TRAPPIST-1 c Light Curve

Extended Description

Infographic titled “Rocky Exoplanet TRAPPIST-1 c Secondary Eclipse Light Curve, MIRI Time-Series Photometry (F1500W).”
The graphic has two parts. At the top is a diagram showing a planet moving behind its star (a secondary eclipse). Below the diagram is a graph showing the change in relative brightness of the star-planet system over time. The diagram and graph are aligned vertically to show the relationship between the geometry of the star-planet system as the planet orbits, and the measurements on the graph.

Diagram of Secondary Eclipse

At the center is a bright red-orange circle representing the star. A slightly arcuate gray line with an arrow pointing to the right represents a portion of the orbital path of the planet. Along the gray line, and on either side of the star, is a gray circle with a textured pattern. These represent the planet before (at left) and after (right) it moves behind the star. Both show a subtle brightening on the star-side of the planet. Along the line, in the middle of the star is an open circle with a dashed outline representing the position of the planet in the middle of the secondary eclipse, when it is behind the star. The star and planet are not to scale.

Graph

Below the secondary eclipse diagram is a graph of Brightness of 15-micron emitted light on the vertical y-axis versus Elapsed Time in hours on the horizontal x-axis.

Axes

The y-axis ranges from dimmer at the bottom to brighter at the top. There are no units or tick marks. The x-axis ranges from 0.00 hours at the origin on the left to 1.75 hours at the far right. There are labeled tick marks every 0.25 hours.

Key

The graph includes a key showing that the large red circles are brightness measurements averaged over 7-minute intervals; the solid blue squares are individual brightness measurements; and the white line represents a best-fit model.

Data and Model

The graph consists of 636 individual brightness measurements plotted as small solid blue squares, and 16 binned brightness measurements (averaged over 7-minute intervals) plotted as larger solid red circles. The points are not connected.

The individual brightness measurements (blue squares) show a broad scattering across the graph. No trend is visible by eye.

The binned brightness measurements (red circles) show a a slight decrease in brightness between 0 and about 0.75 hours, and a slight increase with some variability between 0.75 and 1.75 hours.

A best-fit model is shown as a thin white line running left to right across the graph. The line forms a shallow U-shaped valley in the center, with flat plains on either side. The valley has steep sides and a flat floor. It begins at about 0.55 hours and ends at 1.25 hours. The line intersects some, but not all, of the red binned brightness measurements

Labels

There are three labels above the model and binned brightness measurements. The label in the center, above the dimmer, U-shaped section of the model and data points, is labeled “Starlight only.” The brighter sets of measurements on the left and right sides of the graph are both labeled, “Starlight + planet dayside.”

Relationship between the Diagram and Graph

Vertical gray lines connect each of the three planet positions in the diagram to the corresponding portions of the light curve. From left to right: 1) Before the planet begins to move behind the star, the brightness is high and fairly level; 2) When the entire planet is behind the star and the brightness is at its lowest point (the center of the U-shaped valley); 3) When the planet has moved out from behind the star, the brightness has increased back to the level it was before the decrease.

Image Alt Text

Graphic titled “Rocky Exoplanet TRAPPIST-1 c Secondary Eclipse Light Curve” showing a diagram of a secondary eclipse and a graph of change in brightness over time.