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Chamaeleon I Dark Cloud (NIRCam, NIRSpec, and MIRI Spectra)
Astronomers have taken an inventory of the most deeply embedded ices in a cold molecular cloud to date. They used light from a background star, named NIR38, to illuminate the dark cloud called Chamaeleon I. Ices within the cloud absorbed certain wavelengths of infrared light, leaving spectral fingerprints called absorption lines. These lines indicate which substances are present within the molecular cloud.
These graphs show spectral data from three of the James Webb Space Telescope’s instruments. In addition to simple ices like water, the science team was able to identify frozen forms of a wide range of molecules, from carbon dioxide, ammonia, and methane, to the simplest complex organic molecule, methanol.
In addition to the identified molecules, the team found evidence for molecules more complex than methanol (indicated in the lower-right panel). Although they didn't definitively attribute these signals to specific molecules, this proves for the first time that complex molecules form in the icy depths of molecular clouds before stars are born.
The upper panels and lower-left panel all show the background star’s brightness versus wavelength. A lower brightness indicates absorption by ices and other materials in the molecular cloud. The lower-right panel displays the optical depth, which is essentially a logarithmic measure of how much light from the background star gets absorbed by the ices in the cloud. It is used to highlight weaker spectral features of less abundant varieties of ice.
Extended Description and Image Alt Text
Extended Description
Graphic titled “Chamaeleon I Dark Cloud Background Star NIR38 – Ice Chemical Composition.” The graphic includes four graphs — spectra — arranged in a 2 by 2 grid.
The two upper graphs and lower-left graph show the brightness of the background star on the vertical y-axis versus wavelength of light in microns on the horizontal x axis. The y axis ranges from 0.0 at the bottom to 1.0 at the top with labeled tick marks at 0.01 and 0.10. The x-axis for each graph ranges from 2.00 microns to 5.50 microns on the right, with labeled tick marks every 0.5 microns.
The graph at lower-right shows optical depth on the vertical y-axis versus wavelength of light in microns on the horizontal x-axis. The y-axis ranges from 0.20 at the bottom to -0/05 at the top with labeled tick marks at intervals of 0.05. A dashed white line across the graph marks a y value of 0.0. The x-axis for each graph ranges from about 6.8 microns to 8.4 microns on the right, with labeled tick marks every 0.2 microns.
Top Left: NIRSpec G395H
This graph consists of a jagged white line that extends horizontally from about 2.75 to 5.25 microns with prominent dips, one wide and two narrow. Seven bands are highlighted with colored semi-transparent vertical bars, each labeled with a chemical compound. These correspond to spectral features. Some of the features overlap.
- A water feature, highlighted in blue, spans from about 2.75 to 3.6 microns
- A methanol feature, highlighted in yellow, spans from about 3.4 to 3.55 microns
- Two narrow carbon dioxide features, highlighted in green, are located at about 4.3 and 4.4 microns
- A weak cyanate anion feature, highlighted in teal, is located at about 4.6 microns
- Two carbon monoxide features, highlighted in red, are located between 4.6 and 4.8 microns
- A carbonyl sulfide feature, highlighted in orange, is located at about 4.85 microns.
Some of the features — including water and carbon dioxide — are characterized by prominent peaks apparent in the data and model, and others are subtler.
Top Right: MIRI LRS P750L
This graph consists of a jagged white line that extends horizontally with a gradual slope from upper left to lower right. Seven bands are highlighted with colored semi-transparent vertical bars, each labeled with a chemical compound. These correspond to spectral features. Some of the features overlap.
- A water feature, highlighted in blue, spans from about 5.75 to 6.5 microns
- A methanol feature, highlighted in yellow, spans from about 6.7 to 7.1 microns
- A methane feature, highlighted in pink, spans from about 7.7 to 7.8 microns
- A broad silicate feature, highlighted in brown, spans from about 8.5 to 10.5 microns
- An ammonia feature, highlighted in purple, spans from about 8.8 to 9.2 microns
- A second methanol feature, highlighted in yellow, spans from about 9.5 to 9.8 microns
- A second water feature, highlighted in blue, spans from about 10.8 to 11.8 microns
Bottom Left: NIRCam F322W2
This graph consists of a jagged white line that extends horizontally. Three bands are highlighted with colored semi-transparent vertical bars, each labeled with a chemical compound. These correspond to spectral features. Some of the features overlap.
- A carbon dioxide feature, highlighted in green, is located at about 2.7 microns
- A water feature, highlighted in blue, spans from about 2.75 to 3.6 microns
- A methanol feature, highlighted in yellow, spans from about 3.4 to 3.55 microns
Bottom Right: MIRI LRS P750L Zoom-in
This graph consists of a jagged white line that extends horizontally with a gradual slope from upper left to lower right. Seven bands are
- highlighted with colored semi-transparent vertical bars, each labeled with a chemical compound. These correspond to spectral features.
- A feature from a combination of acetaldehyde, acetone, and methanol, highlighted in blue, spans from about 6.8 to 7.2 microns
- A feature from a combination of acetaldehyde, acetone, and methanol, highlighted in green, spans from about 7.2 to 7.5 microns
- A methane feature, highlighted in pink, spans from about 7.6 to 7.8 microns
Image Alt Text
Graphic titled “Chamaeleon I Dark Cloud Background Star NIR38 – Ice Chemical Composition.” The graphic includes four graphs—spectra—arranged in a 2 by 2 grid. The two upper graphs and lower-left graph show the brightness of the background star on the vertical y axis versus wavelength of light in microns on the horizontal x axis. The graph at lower-right shows optical depth on the vertical y axis versus wavelength of light in microns on the horizontal x axis.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.11:06:46.47
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.-77:22:32.93
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Chamaeleon
- DistanceDistanceThe 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.630 light-years
About the Data
- Data DescriptionData 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.This image was created with Webb data from proposal: 1309 (M. McClure).
- InstrumentInstrumentThe science instrument used to produce the data.NIRCam, NIRSpec, and MIRI
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.03 July 2022, 19 July 2022, 11-12 Aug 2022
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Chamaeleon I
- Object DescriptionObject DescriptionThe type of astronomical object.Molecular cloud
- Release DateJanuary 23, 2023
- Science ReleaseWebb Unveils Dark Side of Pre-stellar Ice Chemistry
- CreditIllustration: NASA, ESA, CSA, Joseph Olmsted (STScI); Science: Klaus Pontoppidan (STScI), Nicolas Crouzet (LEI), Zak Smith (The Open University), Melissa McClure (Leiden Observatory)
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Chamaeleon I Molecular Cloud (NIRCam Image)
This image by NASA’s James Webb Space Telescope’s Near-Infrared Camera (NIRCam) features the central region of the Chamaeleon I dark molecular cloud, which resides 630 light years away. The cold, wispy cloud material (blue, center) is illuminated in the infrared by the glow of...
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Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov
NASA, ESA, CSA, Joseph Olmsted (STScI)
Klaus Pontoppidan (STScI), Nicolas Crouzet (LEI), Zak Smith (The Open University), Melissa McClure (Leiden Observatory)
