Posts Tagged ‘milky way galaxy’
A Cosmic Mystery: Diffuse Interstellar Bands
Diffuse Interstellar Bands. (DIBS) What are they? No one knows. Where are they? In deep space. Were they the inspiration for Pink Floyd? I seriously doubt it. What am I talking about? Diffuse Interstellar Bands. Sheesh, pay attention.
OK, let’s start at the beginning, the early 20th century to be exact. Scientists by then were studying the light of stars. A spectrum is the light emitted by a star or bright object passed through a prism. Molecules in and near a star will block some of the spectrum, making dark stripes as seen above, these are called absorption or spectral lines. Thus scientists can tell what a star is made of. It even works with reflected light, this is how they tell what planets and asteroids are made of. This is all of course terribly simplified, because I have a very dim grasp of it all myself. All well and good until 1922, scientists happily studied what stars were made of. However, in 1922 astronomer Mary Lea Heger discovered some absorption lines that were much more diffuse than the typical lines in a star’s spectrum. She also found that the lines were associated with the galactic interstellar medium, not stars.
This was a head scratcher. People commonly think that space is a perfect vacuum. It isn’t, it varies widely, but one atom per cubic centimetre is the “average” density of interstellar space. It was thought this matter was so diffuse that while it might dim an entire spectrum slightly, it wouldn’t make lines. Well, sciencists were wrong, some molecules in interstellar space were apparently common enough to cause absorption lines. Mary discovered a few such lines, and by 1975 about 25 had been discovered. By 1994 when the first conference on DIBs was held, about 50 were known. Today about 300 have been discovered, illustrated above. The reason it’s a head scratcher is because no one knows exactly what molecules are creating these lines. Despite scientist’s best efforts, they have not been able to replicate the lines experimentally, or even come up with a theoretical calculation that explains the lines.
This is a major scientific mystery and has been for decades. For reasons I don’t understand, let alone can explain, it does seem pretty certain that the lines are caused by molecules, not single atoms. And it also is clear that numerous different molecules are involved, a single type of molecule couldn’t produce over 300 DIBs. The best guess is that they are being caused by long chain molecules. Polycyclic aromatic hydrocarbons, long carbon-chain molecules, and fullerenes are all strong suspects. And that’s that. Somehow our galaxy contains dust or gas of unknown origin or composition, what it is and how it is created is still a complete mystery.
Is this important? In a practical sense, no, figuring this out isn’t going to change our lives. Not figuring it out will have the same effect. It’s important though to understand that there are plenty of complete mysteries in our scientific understanding of the Universe. A lot of people, especially certain religious types, don’t seem to understand that. Science can’t currently explain everything, and there doesn’t appear to be any chance that it will ever explain everything. This isn’t a failure of science, th0ough it is oft presented as such by science-deniers, it is one of science’s greatest strengths. So whenever I stumble across an unsolved scientific mystery, I am impressed by the mystery itself, and I’m impressed by the fact that science even uncovered the mystery. Is there any chance that the solution to DIBs will force a re-examination of other aspects of science? Possibly, but I don’t know how possible. When it comes right down to it, our understanding of the cosmos is still in its infancy.
One last little observation is that I am always curious that science deniers miss things like this. If one was going to construct logical sounding attacks on science, mysteries like this would be a great place to start. Instead, the science deniers seem to make very little effort to find new arguments, and simply recycle old arguments. Some of the “objections” raised about evolution date from the nineteenth century for God’s sake. And while some of them were valid concerns then, a hundred years later they have long been laid to rest. I suppose it’s further evidence that science deniers are in actual denial about science, since few of them seem to take the time to even understand it well enough to construct modern arguments against it. Or it could mean that when people study science hard enough they realize its true, they are converted to science and reason?
Pause for laughter. Beats me. The older I get the more I find people and their motivations both painfully predictable … and painfully puzzling. It’s a conundrum it is.
(The above image is claimed as Fair Use under US copyright law. I got it off of Wikipedia so it’s safe to say that non-commercial use of the image is OK. And I left the copyright information on the image itself. Next a furniture history post, or a post about the recent discovery that the Universe is flat.)
What the Hell is That? (Number 3 in a series, if you want to guess, don’t read below the image.)
OK, we’ve all seen this before, on the view screen of the Starship Enterprise:
Kirk: “What is it Mr Spock?”
Spock: “I don’t know Captain, it’s not showing up on our sensors. It appears to be some sort of void in space.”
Kirk: “It’s avoiding us?! Arm phasers, load photon torpedoes!”
Spock: “It doesn’t appear to be hostile Captain, is that necessary?”
Kirk: “You heard me Mr. Spock. Fire!”
Dr McCoy: “Jim, did you take your medications this morning?”
Kirk: “Fire! Fire! Fire!”
Ah, I loved that show. We all did, what wonderful memories. Alas, that particular episode didn’t end very well as I recall. Moving right along, so, is that a void in space? Well, at one time that’s exactly what astronomers thought, they thought it was just what it appears to be, a region of space where for whatever reason there are no stars. Not for long though, astronomers quickly realized that these voids were clouds of gas and dust obscuring the view of background stars and galaxies. (There are actually a few small areas like this that are indeed voids in space, but that’s fodder for another post.) And in their usual exciting lexicographic way, astronomers dubbed these “molecular clouds” or “dark globules.”
OK, so what are we looking at here? A cloud of gas called Barnard 68. It’s about 500 light years away and about half a light year across, it could swallow up hundreds of solar systems. Well, gas and dust. Inside the cloud, its about as dark and cold as it gets in this universe. There’s a lot of these puppies in the Milky Way, our galaxy. They are like 1% of the volume of the galaxy, but about half the mass of the gas in the galaxy. They come and go very quickly as galactic times go, in the millions of years. We think of the galaxy as static, but in the long term it’s a wildly swirling mess, and these clouds of gas are a big part of the picture. It’s not even really understood how they form at this point.
Speaking of points, is there one? Of course! These clouds are where stars are born. For as of yet some unknown reason, the gas collapses or condenses into new stars. Our sun and the Earth and the very atoms that make up our beings were once part of a cold dark cloud such as this some billions of years ago. Look at your hand, it was literally once molecules scattered across a cloud as imaged above. And were people in some long dead alien species looking at images of the cloud that formed our solar system and wondering what it would spawn? Barnard 80 is the future, the cloud you are looking at now will, billions of years from now, be stars and planets such as our own.
By then though, Earth will be an airless cinder orbiting a near dead star. Doug’s Darkworld will no longer be updating. Will any hint of humanity remain? I think so … and again fodder for anther blog. I could blog forever, or at least die trying.
(The above image is from APOD, a bigger version of the above image and various details including copyright info can be seen here: Barnard 80. I chose to write about this image because of the basic wonder of it all. And as part of a bigger writing project, I have decided that Genesis needs to be rewritten, the late Bronze Age shepherds who wrote the first version were sincerely trying, but they lacked the tools to see how grand God’s creation really is. Time for Genesis 2.0 )
What the Hell is That? (Number 2 in a series, if you want to guess, don’t read below the image.)
Yeast cells in a petri dish? Higgs Boson particles in the LHC? Nope, this fascinating image is an infrared view of the exact centre of our galaxy. The image is about one light year wide, and the animation loop covers a period of eight years. And it’s not obvious, but the moving stars are actually orbiting around the yellow cross at the centre of the image. In fact our sun is orbiting around that yellow cross, every orbit taking about 200 million years. That means the Sun is 22 1/2 in galactic years, just a young whippersnapper in it’s prime.
Cool new tunas so far, but it gets cooler. Again, it may not be obvious, but those stars are really moving. Look how slowly the other stars in the image are moving compared to the central stars. The only explanation so far is that they are orbiting something really massive at the yellow cross. In fact calculations show that whatever it is, it masses more than five million Suns! Well, astronomers have a pretty good idea what it is, they think it is a black hole, something that appears to reside at the centre of most if not all galaxies like our Milky Way.
Being a black hole, we can’t see it of course. It only reveals itself in x-rays and the motion of stars orbiting it. Is it eventually going to suck up the entire galaxy? No, more than the Sun is going to suck up the entire Solar System. Well, OK, yes, eventually everything in the Universe will get sucked into black holes. Black holes do slowly decay becasue they emit Hawking radiation, and eventually they will all be gone, there will be no more entropy possible, and the Universe will experience heat death, and be nothing but a near infinite incredibly thin cold near vacuum. That won’t be for about 10100 years though, so it’s safe to say that humanity has far more pressing concerns to worry about.
It’s still amazing to me what we know about our Universe now compare to when I was a kid. And I will continue to share images that amaze me. The black hole at the centre of our galaxy is now in the process of gobbling up a huge cloud of gas, if I can find a good picture of this I will post it.
(Image Credit: A. Eckart (U. Koeln) & R. Genzel (MPE-Garching), SHARP I, NTT, La Silla Obs., ESO It’s basically a NASA image and as such may be used pretty much freely for non-commercial purposes. “It is estimated that 3.71 X 10^10 “first-star-tonight” wishes have been wasted on Venus.” OK, a little astronomer humor there. With emphasis on little, I think it’s safe to say that not many stand up comics got their start in astronomy.)
Doug's Darkworld 