For the introduction chapter of my Ph.D. thesis, I wanted to make some attractive minimalist figures. I knew I had a lot of specialist jargon to explain in the public portion of my defense, and wanted to minimize distractions. Someone suggested that I make these figures available for others to use, so I'm taking that suggestion (albeit somewhat late).
Feel free to use these figures for any non-commercial application, provided you preserve the attribution in them! See details.
Since I already wrote captions for these figures in my thesis, I'm reusing them here.
Adaptive optics system
Diagram of an adaptive optics system. Starlight (orange) arrives at Earth as planar wavefronts above the atmosphere (upper left), then propagates through atmospheric inhomogeneities (blue circles), picking up aberrations. This aberrated light is collected by a telescope, and the beam is bounced off of a deformable mirror (DM) to cancel the aberrations. Residual aberrations remain due to lag and the limitations of the hardware. The light passes through a beamsplitter that sends part of the light to the wavefront sensor (WFS), where the residual aberrations are measured. The measurement is used by the controller to compute an updated deformable mirror position to cancel the residual wavefront error, which is then applied to the DM, closing the control loop.
Transit method
Illustration of the systematic bias inherent in transit observations using three configurations of a notional planet in orbit around a distant star. The observer views the scene in the square panel (albeit without resolving planet from star) as the planet moves from left to right between the observer and the star. They record the brightness of the host star over time, resulting in the light curve below.
Configuration A
In configuration A, the planet is on a short orbit in a plane aligned with the observer’s line of sight.
Configuration B
In configuration B, the planet’s orbit is inclined relative to the line of sight. However, the planet still transits the star, providing a very similar light curve to configuration A.
Configuration C
In configuration C, the angle of inclination is the same, but the planet is on a longer orbit. Consequently, that the planet proceeds on its orbit without ever occulting the star, producing no transit signal to detect.
Alternative non-transiting configuration
In this configuration, the planet follows an orbit that is face-on from the observer's perspective and therefore does not transit its host star and cannot be detected by the transit method.
Radial velocity method
Illustration of the radial velocity exoplanet detection method. A planet is depicted at three points (A, B, and C) in its orbit about its host star. The gray inset shows a view from above the plane of the orbit, indicating the common center of mass both bodies orbit with ×. At point A, the planet’s velocity towards the observer is maximized, and therefore so is the star’s velocity away from the observer. A hypothetical feature in the star’s spectrum would then be red-shifted by some amount ∆λ that can be measured with a spectrograph. At point B, the planet’s velocity is perpendicular to the line of sight, and there is no detectable red- or blue-shift. At point C, the planet is moving away from the observer, and the star towards them, blue-shifting the spectrum.
Flat wavefronts approximation
Illustration of how a spherical wavefront can approach an idealized flat one when seen at Earth.
Off-axis source wavefronts
Illustration of light from two sources arriving as a combination of an on-axis and an off-axis plane wave, brought to focus to create an image of a star and a companion. Right square panel shows the image at the detector.
Sky rotation
Illustration of sky rotation from target rise to transit to set time. When a ground-based telescope tracks a target from horizon to horizon, the apparent orientation of the scene changes (unless a field rotator is used to compensate).
Alternative figure
This figure has been adapted to fill a widescreen presentation slide.
Angular differential imaging
Illustration of angular differential imaging (ADI). A: Capture a sequence of exposures as the scene appears to rotate during the target’s passage across the sky—from rise to set—as the parallactic angle changes. (Or, for space-based imaging, as the roll about the telescope pointing vector changes.) B: Combine (e.g. by median stacking) the images in the sequence to provide a better estimate of the PSF of the host star while ignoring planet light. C: Subtract this estimate from each frame separately. D: Rotate the resulting images by their parallactic angle (and any offset) to place north up and east to the left in all the images. E: Stack the subtracted images in the rotated frame to combine signal from the planet while averaging out noise from the residual starlight.
Licensing and reuse
This work is licensed under CC BY-NC 4.0
.
Non-commercial distribution and adaptation are permitted within the terms of the license, as long as attribution is preserved.