Scientific Instruments on the James Webb Space Telescope: Near-Infrared Spectrograph (NIRSpec)
Infographic titled “NIRSpec: Near-Infrared Spectrograph.” The infographic is divided into four sections arranged vertically. From top to bottom: Components, Wavelength, Field of View, and Spectroscopy Modes.
Section 1: Components
Three labeled icons, one for each of NIRSpec’s components.
- Left icon labeled “spectrographs”: Line drawing of light being refracted by a prism. Triangle with a white line entering at an angle from the left side, passing straight through the triangle, and then exiting as a rainbow on the right.
- Center icon labeled “microshutter array”: Line drawing of a three by three grid of horizontal rectangles, with space between the rectangles. Each rectangle contains a set of thin vertical lines, all of the same height. The lines do not touch the edges of the rectangle.
- Right icon labeled “integral field unit”: Line drawing of a rectangular prism with a spiral galaxy and stars on the front and rainbow pattern on the sides. The prism appears to be made of a stack of colors, from purple at the front to red at the back.
Section 2: Wavelength
Graphic showing that the wavelength range of NIRSpec is red to near-infrared.
The graphic consists of a horizontal bar with a sine wave pattern running through the middle from left to right. The wavelength (distance between peaks) of the waves in the wave pattern increases from left to right. The bar is divided into thirds from left to right. The left third of the bar, labeled “visible,” has a subtle rainbow coloring, from purple at the left to red at the right. The middle third, labeled “infrared,” is divided into three sections labeled “near,” “mid,” and “far.” The right third of the bar, labeled “microwave,” is almost black.
The far right end of the visible through the near-infrared section of the bar is called out prominently with bright to dark red coloring.
Section 3: Field of View
Graphic showing the field of view of NIRSpec relative to a Hubble image of the Whirlpool Galaxy.
Black-and-white space telescope image showing a spiral galaxy with two arms. One arm spirals counterclockwise around the bright core of the galaxy, ending at the top right of the image. The galaxy’s other arm ends at the bottom left. A smaller elliptical galaxy lies at the tip of the top arm. The larger spiral galaxy covers about two-thirds of the width of the infographic. The smaller elliptical galaxy covers about one-tenth of the width.
Four open rectangles are overlaid on the image. The rectangles are arranged in a two-by-two grid with space in between. Together, they form a square roughly centered on the bright core of the large spiral galaxy. The square of four rectangles is oriented with the corners at the top, bottom, left, and right. Together, the four rectangles cover approximately 15% of the image.
Section 4: Spectroscopy Modes
Four labeled icons, one for each of NIRSpec’s spectroscopy modes, arranged in a two-by-two grid.
- Top left icon labeled “slitted”: Simple drawing showing two vertical white bars, one above the other with a space in between. To the left of the bar is a star. To the right is a vertical rainbow. A cone of light passes from the star, through the space between the white bars, to the rainbow.
- Top right icon labeled “multi-object”: Four-by-three grid of rectangles. Three rectangles have an icon of an astronomical object: a star, spiral galaxy, and planet. The remaining nine rectangles have a solid white fill. Below the grid is a set of three rectangles arranged horizontally. Each of these rectangles is filled with a rainbow pattern.
- Bottom left icon labeled “integral field unit”: Line drawing of a rectangular prism with a spiral galaxy and stars on the front and rainbow pattern on the sides. The prism appears to be made of a stack of colors, from purple at the front to red at the back.
- Bottom right icon labeled “time-series”: Two-by-two grid with four wave patterns, one in each square. Each of the four wave forms changes color from purple on the left to red on the right. The wave pattern (the heights and locations of the peaks on the wave) is different in each square.
About This Image
Caption
The Near-Infrared Spectrograph (NIRSpec) is one of Webb’s four scientific instruments. NIRSpec is one of Webb’s versatile tools for near-infrared spectroscopy. In addition to standard single-slit spectroscopy to gather spectra of specific objects, NIRSpec also has an integral field unit to investigate spatial variations in spectra and a microshutter array to capture individual spectra of dozens of objects at once. This highly efficient design is part of what makes Webb ideal for studying extremely distant, faint galaxies. NIRSpec was built for the European Space Agency by Airbus Industries with the microshutter array (MSA) and detector sub-systems fabricated by NASA.
NIRSpec Components Spectrographs spread light out into a spectrum so that the brightness of each individual wavelength can be measured. Webb’s microshutter array (MSA) is a grid of 248,000 tiny doors that can be opened and closed to transmit or block light in order to capture spectra of 100 individual objects or points in space at the same time. An integral field unit (IFU) is a combination of camera and spectrograph used to capture and map spectra across a field of view in order to understand variation over space.
NIRSpec Wavelength Range NIRSpec is designed to capture light ranging in wavelength from 0.6 microns (visible red) to 5 microns (mid-infrared).
NIRSpec Field of View An instrument’s field of view is the amount of sky that it can observe at any given point in time. (The actual area that can be observed depends on the distance of the object being observed.) In this graphic, a Hubble Space Telescope image of the Whirlpool Galaxy (M51) is shown for scale. The image covers an area of 9.6 × 6.6 arcminutes. (The full Moon has a diameter of about 31 arcminutes across the sky.) NIRSpec’s field of view covers a total area of roughly 3 × 3 arcminutes.
NIRSpec Imaging Modes None, with the exception of images collected during Integral Field Unit Spectroscopy.
NIRSpec Spectroscopy Modes Slitted Spectroscopy provides the ability to capture the spectrum of a single object—a single star, a single exoplanet, or a single distant galaxy—in a wide field of view. Multi-Object Spectroscopy involves using a microshutter array to capture individual spectra of up to 100 objects or locations in space at one time. Multi-object spectroscopy is important for efficiency, in particular when observing very distant and dim targets, such as ancient galaxies, which require hundreds of hours of observation time. Integral Field Unit Spectroscopy (IFU) involves a combination of imaging and spectroscopy. During an IFU observation, the instrument captures an image of the field of view along with individual spectra of each pixel in the field of view. IFU observations allow astronomers to investigate how properties—such as composition, temperature, and motion—vary between different objects such as stars in a crowded star field, or from place to place over a large region of space such as a galaxy or nebula. Time-Series Spectroscopy involves capturing the spectrum of an object or region of space at regular intervals in order to observe how the spectrum changes over time. Time-series spectroscopy is used to study planets as they transit their stars.