Exoplanet WASP-96 b (NIRISS Transmission Spectrum)

 Exoplanet WASP-96 b (NIRISS Transmission Spectrum)

A transmission spectrum made from a single observation using Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) reveals atmospheric characteristics of the hot gas giant exoplanet WASP-96 b.  

A transmission spectrum is made by comparing starlight filtered through a planet’s atmosphere as it moves across the star, to the unfiltered starlight detected when the planet is beside the star. Each of the 141 data points (white circles) on this graph represents the amount of a specific wavelength of light that is blocked by the planet and absorbed by its atmosphere. 

In this observation, the wavelengths detected by NIRISS range from 0.6 microns (red) to 2.8 microns (in the near-infrared). The amount of starlight blocked ranges from about 13,600 parts per million (1.36 percent) to 14,700 parts per million (1.47 percent).

Researchers are able to detect and measure the abundances of key gases in a planet’s atmosphere based on the absorption pattern – the locations and heights of peaks on the graph: each gas has a characteristic set of wavelengths that it absorbs. The temperature of the atmosphere can be calculated based in part on the height of the peaks: a hotter planet has taller peaks. Other characteristics, like the presence of haze and clouds, can be inferred based on the overall shape of different portions of the spectrum.  

The gray lines extending above and below each data point are error bars that show the uncertainty of each measurement, or the reasonable range of actual possible values. For a single observation, the error on these measurements is remarkably small.

The blue line is a best-fit model that takes into account the data, the known properties of WASP-96 b and its star (e.g., size, mass, temperature), and assumed characteristics of the atmosphere. Researchers can vary the parameters in the model – changing unknown characteristics like cloud height in the atmosphere and abundances of various gases – to get a better fit and further understand what the atmosphere is really like. The difference between the best-fit model shown here and the data simply reflects the additional work to be done in analyzing and interpreting the data and the planet. 

Although full analysis of the spectrum will take additional time, it is possible to draw a number of preliminary conclusions. The labeled peaks in the spectrum indicate the presence of water vapor. The height of the water peaks, which is less than expected based on previous observations, is evidence for the presence of clouds that suppress the water vapor features. The gradual downward slope of the left side of the spectrum (shorter wavelengths) is indicative of possible haze. The height of the peaks along with other characteristics of the spectrum is used to calculate an atmospheric temperature of about 1350°F (725°C).  

This is the most detailed infrared exoplanet transmission spectrum ever collected, the first transmission spectrum that includes wavelengths longer than 1.6 microns with such high resolution and accuracy, and the first to cover the entire wavelength range from 0.6 microns (visible red light) to 2.8 microns (near-infrared) in a single shot. The speed with which researchers have been able to make confident interpretations of the spectrum is further testament to the quality of the data. 

The observation was made using NIRISS’s Single-Object Slitless Spectroscopy (SOSS) mode, which involves capturing the spectrum of a single bright object, like the star WASP-96, in a field of view. 

WASP-96 b is a hot gas giant exoplanet that orbits a Sun-like star roughly 1,150 light-years away, in the constellation Phoenix. The planet orbits extremely close to its star (less than 1/20th the distance between Earth and the Sun) and completes one orbit in less than 3½ Earth-days. The planet’s discovery, based on ground-based observations, was announced in 2014. The star, WASP-96, is somewhat older than the Sun, but is about the same size, mass, temperature, and color.

The background illustration of WASP-96 b and its star is based on current understanding of the planet from both NIRISS spectroscopy and previous ground- and space-based observations. Webb has not captured a direct image of the planet or its atmosphere.

NIRISS was contributed by the Canadian Space Agency. The instrument was designed and built by Honeywell in collaboration with the Université de Montréal and the National Research Council Canada.

For a full array of Webb’s first images and spectra, including downloadable files, please visit: https://webbtelescope.org/news/first-images

Credits

Illustration

NASA, ESA, CSA, STScI

About The Object
Object Name WASP-96 b
Object Description Hot Gas Giant Exoplanet
R.A. Position 00:04:11.18
Dec. Position -47:21:38.29
Constellation Phoenix
Distance 350 parsecs (1,150 light-years)  
Dimensions 1.2 times the radius of Jupiter (13.5 times the radius of Earth)
0.48 times the mass of Jupiter (153 times mass of Earth)
About The Data
Data Description This image was created with Webb data from proposal . It is part of Webb Early Release Observations. The Early Release Observations and associated materials were developed, executed, and compiled by the ERO production team: Jaclyn Barrientes, Claire Blome, Hannah Braun, Matthew Brown, Margaret Carruthers, Dan Coe, Joseph DePasquale, Nestor Espinoza, Macarena Garcia Marin, Karl Gordon, Alaina Henry, Leah Hustak, Andi James, Ann Jenkins, Anton Koekemoer, Stephanie LaMassa, David Law, Alexandra Lockwood, Amaya Moro-Martin, Susan Mullally, Alyssa Pagan, Dani Player, Klaus Pontoppidan, Charles Proffitt, Christine Pulliam, Leah Ramsay, Swara Ravindranath, Neill Reid, Massimo Robberto, Elena Sabbi, Leonardo Ubeda.  The EROs were also made possible by the foundational efforts and support from the JWST instruments, STScI planning and scheduling, Data Management teams, and Office of Public Outreach.  
Instrument Near-Infrared Imager and Slitless Spectrograph (NIRISS), time-series Single-Object Slitless Spectroscopy (SOSS) mode 
Exposure Dates June 21, 2022 (6.4-hour observation time)
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.