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Phenomena across the Universe emit
radiation spanning the entire electromagnetic
spectrum — from high-energy gamma rays,
which stream out from the most energetic
events in the cosmos, to lower-energy
microwaves and radio waves.
The two galaxies shown here, imaged by
the NASA/ESA Hubble Space Telescope, are
named MCG+01-38-004 (the upper, red-tinted
one) and MCG+01-38-005 (the lower, blue-
tinted one). MCG+01-38-005 (also known as
NGC 5765B) is a special kind of megamaser;
the galaxy’s active galactic nucleus pumps
out huge amounts of energy, which stimulates
clouds of surrounding water. Water’s
constituent atoms of hydrogen and oxygen
are able to absorb some of this energy and
re-emit it at specific wavelengths, one of which
falls within the microwave regime, invisible
to Hubble but detectableby microwave
telescopes. MCG+01-38-005 is thus known as
a water megamaser!
Astronomers can use such objects to probe
the fundamental properties of the Universe.
The microwave emissions from MCG+01-
3 8-005 were used to calculate a refined
value for the Hubble constant, a measure
of how fast the Universe is expanding. This
constant is named after the astronomer
whose observations were responsible for
the discovery of the expanding Universe and
after whom the HubbleSpace Telescope was
named, Edwin Hubble.
PHOTO: ESA/Hubble & NASA
TEXT:European Space Agency
Hubble’s
Megamaser
Galaxy