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Secondary Eclipse Light Curve

Graphic titled, “Change in Brightness as Rocky Exoplanet TRAPPIST-1 b Moves Behind Its Star; Secondary Eclipse Light Curve” includes a graph showing change in brightness of mid-infrared light emitted by the star-planet system over the course of 3.5 hours.

A secondary eclipse light curve shows the decrease in brightness of a star-planet system as the planet moves behind the star. The amount of light contributed by the planet is the difference between the brightness of the star and planet combined (as observed before and after the secondary eclipse) and the brightness of the star on its own (during the secondary eclipse). This light curve shows real Webb data from TRAPPIST-1 b, a rocky planet orbiting a red dwarf star 40 light-years from Earth. TRAPPIST-1 b is not part of the Rocky Worlds program. 

About the Object

  • R.A. Position
    R.A. PositionRight ascension – analogous to longitude – is one component of an object's position.
    23h 06m 30s
  • Dec. Position
    Dec. PositionDeclination – analogous to latitude – is one component of an object's position.
    -05d 02m 30s
  • Constellation
    ConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.
    Aquarius
  • Distance
    DistanceThe 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.
    40 light-years

About the Data

  • Data Description
    Data DescriptionProposal: 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.

    time-series photometry of secondary eclipse

  • Instrument
    InstrumentThe science instrument used to produce the data.
    MIRI
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    2022: November 8, 12, 20, 24, and December 3
  • Filters
    FiltersThe camera filters that were used in the science observations.
    F1500W
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    TRAPPIST-1 b
  • Object Description
    Object DescriptionThe type of astronomical object.
    Rocky exoplanet orbiting red dwarf (M-dwarf) star
  • Release Date
    September 30, 2025
  • Credit
    Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI), Andi James (STScI); Science: Thomas Greene (NASA Ames)

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Details

Last Updated
Sep 30, 2025
Location
NASA Goddard Space Flight Center
Contact
Media

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

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