Physics

Question 1

Describe the process of Direct Imaging of an exoplanet

Answer 1

• directly taking a photo of the exoplanet using telescopes

- Glare from the star can be blocked using filters

Question 2

Describe the process of Doppler detection of exoplanets

Answer 2

• when an exoplanet orbits a star, it causes the star to follow its own orbit
• this causes the light we see from the star to be either blue-shifted or red-shifted as the star moves towards or away from us
• this shift is the indication of an exoplanet

Question 3

Describe the process of Transit detection of exoplanets

Answer 3

• when a large star passes in front of / transits the surface of a star, the intensity of the star light we see will decrease for the period of time the exoplanet is in front of the star
• this observable dip in light intensity is the indication of an exoplanet

Question 4

What is Kepler’s first law of planetary motion?

Answer 4

Planets orbit stars in elliptical orbits with the star at one of the focii

Question 5

What is Kepler’s second law of planetary motion?

Answer 5

Orbits of planets trace out equal areas of space in equal times

Question 6

What is Kepler’s third law of planetary motion?

Answer 6

The period and radius of orbit relationship:

p^2 is proportional to r^3

Question 7

At what radius are planets typically rocky planets ?

Answer 7

Anything less than or equal to 1.6 times the radius of earth

Question 8

What is the relationship between planet size and density?

Answer 8

as the planet size (and hence radius) increases, the density of the planet decreases

Question 9

Describe what is meant by “the habitable zone”

Answer 9

a region of space around a star where temperatures on a planet allow for surface liquid water

Question 10

What happens to the overall life time of a star as its mass increases?

Answer 10

• t is proportional m^-3

- so as m increases, t decreases

Question 11

What is the region of space called “the Goldilocks zone” and what is it for our sun?

Answer 11

• again, similar to the habitable zone of a star. where liquid water can be present on the surface of a planet
• for earth, the zone lies between 0.95 and 1.37 Au

Question 12

What is Fermi’s paradox?

Answer 12

If the galactic crossing time is less than that of the age of the earth then why haven’t we encountered any extra-terrestrial life if there is any?

Question 13

What does the drake equation tell us?

Answer 13

It tells us the probability of finding intelligent life in the universe

Question 14

what is the Copernican principle?

Answer 14

That our place in the universe isn’t special and we aren’t at the centre of anything

Question 15

How long have we as an intelligent species been detectable?

Answer 15

For about a century with the invention of the radio and radio waves

Question 16

What is the frost line

Answer 16

distance from a star at which water will freeze on the surface of a planet

Question 17

What main astrobiological targets orbit Jupiter?

Answer 17

• Europa

- Callisto

Question 18

What main astrobiological targets orbit Saturn?

Answer 18

• Enceladus

- Titan

Question 19

State a disadvantage of each of the three types of detection of exoplanets

Answer 19

Direct imaging
-Planet must be very large and in a very large orbit of the star to be seen
Doppler
-multiple planets or stars orbiting the primary star can cause the redshifted and blueshifted light to be distorted, giving false positives and negatives
Transit
-the Planet must be large enough to be seen crossing the star and it has to transit the star edge on or we wont be able to see it

Question 20

What is tidal locking ?

Answer 20

Tidal locking is when a planet or moon is far enough out in its orbit that the same side is always facing the object it is orbiting

Question 21

Where do x-ray flares occur and why?

Answer 21

• x-ray flares occur in low mass stars

- this is due to the erratic magnetic fields

Question 22

Name a system that is very similar to that of our solar system (and how far away is it?)

Answer 22

Trappist-1 has very similar features to that of our own solar system
-12 Pc

Question 23

Name some disadvantages to living near a hot star

Answer 23

• Star doesn’t live for very long

- Star doesn’t have a continuous habitable zone

Question 24

Name some disadvantages to living near a cold star

Answer 24

• tidal locking will occur more frequently

- exposed to x-ray flares