Super-Earth Exoplanet 55 Cancri e (NIRCam + MIRI Emission Spectrum)

 Super-Earth Exoplanet 55 Cancri e (NIRCam + MIRI Emission Spectrum)

A thermal emission spectrum captured by Webb’s NIRCam (Near-Infrared Camera) in November 2022, and MIRI (Mid-Infrared Instrument) in March 2023, shows the brightness (y-axis) of different wavelengths of infrared light (x-axis) emitted by the super-Earth exoplanet 55 Cancri e. The spectrum shows that the planet may be surrounded by an atmosphere rich in carbon dioxide or carbon monoxide and other volatiles, not just vaporized rock.

The graph compares data collected by NIRCam (orange dots) and MIRI (purple dots) to two different models. Model A, in red, shows what the emission spectrum of 55 Cancri e should look like if it has an atmosphere made of vaporized rock. Model B, in blue, shows what the emission spectrum should look like if the planet has a volatile-rich atmosphere outgassed from a magma ocean that has a similar volatile content as Earth’s mantle. Both MIRI and NIRCam data are consistent with the volatile-rich model.

The amount of mid-infrared light emitted by the planet (MIRI) shows that its dayside temperature is significantly lower than what it would be if it did not have an atmosphere to distribute heat from the dayside to the nightside. The dip in the spectrum between 4 and 5 microns (NIRCam data) can be explained by absorption of those wavelengths by carbon monoxide or carbon dioxide molecules in the atmosphere.

The spectrum was made by measuring the brightness of 4- to 5-micron light with Webb’s NIRCam GRISM spectrometer, and 5- to 12-micron with MIRI low-resolution spectrometer, before, during, and after the planet moved behind its star (the secondary eclipse). The amount of each wavelength emitted by the planet (y-axis) was calculated by subtracting the brightness of the star alone (during the secondary eclipse) from the brightness of the star and planet combined (before and after the eclipse). Each observation lasted about 8 hours.

Note the NIRCam data have been shifted vertically to align with Model B. Although the differences in brightness between each wavelength in the NIRCam band was derived from the observation (the data suggest a valley between 4 and 5 microns), the absolute brightness (the vertical position of that valley) could not be measured precisely because of noise in the data.



NASA, ESA, CSA, Joseph Olmsted (STScI)


Renyu Hu (NASA-JPL), Aaron Bello-Arufe (NASA-JPL), Michael Zhang (University of Chicago), Mantas Zilinskas (SRON)

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 NIRCam grism time-series spectroscopy (F444W); MIRI low-resolution time-series spectroscopy (5-12 microns)
Instrument NIRCam and MIRI
Exposure Dates NIRCam: November 24, 2022 MIRI: 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.