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Fraser
2004-Aug-12, 10:51 PM
SUMMARY: The Hubble Space Telescope has revealed an unusual situation where a young, hot star is carving out a cavity in a region of space that was once filled with cold, dense material. The massive star is known as N44F, and its stellar wind is moving nearly 5 times as fast as our Sun's solar wind. It's also ejecting 100 million times more material than the Sun. The fast moving torrent of particles collides with the colder surrounding material, pushes it away, and heats it up. N44F is in the Large Magellanic Cloud, located 130,000 light-years from Earth in the direction of the southern constellation Dorado.

What do you think about this story? Post your comments below.

om@umr.edu
2004-Aug-12, 11:24 PM
An interesting story, Fraser.

What is the basis for concluding that winds from this star are "carving out a cavity in a region of space that was once filled with cold, dense material"?

How do they know the surrounding material was once cold and dense?

With kind regards,

Oliver
http://www.umr.edu/~om

Littlemews
2004-Aug-13, 01:27 AM
Interseting stroy, by the way what is the average speed of solar wind of our Sun anyway :unsure: ?

Eric Vaxxine
2004-Aug-13, 02:13 PM
Do you suppose one day we'll be able to travel to these places (and view from a safe distance,obviously)

Guest
2004-Aug-14, 02:36 PM
What's the difference between this star's situation and our Sun's when it was young?

jitte
2004-Aug-14, 07:01 PM
Originally posted by Littlemews@Aug 13 2004, 01:27 AM
Interseting stroy, by the way what is the average speed of solar wind of our Sun anyway :unsure: ?
The solar wind is a flow of gases from the Sun that streams past the Earth at speeds of more than 500 km per second, or one million miles per hour.

VanderL
2004-Aug-14, 07:22 PM
The solar wind is a flow of gases from the Sun that streams past the Earth at speeds of more than 500 km per second, or one million miles per hour.


It is a plasma, and the speed varies from almost zero at the solar surface to the 500 km/s at Earth's orbit to even higher speeds further away. It can also suddenly stop (as it happened a few years back) and it is thought to end at the hlioesphere boundary, close to where the Pioneer probes are.

Cheers.

jitte
2004-Aug-14, 07:29 PM
Plasma is a hot ionized gas.

The solar wind is the supersonic outflow into interplanetary space of plasma from the Suns corona, the region of the solar atmosphere beginning about 4000 km above the Suns visible surface and extending several solar radii into space. It is composed of approximately equal numbers of ions and electrons; the ion component consists predominantly of protons (95%), with a small amount of doubly ionized helium and trace amounts of heavier ions. Embedded in the outflowing solar wind plasma is a weak magnetic field known as the interplanetary magnetic field (IMF).

The solar wind varies in density, velocity, temperature, and magnetic field properties with the solar cycle, heliographic latitude, heliocentric distance, and rotational period. It also varies in response to shocks, waves, and turbulence that perturb the interplanetary flow. Average values for solar wind velocity, density, and magnetic field strength at the orbit of the Earth are 468 km per second; density, 8.7 protons per cubic centimeter, and 6.6 nT, respectively.

VanderL
2004-Aug-14, 07:47 PM
Sorry Jitte,

My comment wasn't meant as a challenge, just some added info.
On more thing, if only a part of a gas is ionized it still qualifies as a plasma, it responds to magnetic/electric fields as the solar wind clearly does when it interacts with other plasma spheres.
And the solar wind has been recorded as being almost zero (in May 2002, I believe), which is pretty amazing.

Cheers.

May 1999, I looked it up.

jitte
2004-Aug-14, 08:09 PM
It was my fault, VanderL. Sorry if I seemed arguementative. :)

VanderL
2004-Aug-14, 08:50 PM
It was my fault, VanderL. Sorry if I seemed arguementative. :)


Forget it, no offense taken. ;)
Btw what do you think caused this solar wind stop, I've seen reports where someone thought a Gamma-Ray Burst ( I forget which one) would have been able to make it stop. Not likely I think, but it should somehow be tied to the magnetic (solar) cycle and it's apparent variability.

Cheers.

jitte
2004-Aug-14, 11:24 PM
I remember reading about it having stopped but not if they knew why, I didn't start my site till Nov 99. That was right at Solar Max though and you're probably right about it being a factor.

I removed some of the SEC space weather bulletins to make the page load faster but may still have them on disk for 99. I'll see if I can dig something up on it. ;)

jitte
2004-Aug-15, 12:34 AM
This is from the page for the NASA report on the solar wind stopping:

"According to observations from the ACE spacecraft, the density of helium in the solar wind dropped to less than 0.1% of its normal value, and heavier ions, held back by the Sun's gravity, apparently could not escape from the Sun at all. Data from NASA's SAMPEX spacecraft reveal that in the wake of this event, Earth's outer electron radiation belts dissipated and were severely depleted for several months afterward. "

http://science.nasa.gov/newhome/headlines/...st13dec99_1.htm (http://science.nasa.gov/newhome/headlines/ast13dec99_1.htm)

VanderL
2004-Aug-15, 09:31 AM
Thanks Jitte,

Ok, let's take a look at this NASA comment:


"According to observations from the ACE spacecraft, the density of helium in the solar wind dropped to less than 0.1% of its normal value, and heavier ions, held back by the Sun's gravity, apparently could not escape from the Sun at all. Data from NASA's SAMPEX spacecraft reveal that in the wake of this event, Earth's outer electron radiation belts dissipated and were severely depleted for several months afterward. "

From the same source it was said that the protons were down to 1% of their normal average value, helium even more as stated in the quote and the heavier ions were even absent. So we see a different behaviour of the ions due to either their mass, or charge. The radiation belts disappeared as well, making it plausible that there wouldn't be radiation belts without the solar wind. But there is no telling why this event happened, standard models tell us that the solar wind is produced by the radiation pressure from the Sun, so would that mean that the Sun stopped producing enough pressure to create the solar wind?
It takes 100,000 years for energy produced at the core to reach the surface, or so it is believed. Does that mean that 100,000 years ago the Sun had a severe hiccup? What happened, and why is this finding not one of the big questions that needs answering?
And if we know what makes the solar wind behave the way it does, we can maybe see how the "bubble" that started this topic is created.

Cheers.

jitte
2004-Aug-15, 01:44 PM
Maybe we should start a new thread, so as not to hijack this one, but I think we have to look at the big picture. The solar wind stopping and the 3 largest solar storms ever recorded happened within the past few years, barely an interval between them in a stars lifetime.