Lecture 15

Question 1

What is a technosignature?

Answer 1

Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not.

Question 2

Megastructure (Dyson Sphere)

Answer 2

Hypothetical constructs built by advanced civilizations in order to collect nearly all the energy of their parent star.

Dyson sphere = spherical shell at same distance from star as the home planet. The intercepted energy is somehow channeled to planet. But shell is heated by the incident radiation.

Question 3

Artifact SETI

Answer 3

1964 —Kardashev classifies extraterrestrial civilizations by their total power supply (i.e. potential for transmission power)

Type I: Can harness a planet’s entire energy supply (K1)
Type II: Can harness a star’s entire output (K2)
Type III: Can harness an entire galaxy’

Question 4

KIC 8462852: “Tabby’s star”

Answer 4

*Transiting planet with large ring system
*Comet swarm
*Asymmetric Dust ring
*Disintegrating planet/asteroid/comets
*Unusual magnetic activity
*Artificial Megastructure (Dyson Swarm)?

Question 5

Classical SETI vs Artifact SETI

Answer 5

Communication and Artifact SETI are complementary:

Artifact SETI: hard-pressed to prove phenomena cannot be natural

Classical SETI: must cast an impossibly wide net
(frequencies, duty cycles, bandwidth, power, targets…)