Discoveries on Mysterious Galactic Blue Aura
a case of elusive quarry, scientists using NASA’s Chandra X-ray
Observatory have found for the first time a theorized dim halo
of hot gas around a spiral-shaped galaxy. This new discovery helps
to justify a highly regarded, yet unproven model for spiral galaxy
blue halo 60,000 light years across surrounds galaxy
NGC 5746 about 100
million light years away from Earth.
Copenhagen / K.Pedersen et al
"The halos exist, but are so faint that an extremely sensitive
telescope such as Chandra is needed to detect them," said
Kristian Pedersen of the University of Copenhagen in Denmark,
and lead scientist for the discovery. "Our observations
solve the mystery of the missing hot halos around spiral galaxies."
The galaxy is called NGC 5746 and is the same type as our own
Milky Way. The spiraling mass of stars and stellar objects sits
roughly 100 million light years from Earth. According to the
model, galaxies like NGC 5746 are thought to emerge from clouds
of intergalactic gas that cool and collapse to form giant, spinning
pinwheels of stars and debris. If the model is true, then the
gas left over from the formation of the galaxies will gradually
fall inwards, creating a halo of glowing gas. Despite scientists’
confidence in the concept and its associated predictions, the
hallmark halo has never been seen until now.
"We targeted NGC 5746 because we thought its distance and
orientation would give us the best chance to detect a hot halo," said
Jesper Rasmussen of the University of Birmingham in the United
Kingdom and a co-researcher in the study. "What we found
is in good agreement with computer simulations."
X-ray image of NGC 5044 (left) shows turbulence not visible
in optical images (right).
NASA/CXC/U. Ohio/T. Statler & S. Diehl; Optical:
Like a cosmic
riptide, supermassive black holes are creating a violent undertow
in seemingly calm elliptical galaxies.
This finding comes from astronomers
reviewing data gathered by Chandra on 56 of the oblong galaxies.
"Most elliptical galaxies have traditionally been considered
to be quiet places, like placid lakes," said astronomer
Thomas Statler from the Ohio University in Athens, Ohio. "Our
results show these galaxies are a lot stormier than we thought."
When viewed through optical telescopes in space
or on mountaintops, the elliptical galaxies appear docile.
It’s not until the galaxies
are examined in X-ray light by Chandra that they take on their
more unruly character. "This is another example of how valuable
it is to observe the universe at different wavelengths besides
just the traditional optical wavelengths," said scientist
Wilt Sanders of NASA’s Chandra program.
Statler and research partner Steven Diehl, also
of the Ohio University, believe massive clouds of hot gas within
are being stirred up by intermittent explosions. "Something
is definitely making a mess there, and pumping energy equivalent
to a supernova every century into the gas," said Diehl.
The source of the turbulent blasts? Statler and Diehl point to
supermassive black holes at the centers of the galaxies. Black
holes regularly devour nearby objects, and the two scientists
believe the violent ingestion of local gases is causing the galactic