Super-Earth Exoplanet 55 Cancri e (MIRI Secondary Eclipse Light Curve)

 Super-Earth Exoplanet 55 Cancri e (MIRI Secondary Eclipse Light Curve)

This light curve shows the change in brightness of the 55 Cancri system as the rocky planet 55 Cancri e, the closest of the five known planets in the system, moves behind the star. This phenomenon is known a secondary eclipse.

When the planet is next to the star, the mid-infrared light emitted by both the star and the dayside of the planet reaches the telescope, and the system appears brighter. When the planet is behind the star, the light emitted by the planet is blocked and only the starlight reaches the telescope, causing the apparent brightness to decrease.

Astronomers can subtract the brightness of the star from the combined brightness of the star and planet to calculate how much infrared light is coming from the dayside of the planet. This is then used to calculate the dayside temperature and infer whether or not the planet has an atmosphere.

The graph shows data collected using the low-resolution spectroscopy mode on Webb’s Mid-Infrared Instrument in March 2023. Each of the purple data points shows the brightness of light ranging in wavelength from 7.5 to 11.8 microns, averaged over intervals of about 5 minutes. The grey line is the best fit, or model light curve that matches the data most closely. The decrease in brightness during the secondary eclipse is just 110 parts per million, or about 0.011 percent.

The temperature of the planet calculated from this observation is about 1,800 kelvins (around 2,800 degrees Fahrenheit), which is significantly lower than would be expected if the planet has no atmosphere or only a thin rock-vapor atmosphere. This relatively low temperature indicates that heat is being distributed from the dayside to the nightside of the planet, possibly by a volatile-rich atmosphere.



NASA, ESA, CSA, Joseph Olmsted (STScI)


Aaron Bello-Arufe (NASA-JPL)

About The Object
Object Name Planet: 55 Cancri e, also called Janssen; Star: 55 Cancri, also called Rho-1 Cancri, Copernicus
Object Description Super-Earth Exoplanet orbiting a K-Star
R.A. Position 08h52m35.24s
Dec. Position +28d19m47.34s
Constellation Cancer
Distance 41 light-years
About The Data
Data Description MIRI low-resolution time-series spectroscopy (5-12 microns)
Instrument MIRI
Exposure Dates March 24, 2023
About The Object
Object Name A name or catalog number that astronomers use to identify an astronomical object.
Object Description The type of astronomical object.
R.A. Position Right ascension – analogous to longitude – is one component of an object's position.
Dec. Position Declination – analogous to latitude – is one component of an object's position.
Constellation One of 88 recognized regions of the celestial sphere in which the object appears.
Distance The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
Dimensions The physical size of the object or the apparent angle it subtends on the sky.
About The Data
Data Description
  • Proposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
  • Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.
Instrument The science instrument used to produce the data.
Exposure Dates The date(s) that the telescope made its observations and the total exposure time.
Filters The camera filters that were used in the science observations.
About The Image
Image Credit The primary individuals and institutions responsible for the content.
Publication Date The date and time the release content became public.
Color Info A brief description of the methods used to convert telescope data into the color image being presented.
Orientation The rotation of the image on the sky with respect to the north pole of the celestial sphere.