Scientists have discovered the forces that bind together a strange
network of 100-million-year-old, rope-like gas filaments that extend from an
enormous elliptical galaxy.
The filaments presented a puzzle because they should normally
collapse under the pressure of the hotter surrounding gas. New images from the Hubble Space
Telescope showed individual gas threads bundled together within the
filaments, which allowed researchers to estimate the magnetic fields necessary
to hold everything together.
"When you see a piece of rope from a distance it looks solid,
but when you look closely there's a lot of threads," said Andrew Fabian,
an astrophysicist at the University of Cambridge, U.K., who led the study
detailed in this week's issue of the journal Nature.
Previous images of the galaxy NGC 1275 barely showed bits of the
filaments, but Hubble's snapshots improved the view with 10 times more detail.
Individual threads now appear to stretch about 20,000 light-years. (A light-year
is the
distance light will travel in a year, or about 6 trillion miles or 10 trillion
kilometers.)
"It's not an astounding surprise, but the thing we can do is
calculate the magnitude of the magnetic field from the size of the
filaments," Fabian told SPACE.com. "Everything checks
out."
The filaments may represent the most visible effect of the
galaxy's central black hole on its gaseous surroundings. The black hole's high-energy
jets have heated up the gas to about 70 million degrees Fahrenheit (40
million Kelvin), which in turn produces glowing bubbles that float outward from
the galaxy center.
The bubbles pull colder gas outward behind them in the form of the
trailing filaments. Some filaments extend in radial lines outward from the
galaxy center, while others appear as horseshoe shapes.
Cold gas within the filaments could normally begin to condense and
start
forming stars, but the filaments' magnetic fields push against the
gravitational pressure and prevent star-birth.
Fabian and his study coauthors from the U.K. and United States see
NGC 1275 as just the closest example of many objects that could have filament
structures.
"It's known that many distant, massive galaxies are
surrounded by nebulae of gas which must be filamentary or clumpy," Fabian
noted. "We think similar filaments are there in those distant
objects."
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