We are all expecting the start of data collection by the summer of 2022 that will lead to discoveries by the telescope. James Webb. But, in the meantime, the astrophysicists continue to push the instruments at their disposal to their limits in order to go even further back into the past of the observable cosmos, in search of the first galaxies and the first supermassive black holes. We can convince ourselves of this with two publications today, one in Astrophysical Journal and the other in Monthly Notices of the Royal Astronomical Society Letters.
Astrophysicists report the discovery of a star named HD1 which is the farthest ever discovered to date since it has a value of z record, the quantity introduced by cosmologists to speak of a spectral redshift with the Hubble-Lemaître law linking this shift to a distance. It is also the oldest object detected since according to the equations of general relativity and the standard cosmological model strongly supported by, among other things, data from the Planck satellite concerning cosmic radiation (and despite the tension between these data and those of the supernovae for the estimate of theaccelerating expansion of the Universe observable), HD1 would be seen as it was about 13.5 billion years ago, i.e. only about 300 million years after the big Bang.
A quasar?
As explained in a press release from Center for Astrophysics | Harvard & Smithsonian in the United States, HD1 was discovered after more than 1,200 hours of observation with the Japanese Subaru telescope on the ground in Hawaii and the telescope Vista (acronym of English Visible and Infrared Survey Telescope for Astronomy) of the’ESOand in space the deceased the spitzer space telescope.
” It was very difficult to find HD1 among more than 700,000 objects », Explains in this press release Yuichi Harikane, astronomer at the University of Tokyo which discovered the galaxy. The researcher adds: The color red of HD1 matched surprisingly well the characteristics expected of a galaxy at 13.5 billionlight yearswhich gave me a little goosebumps when I found it. The astrophysicists then made observations using theAtacama Large Millimeter/submillimeter Array (Alma) to confirm the distance of HD1, which is about 100 million light-years further than GN-z11, the current confirmed holder of the record for the most distant galaxy.
Two things about HD1 remain to be established more firmly. First of all its distance, and it is planned to do so by observing it with the James-Webb. But also its exact nature because astrophysicists do not yet know very well whether they are observing an ordinary galaxy or a quasar with a supermassive black hole that would already contain around 100 million masses solar cells, which would be spectacular for a galaxy observed so soon after the Big Bang. The supermassive black hole of our Milky Way currently only contains 4 million, but it is true that in the case of M87* that’s just over 6 billion solar masses.
Or population III stars?
In fact, talking about an ordinary galaxy is not correct, and astrophysicists are even considering a more exotic than the observation of the most distant quasar discovered to date. Indeed, HD1 being very bright in the ultraviolet range, the researchers had first put forward the hypothesis that they were observing a galaxy with an outbreak ofstars (galaxy starburst in English) like the ones we already know. But the estimate of the star formation rate needed to explain the brightness of HD1 implies that the galaxy would form more than 100 new stars each year, which is 10 times more than theoretically expected from starburst galaxies based on those observed.
However, as the astrophysicist explains Fabio Pacucci stationed at Center for Astrophysics | Harvard & Smithsonianlead author of the study published in Mnras and co-author of the article in ApJ: “ The very first population of stars that formed in the universe were more massive, brighter and hotter than modern stars. If we assume that the stars produced in HD1 are these first stars, say of People III, then its properties could be explained more easily. In fact, the stars of the people III are capable of producing more UV light than normal stars, which could account for HD1’s extreme ultraviolet luminosity. »
This is one more reason to wait impatiently for the observations of the James-Webb.
The telescopes atop Mauna Kea, like here, including the Keck Observatory telescopes shown in this video, allow us to probe the secrets of the cosmos. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Explore Documentary Films
Record: a galaxy 380 million years after the Big Bang?
Article of Laurent Sacco published on 14/12/2012
A group of astronomers has discovered 7 of the most distant galaxies known, observed over a period extending between 350 and 600 million years after the Big Bang. One of them might even hold a record. Hubble shows it maybe when the cosmos was only 380 million years old.
Astronomers have been studying the Hubble Ultra Deep Field (HUDF). From 2003 to 2004, the Hubble instruments observed for several hours, spread over a period of 11 days in total, a small region of the celestial vault located in the constellation of the Furnace. The astrophysicists had thus obtained an image in the visible on which there were both galaxies nearest and oldest known at the time. In 2009, the arrival of the Wide Field Camera 3 (WFC3) aboard Hubble had made it possible to make observations in infraredrevealing even older galaxies that are difficult to observe due to their low luminosity and greater redshift.
A group of astronomers has just published an article on arxiv covering observations of part of the HUDF in the near infrared for 6 weeks, from August to September 2012.
The Du Big Bang au Vivant site is a French-speaking multiplatform project on the cosmology contemporary. Hubert Reeves, Jean Pierre Luminet and other researchers there answer questions using videos. © ECP Group, www.dubigbangauvivant.comYoutube
The balance sheet ofHubble Ultra Deep Field 2012 has arrived
The harvest turned out to be good as the researchers obtained more precise measurements and more solid concerning galaxies observed when the age of the observable universe did not exceed 600 million years. With the observable cosmos estimated to be 13.7 billion years old, new Hubble images reveal 7 galaxies to us while our space and the matter it contains were only 4% of their current age, in the words of the researchers.
Observations still consistent with the Big Bang
These 7 galaxies would have ages between 350 and 600 million years after the birth of the observable universe, so at the time when the first stars and the first galaxies reionized the universe, according to information recently deduced from the cosmic radiation. One of these galaxies is particularly interesting and it is not unknown. It is UDFj-39546284.
Almost two years ago, it was already presented as the most distant galaxy known, but the estimate of its age, and therefore of its distance, was still uncertain. Another galaxy had been proposed for the title of oldest and most distant observed: SXDF-NB1006-2.
UDFj-39546284 could be observed when only 380 million years have passed since theepisode fossil radiation. If that’s the case, it’s further away than we first thought, and it even holds the distance record. Technically, its redshift, z, was initially thought to be around 10, when it appears to be 11.9.
The 2012 observation campaign of the Hubble Ultra Deep Field has not only pushed the limits of the observable universe in the infrared even further with Hubble. The images and measurements obtained also show a very young cosmos in formation, such as it has not been for billions of years, and in full agreement with the theory of the big Bang. They give us a taste of what the telescope should reveal to us James Webb in a few years, with much more detail.
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