Does the Galaxy

need Guarding?

Number of Habitable Exo-Planets.

How to find Exo-Planets.

Alien Life.

Travelling to Exo-Planets.

Big Question 1.Are there other Earth-like planets in our universe?

There are many planets in the Guardians’ universe. The Nova Empire home world of Xandar in the Andromeda Galaxy is very Earth-like. The big question is how many planets and ‘Earth-like’ planets could there be in our Galaxy and the rest of the universe?

How many Stars the there?Astronomers estimate that the Milky Way (our Galaxy) has around 400,000,000,000 stars (400 billion) [1] and about a trillion stars in the Andromeda galaxy. There are an estimated 100 billion galaxies in the known universe [2].Which leads to an estimate in the magnitude of 10,000,000,000,000,000,000,000 stars in the known universe [2].

How many Stars have planets? Current evidence suggests that on average every star has at least 1 planet orbiting it. Although you don’t tend to get just one planet forming around a star, so it is likely that the number of planets is 5 to 10 times the number of stars [3].

So that puts an estimate of between 2,000,000,000,000

and 4,000,000,000,000 planets in our galaxy and something possibly around 100,000,000,000,000,000,000,000 planets in the known universe.

How many of the planets could possibly support life?Observations during 2014 show that at least 25% of the red dwarf stars have Earth sized or super-Earth sized planets orbiting in their habitable zone [4]. In 2014 there

Exo-planet[B]

Planet Xandar [A]

are 21 recorded planets that have a chance of supporting life as we know it [5]. We still need to learn more about their environments as there is a lot more that a planet needs than just to be within the habitable zone.

Big Question 2.

What does a planet need in order to support life?Morag is one of the least hospitable planets in Guardians of the Galaxy, but life still exists there. So what does a planet actually need in order to support life?

A solventWater is a vital component of all life on Earth and also allows life to form by being a solvent , however it is possible that alien life could use a different solvent like ammonia or methane.

TemperatureThe planet needs to be in the habitable zone around a star where it is at a temperature where water can be in liquid form. Although if it uses another liquid or has a thick atmosphere it could be at temperatures outside what we believe is within the habitable zone.

Protection / atmosphereThe Earth’s atmosphere does two important jobs for us, it keeps water evaporating into space and it blocks most of the harmful parts of the Sun’s rays from reaching Earth. The same job could be performed by ice. A planet might have liquid trapped below a sheet of ice. This would also provide gases needed for life.

ElementsLife on Earth is Carbon based, but we also need and use many heavier elements, which are believed to come from early asteroid impacts and from heavy atoms produced in supernovas. Therefore the planet would have need to collect a good mix of elements.

Some of the other possibly important factors.The Moon: Keeps our axis stable to give regular seasons.Outer Planets: Deflect dangerous comets protecting earth. Magnetic field: Protects Earth from solar winds. Plate tectonics: This is actually about keeping the balance of C02 and temperature.

Surprisingly Oxygen isn’t necessarily needed for life. It is a theory that early on organisms on Earth actually produced Oxygen and did not need it.

[6]

Morag [C]

Big Question 3.

How many planets do we know of that might support life?

Habitable planets so far.We have found around 50 planets so far (2014) that are witin a habitable zone of a star . Around 10 of these planets have a confirmed status as being likely habitable planets [7]. All of which are in our Galaxy, the Milky way. Most of the Guardians of the Galaxy story takes place in one of our closest neighbour galaxies Andromeda.

Have we found them all in our galaxy?Almost 2000 planets in our galaxy have been discovered so far (habitable and non-habitable), but this number is increasing all the time.

This means though that roughly 1 in 40 of the planets we have found is a potentially habitable planet.

Does that mean 1 in 40 of all the planets will be habitable?Probably not. The current methods of detecting planets in our galaxy are better at finding certain types of planets and don’t yet find every planet that orbits a star. Also most planets we have detected so far are within 1,000 light years, the Milky Way is 100 times wider than that. Andromeda is 2.5 million light-years away and we can’t yet detect planets that far away.

Both star wobble and the transit method for detecting planets require the planet to be orbiting flat compared to earth. Gravitational lensing and direct imaging can detect planets with other orbit orientations.

If the current methods were used on our solar system from elsewhere in the galaxy we would most likely only find Venus, Earth and possibly Jupiter.

‘Edge-on’ orbit; All methods can detect.

Flat orbit: Only Gravitational lensing and direct imaging.

Andromeda Galaxy [D]

Real Exo-planet - Gliese 581c

22 light years from Earth, the Star Gliese 581 has three confirmed Exo-planets orbiting it (b, c and e). Of the three ‘c’ is the most ‘Earth-like’ with temperatures predicted to be between -3 and 40 OC. 581c takes just 13 Earth days to orbit Gliese 581.

Real Exo-planet - Gliese 832cAt a distance of 16.1 light years the red dwarf star Gliese 832 host a planet (Gliese 832c) which is believed to be the closest ‘habitable’ planet to Earth. Gliese 832c has a mass 5.4 times that of Earth and so would have higher gravity. This means it probably has a denser atmosphere than Earth and would then be warmer due to greenhouse effects.

Real Exo-planet – Kepler 22b

Kepler 22 is a slightly smaller star than the Sun about 620 light years away. It has one known Exo-planet.Kepler 22b orbits its star in 290 earth days within its habitable zone. It has a mass 2.4 times that of Earth. It is thought to be an ocean rich planet.

GotG planet – Morag

The once populated planet of Morag is now a rather geologically unstable planet. Still technically capable of sustaining life, but now only inhabited by lizard like creatures called Orloni and other lower life forms.

GotG Location – Nowhere

Nowhere Is the head of a long dead Celestial being. Celestial beings are the most ancient known race of the Marvel universe and are responsible for most alien life and super-powered beings including the X-gene.

GotG planet – Xandar.

Home to the intergalactic police force, the Nova Corps. Xandar is very Earth-like and has large oceans with constructed/ modified islands. The main city’s shape is modelled on the Nova Corps logo.

[F]

[C]

[A]

[H]

[E]

[G]

Method 1.

Star wobble.A planet orbits a star because of the star’s gravitational pull, but a star also experiences an equal and opposite pull from the planet’s gravity. This causes the star to wobble (shift back and forward) as the planet orbits it. So if a star is wobbling we know a planet must be orbiting it.

How is the ‘wobble’ detected?If an object is moving away the light waves it gives out are ‘stretched’ and have an increased wavelength (with a lower frequency). This is called Red Shifrt. Similarly if an object moves towards an observer then the wavelength is shortened (and has a higher frequency). This is called Blue Shift.

When a light wave is lengthened the colour becomes more red and becomes more blue when it is shortened. This shift in colour is detected and the frequency of the shift is used to determine the orbit period and the orbit radius of the exoplanet. The amount of red shift that occurs can be used to find the mass of a exoplanet.

Calculating the orbit distance.An orbit depends on the force acting on the orbiting object. The force depends on gravity.

Orbit speed formula: F=mv2

r Force due to gravity formula: F=GMmr2

Replacing v with 2πr/T (orbit radius / period of orbit) and combining the two formulae we get an equation known as Kepler’s (third) law.

T 2=4 π 2

GMr3

Kepler’s law gives the exact orbit radius of a planet (r) based on the period of its orbit (T) (found from the star wobble) and the mass of the star (M).

Star Movement

Method 2.Transit.

If an exoplanet crosses in front of a star it blocks out light. This can be detected from earth as the change in brightness of a star.

If dimming is detected at regular intervals and for a fixed time then the orbit time (period) of the exoplanet can be calculated. Once the period of the orbit is known the orbit radius can be calculated using Kepler’s law (just like the wobble method).The size of a star can be accurately calculated from the spectrum it gives off; the size of the exoplanet can then be calculated by the amount of dimming that occurs. Combining this information on the size of the exoplanet with the mass of the exoplanet from star wobble, the density can be calculated. This helps give an idea of what it is made of. Limitations. A transit is a rare event and requires an exoplanet to pass between the star and the Earth. It means its orbit must be almost exactly ‘edge-on’ to Earth.

It is often a very subtle change in the brightness of a star, it takes very sensitive equipment which is normally very accurate, however, even with this equipment there have been a number of examples of false results.

[8]

Time in hours

Brightness

[I]

Kepler’s Law.T 2=4 π 2

GMr3

Observatory

Lensed Images

Lensing star and planet

Source star

Method 3.Gravitational microlensing.

Microlensing requires a unique event that can only be observed once and does not repeat itself. It requires one star to pass exactly behind another in line with earth.Under the influence of gravity light is bent very slightly, much like light refracting through a convex lens. This becomes more obvious over large distances and means that microlensing allows us to find exoplanets at huge distances (10,000 light years) away. However the distance is not always accurately known and can be 1000 light years out.

As the source star moves behind the lensing star it creates two distorted images of the star that then stretch into a full ring around the lensing star (called an Einstein ring). When this happens the brightness of the lensing star spikes (up to 100 times as bright). If there is a exoplanet near the star it creates another image of the star as it passes and temporarily increases the brightness. A microlensing event can last weeks or months, the blip in brightness caused by a exoplanet lasts a few days.

[9]Time (days)

Brig

htne

ss o

f the

Le

nsin

g st

ar

Brightness spike from the source star and lensing star.

Brightness spike from a planet.

Sunshade

TelescopeExoplanet

Star

+ =When two waves from the same source arrive ‘out of phase’ they cancel each other out (destructive interference).

Method 4.Direct imaging.

Taking a picture of a distant exoplanet is very difficult because an exoplanet is very faint compared to the star it orbits.

There is a relatively simple method that allows exoplanets to be seen more clearly. This is to shape/block out the light of the star so the dimmer exoplanets orbiting it can be seen. This method is called coronography.

The other method to block the light from a star is to combine images of the star from multiple telescopes in a way that the light from the star destructively interferes with itself (cancelling out the light). This method is called interferometry.

While most people know about the Hubble telescope, there are around 30 space based observation satellites looking out into space. Evidence of exoplanets has been gathered by these satellites as well as a larger number of Earth based observatories.

One of the better know space telescopes looking for exoplanets is the Kepler telescope which has gathered evidence to confirm 100s of exoplanets.

A list of observation stations can be found at: http://exoplanet.eu/research/

Two telescopes receiving the light of the star and exoplanet

Alien Life – the building blocksThe Marvel universe is filled with diverse forms of life from the humanoids (Nova and the Kree), symbiotes (Venom and Carnage) to intelligent plant life like Groot. The big question though is how does different life begin?

What do you need for life? The short answer is amino acids.

Amino acids are chemical compounds that form proteins. Proteins give cells their structure and are involved in all of the processes in cells and living bodies.

There are only 20 naturally occurring amino acids, however amino acids join in unique long chains to form different proteins.

Can an amino acid form naturally?Yes. Experiments have shown that simple chemicals like ammonia, methane and hydrogen can, with heat and pressure, naturally form into amino acids. Bob Hazen began experiments in 1996 using ‘an extreme pressure cooker’ to form amino acid, sugars and other organic compounds[10]. The conditions Hazen produced occur naturally in deep ocean trenches where geothermal activity provides the heat needed.

Some other ways organic compounds could naturally form.Electrical sparks – An experiment by Miller and Urey in 1953 suggested that lightning could have created the key building blocks to life.

Community Clay – Alexander Graham Cairns-Smith suggests that minerals in clay can arrange themselves into organic patterns.

In the atmosphere – Some theories suggest that organic compounds can form in the atmosphere and are rained down into oceans.

Are we all aliens? Life could have come from elsewhere in the galaxy hitchhiking on comets from other star systems. Alternatively as in the case of the marvel universe from some meddling ancient celestial beings. [11]

Glycine, a amino acid

[J]

Alien Life – the next steps

What happens once Amino Acids are formed? The first evidence of life is microbe-like cellular filaments that have been found in 3.5 billion year old rocks. The question is how do you go from organic compounds like amino acids to a cell?

Step 1 - formation.Simple organic molecules (once formed) join together to form longer more complex chains.

Step 2 - Replication.Reproduction is a key feature of life. Biologists believe that the first molecules to self-replicate were RNA molecules. There is a recognised evolutionary era, referred to as the ‘RNA world’ in which RNA did everything and was a precursor to DNA.

RNA (ribonucleic acid) is a nucleic acid (like DNA) that is present in all living cells. It acts as a messager, carrying instructions from DNA, controlling protein synthesis. Some viruses still use RNA rather than DNA to carry their genetic information.

Step 3 - Cells. Evolution of a membrane would have meant that the RNA was more protected and able to replicate without interference from its surroundings. So ‘encased’ replicators (or early organisms) would out compete ‘naked’ RNA replicators.

Step 4 – Modern metabolic processes.RNA would have slowly given way to other types of molecules for different functions. DNA would become the main genetic material. It is more stable and efficient at making proteins. DNA-containing cells would have had many advantages over RNA-containing cells and would have out-competed them.

Step 5 – Multicellular.An estimated 2 billion years ago some cells evolved functions that kept them together to form multicellular organisms. One example is a 1.2 billion year old algae found in fossils.

[12]

Alien Life – Is there evidence on other planets?

Most of the Marvel universe life forms are from well outside our solar system and galaxy. NASA, however, is looking for signs of life in our solar system. There are a number of possible candidates for organic molecules on other objects in our solar system: Mars being the first, but more likely some of the moons of our outer planets like Europa and Titan.

Mars.NASA has had their Curiosity rover rolling around on Mars since August 2012. So far it has found no real evidence of life itself, but it has some evidence that there might have once been conditions suitable for life.

Europa.

Europa is a moon of Jupiter visited by NASA’s Galileo spacecraft (which took the picture to the right). The photos and data from Europa show a huge likelihood of water and minerals required for life.

Titan.Saturn’s moon Titan has turned up evidence for organic molecules in its atmosphere. Both NASA’s Cassini spacecraft and the Atacama Large Millimetre/sub-millimetre Array (ALMA) have detected organic molecules in Titan’s atmosphere.

[13]

Titan is considered to be the most Earth-like body in the solar system. It has plenty of water in lakes and seas as well as a thick atmosphere.

[K]

However due to its distance from the Sun it is a lot colder than Earth at minus 179 degrees Celsius.

Alien Life – Where are they?Enrico Fermi proposed (in conversation at lunch) that if there was intelligent life in our universe we should have heard from them by now. So if we haven’t heard from them does that mean they are not there? (Fermi Paradox)

You can argue about the distances of space and travel and signal speed, but for the age of the universe the time differences become insignificant. If something intelligent is out there we should have heard or seen something. [14]

Solutions to Fermi’s Paradox.The main solutions revolve around a few key ideas; 1. It isn’t easy for life to start and then evolve to a technologically advanced level, so we are quite probably the only ones in the galaxy. 2. Advanced civilizations destroy themselves in short time scales. 3. Planets that have survived the dangers of space with the right conditions and resources for life are rare.

Some weirder solutions to Fermi’s Paradox: The Zoo Hypothesis: Aliens already know we are here and for whatever reason prefer to watch from afar (probably for entertainment or study). We are monkeys in some kind of cosmic cage. Much like the ancient Watchers of the Marvel universe who watch and very infrequently intervene.

Self-imposed quarantine: Space is dangerous, alien life could be dangerous, so why not just stay home and keep to yourselves? This is quite possibly what intelligent alien life has decided. Deciding to stay home and look after themselves might be preferable to risking the perils of deep space.

The Whack-a-Mole Hypothesis: a bit like the zoo hypothesis, intelligent life is watching us waiting to see how we turn out: if things go bad, they take action. This is most like the Marvel Earth-616 universe in which Earth is declared off limits by the Galactic council as Humans are considered unpredictable and dangerous.

We don’t know what you’re saying! What are the chances that alien life communicates the same way we do? Maybe we just don’t understand the messages that are already coming our way. [15]

A Watcher[O]

Galactic Council[P]

Speed of light

Speed

Energy

Space Travel – How far can we get?Peter Quill’s Milano is the muscle car of spaceships, but unless it is equipped with some kind of space bending ‘faster than light’ system (FTL) it would still take a long time to travel between planets.

How fast can we go?The fastest object humans have put into space was a solar probe which achieve a velocity of close to 200 km/sec. At that speed it would take about 8.5 days to travel the 149,600,000 km to the Sun and about 1 year to get to Pluto.

The closest star is Proxima Centauri, located just a short 4.24 light-years (4.01 × 1013 km) away. It would take the solar probe over 6000 years to get there. The closest potentially habitable planet we have found is 11.9 Light years away, which would take us 17,800 years to get to at current speeds.

Just go faster!Even at the speed of light that is still 11.9 years to get to the closest ‘potentially’ habitable planet. The problem with getting to light speed is that the energy required to reach it becomes infinite. Basically, there is not enough energy in the universe to accelerate an electron to the speed of light.

Light is the fastest thing in the universe because it doesn’t interact with the Higgs field and so can go as fast as possible. Why not any faster? The speed of light is a fundamental universal constant like the gravitational constant or the charge on an electron and so it cannot be increased.

Warp speed!

So is the best we can hope for longer than 12 years to the nearest habitable exo-planet? Maybe not, there are some theories on faster than light travel that involve space time bubbles etc... NASA is ‘working’ on one such idea that would shorten year long trips to a day.

Space Travel – Other difficulties of space travel?Peter Quill (although you might know him by another name - Starlord? ) has a mask that allows him to survive in the vacuum of space. This could actually work if it is an airtight seal. His only other problem would be radiation. So as long as he has protective clothing he would be safe for a short period of time, however, spending a long time in space provides more health and survival difficulties.

Some of problems faced in space travel.Oxygen is our first and possibly most pressing need. Oxygen can be produced from electrolysis of water, splitting water into hydrogen and oxygen. Ultimately it would be better to use plants to recycle CO2 humans breathe out into oxygen. Air also needs to be kept clean in a confined space and any pollutants filtered out.

Food & Water. Water can be largely recycled so only relatively small stores are needed. Food on the other hand is more difficult and a 1000 day mission to mars would need 1830 kg of food for each astronaut[16]. Creating or growing food using plants and maybe animals would be needed to survive longer journeys.

Energy is relatively easy to obtain near a star. Large solar panels can supply enough electricity to run both life support and technical systems. More energy would be needed for engines. Several companies are working on small scale nuclear fusion reactors that could produce a lot of power with simple fuels (isotopes of hydrogen). They would produce very little radioactivity and are relatively clean, especially compared to Nuclear Fission.

Radiation on Earth our atmosphere protects us from radiation from the Sun, space

ships need shielding to protect astronauts.

Gravity is surprisingly important for keeping humans healthy. We are built to live with gravity; without it our circulatory system weakens, along with our muscles and spine. If a human spends too long in space they suffer some severe health issues on returning to Earth’s or another planet’s gravity[17].

Other difficulties include eye damage from contrasts of light, asteroid and space junk impacts, maintaining pressure.

Space Travel – Getting to Space.Most sci-fi movies like Guardians of the Galaxy make it seem very simple and easy to get to space, even for a monolithic ship like the Kree Dark Aster. In reality it takes a lot of energy just to get away from our atmosphere.

Energy to get to space.Getting to space takes a large amount of energy. To work against gravity alone it takes 3,300,000 joules of energy to lift 1 kg of mass up to the height of the international space station (355 km). Add to that the speed needed just to stay in orbit and this would take about 10 times the energy. At present this energy is provided by burning vast amounts of fuel.

Aside from making more efficient rockets, other options being researched include hydrogen balloons and a space elevator.

Balloon to space.Balloons are often used to send experiments to the edge of the stratosphere, but any higher becomes extremely difficult. Amateur racketeers, however, are launching rockets from balloons to get to much higher altitudes with their rockets with less fuel.

Space elevator.The idea of an elevator to space has been discussed for years. It would use a geostationary satellite and a high strength cable/pole. Using counter weight systems, loads could easily be lifted into space.

Ground-Based Lasers.A relatively new idea is laser ablation, which is firing a laser at surface heating it up and causing a plasma plume off the surface that propels the object forwards. New theories combine this with gas-blasting nozzles to reduce fuel use and increase speeds [18].

Gravitational potential Energy.

U=GMmr

G = 6.672 x 10-11 N m2 kg-2

Dark Aster [Q]

Space Travel – Moving in space.Although there is no friction in space and you can keep moving without a force, you still need an engine to accelerate and change direction. All propulsion methods in space work by pushing away fuel in one direction to push the space craft the other way (also conserving momentum). Conventional rockets take a lot of fuel, so what are some other ways of pushing matter out the back of a spaceship?

Solar sails.A solar sail does as the name suggests it uses light from a star hitting the sail to propel a ship forward. The main advantage is that no fuel is required. The disadvantage is that it isn’t very fast and works best within the solar system heading away from the Sun.

Antimater Engine.Antimatter particles have exactly the same properties as matter except they have an opposite charge i.e. An electron (matter) and a positron (antimatter). When a matter particle meets its antiparticle they annihilate each other turning into gamma photons. These photons could be used to propel a ship forward. The advantage is the vast amount of energy for very little mass. The disadvantage is that it is difficult to make and store large amounts of antimatter without annihilation accidentally occurring. It is also currently very expensive to produce antimatter.

Nuclear Fusion.Fusion is the joining of small atoms into larger ones. This process releases energy in much larger amounts than fission (splitting large atoms into small ones). The main advantage is the large amounts of energy produced for relatively small mass. The main

disadvantage is that fission is currently needed to get fusion going and this involves a lot of radioactive material which, in an accident, could be an issue.

Ion Rockets.Ion propulsion systems are already in use already on many commercial satellites. They are capable of propelling ships at very high speeds (200,000 mph) for less fuel, although the trade off is low acceleration. An ion is an atom or molecule that is electrically charged. The ions are essentially fired out of the engine by electrostatic forces.

Force pushing backwards on fuel

Fuel pushing back on the ship, pushing it forwards.

Simplified idea,

∆ v ship=m fuel∆ v fuel

mship

[R]

[S]

[T]

Space Travel – Getting between stars.Even in the Milano it would still take a very long time to travel between stars (many many years). Even if we could propel a craft to more than half the speed of light it would still take years to reach even the closest habitable planets.

The space fairing craft of Guardians of the Galaxy must have some warp capablities. If we have any real hope of reaching any Exo-planets we really will need to develop warp capabilities as well.

Is faster than light possible?Not by any conventional means of propulsion, but NASA and other physicists believe it might be possible by bending space and time.

NASA’s Warp Engine NASA is in the very early speculation phase of an idea for faster than light travel. It is called an Alcubierre drive and involves creating a space-time warp bubble. The ‘bubble’ shifts space around the bubble, moving the object through the surrounding space. It’s a bit like walking on a travellator (moving walkway). You can only walk so fast, but if the ground you are walking on moves as well you travel much faster.

Will it really be possible?

Sadly, not in the foreseeable future. While the idea is theoretically and mathematically sound the practicality of making it work is impossible for us at the moment. There are a couple of main reasons for this: firstly it requires negative energy density (negative mass) which is at the moment only a theoretical possibility; secondly the drive would also require a large volume of anti-matter (~700 kg).

There are also questions about survival inside the bubble and the effect the bubble would have on the destination space. [18]

Warp bubble [U]

NASA’s warp ship concept [V]

Thanks to Eamonn Kerins from Manchester University whose talk at the Physics and Maths teachers conference in 2014 on the hunt for Earth-2 inspired some of the content.

References.

1 http://www.universetoday.com/102630/how-many-stars-are-there-in-the-universe/

2 http://www.rmg.co.uk/explore/astronomy-and-time/astronomy-facts/faqs/what-is-a-galaxy-how-many-stars-in-a-galaxy-how-many-stars/galaxies-in-the-universe

3: On Average, Every Star Has At Least One Planet, New Analysis Shows, Rebecca Boyle, Nov 01, 2012, http://www.popsci.com/science/article/2012-01/new-exoplanet-analysis-determines-planets-are-more-common-stars-milky-way

4: Nearly Every Star Hosts at Least One Alien Planet, Mike Wall, March 04, 2014, http://www.space.com/24894-exoplanets-habitable-zone-red-dwarfs.html

5: 10 Exoplanets That Could Host Alien Life, Elizabeth Howell,  April 17, 2014, http://www.space.com/18790-habitable-exoplanets-catalog-photos.html

6: Discovering planets beyond, alien atmospheres. http://hubblesite.org/hubble_discoveries/discovering_planets_beyond/alien-atmospheres

7: List of potentially habitable exoplanets http://en.wikipedia.org/wiki/List_of_potential_habitable_exoplanets

8: Transit Photometry, A Method for Finding Earthshttp://www.planetary.org/explore/space-topics/exoplanets/transit-photometry.html

9: Planet Detection through Microlensinghttp://www.planetary.org/explore/space-topics/exoplanets/microlensing.html

10. The Origins of Life. By Helen Fields, October 2010, Smithsonian magazine.http://www.smithsonianmag.com/science-nature/the-origins-of-life-60437133/?no-ist

11. 7 Theories on the origin of life. By Charles Q. Choi. March 22, 2011. Live Science. http://www.livescience.com/13363-7-theories-origin-life.html

12. How did life originae? Evolution 101 from University of California museum of Paleontology.http://evolution.berkeley.edu/evosite/evo101/IIE2bDetailsoforigin.shtml

13. Organic Molecules in Titan's Atmosphere Are Intriguingly Skewed. October 22, 2014https://public.nrao.edu/news/pressreleases/organic-molecules-titan

14.The Fermi Paradox http://www.seti.org/seti-institute/project/details/fermi-paradox

15. 11 of the Weirdest Solutions to the Fermi Paradox http://io9.com/11-of-the-weirdest-solutions-to-the-fermi-paradox-456850746

16. Sustaining life -- Where Would a Space Explorer Find Water and Oxygen? NASA http://www.nasa.gov/audience/foreducators/stseducation/materials/Sustaining_Life.html

17. Known effects of long-term space flights on the human body – Discovery Channel.

http://www.racetomars.ca/mars/article_effects.jsp

18. Could We Use Ground-Based Lasers To Propel Rockets Into Space? – i09 George Dvorsky - 31/10/14 http://io9.com/could-we-use-ground-based-lasers-to-propel-rockets-into-1653255068

19. Alcubierre drive, Wikipedia. – 03/11/14 http://en.wikipedia.org/wiki/Alcubierre_drive#Mass.E2.80.93energy_requirement

Images

A. Planet Xanda: http://www.8cn.tv/content/guardians-galaxy-check-out-5-pieces-xandar-concept-art

B. Planet: http://www.nasa.gov/topics/universe/features/pia14093.html

C. Morag: http://comicsen8mm.com/wp-content/uploads/2014/08/GotG-Curiosidades-06.jpg

D. Andromeda Galaxy http://en.wikipedia.org/wiki/Andromeda_Galaxy#mediaviewer/File:Andromeda_Galaxy_(with_h-alpha).jpg

E.Gliese 581, http://en.wikipedia.org/wiki/Gliese_581#mediaviewer/File:Gliese_581.jpg

F. Gliese 832c, http://en.wikipedia.org/wiki/File:Gj832c.png

G.Kepler 22, http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-22b-diagram.html

H. Nowhere. http://billdesowitz.com/framestore-animates-rocket-for-guardians-of-the-galaxy/

I. Transit graph diagram: http://commons.wikimedia.org/wiki/File:Transit_Method_of_Detecting_Extrasolar_Planets.jpg

J. Guardians of the Galaxy team http://www.filmdivider.com/4394/james-gunns-visual-guide-to-guardians-of-the-galaxy/

K. Europa surface.http://www.nasa.gov/sites/default/files/styles/673xvariable_height/public/14-186_europa_image_0.jpg?itok=PYl70EE4

L. Titan.http://upload.wikimedia.org/wikipedia/commons/5/5a/Titan_multi_spectral_overlay.jpg

O. A Watcher. http://marvel.com/universe/Uatu_the_Watcher

P. Galactic Council. Frame from Guardians of the Galaxy (2013) #2.

Q. Dark Aster. http://www.filmdivider.com/4394/james-gunns-visual-guide-to-guardians-of-the-galaxy/

R. Solar Sail. http://en.wikipedia.org/wiki/Solar_sail#mediaviewer/File:IKAROS_solar_sail.jpg

S. Fusion engine http://en.wikipedia.org/wiki/Nuclear_thermal_rocket#mediaviewer/File:Nuclear_thermal_rocket_en.svg

T. Ion engine http://en.wikipedia.org/wiki/Ion_thruster#mediaviewer/File:Ion_Engine_Test_Firing_-_GPN-2000-000482.jpg

U. Alcubierre drive, bubble http://en.wikipedia.org/wiki/Alcubierre_drive#mediaviewer/File:Alcubierre.png

V. Nasa concept warp ship. http://io9.com/heres-nasas-new-design-for-a-warp-drive-ship-1588948192