This light curve shows the change in brightness of the TRAPPIST-1 system as the innermost planet, TRAPPIST-1 b, moves behind the star. This phenomenon is known as a secondary eclipse.
Astronomers used Webb’s Mid-Infrared Instrument (MIRI) to measure the brightness of mid-infrared light. When the planet is beside the star, the light emitted by both the star and the dayside of the planet reach 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 planet’s dayside. This is then used to calculate the dayside temperature.
The graph shows combined data from five separate observations made using MIRI’s F1500W filter, which only allows light with wavelengths ranging from 13.5-16.6 microns to pass through to the detectors. The blue squares are individual brightness measurements. The red circles show measurements that are “binned,” or averaged to make it easier to see the change over time. The decrease in brightness during the secondary eclipse is less than 0.1%. MIRI was able to detect changes as small as 0.027% (or 1 part in 3,700).
This is the first thermal emission observation of TRAPPIST-1 b, or any planet as small as Earth and as cool as the rocky planets in our solar system.
The observations are being repeated using a 12.8-micron filter in order to confirm the results and narrow down the interpretations.
Credits
Illustration
NASA, ESA, CSA, Joseph Olmsted (STScI)
Science
Thomas P. Greene (NASA Ames), Taylor Bell (BAERI), Elsa Ducrot (CEA), Pierre-Olivier Lagage (CEA)
| About The Object | |
|---|---|
| Object Name | TRAPPIST-1 b |
| Object Description | Rocky Exoplanet |
| R.A. Position | 23h 06m 30s |
| Dec. Position | -05d 02m 30s |
| Constellation | Aquarius |
| Distance | 40 light-years |
| Dimensions | Diameter: 1.1 Ă— Earth; Mass: 1.4 Ă— Earth |
| About The Data | |
| Data Description | time-series photometry of secondary eclipse |
| Instrument | MIRI |
| Exposure Dates | 2022: November 8, 12, 20, 24, and December 3 |
| Filters | F1500W |
| 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 |
|
| 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. |
