Goal: To understand life in our galaxy. Objectives: 1)To understand the Basic building blocks for life in general 2)To learn about What type of stars and planets to look for if we want to find life 3)To understand How to find these planets 4)To examine The search for intelligent life 5)To learn about The Drake equation

Brainstorm! Try to find 6 characteristics of the most basic life (note this is life in general – so if you can think of a life form that does not need it, it is not a basic building block). Note also this is not for human life, just the most basic life (like bacteria). Finally, this is for life as we know it.

Lets find them in our solar system! Venus – too hot, not enough water, very unpleasant. Earth – I am not 100% sure, but I think we may have those building blocks on that planet. Moon – maybe some ice at the pole, but nope not going to find life there. Mars – very tempting to be optimistic. It has most of what you need (underground water, frozen surface, but below that…). However, it is lacking in Nitrogen.

I think the best place to look: Is a moon of Jupiter called Europa. About the size of our moon. No atmosphere. However, due to tidal heating, underneath about 1-10 miles of frozen surface lies a gigantic underground ocean! It has all the possible blocks for life – so does it have life? We need to send a probe there to find out.

SIM PlanetQuest Is a NASA mission scheduled to launch in 2015 (which means you should expect it about 2020…). What this instrument will do different is that it will be an interferometer. An interferometer is a telescope that is slit into two or more parts and spread out over a large area. What this does is effectively gives you a bigger diameter to your telescope. Since resolution ONLY depends on diameter, and not the amount of light your collect, this can give you very good resolution.

Why not done already One complication, you have to be able to know the distance between telescopes accurate to the wavelength of light. For radio this is easy because the wavelengths are long. For infrared and optical this is hard because the wavelengths are very tiny. For more info go to:

What it will do With a really good resolution you can measure the positions of stars very accurately. Measure their positions once every month or so and you can watch the stars move with time. Some of this will be due to parallax motion (due to the earth’s motion around the sun). Some will be due to “proper” motion – which is the motion of the star with respect to our sun. Once you subtract those out you get the orbital motion – yes you will be able to watch the star orbit around an imaginary point.

Advantages Can be used on any star. Can be used to detect planets as small as the earth! Can be used to find planets further away. Disadvantage – you are still finding the planet indirectly. You have no real info on the planet other than its mass and orbital characteristics.

We want to find LIFE! To do this we have to look at a planet. However, planets are so small that we have no hope of actually imagine their surface features from many light years away – sorry no finding oceans and continents. So what can we do?

Chronographs When you have multiple detectors for measuring light you can determine how you add those together. If you are clever you can get them to add together. If you are even more clever you can get them to cancel out!

Blocking the star To image a planet directly you have to get rid of all the light from the star. If you can do that then you have a better shot at imagine a planet. If you can image the planet you can take its spectrum. What will the spectrum tell you about the planet?

Which molecule, if found in some abundance, would indicate that there was some form of life on the planet? A) Carbon Dioxide B) Nitrogen C) Water D) Ozone

What determines the makeup of the atmosphere? There are 3 processes: 1) geological – volcanoes mostly. Volcanoes spew water, Carbon Dioxide, Nitrogen, and Sulfur Dioxide into the atmosphere

Interactions with the sun Two ways here: 1) UV rays can break apart molecules. This will form some oxygen in an atmosphere for example, but only trace amounts. As we saw for the earth, this can also break apart water molecules. 2) Solar wind – if a planet has no sizable magnetic field certain gasses (such as water vapor) will be removed from the atmosphere.

Biological This is the one we want to search for. If there are molecules that are a result of biological processes, are short lived, and do not occur much naturally, if we find them, we have found life! Note this will be life in general, like bacterial and plant life, not intelligent life. So, what do we look for?

Smoking guns for life? Nitrogen can be useful. However, it is difficult to detect, and many atmospheres have it naturally (Venus + Mars have 3%, and Titan has mostly Nitrogen). How about molecular Oxygen (O 2 )? Well, it is even more difficult to observe. Very trace amounts are produced naturally, so you would have to show a lot of it (like our 26%) to be able to say it was life induced, but we still can’t detect it…

The true guns Methane and Nitrous Oxide Methane does not survive long in an atmosphere as it gets destroyed by UV rays. NO tends to react with Oxygen or goes to molecular Nitrogen. Either way both are too trace to be seen with the instruments coming out. However OZONE is the key! To have significant amounts of Ozone you need a lot of free Oxygen, which means life! Also, Ozone is fairly easy to detect!

With what will we find it? Now that we know what to look for, what will actually be doing the looking? NASA’s Terrestrial Planet Finder (TPF for short) should be able to do all of this and is scheduled for completion in However, their funding is being cut, so there is a chance it won’t get off for awhile (2030?). Anyhow, within our lifetimes we should be able to find life outside our solar system!

Intelligent life This is great for life in general, but what about ET? There is an agency that is searching for intelligent life: SETI (Search for Extra Terrestrial Intelligence).

What does SETI look for? SETI scours the radio section of the electromagnetic spectrum. SETI tries to find signals that could not occur naturally. Some examples include beamed transmission, repeated patterns, very narrow band emission, or anything else that can only be created intentionally by an alien civilization.

Suppose we find life, then what? If it is unintelligent life – we can do NOTHING! Lets suppose we sent a craft to the alpha Centauri system at a speed of 0.1 c. It would take 43 years to get there… The large distances make interplanetary travel unlikely for a long time – and even then very impractical.

How far away will life be? Do figure this one out we will use what is called the Drake Equation. The Drake Equation is just a giant unit conversion basically… There are a few forms to it. We will be examining an offshoot here…

Number of stars in galaxy 400 billion

However, how many of those stars can have planets with intelligent life? Big stars die too fast – not enough time to evolve and a lot of UV light Small stars have planets tidally locked Slow rotation of planet means no magnetic field which means no life on surface

So, need Stars like our sun Only about 10% are like our sun 2/3 rd s of those are in binary systems So, that leaves about 10 billion possible intelligent life bearing suns

What fraction of those have planets? This is the last of the factors that we know well. It seems that 50-90% of stars form a planet system. But even if it is only 1 in 10 then we still have 1 billion useful planetary systems.

How many planets or moons like our Earth in a region where you can have life (in general)? This one is tricky. Stars with too low metals won’t form big enough planets. Stars with too much metal will form hot Jupiters. Also, some of these systems will have more than 1 planet in a habitable zone (we have 3) If we say 1 planet per say 10 systems then we still have 100 million Earth like planets in a habitable zone.

What fraction of those have actually developed life? Here we have to guess. Is life really easy to form when conditions are right or were we fortunate? If only 1 in a thousand form life though that is 100,000 planets with life on it!

What fraction of those have develop intelligent life? This one is the biggest guess. However if only 1 in a thousand develop intelligent life that is 100 intelligent civilizations in just our own galaxy.

For what fraction of their planet’s life do they use technology that we could use to communicate with them? We have only been at this for 60 years. Even if the average is a million years well there would have to have been 5000 civilizations for us to be able to detect one. So that would now mean that we would need 50 galaxies such as ours to find another intelligent civilization such as ours.

Light speed! Instead of going there, lets just communicate (if we can figure out how to do this and we both have a wish to). How long will it take us to get a response?

Universe Remember there are about 100 billion spiral galaxies in the observable universe! It would be very unlucky, a great shame, and a big waste of space if we truly were alone in the universe. Will we find life – probably (and maybe within our own solar system too) – and maybe within our lifetimes! Intelligent life? Well, we shall see.

Conclusion We have found what a planet needs to be capable of supporting life. We have found what to look for to determine if a planet has life. We have estimated the # of intelligent civilizations in our galaxy. Sadly, getting from place to place is really hard (after all as we found at the start of the semester, the distances between stars is really big).