February 5, 2008

Cosmic Finger Taps Our Galaxy’s Shoulder

As if
reaching out with a come-hither motion, a giant gas finger emanating from two neighboring
galaxies has hooked into the starry disk of the Milky Way and is pulling all three
galaxies closer.

extremity of hydrogen gas is actually the pointy end of the so-called Leading
Arm of gas that streams ahead of two irregular galaxies called the Large and
Small Magellanic Clouds.

The fate of
these nearby galaxies, which are impacted by the Milky Way's gravity, has been
somewhat of a mystery. The new finger findings suggest that the Magellanic
Clouds will eventually merge with the Milky
rather than zooming past.

about 160,000 light-years from Earth, the Large Magellanic Cloud (LMC) is only
one-twentieth the diameter of our galaxy and contains one-tenth as many stars.
The Small
Magellanic Cloud
resides 200,000 light-years from Earth and is about 100
times smaller than the Milky Way.

thrilled because we can determine exactly where this gas is plowing into the
Milky Way," said research team leader Naomi McClure-Griffiths of CSIRO's
Australia Telescope National Facility.

HVC306-2+230, the gas finger is gouging into our galaxy's starry disk about
70,000 light-years away from Earth. In the night sky, the contact point would
be nearest the Southern Cross.

Until last
year, astronomers thought the Magellanic Clouds had orbited our galaxy many
times. This scenario held a gloomy outlook for the clouds, which were said to
be doomed to be ripped apart and swallowed by the gravitational goliath.

But then
new Hubble Space Telescope measurements revealed the clouds are paying our galaxy
a one-time
rather than being its lunch.

results, however, are more in line with the previous tale pegging the Milky Way
and the Magellanic Clouds as long-time companions. McClure-Griffiths remarks
that this isn't the final word and that both theories are still on the table.

By pointing
out the spot of contact between the Leading Arm and our galactic disk, the
recent study will help astronomers to predict where the clouds themselves will
travel in the future.

"We think
the Leading Arm is a tidal feature, gas pulled out of the Magellanic Clouds by
the Milky Way's gravity," McClure-Griffiths said. "Where this gas goes, we'd
expect the clouds to follow, at least approximately."

In the
distant future, the three galaxies could become one.