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Nearby Dust Clouds in the Milky Way


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#1    Waspie_Dwarf

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Posted 04 April 2006 - 04:43 PM

Nearby Dust Clouds in the Milky Way


NASA's Hubble Space Telescope has photographed dense knots of dust and gas in our Milky Way Galaxy. This cosmic dust is a concentration of elements that are responsible for the formation of stars in our galaxy and throughout the universe. These dark, opaque knots of gas and dust are called "Bok globules," and they are absorbing light in the center of the nearby emission nebula and star-forming region, NGC 281. These images were taken with Hubble's Advanced Camera for Surveys in October 2005. NGC 281 is located nearly 9,500 light-years away in the direction of the constellation Cassiopeia.

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Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Acknowledgment: P. McCullough (STScI)


The yearly ritual of spring cleaning clears a house of dust as well as dust "bunnies," those pesky dust balls that frolic under beds and behind furniture. NASA's Hubble Space Telescope has photographed similar dense knots of dust and gas in our Milky Way Galaxy. This cosmic dust, however, is not a nuisance. It is a concentration of elements that are responsible for the formation of stars in our galaxy and throughout the universe.

These opaque, dark knots of gas and dust are called "Bok globules," and they are absorbing light in the center of the nearby emission nebula and star-forming region, NGC 281. The globules are named after astronomer Bart Bok, who proposed their existence in the 1940's.

Bok hypothesized that giant molecular clouds, on the order of hundreds of light-years in size, can become perturbed and form small pockets where the dust and gas are highly concentrated. These small pockets become gravitationally bound and accumulate dust and gas from the surrounding area. If they can capture enough mass, they have the potential of creating stars in their cores; however, not all Bok globules will form stars. Some will dissipate before they can collapse to form stars. That may be what's happening to the globules seen here in NGC 281.

Near the globules are bright blue stars, members of the young open cluster IC 1590. The cluster is made up of a few hundred stars. The cluster's core, off the image towards the top, is a tight grouping of extremely hot, massive stars with an immense stellar wind. The stars emit visible and ultraviolet light that energizes the surrounding hydrogen gas in NGC 281. This gas then becomes super heated in a process called ionization, and it glows pink in the image.

The Bok globules in NGC 281 are located very close to the center of the IC 1590 cluster. The exquisite resolution of these Hubble observations shows the jagged structure of the dust clouds as if they are being stripped apart from the outside. The heavy fracturing of the globules may appear beautifully serene but is in fact evident of the harsh, violent environment created by the nearby massive stars.

The Bok globules in NGC 281 are visually striking nonetheless. They are silhouetted against the luminous pink hydrogen gas of the emission nebula, creating a stark visual contrast. The dust knots are opaque in visual light. Conversely, the nebulous gas surrounding the globules is transparent and allows light from background stars and even background galaxies to shine through.

These images were taken with Hubble's Advanced Camera for Surveys in October 2005. The hydrogen-emission image that clearly shows the outline of the dark globules was combined with images taken in red, blue, and green light in order to help establish the true color of the stars in the field. NGC 281 is located nearly 9,500 light-years away in the direction of the constellation Cassiopeia.

Ground-Based Image of the Star-Forming Region NGC 281

user posted image

This wide-field view of the star-forming region NGC 281 in the constellation Cassiopeia was taken with the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, AZ.

Credit: T.A. Rector/University of Alaska Anchorage and WIYN/AURA/NSF

Image of the Constellation Cassiopeia

user posted image

This back-yard view of the constellation Cassiopeia was taken by Akira Fujii. The center bar of the Milky Way Galaxy runs through the middle of the constellation and the image.

Credit: A. Fujii


Source: Hubble - News Centre

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#2    Avinash_Tyagi

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Posted 04 April 2006 - 05:48 PM

I heard NASA is going to take Hubble off line soon, any word on when that's supposed to happen?

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#3    Waspie_Dwarf

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Posted 04 April 2006 - 06:32 PM

Quote


I heard NASA is going to take Hubble off line soon, any word on when that's supposed to happen?


It all depends on an on/off shuttle mission. For Hubble to remain healthy it needs another service from a space shuttle. However a shuttle which is in the correct orbit to service Hubble can not make it to the International Space Station in an emergency, something that is considered a safety requirement since the Columbia accident. As a result of this the service mission was cancelled by Sean O'Keefe, the previous NASA administrator, as being too risky.

This caused a lot of protests amongst the scientific community who said that the small risk was worth it for the great gains. When Dr. Michael Griffin, the new NASA administrator, took over in April 2005 he reinstated the mission. However since the publication of the FY2007 NASA budget it seems that this mission is no longer on the cards.

Hubble has some health issues. It needs gyros to point accurately, but as these are moving parts they will wear out. In August 2005 Hubble's software was been modified so that it can operate using 2 out of it's 3 gyros. A healthy gyro was switched off thus keeping it in reserve as a back up in case of failure.

NASA is likely to order the deliberate re-entry of Hubble at sometime in the future. It is a large object and would represent a potential hazard if it were allowed to fail in orbit and re-enter in an un-controlled manner. When this will be is likely to depend on the telescopes health.

NASA is building a Next Generation Space Telescope called the James Webb Space Telescope (JWST). This however will not be launched until at least 2013, several years after Hubble dies. The JWST will not be in a low Earth orbit, as Hubble is but will be in an orbit known as the second Lagrange Point (L2). This L2 point is a point where the Sun and Earths gravitational pulls cancel each other out. It is nearly a million miles form Earth (4 times the moons distance). JWST will have a 20 foot primary mirror as opposed to Hubbles 8foot. However it will do virtually all of it's observing in infra-red rather than optical wavelengths.


"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#4    zandore

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Posted 04 April 2006 - 07:01 PM

Yesterdays APOD

It goes with this thread.

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#5    OracleTracker

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Posted 05 April 2006 - 04:48 PM

Those are some pretty good pictures of.... space dust? hmm. fascinating.


#6    DR. YO

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Posted 05 April 2006 - 04:50 PM

Nice pic, I think I'm going to use one on my desktop.  thumbsup.gif  thumbsup.gif

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1. Those who make things happen.
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The vast majority of mankind find themselves in the last two categories. Most have "eyes to see" but don't "see" what is happening. Most have "ears that hear" but don't "understand" what IS happening --

#7    zandore

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Posted 05 April 2006 - 05:56 PM

Quote


Nice pic, I think I'm going to use one on my desktop.  thumbsup.gif  thumbsup.gif

More for you to look at Doc

space.com
same site different spot
Explore space.com there is a lot more than this.


But if you are more into the fantasy aspect.....Visual paradox

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Man would indeed be in a poor way if he had to be restrained by fear
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#8    frogfish

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Posted 05 April 2006 - 07:36 PM

The L2 point in which the NGST will be going up will obtain much better pictures than Hubble.

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#9    Waspie_Dwarf

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Posted 05 April 2006 - 09:16 PM

Quote


The L2 point in which the NGST will be going up will obtain much better pictures than Hubble.


Very true. The reason it will be at the L2 point is that being an infra-red instrument it needs to be well away from the heat of Earth. The down side of being at the L2 point is that if the JWST has a problem at launch, likr Hubble did, then it will not be repairable and the mission will be over before it starts.


"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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