This simplified diagram of an exoplanet phase curve shows the change in total brightness of a star–planet system as the planet orbits the star. The system looks brighter when more of the lit side of the planet is facing the telescope (full phase), and dimmer when more of the dark side is facing the telescope (new phase).
(Top) Diagram showing the change in a planet’s phase (the amount of the lit side facing the telescope) as it orbits its star. (Middle) Three-dimensional graph showing the change in the total brightness of the star–planet system as the planet orbits its star. In this graph, known as a light curve, the horizontal plane is orbital location and the vertical axis is brightness. (Bottom) Color scale bar. In both the orbital diagram and the light curve, brightness is color-coded from blue (least amount of light detected) to red (most light detected).
Researchers will use Webb’s Mid-Infrared Instrument (MIRI) to measure the brightness of different wavelengths of mid-infrared light as exoplanet GJ 1214 b completes one full orbit around its star. Although Webb will not be able to observe the planet directly on its own – the star is too bright and the planet too close to see separately – it is sensitive enough to measure very subtle changes in the total amount of light from the star and planet together, as the planet moves.
Because it is so close to its star, GJ 1214 b is thought to be tidally locked: One side of the planet faces toward the star at all times and is permanently lit, while the other side faces away in permanent darkness. As a result, the day side of the planet is expected to be significantly hotter, emitting more infrared light than the night side. However, the detailed difference in temperature with longitude depends on how much the atmosphere reflects or absorbs starlight, how well it retains heat, and how it moves heat from one side of the planet to the other. This in turn depends on the composition of the atmosphere. (A water steam atmosphere, for example, would transport a very different amount of heat to the night side than an atmosphere dominated by hydrogen.) Researchers will use the mid-infrared phase curve of GJ 1214 b to map the temperature of the planet by longitude, and then use that information to narrow down possible atmospheric characteristics.
Credits
Illustration
NASA, ESA, CSA, Dani Player (STScI)
| About The Object | |
|---|---|
| Object Name | GJ 1214 b |
| Object Description | Warm sub-Neptune exoplanet |
| R.A. Position | 17:15:19.54 |
| Dec. Position | +4:57:38.45 |
| Constellation | Ophiuchus |
| Distance | 48 light-years |
| 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. |
