it Seems that the Universe is more crowded than we had until now expected. According to a new census made thanks to the Hubble space telescope the number of galaxies could reach a total of two thousand billion, about ten times more than the previous estimates.
In this shot, collected by the Hubble space telescope, are revealed thousands of galaxies located in distant eras billion light-years. The image represents a part of a large census of galaxies called the Great Observatories Origins Deep Survey (GOODS). According to the researchers, who analyzed data from Hubble, about 90 percent of the galaxies in the observable Universe is too weak and too far away to be seen with the telescopes currently available to us. Credits: NASA, ESA, the GOODS Team and M. Giavialisco (University of Massachusetts, Amherst)
An international team of researchers, led by Christopher Conselice of the University of Nottingham, analyzed the data collected by Hubble in a volume of space that dates back to the times primordial of the Universe, finding a number of galaxies that are ten times higher than what was expected. The results were presented in the scientific journal The Astrophysical Journal and have important implications on the processes of the formation of galaxies.
most of the galaxies discovered are small and weak in brightness, with masses similar to those that today are satellites of our Milky Way galaxy. These objects of small size, reside in remote ages of the way of life of the Universe, and are then fused to form the biggest galaxies, leading to a decrease of density in more recent times.
“our results represent an important proof of the fact that the galaxies have undergone a significant evolution in the course of the history of the Universe, and it was reduced drastically in number through mergers later,” says Conselice. The work of Conselice and colleagues, designed to get to know with greater precision the number of galaxies present in the Universe, attempts to answer one of the fundamental questions of astronomy, who has kept busy generations of researchers.
artistic Representation of the space telescope the NASA/ESA Hubble in orbit around the Earth at around 600 km height. Credits: ESA
Between the mid-Nineties and early two thousand, the Hubble telescope has made two observations deep sky: the Hubble Deep Field and the Hubble Ultra Deep Field, acquired by pointing them in the same region of the sky for several hours, bringing the instrument to the limit of their capacity of observation. These first in-depth looks on our Universe have allowed us to estimate the number of galaxies observable at approximately 100 billion. The new study provides a new estimate of this number, which comes at least 10 times as much.
Conselice and his team reached this conclusion by studying in detail the deepest images from Hubble and the results already published by other research groups. Have rebuilt a profile, three-dimensional, in order to go back to different historical periods are observed. They also used mathematical models thanks to which they have been able to deduce the existence of a population of galaxies that are currently not visible from the telescopes at our disposal.
The final estimate shows that about 90 percent of the galaxies present in the Universe are currently too weak and distant to be seen. It is a myriad of small clumps of stars that merged over time to form galaxies as we know them today. One of the best candidates to reach in the future this large portion of small objects is the James Webb Space Telescope (JWST) NASA, the launch of which is expected in 2018.
Among the previous works, cited by Conselice and his colleagues in the course of the scientific article, there are many studies conducted by Adriano Fontana and his research group at the INAF – Astronomical Observatory of Rome. So we asked Fountain a comment to this result, which has attracted the attention of many.
“The number of galaxies present in the Universe is much greater than what we see, and this is known for a long time”, explains to the microphones of the Media INAF Fountain. “Colleagues have done a count up to date to quantify the number of objects that are intrinsically faint and very far away. They are structures that we cannot see, but we can extrapolate an estimate of their number from the distribution of brightness of the galaxies.”
“imagine, to observe the distribution of people on Earth. Also in this case there will be few large cities, and as they decrease in size, an increasing number of small countries. The same thing happens to the galaxies: looking at the Universe we see a number of objects of large size, but we know that there are a lot of smaller size that we can’t see exactly as we do not see the villages, observing the Earth from above”.
“We know that these galaxies are very small and light exist, we are able to stimarle. The point is that the majority of the stars contained in the galaxies, while these small contain a much smaller number,” continued Fountain. “The result is interesting, because it confirms something that we already knew: in the primordial age, there existed a large number of galaxies, very small, that for now are invisible to our eyes.”
“it is Also important to know what can be the small galaxies, because their minimum size depends on the type of dark matter present in the Universe. This is because in the past the dark matter, is thickened into lumps, and if the particles of which it is composed are cold, these lumps can be small, while if it is made of particles, the hot, the lumps of the initial must be larger in size, and then this second scenario, the galaxies are very small are formed in numbers very inferior.”
“The current limits of our observations does not allow us to arrive at an accurate estimate,” says Fountain. “Certainly, with JWST, the successor to the Hubble Space Telescope that will be launched in two years, we will be able to reach galaxies that are much smaller, and we can begin to explore this portion of the Universe.”
read more:
Watch the video on the INAF-TV:
Source: Media INAF | Written by Elisa Nichelli
No comments:
Post a Comment