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From NASA
Spitzer Space Telescope revealed that some of the oldest in the universe
the galaxies were brighter than expected. Excess light is a byproduct of the
galaxies releasing incredibly high amounts of ionizing radiation. Discovery
offers clues to the cause of the era of reionization, a major cosmic event
which turned the universe from being mostly opaque to brilliant
starscape seen today.
In a new study,
researchers report observations of some of the first galaxies to form in the
the universe, less than a billion years after the big bang (or a little more than
13 billion years ago). The data show that in a few specific wavelengths of
infrared light, galaxies are considerably brighter than scientists
anticipated. The study is the first to confirm this phenomenon for a large
sampling of galaxies from this period, showing that they were not special
cases of excessive brightness, but that even the average galaxies present at this
the weather was much brighter in these wavelengths than the galaxies we see today.
Nobody
know for sure when the first stars of our universe come to life. But evidence
suggests that between about 100 million and 200 million years after the big
bang, the universe was mostly filled with neutral hydrogen that had maybe
has just begun to merge into stars, which then began to form the first galaxies.
About a billion years after the big bang, the universe had become a spark
firmament. Something else had changed too: the electrons of the ubiquitous neuter
the gaseous hydrogen had been removed by a process called ionization. L & # 39; s time
of reionization – the passage from a universe filled with neutral hydrogen to
one filled with ionized hydrogen – is well documented.
Before
this scale-wide transformation of the universe, long-wave light forms, such as radio
waves and visible light, have crossed the universe more or less unencumbered. But shorter
wavelengths of light – including ultraviolet light, x-rays and gamma rays –
were stopped short by neutral hydrogen atoms. These collisions would strip the neutral
the hydrogen atoms of their electrons, ionizing them.
But
which could possibly have produced enough ionizing radiation to affect all
hydrogen in the universe? Was it individual stars? Giant galaxies? If one or the other
the culprit, these early cosmic colonizers would have been different from most
modern stars and galaxies, which usually do not release large amounts of
ionizing radiation. Then again, maybe something else has entirely caused the
like quasars – galaxies at the center incredibly bright, powered by
huge amounts of material orbiting supermassive black holes.
"His
one of the biggest open questions of observational cosmology ", said
Stephane De Barros, lead author of the study and postdoctoral researcher at
the University of Geneva in Switzerland. "We know it happened, but what
the cause? These new discoveries could be a big clue. "
In search of light
AT
look at the time just before the end of the reionization era, Spitzer
looked at two regions of the sky for more than 200 hours each, allowing the
space telescope to collect the light that had traveled for over 13 billion
years to reach us.
Like some
longest scientific observations ever made by Spitzer, they were part of
of an observation campaign called GREATS, abbreviation of GOODS Re-ionization Era
Spitzer wide area treasure. GOODS (itself an acronym: Great Observatories
Origins Deep Survey) is another campaign that made the first observations
some GREATS targets. The study, published in the Monthly Notices of
Royal Astronomical Society, also used NASA's Hubble Space archive data
Telescope.
Using
these ultra-deep observations of Spitzer, the team of astronomers observed 135
distant galaxies and found that they were all particularly bright in two
Specific wavelengths of infrared light produced by ionizing radiation
interact with hydrogen and gaseous oxygen in galaxies. That implies
that these galaxies were dominated by massive young stars composed mostly of
hydrogen and helium. They contain very small amounts of "heavy" elements
(like nitrogen, carbon and oxygen) compared to the stars found in the modern average
galaxies.
These
the stars were not the first stars to form in the universe (these would have been
composed only of hydrogen and helium) but still belonged to a very old generation
d & # 39; stars. The era of reionization was not an instant event.
the new results are not enough to close the book on this cosmic event, they do it
provide new details on how the universe evolved at that time and on the
the transition has taken place.
"We
did not expect Spitzer, with a mirror no larger than a Hula-Hoop, to be
able to see galaxies so close to the dawn of time, "said Michael
Werner, project manager at Spitzer at NASA's Jet Propulsion Laboratory in
Pasadena, California. "But nature is full of surprises and unexpected
the brightness of these first galaxies, as well as the superb performance of Spitzer,
puts them within reach of our small but powerful observatory. "
From NASA
The James Webb Space Telescope, to be launched in 2021, will study the universe
many of the same wavelengths observed by Spitzer. But where primary Spitzer
the mirror measures only 85 centimeters (33.4 inches) in diameter, Webb measures 6.5 meters
(21 feet) – about 7.5 times larger – allowing Webb to study these galaxies from a distance
More details. In fact, Webb will try to detect the light of the first stars and
galaxies in the universe. The new study shows that because of their brightness in
In these infrared wavelengths, the galaxies observed by Spitzer will be easier to
Webb to study than previously planned.
"These
the results of Spitzer are certainly another step in the resolution of the cosmic mystery
reionisation, "said Pascal Oesch, assistant professor at the university
of Geneva and a co-author of the study. "We now know that the physical
the conditions in these early galaxies were very different from those of typical galaxies
aujourd & # 39; hui. The James Webb Space Telescope will be responsible for determining the
detailed reasons for which. "
JPL
manages the Spitzer Space Telescope mission for NASA's scientific mission
Direction to Washington. Scientific operations are conducted at Spitzer
Scientific Center at Caltech in Pasadena. Space operations are based in Lockheed
Martin Space Systems in Littleton, Colorado. The data is archived in the infrared
Scientific Archives hosted at IPAC in Caltech. Caltech manages the JPL for NASA.
For more
information about Spitzer, visit:
www.nasa.gov/spitzer
and www.spitzer.caltech.edu/
Media contact
Calla Cofield
Jet Propulsion Laboratory, Pasadena, California
626-808-2469
[email protected]
2019-084
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