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Spitzer's M101 (APOD 25 Jul 2008)

Posted: Fri Jul 25, 2008 4:32 pm
by emc
http://apod.nasa.gov/apod/ap080725.html

Looking outside our human vision spectrum sheds beautiful new light on old subjects. A most picturesque view indeed!

M101 being such a large galaxy... are there any evidences of having "eaten" smaller galaxies?

Also, aren't there evidences that our own Milky Way (such a wimpy name... how are we going to impress hostile aliens with that???) gobbled up other smaller galaxies?

BTW - I found M101 on sale today at only $27.50!!!! :wink:

Re: Spitzer's M101: APOD 20080725

Posted: Fri Jul 25, 2008 5:07 pm
by Case
emc wrote:M101 being such a large galaxy... are there any evidences of having "eaten" smaller galaxies?
Not sure about 'evidence', but it is the leading theory of how galaxies grow from small to large.
emc wrote:Also, aren't there evidences that our own Milky Way gobbled up other smaller galaxies?
http://apod.nasa.gov/apod/ap031117.html
http://apod.nasa.gov/apod/ap050529.html

Posted: Fri Jul 25, 2008 5:35 pm
by emc
Thanks for the reply and links Case!

Posted: Fri Jul 25, 2008 7:14 pm
by jesusfreak16
Wouldn't a collision between galaxies make life impossible inside them though?I mean wouldn't it produce too much radiation?

(just another of my patented amateur questions :wink: )

Posted: Fri Jul 25, 2008 7:18 pm
by Arramon
The space between is far and wide....

Posted: Fri Jul 25, 2008 7:25 pm
by bystander
What Arramon is saying, due to the distance between them, individual star systems would be largely unaffected by collisions of galaxies.

This is what everybody says, but sometimes I think it's like saying, "Because the space between atoms are so great, when two solids collide, they will simply pass through each other." I know from experience that this just doesn't happen, having beat my head against the wall many times.

Posted: Fri Jul 25, 2008 7:25 pm
by emc
jesusfreak16 wrote:Wouldn't a collision between galaxies make life impossible inside them though?I mean wouldn't it produce too much radiation?
I imagined some sort of "head bashing" myself at first but my Asterisk friend neufer explained a more realistic view pretty well...

http://asterisk.apod.com/vie ... tars#91123 link to his post

Posted: Fri Jul 25, 2008 7:34 pm
by bystander
:lol: Hello, Ed! I see we both have head bashing on our minds. I see also you figured out how to link to specific posts.

Posted: Fri Jul 25, 2008 7:41 pm
by emc
:lol: Hi bystander! Scared me at first... posting at the same time talking about head bashing... you know all that talk I do about aliens... made me start to wonder if I might be right???

Thanks for your help with pointing to other's posts.... 8)

Posted: Fri Jul 25, 2008 7:43 pm
by apodman
According to NASA/Spitzer ...

"Spitzer is particularly adept at observing [PAHs], which are useful indicators of organic chemistry and the possibilities for life throughout the universe."

and

"To an astronomer, PAHs are powerful tools for exploring the building blocks necessary for the origins of life in the stars and galaxies beyond the Earth."

and

"PAHs provide a useful probe into such regions, and provide clues to the abundance of potentially life-bearing chemicals."

So it appears that the presence of PAHs is taken to be a good sign for the possibility of life.

However, according to APOD ...

"PAHs are likely destroyed ... by energetic radiation in intense star forming regions."

So if I want life around my star, do I want it to be formed somewhere other than an "intense" star forming region?

If I want life around my star that was formed in an "intense" star forming region, how long do I have to wait after the radiation dies down for the galaxy's dust clouds to drift by and seed my system with organic molecules?

It appears to me they're not saying that PAHs are building blocks of life, but that they're an indicator that useful organic building blocks might be nearby. And I'm taking the leap of concluding that if the radiation destroys PAHs, it will do the same for other organic componds.

---

Hello emc and bystander,

Thanks for asking, answering, and providing the example for linking to a post. I wanted to know but didn't want to ask. You can also constuct the link manually (the hard way) if you have the post number - which you can get by viewing the html source code, finding the post, and looking for the <a name="nnnnn"> tag. Substitute the actual "nnnnn" digits (twice) in a link of the following form:

http://asterisk.apod.com/vie ... 5869#95869

(The "95869" in the example above is the number for this post.)

Whoops! The question and answer to which I refer are in another topic and so I will duplicate them here:
bystander wrote:
emc wrote:How did you link to RJN's post?
  • Go to Asterisk Search.
    Type in the desired username in Search for Author:.
    Limit the search by Category, Forum, Keywords, etc.
    Click Display results as: Posts.
    Start your search,
    Select the appropriate post and
    Copy the shortcut.

Posted: Fri Jul 25, 2008 8:15 pm
by bystander
apodman wrote:... So it appears that the presence of PAHs is taken to be a good sign for the possibility of life.
...
So if I want life around my star, do I want it to be formed somewhere other than an "intense" star forming region?

If I want life around my star that was formed in an "intense" star forming region, how long do I have to wait after the radiation dies down for the galaxy's dust clouds to drift by and seed my system with organic molecules?

It appears to me they're not saying that PHPs are building blocks of life, but that they're an indicator that useful organic building blocks might be nearby. And I'm taking the leap of concluding that if the radiation destroys PAHs, it will do the same for other organic componds.
http://en.wikipedia.org/wiki/Polycyclic ... ydrocarbon

<PAHs> are also found in the interstellar medium, in comets, and in meteorites and are a candidate molecule to act as a basis for the earliest forms of life.
I would think that the radiation in any star forming region would be too intense to support life. Even good ole Sol, in its exuberant youth, would have fried life on Earth. I'm thinking that the source of any PAHs on Earth came during the bombardment by asteroids and meteorites.
apodman wrote:... Thanks for asking, answering, and providing the example for linking to a post. I wanted to know but didn't want to ask. You can also constuct the link as shown manually (the hard way) if you have the post number - which you can get by viewing the html source code, finding the post, and looking for the <a> tag.
emc wrote:Thanks for your help with pointing to other's posts.
You are both quite welcome.

Posted: Fri Jul 25, 2008 9:23 pm
by Martin
However, life appears to have a strange ability to adjust to extreme conditions and the possibility of non-organic life might exist :idea:
A beautiful Apod image nonetheless.

Posted: Fri Jul 25, 2008 9:58 pm
by Arramon
http://query.nytimes.com/gst/fullpage.h ... yt&emc=rss
The first clue of interstellar collisions came in the 1950's when astronomers looked at clusters of stars they knew to be nearly as old as the universe and saw what appeared to be large, young blue stars. Blue stars contain more hydrogen than smaller stars, but burn hotter and burn out more quickly.

Within the star groups, known as globular clusters, the clouds of gas and dust that give birth to stars had been exhausted billions of years ago, which raised the question: where did these young blue stars come from?

At first, some astronomers speculated that these ''blue straggler'' stars had somehow conserved their fuel, but with the help of the Hubble Space Telescope, astronomers have concluded that a blue straggler star is actually two small, old stars that combined to form a rejuvenated blue star.

Collisions are more frequent in globular clusters, because there are many more stars. In the outer region of the galaxy where our solar system lies, the density of stars is about one per 10 cubic light-years. In a globular cluster, there may be several hundred thousand stars in that same space.

Dr. Shara's estimate of several hundred collisions per hour may seem frequent, but with 100 billion galaxies in the observable universe and each galaxy containing, on average, 30 globular clusters, most of the collisions occur far away and out of view.

According to his calculations, over the 10 billion-year lifetime of the Milky Way, Earth's home galaxy, there have been at least one million collisions within globular clusters -- or about one every 10,000 years.

While astronomers can spot the results of the collisions, the blue straggler stars, they almost certainly will never see the collisions.

This means that they cannot directly determine whether a particular blue straggler star originated in a binary system whose components coalesced or is the wreckage of two unrelated stars that happened to collide.

In one case, however, the answer appears to be the latter.

At the symposium, Dr. Rex Saffer, an assistant professor of astronomy and astrophysics at Villanova University, presented observations of several blue straggler stars within the globular cluster NGC 6397, located in the Milky Way about 7,000 light-years from Earth.

Based on the age of the cluster, its surviving stars should have masses of no more than 80 percent of the mass of the Sun; more massive stars should have burnt out.

However, four of the blue stragglers in the cluster were about 1.6 times the mass of the Sun, so they presumably represent the mergers of two stars.

One blue straggler was a whopping 2.4 times heavier -- ''so massive that it can't have formed by the merger of two stars,'' Dr. Saffer said. That straggler, he said, was probably born from a three-star collision, when an outsider star flew into a binary system.

''The stars go into a chaotic dance around each other,'' he said, and eventually bump into one another.
Old article, but still useful... =)

Posted: Fri Jul 25, 2008 10:09 pm
by Arramon
No Life Possible at Edges of the Pinwheel Galaxy

http://www.universetoday.com/2008/07/22 ... el-galaxy/
Using Spitzer's Infrared Array Camera and the Infrared Spectograph to carefully analyze the spectra of the PAHs, astronomers can more precisely identify the PAH features, and even deduce information about their chemistry and temperature. The astronomers found that, like the metals, the polycyclic aromatic hydrocarbons decrease in concentration toward the outer portion of the galaxy. But, unlike the metals, these organic molecules quickly drop off and are no longer detected at the very outer rim.

"There's a threshold at the rim of this galaxy, where the organic material is getting destroyed," said Gordon.

The findings also provide a better understanding of the conditions under which the very first stars and galaxies arose. In the early universe, there were not a lot of metals or PAHs around. The outskirt of the Pinwheel galaxy therefore serves as a close-up example of what the environment might look like in a distant galaxy.
----
Resisting Radiation

http://www.astrobio.net/news/modules.ph ... d&sid=1901
Lynn Rothschild of the NASA Ames Research Center says that radiation has always been a danger for life on Earth, and so life had to find ways to cope with it. This was especially important during the Earth’s earliest years, when the ingredients for life were first coming together. Because our planet did not initially have much oxygen in the atmosphere, it also lacked an ozone (O3) layer to block out harmful radiation. This is one reason why many believe life originated underwater, since water can filter out the more damaging wavelengths of light.

Yet photosynthesis – the transformation of sunlight into chemical energy – developed relatively early in the history of life. Photosynthetic microbes like cyanobacteria were using sunlight to make food as early as 2.8 billion years ago (and possibly even earlier).

Early life therefore engaged in a delicate balancing act, learning how to use radiation for energy while protecting itself from the damage that radiation could cause. While sunlight is not as energetic as X-rays or gamma rays, the UV wavelengths are preferentially absorbed by DNA bases and by the aromatic amino acids of proteins. This absorption can damage cells and the delicate DNA strands that encode the instructions for life.

“The problem is, if you’re going to access solar radiation for photosynthesis, you’ve got to take the good with the bad -- you’re also exposing yourself to the ultraviolet radiation,” says Rothschild. “So there’s various tricks that we think early life used, as life does today.”

Besides hiding under liquid water, life makes use of other natural UV radiation barriers such as ice, sand, rocks, and salt. As organisms continued to evolve, some were able to develop their own protective barriers such as pigmentation or a tough outer shell.

Thanks to photosynthetic organisms filling the atmosphere with oxygen (and thereby generating an ozone layer), most organisms on Earth today don’t need to contend with high energy UV-C rays, X-rays or gamma rays from space. In fact, the only organisms known to survive space exposure – at least in the short term - are bacteria and lichen. Bacteria need some shielding so they won’t get fried by the UV, but lichen have enough biomass to act as a protective spacesuit.

Spitzer's M101

Posted: Fri Jul 25, 2008 10:26 pm
by astrolabe
Hello all,

Does this mean that molecular clouds are only present within a galaxy? Sounds like PAHs are destroyed or cannot form at all in open space environments where perhaps purer, harsher doses of cosmic radiation like gamma and other types (tachyon maybe) go undiluted by stellar winds and billions of magnetospheres.

Molecular clouds seem to occur at certain distances within the edges of the x/y plane of a galaxy (like within the arms) and also keep within certain latitudes within the z thickness as well. PAHs and molecular clouds must, being both molecular, posses similar properties even if not the same composition.

Posted: Sat Jul 26, 2008 1:44 pm
by apodman
apodman wrote:You can also constuct the link [to a post] manually ... if you have the post number - which you can get by viewing the html source code, finding the post, and looking for the <a name="nnnnn"> tag. Substitute the actual "nnnnn" digits (twice) in a link of the following form:

http://asterisk.apod.com/vie ... 5869#95869
A discovery:

An easier way to find the "nnnnn" is to use the "Quote" link in the top right corner of the post. If your browser's status line (window bottom left) is enabled, hovering the mouse over the "Quote" link will display a URL that includes the post number. Failing that, actually clicking the "Quote" link as if you are going to respond will produce a page with the post number as part of its URL displayed at the top of the browser. This is post 95887.

We now return you to M101 and the search for life in the Universe.

Posted: Sat Jul 26, 2008 2:33 pm
by emc
Thanks apodman,

I tried your methodology and it works well also, like bystander's search tip... I added the following link to my browser favorites http://asterisk.apod.com/viewtopic.php?p= and simply type in the quote number indicated by the hover at the end of the browser address link (I posted above) and there I am... 8) Thanks for the tip!
apodman wrote:We now return you to M101 and the search for life in the Universe.
Don't worry, we're kinda sorta still on the APOD subject... searching for "life" in Asterisk. I have been here a year and still feel like I am in Asterisk101 (like M101 or Science 101) Yeah, I know, I like to stretccchhh things!!!

Scientists sometimes are a mystery to me... I mean these polycyclic aromatic hydrocarbon molecules... they say they are found in automobile exhaust and used as a primary ingredient in mothballs... yet they call them "aromatic"... AND they leave "fingerprints" too... (which is how we know there resident at M101). Maybe M101 has too many polluting automobiles? But if that is true... they probably don't have many moths. :(

Posted: Sat Jul 26, 2008 3:02 pm
by apodman
emc wrote:polycyclic aromatic hydrocarbon molecules ... found in automobile exhaust and ... mothballs ... yet they call them "aromatic"
I always found that piece of nomenclature odd.

Your carbon bonds can be "aromatic" or "aliphatic". I think aromatic forms closed rings while aliphatic forms open chains. You can buy floor coatings with resins of either type. Both smell. If you buy both and mix them together, they will never dry. Read all labels carefully.

Posted: Sun Jul 27, 2008 1:32 am
by neufer