- 3839 - RADIO ASTRONOMY - probing new distances? The detection of the special radio wavelength from the most distant galaxy means astronomers may be ready to investigate how the earliest stars form. Astronomers have detected a radio signal from the most distant galaxy yet.
--------- 3839 - RADIO ASTRONOMY - probing new distances?
- Radiowaves and astronomy almost seem like a
contradiction. But, radiowaves are just the broad wavelength of
the electromagnetic spectrum. Light,
Ultraviolet and gamma rays are at the other end,with the smallest wavelengths.
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- The signal was detected at a special and
significant wavelength known as the "21-centimeter line" or the
"hydrogen line," which is emitted by neutral hydrogen atoms.
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- The detection of the hydrogen line from
such a galaxy so far away and therefore so early in the universe by the
“Giant Metrewave Radio Telescope” in India could mean astronomers are ready to
begin investigating the formation of the earliest stars and galaxies.
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- The signal from the star-forming galaxy
SDSSJ0826+5630 was emitted when our 13.8 billion-year-old galaxy was just 4.9
billion years old. The signal allowed the astronomers to measure the galaxy's
gas content and find that its mass is double that of the early galaxy's visible
stars.
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- Galaxies emit electromagnetic radiation, or
light, across a wide range of radio wavelengths, but thus far 21-cm-wavelength
radio waves have only been seen from nearby and thus more recent galactic
sources.
-
- It's the equivalent to a look-back in time
of 8.8 billion years. A galaxy emits
different kinds of radio signals. Until now, it's only been possible to capture
this particular signal from a galaxy nearby, limiting our knowledge to those
galaxies closer to Earth.
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- The difficulty in spotting these
wavelengths from more distant galaxies is due to the fact that as
electromagnetic radiation from early galaxies travels vast distances to Earth,
the expansion of the universe stretches its wavelength and causes its energy to
reduce. That means telescopes here on Earth need a natural boost to see
long-wavelength, low-energy radio waves like the hydrogen line signal.
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- General relativity suggests that objects
with mass warp spacetime similar to how a ball placed on a stretched rubber
sheet would weigh it down in the center, and just like in that analogy, the
greater the mass, the more extreme the curvature.
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- That means a tremendously massive object
like a black hole or galaxy causes extreme curvature in spacetime just as a
bowling ball would cause the extreme curvature of the rubber sheet in the
analogy.
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- This curving of spacetime causes light to
bend as well as it passes by objects of tremendous mass. A phenomenon known as
gravitational lensing occurs when a foreground or lensing object of tremendous
mass sits between an observer and a background source, causing the light from
the background object to curve and take different paths through and around the
lensing object. This can not only make a single object appear at multiple
points in the sky, but it can also have the effect of magnifying this light.
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- In the case of SDSSJ0826+5630, the radio
wave signal was magnified by another galaxy between the early galaxy acting as
a lensing body. This effectively results
in the magnification of the signal by a factor of 30, allowing the telescope to
pick it up.
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- This could in turn open up a new way of
using long-wavelength radio telescopes to probe the evolution of stars and
galaxies and how the early universe evolved into the cosmos we see around us in
its current era.
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January 23, 2022 RADIO
ASTRONOMY - probing new distances 3839
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--------------------- --- Monday, January 23, 2023 ---------------------------
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