June 09, 2010
This galaxy [in the white square above] was spotted 10 billion light years away, and gives us a glimpse of what the Universe looked like when it was only about one-quarter of its current age.
Measurements show that the galaxy is as large and equally dense as elliptical galaxies that can be found much closer to us. Coupled with recent observations by a different research team - which found a very compact and extremely dense elliptical galaxy in the early Universe - the findings deepen the puzzle over how ‘fully grown’ galaxies can exist alongside seemingly ‘immature’ compact galaxies in the young Universe.
‘What our observations show is that alongside these compact galaxies were other ellipticals that were anything up to 100 times less dense and between two and five times larger - essentially ‘fully grown’ - and much more like the ellipticals we see in the local Universe around us,’ explains Michele Cappellari of Oxford University’s Department of Physics, an author of a report of the research in The Astrophysical Journal Letters.
‘The mystery is how these two different extremes, ‘grown up’ and seemingly ‘immature’ ellipticals, co-existed so early on in the evolution of the Universe.’
Elliptical galaxies, which are regular in shape, can be over ten times as massive as spiral galaxies such as our own Milky Way and contain stars which formed over 10 billion years ago. One way of checking the density of such galaxies is to use the infrared spectrum they emit to measure the spread of the velocities of their stars, which has to balance the pull of gravity.
Measurements of a distant compact elliptical galaxy have shown that its stars were dispersing at a velocity of about 500 km per second, consistent with its size but unknown in local galaxies.
The new study, using the 8.3-m Japanese Subaru telescope in Hawaii, found a ‘fully grown’ elliptical with stars dispersing at a velocity of lower than 300 km per second, much more like similar galaxies close to us.
‘Our next step is to use the Subaru telescope to find the relative proportion of these two extremes, fully grown and compact ellipticals, and see how they fit in with the timeline of the evolution of the young Universe,’ Michele tells us. ‘Hopefully this will give us new insights into solving this cosmic puzzle.’
In earlier surveys, the Advanced camera for Survey (ACS) and the Infrared Camera for Multi-object Spectrometer (NICMOS), the Hubble Ultra Deep Field (HUDF) have revealed the presence of estimated 10,000 fully formed galaxies in a patch of sky in the constellation, Formax - a region just below the constellation, Orion. According to the NASA, these fully formed galaxies emerged just 700 million years after the Big Bang, when the universe was barely 5% of its current age.
Also, using ISAAC near- infrared instrument aboard ESO's Very Large Telescope(VLT), and the phenomenon of gravitational lensing, a team of French and Swiss astronomers using Very Large Telescope (VLT) of the European Southern Observatory, have identified an extremely faint galaxy, Abell 1835 (image left).
According to interpretations, Abell 1835 must have formed just 460 million years after the universe was born, during the "Dark Age" when the first stars and galaxies were supposedly being born More recently, fully formed galaxies were discovered which are at a greater distance, over 13.1 billion light years (American Astronomical Society 2010), and which may have already been billions of years in age, over 13 billion years ago .
There are fully formed distant galaxies that must have already been billions of years old over 13 billion years ago; which would make them older than the Big Bang. Then there is the problem of the oldest globular clusters so far discovered, whose ages are in excess of 16 billion years. The Milky Way and other galaxies are also so old that they must have formed before the so called "Dark Ages" and thus almost immediately after the Big Bang, which is not consistent with theory.
Using the Infrared Array Camera (IRAC) aboard NASA's Spitzer Space Telescope, astronomers have detected about a dozen very red galaxies at a distance of 10 to12 billion light years from Earth (cfa Harvard 2005). According to the Big Bang model, these galaxies existed when the universe was only about 1/5 of its present age of 13.75 billion years. The unpredicted existence of "red and dead" galaxies so early in the universe challenges Big Bang theories relating to galaxy formation (cfa Harvard 2005). Analysis show that galaxies exhibit a large range of properties. Young galaxies with and without lots of dust, and old galaxies with and without dust. There is as much variety in the so called "early universe" as we see around "today" in galaxies closer to Earth.
Moreover, Spitzer Space Telescope, which is sensitive to the light from older and redder stars, has also revealed evidence for mature stars in less massive galaxies at similar distances (Spitzer 2005), when the Universe was supposedly less than one billion years old.