Hot Gas Giant Exoplanet WASP-39 b Transit Light Curve (NIRSpec)

Extended Description

Infographic titled “Infographic titled Hot Gas-Giant Exoplanet WASP-39 b Transit Light Curve, NIRSpec PRISM”

The graphic has two parts. At the top is a diagram showing a planet transiting (moving in front of) its star. 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

At the center is a bright orange circle representing the star. A gray line looping around the star represents the orbital path of the plant. The line has two arrows pointing counter-clockwise to indicate the direction of motion of the planet. Three dark gray circles surrounded by light gray haloes represent the planet and its atmosphere at three different times during the orbit. From left to right: 1) At the beginning of the transit when the planet begins to move in front of the star; 2) in the middle of the transit when the planet is directly in front of the star; and 3) at the end of the transit as the planet ceases to block any part of the star.

Graph

Below the transit diagram is a graph of Relative Brightness in percent on the vertical y-axis versus Elapsed Time in hours on the horizontal x-axis.

Axes

The y-axis ranges from 97 percent relative brightness at the origin at the bottom to 100 percent at the top, with labeled tick marks every .5 percent. The x-axis ranges from 0 to 7 hours. There are labeled tick marks every hour.

Data

The graph consists of hundreds of data points that together form a U-shaped valley with flat plains on either side. The curve is almost perfectly symmetrical about the lowest point of the valley. The points are not connected, but are dense enough that they almost appear to be connected.

The first data point is at 0 hours. and the last is at 7.5 hours. Hundreds of blue data points form a thick, clear pattern with very little scatter. Some data points are overlapping.

Between the beginning of the curve at 0 hours. and the beginning of the transit at about 2 and a half hours, the relative brightness of the star-planet system remains flat around 100%.

Around 2 and a half hours., the brightness begins to decrease at a steady rate. Around 3 hours elapsed time, it levels off at a relative brightness of about 97.5 percent. The curve continues with a slightly concave-up shape until 5 hours have elapsed. when it begins to rise, showing a steady increase in brightness. The rise continues until the end of the transit at about 5 and half hours elapsed when the brightness levels off again at 100 percent. The curve then remains almost flat, with almost no variability, until the last data point until 7 and a half hours have elapsed.

There are two labels on the curve. The flat segment of 100 percent relative brightness to the left of the U-shaped valley is labeled “Starlight.” The U-shaped portion of the curve with brightness less than 100 percent is labeled “Starlight blocked by planet and its atmosphere.”

Relationship between the Diagram and Graph

A vertical gray line connects each of the three planet positions in the diagram to the corresponding points on the light curve. From left to right: 1) A small portion of the right side of the planet blocks the star and the relative brightness begins to decrease; 2) the entire planet is in front of the star and the relative brightness is at its lowest point (the center of the U-shaped valley); 3) a small portion of the left side of the planet is blocking the star and the relative brightness is almost back up to 100 percent.

Background

In the background of the graphic is an illustration of the planet’s terminator zone.

Image Alt Text

Infographic titled “Hot Gas-Giant Exoplanet WASP-39 b Transit Light Curve, NIRSpec PRISM.” At the top of the infographic is a diagram showing a planet transiting (moving in front of) its star. Below the diagram is a graph showing the change in relative brightness of the star-planet system over 7 hours. 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. The infographic shows that the brightness of the system remains steady until the planet begins to transit the star. It then decreases until the planet is directly in front of the star. The brightness increases again until the planet is no longer blocking the star, at which point it levels out. Please reference the extended text description for more details.