In a first, researchers using the Atacama Large Millimeter/submillimeter
Array (ALMA) telescope have detected the faintest and mysterious
infrared light ever from space.
By accumulating millimetre-waves from
faint objects like this throughout the universe, the team determined
that such objects were 100 percent responsible for the enigmatic
infrared background light filling the universe.
By comparing these
to optical and infrared images, the team found that 60 percent of them
were faint galaxies whereas the rest had no corresponding objects in
optical/infrared wavelengths and their nature was unknown.
Astronomers
have found that there was faint but uniform light, called the "cosmic
background emission", coming from all directions.
This background
emission consists of three main components: Cosmic Optical Background
(COB), Cosmic Microwave Background (CMB) and Cosmic Infrared Background
(CIB).
The origins of the first two have been revealed. The COB
comes from a huge number of stars and the CMB comes from hot gas just
after the Big Bang.
However, the origin of the CIB was still to be solved.
A
research team led by graduate student Seiji Fujimoto and associate
professor Masami Ouchi from the University of Tokyo tackled this
mysterious infrared background by examining the ALMA data archive.
They went through the vast amount of ALMA data taken during about 900 days in total looking for faint objects.
"The
origin of the CIB is a long-standing missing piece in the energy coming
from the Universe. We devoted ourselves to analyzing the gigantic ALMA
data in order to find the missing piece," said Fujimoto.
Finally, the team discovered 133 faint objects, including an object five times fainter than any other ever detected.
The researchers found that the entire CIB can be explained by summing up the emissions from such objects.
ALMA
detected a part of the CIB with one mm wavelengths. The CIB in
millimetre and submillimetre waves does not become weak even if the
source is located far away.
Therefore, this wavelength is suitable for looking through the universe to the most distant parts, the authors said.
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