties
of the galaxy’s light, and to confirm whether or not there are any
older stars in DDO 68. If there are, which there seem to be, this would
disprove the hypothesis that it is entirely made up of young stars. If
not, it would confirm the unique nature of this galaxy. More complex
modelling is needed before we can know for sure but Hubble's picture
certainly gives us a beautiful view of this unusual object.
The image is made up of exposures in visible and infrared light taken with Hubble's Advanced Camera for Surveys.
Notes
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
More information
Image credit: NASA & ESA
Acknowledgement: A. Aloisi (Space Telescope Science Institute)
Links
Contacts
Georgia Bladon
Hubble/ESA
Garching, Germany
Tel: +49-89-3200-6855
Email: gbladon@partner.eso.org
