Tug of War: The Radial Velocity Method Quiz

If radial velocity specifically measures "line-of-sight" motion, and if a face-on orbit moves the star in a circle that is always the same distance from Earth, then there is no "toward" or "away" component to create a Doppler shift.

If acceleration is equal to force divided by mass (F=ma), and if a massive star is harder to move than a small star, then a more massive star will show a slower, less obvious velocity change than a lower-mass star.

If the wobble method is biased toward finding large masses close to their stars, and if these planets are gas giants that become very hot due to their proximity, then the term for this class of planets is Hot Jupiters.

If Earth-like planets cause very tiny tugs on their stars, and if scientists need to detect those tiny changes to find small worlds, then spectrographs must be precise enough to measure speeds as slow as a person walking (meters per second).

If the transit method provides the size/radius (volume) and the radial velocity provides the mass, and if density is mass divided by volume, then combining these methods allows scientists to determine what the planet is likely made of.

If an orbiting planet exerts a gravitational pull on its host star, and if that pull causes the star to move in a small circle or ellipse, then astronomers can measure the component of that motion that moves directly toward or away from our line of sight.

If gravity is a mutual force between two masses, and if Newton's Third Law states every action has an equal and opposite reaction, then the planet's orbit must be balanced by a corresponding (though much smaller) movement of the star around the barycenter.

If the Doppler effect applies to light, and if motion toward the observer compresses the light waves into shorter wavelengths, then the resulting shift toward the blue end of the visible spectrum is defined as a blueshift.

If a more massive planet exerts a stronger gravitational tug on its star, and if a stronger tug causes the star to move faster in its "wobble," then the measured speed of the star’s radial motion directly reveals the minimum mass of the planet.

If this method relies on measuring changes in light frequency, then a spectrograph is required to see spectral lines; if the star must move relative to us, then a "wobble" and a non-face-on orbit are essential for the motion to be detectable.

If we cannot see the planet directly due to the star's overwhelming brightness, and if we instead measure the star's physical reaction to the planet's gravity, then we are using the star as a proxy to prove the planet is there.

If a larger "wobble" is easier to detect, and if gravitational force is stronger when a planet is more massive and closer to its star, then this method is actually most effective at finding large planets (like Jupiters) with short orbital periods.

If both objects in a system respond to each other's gravity, then they do not orbit the center of the star, but rather the balance point of their combined masses, which is termed the barycenter.

If the Doppler effect dictates that waves are "stretched" as a source moves away from an observer, and if longer wavelengths of visible light are associated with the color red, then the star's spectral lines will exhibit a redshift.

If the signal depends on clear spectral data and measurable motion toward/away from us, then dim light, a "face-on" orientation (no radial motion), and stellar "noise" from spots will obscure the planet's gravitational signature.

If the star's wobble is caused by the planet's orbit, and if the planet completes one orbit in a set amount of time, then the cycle of redshift-to-blueshift will repeat exactly once per orbital period.

If the radial velocity only measures the motion moving toward or away from Earth, and if we don't know how much the orbit is tilted, then we only measure a fraction of the star's total motion; therefore, we can only calculate the "minimum mass" (m sin i).

If a star's cooler outer atmosphere absorbs specific frequencies of light from its hotter interior, then the resulting spectrum will contain dark gaps known as absorption lines, which serve as the "markers" for measuring Doppler shifts.

If the 1995 discovery by Mayor and Queloz changed astronomy by proving planets exist around other Sun-like stars, and if they used the Doppler wobble technique, then the planet they identified was 51 Pegasi b.

If we are measuring a gravitational tug (Newton), calculating orbits (Kepler), using light shifts (Doppler), and assuming the system's center of mass stays balanced (Momentum), then all these principles are core to the method.