Astronomers gain new knowledge about early galaxies

Jul 03, 2013
Quasars are among the brightest objects in the universe and can be used as lighthouses to study the universe between the quasars and Earth. Here researchers have discovered a galaxy that lies in front of a quasar and by studying the absorption lines in the light from the quasar, they have measured the elemental composition in the galaxy in great detail, despite the fact that we are looking approx. 11 billion years back in time. Credit: Graphic: Chano Birkelind, Niels Bohr Institute

The early galaxies of the universe were very different from today's galaxies. Using new detailed studies carried out with the ESO Very Large Telescope and the Hubble Space Telescope, researchers, including members from the Niels Bohr Institute, have studied an early galaxy in unprecedented detail and determined a number of important properties such as size, mass, content of elements and have determined how quickly the galaxy forms new stars. The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society.

"Galaxies are deeply fascinating objects. The seeds of are in the very and thus, understanding of galaxies links the largest scales in the universe with the smallest. It is only within galaxies that gas can become cold and dense enough to form are therefore the cradles of starsbirths", explains Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Early in the universe, galaxies were formed from large clouds of gas and dark matter. Gas is the universe's raw material for the . Inside galaxies the gas can cool down from the many thousands of degrees it has outside galaxies. When gas is cooled it becomes very dense. Finally, the gas is so compact that it collapses into a ball of gas where the gravitational compresion heats up the matter, creating a glowing ball of gas – a star is born.

Cycle of stars

In the red-hot interior of , hydrogen and helium melt together and form the first heavier elements like carbon, nitrogen, oxygen, which go on to form magnesium, silicon and iron. When the entire core has been converted into iron, no more energy can be extracted and the star dies as a . Every time a massive star burns out and dies, it hence flings clouds of gas and newly formed elements out into space, where they form that get denser and denser and eventually collapse to form . The early stars contained only a thousandth of the elements found in the Sun today. In this way, each generation of stars becomes richer and richer in heavy elements.

Using the Hubble Space Telescope, researchers have been able to pinpoint the galaxy causing the absorption in the quasar lying behind it. In the image to the left the quasar is seen as the bright source in the center, while the absorbing galaxy, which lies in front of the quasar, is seen to the left and slightly above the quasar. In the image to the right, most of the light from the quasar is removed so the galaxy is seen more clearly. The distance between the center of the galaxy and point were the light from the quasar passes is approx. 20,000 light years, which is slightly less than the distance between the Sun and the center of the Milky Way. Credit: Hubble Space Telescope

In today's galaxies, we have a lot of stars and less gas. In the early galaxies, there was a lot of gas and fewer stars.

"We want to understand this cosmic evolutionary history better by studying very early galaxies. We want to measure how large they are, what they weigh and how quickly stars and heavy elements are formed," explains Johan Fynbo, who has lead the research together with Jens-Kristian Krogager, PhD student at the Dark Cosmology Centre at the Niels Bohr Institute.

Early potential for planet formation

The research team has studied a galaxy located approx. 11 billion years back in time in great detail. Behind the galaxy is a quasar, which is an active black hole that is brighter than a galaxy. Using the light from the quasar, they found the galaxy using the giant telescopes, VLT in Chile. The large amount of gas in the young galaxy simply absorbed a massive amount of the light from the quasar lying behind it. Here they could 'see' (i.e. via absorption) the outer parts of the galaxy. Furthermore, active star formation causes some of the gas to light up, so it could be observed directly.

With the Hubble Space Telescope they could also see the recently formed stars in the galaxy and they could calculate how many stars there were in relation to the total mass, which is comprised of both stars and gas. They could now see that the relative proportion of heavier elements is the same in the centre of the galaxy as in the outer parts and it shows that the stars that are formed earlier in the centre of the galaxy enrich the stars in the outer parts with heavier elements.

"By combining the observations from both methods – absorption and emission – we have discovered that the stars have an oxygen content equivalent to approx. 1/3 of the Sun's oxygen content. This means that earlier generations of in the galaxy had already built up elements that made it possible to form planets like Earth 11 billion years ago," conclude Johan Fynbo and Jens-Kristian Krogager.

Explore further: The entropy of black holes

More information: dx.doi.org/10.1093/mnras/stt955

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User comments : 11

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govind_reddy_9400
1 / 5 (3) Jul 03, 2013
Visit 4reviewz.net for India's Technology News and Latest Product Reviews. Get more information about Products Comparison here with us.
Fleetfoot
5 / 5 (2) Jul 03, 2013
"This means that earlier generations of stars in the galaxy had already built up elements that made it possible to form planets like Earth 11 billion years ago"


Given that the Solar System formed a mere 4.5 billion years ago, that's 6.5 billion years of star system formation, any of which might have engendered life. This is why the Sci-Fi idea of species making contact at similar stages of development is so unlikely.
katesisco
1 / 5 (4) Jul 04, 2013
It also means that the universe produced Methuselah stars only in an environment of pure gas. What we would give to find a Methuselah star formed only recently. Instead we see more and more hot blues born dying It may be that our Earth has life not due primarily to ox but to magnetism. Or more correctly born in the nova that created the metals.
Fleetfoot
5 / 5 (3) Jul 04, 2013
Troll alert ...

What we would give to find a Methuselah star formed only recently.


"Methuselah" means a very old star. "formed only recently" means a very young star. Try to be a bit less obvious Kate.
GSwift7
5 / 5 (1) Jul 05, 2013
Astronomers gain new knowledge about early galaxies


To be fair, it should really say "...about one early galaxy".

made it possible to form planets like Earth 11 billion years ago


That's the part that caught my attention as well.

This is why the Sci-Fi idea of species making contact at similar stages of development is so unlikely


Impossible to evaluate, with no data to base an opinion on. Would extremely advanced civilizations bother meeting with lower ones? Perhaps everyone WOULD seek out others like themselves. I mean, how much fun would it be talking with someone who couldn't understand pre-school level calculus? It shouldn't be hard for an advanced civ to avoid contact with lower level ones.
Q-Star
1 / 5 (3) Jul 05, 2013
Would extremely advanced civilizations bother meeting with lower ones?

Perhaps everyone WOULD seek out others like themselves. I mean, how much fun would it be talking with someone who couldn't understand pre-school level calculus? It shouldn't be hard for an advanced civ to avoid contact with lower level ones.


Is there anyone spending billions looking for microbes on Mars? Would they like to spend billions more looking on the moons of Jupiter or Saturn?

Ask any microbiologist why he bothers studying and looking at such insignificant things.

They would seek them out for no other reason our own reason,,,, to know it, to understand how it came to be the way it is.

Fleetfoot
5 / 5 (1) Jul 05, 2013
This is why the Sci-Fi idea of species making contact at similar stages of development is so unlikely


Impossible to evaluate, with no data to base an opinion on. Would extremely advanced civilizations bother meeting with lower ones? ...


You misread my reply, I was only commenting on the low probability of any two species reaching the stage of first interstellar exploration at near simultaneous epochs.
GSwift7
not rated yet Jul 09, 2013
They would seek them out for no other reason our own reason,,,, to know it, to understand how it came to be the way it is


Just to be clear, we are talking about the plausibility of the fictional meme of shows like Star Trek, where there are abundant civilized planets.

After the first few thousand planets with intelligent life on them, would you really spend much time investigating the 5876th one you find (especially if it's just a common type)? Just catagorize it, mark it on your map, and try not to get contaminated.

I'm not saying that everyone would develop at the same time, but if there are that many of them, then there would always be plenty at any given level, and they would seek out ones like themselves while avoiding others.

Large scale wars would be a very real danger if civilations are abundant. That would be a really scary situation for newcomers like us. Our life expectancy would drop to near zero.
Fleetfoot
not rated yet Jul 09, 2013
Just to be clear, we are talking about the plausibility of the fictional meme of shows like Star Trek, where there are abundant civilized planets.

I'm not saying that everyone would develop at the same time, but if there are that many of them, then there would always be plenty at any given level


If the galaxy became capable of sustaining life 10.5 billion years ago and there are 6000 tech species, that's about 1 million years gap on average. How much will we have advanced in that time?

After the first few thousand planets with intelligent life on them, would you really spend much time investigating the 5876th one


Why do some humans watch "Big Brother"?

Large scale wars would be a very real danger if civilations are abundant.


Nah, the first to arise would build their galaxy spanning network and everyone else would be constrained to a small volume around their home world. Once you expand to the boundaries, you link with the network and need go no farther.
GSwift7
not rated yet Jul 09, 2013
If the galaxy became capable of sustaining life 10.5 billion years ago and there are 6000 tech species, that's about 1 million years gap on average


OTOH, if there are 600 civilations in the galaxy achieving space travel each year (with a corresponding number being wiped out by some means), then there could be a steady stream. It depends on 'birth' and 'death' rates versus stellar population density and everage lifespan of each civ.

Why do some humans watch "Big Brother"?


Boobies and bicepts, mostly.

Nah, the first to arise would build their galaxy spanning network


Speaking of Big Brother, group dynamics can be surprising. Would it be possible to maintain any kind of unified entity over the distances/time scales you're talking about? I don't think it's likely beyond regional distances. You'd end up with competing empires.
Fleetfoot
not rated yet Jul 10, 2013
OTOH, if there are 600 civilations in the galaxy achieving space travel each year


That's 100 times the rate of new stars!

If one star in 1000 has a habitable planet and one such planet in 1000 produces a technological race, you get roughly one new race every million years. When the first planets arose, the rate would have been much lower, less than one in the time needed to build a galaxy-wide network.

It depends on 'birth' and 'death' rates versus stellar population density and everage lifespan of each civ.


Only if you think of physical travel. It's hard to fight by email with a 10,000 year reply delay ;-)

Nah, the first to arise would build their galaxy spanning network


Would it be possible to maintain any kind of unified entity over the distances/time scales you're talking about? ... You'd end up with competing empires.

Worse, you end up with isolated, unique stellar communities diverging faster than changes could be communicated.