Astro 8 Flashcards
Who discovered the first confirmed exoplanet, and in what year?
The first confirmed exoplanet was discovered in 1992, orbiting a pulsar.
What method was used to discover the first exoplanet around a ‘normal’ star in 1995?
The Doppler (radial velocity) method.
What is one major obstacle to directly imaging exoplanets?
Planets are up to a billion times fainter than their stars and very close to them, making direct imaging difficult.
According to Kepler’s law of harmonies, how are orbit radius and period related?
a^3 ∝ P^2, where a is the semi-major axis and P the orbital period.
Name the six main methods used for discovering exoplanets.
Doppler method, Astrometry, Transit, Gravitational lensing, Pulsars, Direct imaging.
What does the Doppler (radial velocity) method detect?
Changes in the star’s spectrum due to motion caused by an orbiting planet, seen as redshift or blueshift.
What information can the transit method provide about a planet?
The planet’s period, mass, orbital radius, radius, and density.
Which NASA missions have found most exoplanets via transits?
Kepler and TESS satellites.
What is gravitational lensing and how can it detect exoplanets?
Gravitational lensing is the magnification and distortion of light by mass; exoplanets can be detected when their gravity causes additional lensing effects during star alignments.
Why are planets around pulsars not likely to support life?
Pulsars are remnants of supernovae and environments are hostile.
How many exoplanets had been confirmed by April 2025?
5867 confirmed exoplanets.
What are the two main ‘takeaway’ messages about planet-finding methods?
No single method finds all planets; technology limitations define discovery potential.
What is the next major goal in exoplanet research?
Identifying biosignatures (evidence of life) on habitable exoplanets.
What is a lightcurve in exoplanet transit observations?
A plot of stellar brightness versus time, showing dips when a planet transits the star.
Why don’t all planets transit their stars as seen from Earth?
Orbital inclinations are random; only some are edge-on from our viewpoint.
