The “Interpretation of the First Observation Results of the James Webb Space Telescope” series is a series of articles that explain the interpretation of observations and future prospects of James Webb from the perspective of a Science Times reporter and astronomer.
The first observations made by the James Webb Space Telescope were released live on NASA TV on July 12 at 11:30 PM Korean time (July 12, 10:30 AM EST). Five high-resolution images and spectral spectra have been published: the SCAMS 0723 galaxy cluster, the hot gas exoplanet WASP-96b (spectral spectrum), the NGC 3132 nebula known as the Southern Ring Nebula, Stephan’s Quintet, and the Carina Nebula. The edge of NGC 3324 includes the ‘Cosmic Cliff’. (See related article – ‘James Webb Space Telescope Reveals First Observation Results’)
In the James Webb Space Telescope Observation Interpretation series, we dig through high-resolution images one by one to find out what the above picture means and what James Webb’s plans for the above objects are in the future. The first image of James Webb is the SCAMS 0723 galaxy cluster, famous for being the first deep field of the James Webb Space Telescope.
→ This is a continuation of the first part. (See related article – ‘James Webb’s Deep Field Was So Beautiful Part 1’)
Interpretation of results ④ : Gravity lensing effect
The James Webb Space Telescope is far away and has a sharp focus on the galaxy cluster SMACS 0723, which appeared 4.6 billion years ago. Numerous star clusters and their unfolding have been captured, revealing previously unseen small and faint structures of the universe. The combined mass of this cluster acts as a gravitational lens, magnifying the much more distant galaxies behind it.
James Webb’s Deep Field photo showing the gravitational lensing effect © JWST/NASA, ESA, CSA
First, which galaxy is responsible for gravitational lensing? Just the bright white elliptical galaxy in the center of the image and the smaller white galaxies throughout the image.
The above objects, held together by the cluster’s gravitational force, then bend the galaxy’s light as it appears at much greater distances. The combined mass of galaxies and dark matter acts like a giant space telescope, magnifying, distorting, and sometimes mirroring individual galaxies. ) is often shown. Not all galaxies around this show a mirror effect. Some galaxies appear to stretch, while others appear to be scattered through interactions with galaxies.
For reference, according to NASA’s expression, the galaxies, which are spread out, look like clusters of dandelion seeds. Near the bottom of the bright central star’s diffraction spike, just to the right of the long orange arc, a star cluster-speckled galaxy can be seen.
The long, thin ladybug-like upper galaxy is a star forming cluster. The galaxies above are very magnified and individual cathedrals are photographed very clearly. Astronomers hoped that detailed studies that were not possible before could be conducted in galaxies this far away.
The farthest galaxies in the picture above, ie the small galaxies behind the cluster, have completely different appearances from spiral galaxies and elliptical galaxies. They are much more blunt and even have irregular shapes.
Studying these objects could help determine the age and mass of star clusters in distant galaxies. This will allow accurate models of early cosmic galaxies that have not yet taken on the shape of spiral galaxies, and ultimately how early galaxies form and evolve.
Interpretation of results ⑤ : Confirmation of mirror effect through gravitational lensing effect
Emission spectrum results taken with near-infrared spectroscopy (NIRSpec) ⓒ JWST/NASA, ESA, CSA
The above image is a near-infrared image of the galaxy cluster SMACS 0723. The large group of galaxies in the lower right corner of the very bright star above is distorting, magnifying or mirroring many of the galaxies in the deep field above. It can be seen in the lower left that an arc can consist of two similarly shaped galaxies. This is because, despite the sagging appearance, the bright central area mostly coincides. Or it is possible that they are the same galaxy but appear to be two through gravitational lensing. However, there are not many points that we can directly check through the images. This is because more research is needed to confirm whether the above two objects are the same object.
Astronomers began collecting spectra of the two objects to see if they were the same. The above spectrum was observed with a near-infrared imager and slit-less spectroscopy (NIRISS). The central part of the NRISS grism image (instrument with a prism, grating, etc.) shows how the ionized oxygen and hydrogen atom emission lines are distributed along the arc. are giving
As a result of analyzing the spectra of the two galaxies as shown in the figure on the right, it can be seen that the above two spectra coincide. This indicates that the two objects are the same galaxy and are mirror images. Also, the redshift phenomenon proves that the light from both galaxies was emitted 9.3 billion years ago.
James Webb’s team describes such an analysis as opening a treasure chest, adding that astronomers can make unexpected discoveries through the analysis of all galaxies, even if they don’t intend to.
Interpretation of results ⑥: Observation of galaxies that emitted light 13.1 billion years ago through near-infrared spectroscopy(Understanding the history and evolution of galaxies through composition)
The James Webb Space Telescope’s main goal is to find the oldest galaxies in the universe. If successful, astronomers will soon learn more about the mass, age, history and composition of galaxies, and humanity will go deeper into the origins of the universe.
It can be seen that the three lines in the spectrum appear in the same order each time. Redshift analysis can reveal how far apart a galaxy is. ⓒ JWST/NASA, ESA, CSA
The above photo shows the emission spectrum captured by the microshutter array, which is a part of the near-infrared spectroscopy (NIRSpec). It shows the spectrum seen when it emits with a low energy potential).
For reference, a near-infrared spectrometer with equipment such as a micro-shutter array has more than 248,000 small gates that can simultaneously collect the spectra of up to about 150 individual objects. Near-infrared spectroscopy is very high-resolution and very sensitive, allowing us to observe the light of individual galaxies that existed in the early universe.
The amazing performance of the James Webb Space Telescope allows us to observe the spectrum of galaxies so far away. Specifically, 48 of the thousands of distant galaxies behind the SMACS 0723 cluster were simultaneously observed. Astronomers can expand and analyze the above emission spectrum to determine the chemical composition, temperature, and even density of ionized gases in galaxies.
The emission spectrum of galaxies can tell how the stars are forming, how much dust they contain, or even the types of gases. Astronomers have begun to analyze a lot of James Webb data, which allows us to learn about galaxies that have existed throughout the universe’s history and how many galaxies there were.
For example, you can see that three lines in the spectrum appear in the same order each time. One hydrogen line and two ionized oxygen lines are observed, and the red shift of individual galaxies (the phenomenon in which the wavelength of electromagnetic waves moves longer than the standard wavelength on the spectrum: the opposite phenomenon has a blue shift) and changes in the positions of these patterns You can find out the distance to the galaxy.
In other words, the ratio of the wavelengths emitted by distant galaxies to the wavelengths of light reaching James Webb’s space telescope represents the ratio of the relative size of the universe at that time to the current universe (called a scale factor). This is because it is a value determined by age. This eventually allows us to determine how long ago the light was emitted.
Redshift analysis can reveal how far apart a galaxy is. For example, the greater the redshift, the further the galaxy is. ⓒ JWST/NASA, ESA, CSA
Through this comparative analysis, the composition of various elements was known, and through the analysis of the redshift phenomenon, the red galaxy below was found to have emitted light 13.1 billion years ago.
Through analysis of the redshift phenomenon, the red galaxy below was found to have emitted light 13.1 billion years ago. ⓒ JWST/NASA, ESA, CSA
Importantly, astronomers did not analyze all galaxies. Of course, there may be light hidden in the photo above that is older than 13.1 billion years. Even if there is no older light in the picture above, considering that the picture above is a very small part of the universe, it is very likely that the early light of the universe is hidden in another picture and another picture. The James Webb team describes this as a ‘galactic treasure hunt’.
The chemistry of galaxies so far away is a truly astonishing discovery that no telescope has ever made. Astronomers plan to compare and analyze the properties of the old galaxies by comparing them with nearby spiral galaxies and elliptical galaxies. Nearby galaxies can be analyzed very well with other telescopes. It’s just a matter of time depending on how many telescopes are observing how many universes.
When astronomers analyze all of James Webb’s spectrum, they can compare the two groups of galaxies to see how the universe evolved over billions of years. In other words, it is possible to travel back into the past, going back to the early universe.
Interpretation of results ⑦: Comparison after observing the same celestial body with different wavelengths
ⓒ JWST/NASA, ESA, CSA
The above photo shows a comparison of images of the same area taken with mid-infrared wavelengths (left) and near-infrared (right), which are converted to visible light colors similar to the first published photo, but are invisible to our eyes. Also listed below in colored letters are the mid-infrared instrument (MIRI) and NIRCam filter used to collect the light.
The reason the two pictures are different is because they were observed through fundamentally different wavelengths, but the two devices are also technically different. For example, MIRI, which uses mid-infrared rays, emphasizes the presence of dust, an essential component of star formation. However, because the star shines brightly at shorter wavelengths, the diffraction spike image is more prominent in the image from NIRCam.
First, take a look at the largest and brightest blue star in the photo on the right. In the near-infrared image on the right there is a very long diffraction spike, but in the mid-infrared image on the left the small dot looks like a snowflake. If there are small spikes in the left mid-infrared image, the object above is a star. Depending on the wavelength it emits and the filter used, the star may appear yellow or green. If the object is green, it indicates that the galaxy’s dust contains hydrocarbons and other compounds.
Also, if the object is blue and there are no spikes, it represents a galaxy. These galaxies, of course, contain stars, but the amount of dust is likely to be very small. This means that less gas and dust have to coalesce to form new stars, and the stars in these galaxies are usually older. Also, the red objects are more likely distant galaxies surrounded by a thick layer of dust. However, it is possible that they are some stars. Therefore, further studies are needed to fully distinguish them in the mid-infrared image on the left.
A prominent arc at the center of a cluster, a galaxy stretched and enlarged by the gravitational lensing effect, appears blue in mid-infrared images and orange in near-infrared images. As explained above, spectral analysis shows that the above galaxies are old galaxies, but the blue objects in the image on the left represent older and much less dusty galaxies, so this also indicates that the above galaxies are older and less dusty galaxies. can be known
The size of the galaxies in both images gives us clues about how far apart they are. The smaller the object, the farther away it is, and galaxies closer to the mid-infrared have a white color. James Webb’s team will use mid-infrared data and modeling to calculate the amount of dust in stars and galaxies, and to understand how galaxies form and evolve over time.
James Webb Space Telescope’s First Observation Interpretation Series Guide
About the Deep Field: James Webb’s Deep Field Was So Beautiful – Part 1
About the Deep Field: James Webb’s Deep Field Was So Beautiful – Part 2
Exoplanet Related: Discovering water in the atmosphere of a hot gas planet
Star Death Related: Planetary Nebula Surrounded by Dust – Part 1
Star Death Related: Planetary Nebula Surrounded by Dust – Part 2
About the Birth of a Star: James Webb shoots about the birth of a star
Galaxy Related: How galaxies evolve – Part 1
Galaxy Related: How galaxies evolve – Part 2
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