Newly discovered galaxy could explain the birth of the first stars
It is surprisingly bright, opening up for a study of how the universe behaved 11 billion years ago. The galaxy, located by astrophysicist Håkon Dahle and his team of scientists, might more than anything else contribute to the knowledge on how stars where formed when the universe was only a fifth of its present age.
On a picture displaying a part of the universe - taken in 1976 - one can see a formation believed to be seven different stars in our own galaxy. However, the slightly bent pattern of stars has been proven to be something quite different: A very bright and far away galaxy.
– It is quite unbelievable to see clearly something so bright and large that is so far away. If the galaxy had been much brighter, we would have been able to observe it as an extended object rather than a point source on the night sky with our naked eye – as a body as big as Venus when it is closest to Earth! More importantly, this provides us with a unique possibility to understand more regarding the development of the universe, says Dahle.
Earlier this year Håkon Dahle and his team of astrophysicists presented the discovery in an article in the magazine Astronomy and Astrophysics.
The «first» stars of the universe
The galaxy is not the galaxy furthest away that we have been able to observe, but never have we seen a galaxy so far away this clearly.
– Consequently, we are able to obtain a lot of new information! Dahle confirms.
Information that will contribute in our understanding of the universe and its development.
– Studying this galaxy gives us an opportunity to examine how the universe's first stars were formed. Previously we haven’t been able to observe this type of young stars in galaxies so extremely far away, says Dahle.
Looing at this galaxy means looking 11 billion years back in time, to when the universe was only 2.8 billion years old. The universe today is 13.8 billion years old.
Most of the star formation in the universe occurred when the universe was between 2 and 5 billion years old. If we are to understand the development of galaxies through the history of the universe, we have to understand how the stars were created. Now we have that opportunity.
– We are talking about stars that are formed from a much smaller amount of heavy elements than we know from stars closer to us, which were formed far later. Until now we have had very little information regarding these ancient stars, says Dahle.
– In its early history the atoms in the universe almost solely consisted of hydrogen and helium. We now have the opportunity to study exactly how these elements formed the first stars. That is exciting in itself. However, this can furthermore pave the way for new discoveries that are unimaginable today.
A cosmic magnifying glass
The galaxy is very bright. However, there is an additional reason why we can observe this galaxy in such detail: A phenomenon called gravitational lensing.
Gravitational lensing is when light from far away objects is deflected in the gravitational fields of massive objects like galaxies and galaxy clusters. Under the influence of the substantial gravitational pull, the light rays arefocused towards us. This magnifies the image of faraway galaxies.
Consequently, this cosmic phenomenon makes us able to see remote and faint galaxies we otherwise wouldn’t be able to see.
– You might call gravitational lensing our “cosmic magnifying glass”! Without this phenomenon it would be impossible to observe objects as far away as we do today, says Dahle.
The light from this particular galaxy has become extraordinarily magnified because it has been gravitationally lensed by an especially massive galaxy cluster.
– The brightness is a lucky combination of the fact that the galaxy is substantially magnified by gravitational lensing and that it is also unusually bright. The galaxy is so bright in itself because it contains so many bright, young stars. This galaxy creates new stars at a rate 100 times faster than our own galaxy.
Guided in the right direction by Planck
Even the best pictures of the universe taken by the Hubble Space Telescope will only reveal one galaxy in a thousand to be strongly gravitationally lensed. It’s a spectacular phenomenon; the strongly lensed galaxies can be shaped like bright bent objects in the sky or split in several different images at the same time.
It is the gravitational deflection of light rays that creates these effects and distorts the image we observe. Additionally, the light can take several different paths through the lens and thus emerge on several different locations on the sky.
In this case, the gravitationally lensed galaxy is located in a part of the sky with a high density of foreground stars in our own galaxy. This is the reason why this interesting galaxy hasn’t been discovered earlier.
– It wasn’t until the Planck space observatory pointed out candidates for new galaxy clusters that we got on track. We found the gravitational lens itself so to speak, and consequently understood that the arc of light we see on the images actually is a distant galaxy.
The discovery is a result of studies made in the aftermath of working with data from the Planck satellite.
– Most of us working on this project used to work with data from Planck, Dahl confirms.
Read more about the Planck satellite: A glimpse of a new universe?
Hoping for better telescopes
The possibility of getting to know more about galaxies so far away brings on a lot of ideas.
– There is so much we don't know! We haven't been able to se how the physical conditions vary within the galaxy, like the distribution of gas, dust, old and new stars, wind and chemical composition, to name a few. This discovery gives us the perfect opportunity to study in detail how the physical conditions vary from place to place within a galaxy.
To find out more, the group wants time with the best telescopes on earth and in space.
– We have applied for observation time at a lot of telescopes to study the lensed galaxy in more detail than we already do. For instance, the Hubble Space Telescope will provide pictures that are 15 times sharper. And one can only imagine the amazing pictures we could get from the forthcoming James Webb Space Telescope!
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