Alien Species Living In The Inner Milky Way Could Be In Danger

Message To Eagle ^ | 23 March 2012 | Staff

[Windflier]

Few people doubt there is intelligent alien life in the Milky Way galaxy, but where can we expect to find it?

Astronomers think that the inner sector of the Milky Way Galaxy may be the most likely to support habitable worlds.

Unfortunately some of these places are also most dangerous to all life-forms.

According to Michael Gowanlock of NASA's Astrobiology Institute, and his Trent University colleagues David Patton and Sabine McConnel, habitability in the Milky Way can be based on three factors: supernova rates, metallicity (the abundance of heavy elements, used as a proxy for planet formation) and the time taken for complex life to evolve.

The scientists discovered that although the greater density of stars in the inner galaxy (out to a distance of 8,100 light years from the galactic center) meant that more supernovae exploded, with more planets becoming sterilized by the radiation from these exploding stars, the chances of finding a habitable planet there was ten times more likely than in the outer Galaxy.

This contradicts previous studies that, for example, suggested the Galactic Habitable Zone (GHZ) to be a belt around the Galaxy between distances of 22,800 light years (7 kiloparsecs) and 29,300 light years (9 kiloparsecs) from the galactic center.

What's noticeable is that our Sun orbits the Galaxy at a distance of about 26,000 light years (8 kiloparsecs) - far outside GHZ proposed by Gowanlock's team.

Why is their proposed galactic habitable zone so different?

"We assume that metallicity scales with planet formation," says Gowanlock. Heavy elements are produced by dying stars, and the more generations of stars there have been, the greater the production of these elements (or 'metals' as they are termed by astronomers). Historically, the greatest amount of star formation has occurred in the inner region of the Milky Way.

A supernova sterilizes an alien world in this artist's impression. Credit: David A Aguilar (CfA)

"The inner Galaxy is the most metal-rich, and the outer Galaxy is the most metal-poor. Therefore the number of planets is highest in the inner Galaxy, as the metallicity and stellar density is the highest in this region."

Supernovae - a real danger to all extraterrestrial life

However, amongst so much star formation lurks a danger: supernovae. Gowanlock's team modeled the effects of the two most common forms of supernovae - the accreting white dwarfs that produce type Ia supernovae, and the collapsing massive stars of type II supernovae.

Measurements of the galactic abundance of the isotope aluminum-26, which is a common by-product of type II supernovae, have allowed astronomers to ascertain that a supernova explodes on average once every 50 years. Meanwhile, previous studies have indicated that a supernova can have a deleterious effect on any habitable planet within 30 light years.

"In our model, we assume that the build-up of oxygen and the ozone layer is required for the emergence of complex life," says Gowanlock. "Supernovae can deplete the ozone in an atmosphere. Therefore, the survival of land-based complex life is at risk when a nearby supernova sufficiently depletes a great fraction of the ozone in a planet's atmosphere."

The team discovered that at some time in their lives, the majority of stars in our Galaxy will be bathed in the radiation from a nearby supernova, whereas around 30% of stars remain untouched or unsterilized.

"Sterilization occurs on a planet that is roughly [at a distance] between 6.5 to 98 light years, depending on the supernovae," says Gowanlock. "In our model, the sterilization distances are not equal, as some supernovae are more lethal than others."

A supernova can destroy any habitalbe palnet within 30 light years.

Although the outer regions of the Galaxy, with their lower density of stars and fewer supernovae, are generally safer, the higher metallicity in the inner Galaxy means that the chances of finding an unsterilized, habitable world are ten times greater, according to Gowanlock's model. However, their model does not stipulate any region of the Galaxy to be uninhabitable, only that it's less likely to find habitable planets elsewhere.

This explains why our Solar System can reside far outside of the inner region, and it also gives hope to SETI - Gowanlock's model proposes that there are regions of the Galaxy even more likely to have life, and many SETI searches are already targeted towards the galactic center.

We must also not forget that the Galactic Habitable Zone isn't static. The research paper written by Gowanlock's team points out that over time the metallicity of the Galaxy will begin to increase the farther out one travels from the galactic center.

"This is why stars that form at a later date have a greater chance of having terrestrial planets," says Gowanlock. As a result, perhaps the heyday for life in our Galaxy is yet to come.

[Windflier]

There are some common sense rules of thumb about life in the Milky Way. To start with, create a timetable for it that is 14.5 billion years.

In time, I believe that scientists are going to revise that number upwards, again and again. It's my opinion that the known universe is much, much older than people currently believe it is.

[Windflier]

We have absolutely no evidence of “alien species” in the inner Milky Way, but we know they are in danger.

Consider it an exercise in logic. The author postulates that alien species that arose in the inner galaxy would have been wiped out by the effects of supernovas.

[Toddsterpatriot]

The Puppeteers know the core already exploded.

[yefragetuwrabrumuy]

Life of the Milky Way galaxy, not the universe. (I did cite the estimated age of the universe, at 14.5, but the Milky Way is less, at 13.2 billion.)

[Savage Beast]

Good thinking, W.

[Windflier]

Life of the Milky Way galaxy, not the universe. (I did cite the estimated age of the universe, at 14.5, but the Milky Way is less, at 13.2 billion.)

Got it. I still think that in time, scientists will find that the universe (including our own galaxy) is much, much older than previously imagined. I'm talking orders of magnitude older. JMO.

[dragnet2]

I would venture to say that BILLIONS of people doubt there is intelligent alien life in the Milky Way galaxy.

Billions of those people can't count change at the local big cow slop joint, or even point to where the center of their own home galaxy is....But they doubt intelligent life exists on any of the billions of planets in the galaxy?

What a hoot.

[Dr. Sivana]

I would venture to say that BILLIONS of people doubt there is intelligent alien life in the Milky Way galaxy.

Billions of those people can't count change at the local big cow slop joint, or even point to where the center of their own home galaxy is....But they doubt intelligent life exists on any of the billions of planets in the galaxy?

Well, you might say it's a hoot, but it still is a stupid, easily disprovable statement for the author of the original piece to claim that practically everybody believes that there is intelligent alien life in our galaxy. When the author makes such an obvious factual error, it undermines everything he posits afterwards, as his judgement must be called into question.

Of course, there are plenty of folks who can't count change who do believe that there is intelligent alien life in the galaxy, as there are millions of people who CAN count change who are on both sides of the fence.

Discounting incorporeal beings (angels, God, etc.) I doubt you would get a majority of Freepers who believe based only on the number of planets in the galaxy, that there is intelligent alien life elsewhere in the Milky Way.

[dragnet2]

it still is a stupid, easily disprovable statement for the author of the original piece to claim that practically everybody believes that there is intelligent alien life in our galaxy.

Oh, it's a hoot since most, after spending their entire lives on this planet, can't even ID earth's closest planetary neighbors in the night sky. In fact, most when they see the "Milky Way" in the night sky, have no idea it's actually part of their own home galaxy...Ya it's hoot IMO.

You say those same billions of people don't believe intelligent life exists on billions of other planets in our galaxy?

Considering the intelligence level of most people in regards the universe, or our galaxy, it would seem to call into question their beliefs and or opinions. In fact would it not seem to undermine their credibility?

It's easy to disprove most or billions don't believe? Maybe, but I've never seen a world wide survey.

But the fact is, everything considered, and based on the above, what the typical person believes regarding life on other plants, does not impress and is basically meaningless.

BTW, don't know about you, but most people I know, including myself, who have an above average understanding regarding the enormity of the universe and our galaxy, believe there is life out there, beyond our tiny world.

[dragnet2]

I doubt you would get a majority of Freepers who believe based only on the number of planets in the galaxy, that there is intelligent alien life elsewhere in the Milky Way.

BTW, ya ever seen an astronomy thread here? It's quite amusing when Nebula pics are compared to a bowl of Jello or a taco.

Take care.

[Dr. Sivana]

BTW, don't know about you, but most people I know, including myself, who have an above average understanding regarding the enormity of the universe and our galaxy, believe there is life out there, beyond our tiny world.

That's funny, because most of the people I know, including myself, who have an above average understanding regarding the enormity of the rationality and sentience of man, see no evidence whatsoever for intelligent alien life out there, beyond our tiny world.

On a natural level, no matter how big the numerator (# of planets) is, odds cannot be determined until we have a way to figure out the denominator (exact conditions needed to generate intelligent alien life, and the number of planets, if any, that might meet those conditions).

Those who believe in intelligent alien life in the Milky Way do not further their cause by belittling people who think otherwise. For the record, I went through my UFO phase in the 70s (it was a bit of a fad, then), reading three books by that fraudster Erik von Daniken, among others. I know you are not hawking that line, but a lot of people who don't have "an above average understanding" of the physical universe bought into it. My excuse was that I was a fourth grader.

[Yardstick]

Indeed, as someone who totally groks the enormity of our universe, I am psyched about the possibility -- no, the certainty -- of finding a planet shaped just like Alfred E. Newman's head.

Won't that be exciting?

[dragnet2]

That's funny, because most of the people I know, including myself, who have an above average understanding regarding the enormity of the rationality and sentience of man, see no evidence whatsoever for intelligent alien life out there, beyond our tiny world.

Well, it was only a few years ago, ya didn't have any evidence of planets orbiting other star systems either. Boy, that sure changed.

Did ya know our tiny world isn't even visible right down the galactic block? A bit further away, still in our own galactic neighborhood, the giant planets of our solar system aren't even visible. Our galaxy is a big place, most don't realized how big.

On a natural level, no matter how big the numerator (# of planets) is, odds cannot be determined until we have a way to figure out the denominator (exact conditions needed to generate intelligent alien life, and the number of planets, if any, that might meet those conditions).

Fact is, we have no idea what conditions might exist which may support other types of life. Ya see, I've always felt man is really arrogant in this regard.

Some of the things being discovered are literally turning physics on it's head.

Those who believe in intelligent alien life in the Milky Way do not further their cause by belittling people who think otherwise

You got me wrong, I said I felt much of the ignorance regarding astronomy/galaxy/universe was a *hoot*, and were directed at some of your own comments as responses. Public schools and all that. You understand.

Ya see I am happy to tell people who for instance believed the moon emits it's own light, when it's actually reflected sunlight off the lunar surface. Yep...No kidding. But I set them straight and we had a good laugh. Nothing stuffy here.

In fact I've done many of things to help people understand astronomy and the universe. From kids to adults. Lots of them. Lots of work involved in that process too. More than you know.

And BTW, I readily admit, there is much more I don't know than do know or understand here. (For the record.)

I went through my UFO phase in the 70s (it was a bit of a fad,

UFO's? Interesting...I never went through or experienced that fad. I was never into fads anyway.

But since ya brought it up, I sure have seen some objects I was never able to identify. A whole bunch, in fact.

[dragnet2]

I guess anything is possible.

[Dr. Sivana]

Well, it was only a few years ago, ya didn't have any evidence of planets orbiting other star systems either. Boy, that sure changed.

I am aware of that. In fact, I directed the head editor at the publisher I worked for to change a book going into a new edition to reflect that fact.

Our galaxy is a big place, most don't realized how big.

Mmmhmmm. And it is only one of many, many galaxies. Most people also don't know how SMALL creation is. For a while, the atom seemed like the smallest part, until sub-atomic particles were discovered, and then it starts getting really crazy.

Fact is, we have no idea what conditions might exist which may support other types of life. Ya see, I've always felt man is really arrogant in this regard.

That is actually my main point. Until we know, scientifically, we have no business making assumptions. Our algebraic equation has one variable too many. I had an instructor at the University of Chicago in a physical science course who marvelled that with all the life on earth, it is all carbon based. Based on what we know, you need long chains, but he figured silicon would be almost as good, and he assumed it was likely an accident of nature that it didn't happen. The same fellow also came up with a proof AGAINST global warming, or "the greenhouse effect" as it was called then (early '80s). Sounds like you are a "glass is half full" kind of guy. I would say we need to know more about the glass.

You got me wrong, I said I felt much of the ignorance regarding astronomy/galaxy/universe was a *hoot*, and were directed at some of your own comments as responses. Public schools and all that. You understand.

Got it. At no point, though, like original author who wrote the article that led to this exchange, that plenty of intelligent people can come to different conclusions than Carl Sagan, which is part of the reason that he made it such a central part of his cosmology.

But since ya brought it up, I sure have seen some objects I was never able to identify. A whole bunch, in fact.
,br> And here you bringing up an interesting point. Of course there are UFOs ... objects flying in the air that remain unidentified. Until they are identified, we don't know if it is a man-made object, an optical illusion, acts of angels or devils, the work of some secret race living under the world or intelligent alien life.

And of course I explicitly did not suggest that you bought into that stuff. With UFOs, Bigfoot and the Loch Ness Monster, I marvel that we still don't get decent video of them even though 80% of the population carries digital cameras with their phones everywhere. I was trying to show that there is silliness on all sides of these questions.

I do not pretend to be a physical science expert, far from it. But my mostly private education was better than average, and quite broad, if not up to date. I also try to remain well-read in my adult life, a large part of the reason I frequent Free Republic, as it is not limited to the strictly political, but also things that other Freepers think worth posting.

[dragnet2]

I would venture to say that BILLIONS of people doubt there is intelligent alien life in the Milky Way galaxy.

Until we know, scientifically, we have no business making assumptions.

I think you made my point.

Bottom line is everyone is entitled to their opinions regarding this, but the fact is, none of us know for sure.

Considering their are literally *trillions* of planets outside our own solar system, my bet is there are all kinds of life out there. In fact, it would be even stranger or harder to believe, if there wasn't, IMO of course.

[Dr. Sivana]

Bottom line is everyone is entitled to their opinions regarding this, but the fact is, none of us know for sure.

Agreed. Unfortunately, the author of the original piece didn't present it that way.

[dragnet2]

Well, I have yet to see a global survey of billions regarding this, so I won’t assume the author is incorrect.

[dragnet2]

Thought you might find this interesting:

It’s just a poll, not billions ..but interesting the same....
________________________________________________________

Do you believe there is life on other planets?

Yes 90.23% (3,325 votes)

No 5.21% (192 votes)

Not sure 4.56% (168 votes)

Total Votes: 3,685

http://www.cbc.ca/news/pointofview/2010/09/life-beyond-earth-do-you-believe-it-exists.html