Exoplanets Flashcards
How do astronomers obtain evidence for the existence of exoplanets?
Astrometry
By measuring the position of a star very accurately, any minute wobble in the stars position can be due to the tiny pull of a planet on the parent star.
Transit Methods
As a planet moves in front of a star minute changes in light occur. Scientist can then work out the size and orbit of a planet.
Radial velocity
Changes in the movement of a star towards and away from Earth can be detected using the Doppler effect.
What are the difficulties associated with the detection of individual planets?
They orbit stars and the brightness of the star may prevent us from finding them.
Planets may orbit too far away from our line of sight for some methods to detect them e.g. when their ecliptic is too eccentric for them to be noticed.
Why is the presence of liquid water is probably an
essential requirement for life?
It is considered to have been crucial to forming life due to its properities as a solvent allowing various chemicals to form.
What is the origin of water on Earth.
These are the two most likely theories:
Condensation
This theory says that water was part of Earth’s body when it formed. As the Earth cooled, water leaked from rocks and the atmosphere condensed the water into liquid form.
Delivery by Comets
It is thought that Earth was heavily bombarded by comets and other bodies early in its evolution and the Moon bears evidence of this. Comets contain large amounts of ice and this would have fed our oceans on impact. This theory is controversial as it would have taken an enormous amount of water to cover 71% of the surface.
What was the Rosetta probes mission?
The Rosetta probe was launched by the European Space Agency in 2004 to understand the origin and evolution of the Solar System. As well as flybys of Earth and Mars it has encountered asteroids and comets up to 2015. It has launched a Lander to measure isotopes of chemicals to understand how much water it may have carried. If the balance between isotopes is similar to that of our oceans then it may support the theory of our water coming from space.
What is the Drake equation?
The Drake Equation where:
N is the number of civilizations in our galaxy with which communication might be possible;
and
R* is the average rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fℓ is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.
N = R* x fp x ne x fℓ x fc x L
What is the significance of Goldilocks zones?
The Habitable zone is an area surrounding a star in which a planet can have liquid water at its surface. In our Solar System it is thought the zone extends from outside the orbit of Venus to halfway through the asteroid belt (0.75 to 3AU). The habitable zone is of course dependent on a planet fulfilling the criteria of having a suitable atmosphere and magnetosphere capable of keeping liquid water on its surface.
What are the possible benefits and dangers of discovering extra-terrestrial life.
Pro’s:
Alien forms of life could lead to cures for existing illnesses
Intelligent life may share knowledge about science that we have yet to discover.
Intelligent life may share advances in technology such as travel and communication.
Con’s
Intelligent life may be aggressive and set out to invade or hurt Earth life forms including humans
They could also create new bacteria capable of killing all life
Depending on an unknown alien force for knowledge prevents us from advancing as humans
