Welcome To Our Honeycomb-Centered Interstellar Cavity

The "void" between the stars is anything but empty. Interstellar space
is filled with the gaseous remains of supernova explosions, wispy
tendrils of plasma from stellar winds and star-forming nebulae. Some of
this gaseous matter forms magnetized cloud-like structures, the closest
of which is known as the "Local Fluff."

However, our solar system sits inside a volume of space that contains 10
times less gas than the galactic average. The sun -- and many nearby
stars -- is located in a "cavity" (known, unsurprisingly, as the "Local
Cavity") that measures approximately 300 light years across.

The presence of this region has been known for some time, but an
international team of astronomers have now created a 3-dimensional map
of this fascinating region of space in our cosmic backyard.

***
Interestingly, by analyzing one particular absorption line (caused by
doubly ionized calcium -- CaII), it appears that the Local Cavity
contains filamentary structures of partially ionized gas, creating a
honeycomb-like pattern of smaller interstellar cells.

Although the cause of this cell-like structuring is unknown at present,
it is thought that the Local Cavity was formed after a series of
supernovae detonated nearby, blowing the cool, dense interstellar medium
away and replacing it with a very tenuous volume of hot plasma, creating
a 'bubble.'

***
Welcome To Our Honeycomb-Centered Interstellar Cavity : Discovery News
http://news.discovery.com/space/welc...ar-cavity.html

Yousuf Khan wrote:
The "void" between the stars is anything but empty. Interstellar space
is filled with the gaseous remains of supernova explosions, wispy
tendrils of plasma from stellar winds and star-forming nebulae. Some
of this gaseous matter forms magnetized cloud-like structures, the
closest of which is known as the "Local Fluff."

However, our solar system sits inside a volume of space that contains
10 times less gas than the galactic average. The sun -- and many
nearby stars -- is located in a "cavity" (known, unsurprisingly, as
the "Local Cavity") that measures approximately 300 light years
across.
The presence of this region has been known for some time, but an
international team of astronomers have now created a 3-dimensional map
of this fascinating region of space in our cosmic backyard.

***
Interestingly, by analyzing one particular absorption line (caused by
doubly ionized calcium -- CaII), it appears that the Local Cavity

Ca II is singly-ionized...I see the mistake is in the article.

Indeed, these lines have been observed since the early days of stellar
spectroscopy. They were for a long time called "stationary lines" because
if you observed a binary star, the stellar lines would vary in radial
velocity but the Ca II H and K lines (3933 and 3968 A) would stay at
constant velocity. It took a while to realize they were from the
interstellar gas.

contains filamentary structures of partially ionized gas, creating a
honeycomb-like pattern of smaller interstellar cells.

Although the cause of this cell-like structuring is unknown at
present, it is thought that the Local Cavity was formed after a
series of supernovae detonated nearby, blowing the cool, dense
interstellar medium away and replacing it with a very tenuous volume
of hot plasma, creating a 'bubble.'

***
Welcome To Our Honeycomb-Centered Interstellar Cavity : Discovery News
http://news.discovery.com/space/welc...ar-cavity.html

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

Mike Dworetsky wrote:
Yousuf Khan wrote:
Interestingly, by analyzing one particular absorption line (caused by
doubly ionized calcium -- CaII), it appears that the Local Cavity

Ca II is singly-ionized...I see the mistake is in the article.

Yes, this other article has the proper description, it's Sodium that is
doubly-ionized.

A new 3D map of the interstellar gas within 300 parsecs from the Sun
"The team, led by Barry Y. Welsh and his colleagues R. Lallement and
J.-L. Vergely, presents new, high spectral resolution measurements of
the calcium (CaII) K line (at 3933 Ĺ) and the sodium doublet (at 5889
and 5895 Ĺ). These absorption lines have long been used to study the
interstellar medium."
http://www.physorg.com/news184953624.html


Yousuf Khan

"Yousuf Khan" wrote in message
...
Mike Dworetsky wrote:
Yousuf Khan wrote:
Interestingly, by analyzing one particular absorption line (caused by
doubly ionized calcium -- CaII), it appears that the Local Cavity

Ca II is singly-ionized...I see the mistake is in the article.

Yes, this other article has the proper description, it's Sodium that is
doubly-ionized.

A new 3D map of the interstellar gas within 300 parsecs from the Sun
"The team, led by Barry Y. Welsh and his colleagues R. Lallement and J.-L.
Vergely, presents new, high spectral resolution measurements of the
calcium (CaII) K line (at 3933 L) and the sodium doublet (at 5889 and 5895
L). These absorption lines have long been used to study the interstellar
medium."
http://www.physorg.com/news184953624.html


Yousuf Khan

A doublet does not mean "doubly ionized".
http://hyperphysics.phy-astr.gsu.edu...um/sodzee.html

An ionized atom has an electron completely removed or added,
that takes far more energy than kicking it up or down a level or two.

Androcles wrote:
A doublet does not mean "doubly ionized".
http://hyperphysics.phy-astr.gsu.edu...um/sodzee.html

An ionized atom has an electron completely removed or added,
that takes far more energy than kicking it up or down a level or two.


Point taken.

Yousuf Khan

Yousuf Khan wrote:
Mike Dworetsky wrote:
Yousuf Khan wrote:
Interestingly, by analyzing one particular absorption line (caused
by doubly ionized calcium -- CaII), it appears that the Local Cavity

Ca II is singly-ionized...I see the mistake is in the article.

Yes, this other article has the proper description, it's Sodium that
is doubly-ionized.

No, the sodium is actually neutral, designated Na I. The two lines of the
doublet mentioned are what cause the yellow colour of low pressure sodium
lamps.

A new 3D map of the interstellar gas within 300 parsecs from the Sun
"The team, led by Barry Y. Welsh and his colleagues R. Lallement and
J.-L. Vergely, presents new, high spectral resolution measurements of
the calcium (CaII) K line (at 3933 Ĺ) and the sodium doublet (at 5889
and 5895 Ĺ). These absorption lines have long been used to study the
interstellar medium."
http://www.physorg.com/news184953624.html


Yousuf Khan



--
Mike Dworetsky

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