Monday, February 28, 2011

Galactic Habitable Zone

This post is sort of an addendum to the two Kepler posts made last week, here and here. As you can probably tell, I am pretty much obsessed with Kepler information right now. The two things I wanted to add were (1) the concept of a galactic habitable zone and (2) a couple of Kepler Objects of Interest, or KOIs. You'll probably be hearing about a few KOIs in the future, as more and more data gets sifted through.

So first, the galactic habitable zones. When I did the calculations for the Kepler posts for the spacing out of possible civilizations, I assumed that any civilization would be roughly about as far from the galactic center as our own solar system. There is actually a good reason for this.

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Not all locations in the Milky Way seem to be fit for life. Our bodies, the Earth, our entire solar system is made up of a complex chemistry of elements. In astronomy, any elements higher then hydrogen and helium are collectively called 'metal,' even chemically non-metallic elements like oxygen, carbon, and chlorine. From now on, when I mention metals, this is what I'm referring to. Metals make up a small part of things, about 2% of the Sun and the Milky Way, but are hugely important for planet formation and life.

To create metal, you need the energy for nucleosynthesis (think of it a bit like alchemy, creating new atomic nuclei from existing particles). For the kind of metals we're looking for, you need supernova. Our solar system was created out the debris created from supernova. In essence, as Carl Sagan says, you are made up of star stuff. But the activity that creates supernova that can seed stellar nurseries only occurs in certain areas of the galaxy. This occurs in denser regions, where supernova occur close to the stellar nurseries. Once you get further out from the galactic center, near the edge of the galaxy, there isn't much star birth going on and supernova are more spread out. It is a metal poor region, not conducive of life. Therefore, forming the outer edge of the galactic habitable zone.

Now that we have the outer edge defined, we need to define the inner edge. The inner edge is defined by two concepts. The easiest is by radiation, life as we know it has a limit to how much radiation it can withstand. So, looking inward on the Milky Way, the denser it gets, the more radioactive it is. However, knowing some extremophiles thrive in radioactivity, there might be life, but it might not be a civilization. The other concept is with this denseness, stars interact more often. This would cause disturbances to planets, their stability would be low. Life, from our experience, seems to need long stable periods to reach civilization, and planets flying all about are probably not going to be helpful for that. So between these two spots we have out galactic habitable zone, a zone where our solar system appears to be smack dab in the middle of. Lucky us.

Moving onto the KOIs now. The first is KOI 730, which appears to be two planets sharing the same orbit. They are more or less permanently separated by 60 degrees, inside each others Lagrange points. Lagrange points being gravitationally stable regions between a planet an its star, there is one 60 degrees in front of and behind a planets orbital path, along with others. This is an incredibly rare find, and exciting because it lends support to the theory that Earth once shared its orbit with another Mars-sized planet, eventually colliding (probably through Jupiter's gravitational influence) and creating the Moon. The linked article sums it up well.

The other object is KOI 326.01, which is being called the cream of the Kepler crop. It is the closest Earth analog found so far. It's slightly smaller then Earth, within the star's habitable zone, and about 100 light years away, making it 'fairly close' in astronomical terms. This might be where our neighbors are, but it might take 100 years to contact them, and another 100 to hear back from them. So its still an immense distance, but closer then the one I had proposed before for possible civilizations. Heck, it might just turn out to be a Venus or Mars. It will definitely be good to follow the development on this object. Also, it should be mentioned that KOIs are not yet confirmed Kepler finds, they are objects of interest in the data, confirmation is pending. But that said 90% of the Kepler data is thought to be real planets, not false positives.

Hope you enjoyed the update!


30 comments:

HiFi said...

Very interesting. It would be nice to know that there is life out there in the universe. Perhaps the closest KOI is the home planet of the aliens that already have visited us on Earth.

G said...

Dude you post some great info...I'm looking to start some sci-fi writing over the next year and this stuff is a goldmine in terms of background reading - cheers!

ankmanpro said...

Wow that's incredible.. you sure know a lot about this stuff!

rndmg123 said...

would be cool to see a planet similar to earth. even if it didnt have people on it.

ScottD said...

I would assume life could evolve almost anywhere not just our distance. It depends on your definition of life.

Robert Fünf said...

Stupid speed of light. Slowing down our transmissions.

Android News and Resources said...

"cream of the Kepler crop" hehe, I'll remember that one!

Followed!

aphoticdark said...

Wow quite amazing actually. Never knew much about this stuff but it's always fascinated me. Great post dude.

skyman6 said...

this is all very over my head sir

Scott said...

The info on KOI 730 was really cool! I can't even imagine the sort of things we are going to learn about the universe as technology continues to evolve!!

Burger said...

Great post, keep them coming. A thought I had...what if what we consider to be necessary to be habitable for life isn't even true. We are already finding life on Earth where we previously thought impossible. The universe is so vast that life could evolve to withstand or thrive in conditions life as we know it would be impossible.

Astronomy Pirate said...

That's one of the great things about it Burger. We really don't know what surprises life has for us. And it is entirely possible that life could exist in totally unrecognizable forms. But so far we only have one example (Earth), and we are trying to look in the most probably places based on that example. Finding these extremophiles does broaden the search for life though. There are cases for life on a moon of Jupiter and a moon of Saturn (Europa and Titan respectively).

Hombre720 said...

I just want to take a spaceship ride to another planet.

Jesse Brooks said...

Wow, KOI 730 is interesting to read about. I never knew that there was even a theory that Earth shared its orbit with another planet. I suppose the moon had to come from somewhere. Great read.

Also, you won my silly competition, so I made a picture for you on that same post. Be sure to check it out and let me know what you think.

Havuelete said...

very interesting. But they're too far away (with actual technology). 100 light years!

Chuck said...

Makes sense that Earth collided with another planet to create the moon, though I wondered if this was the norm for aquiring a moon? If so did Jupiter and Saturn have many collisions?

sildude said...

It's fascinating that we're finding so many planets now when just a few years ago we thought planets were pretty rare.

ThingsIThinkAbout said...

I don't totally understand everything you write about, but this is really interesting stuff.

synoptixs said...

jeez the creation of metal requires so many huge events o_o

Kindros said...

No need for terraforming there. Wonder if they will make terraforming or reaching an Earth like planet our main objective.

Android News and Resources said...

My second cousin is from KOI 730.

Hehs, just kidding. Interesting read!

Polybius said...

What an informative post. I needed to read something like that. Keep up the good work, man!

Astronomy Pirate said...

@ Chuck, collisions were actually fairly common in the early solar system, almost every planet in our solar system shows evidence of at least once large collision event. Most of them have nothing to do with moon making. Through modeling, it has been determined that our Moon was created from a glancing blow, making it kind of strange. Most moons actually seem to have been captured (Mars' moons and Neptune's Triton) or formed there (most of Jupiter's and Saturn's).

Pedro said...

All those times I've gotten...drunk...and watch Sagan for hours on end are finally paying off. I'm always glad to know more about outer space :D

Venus said...

awesome... there MUST be complex / intelligent life in Space

PekkaK said...

Fascinating stuff. can you recommend some Sagan documentaries?

Astronomy Pirate said...

@PekkaK, do you mean the Sagan has down, or about Sagan's life? Cosmos is probably the greatest series from him, though it is a bit dated now, new discoveries have been made. Youtube videos are always inspiring though. And if you can find it, Carl Sagan's Last Interview with Charlie Rose is a great watch.

husar said...

nice post man

Life Hacks said...

Agree with Venus. There has to be more intelligent life form out there.

Chuck said...

Ahh I see. Thanks for reply!

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