What is a dwarf galaxy?
A dwarf planet, represented by Pluto, does not meet the definition of a planet, but represents a smaller celestial body similar to a planet. That is, it must have enough mass to maintain its circular shape while orbiting the sun, and it must not be a satellite of another planet. However, it must be a celestial body that cannot absorb other celestial objects around its orbit. Of course, it is very difficult to numerically define the size and mass of a radius because the specific numbers depend on the astrophysical properties of the celestial body.
Dwarf galaxies, on the other hand, represent galaxies that meet the definition of a galaxy but are small, such as the small size of a dwarf planet. Galaxies usually consist of up to billions of stars, and these have very few stars compared to our own. Because of their small size, mass, and gravitational pull, they are susceptible to interactions with larger galaxies around them.
For example, they have been observed to be distorted or destroyed as they are attracted by neighboring spiral galaxies. Because of the above, dwarf galaxies are recognized as very important objects in the evolution of galaxies and the universe. Most dwarf galaxies are known to be associated with dark matter, but new types of dwarf galaxies have recently been discovered.
dwarf galaxy WLMsecond filmed James web space telescope
The James Webb Space Telescope (JWST), which specializes in near-infrared light, is showing amazing images of the universe one after another. Professor Christine McQueen of Rutgers University, New Jersey, USA, among the 1,334 astronomers leading the Webb Early Release Science (ERS) program, which focuses on observations of properly resolved stellar populations at James Webb’s sensitive resolution. Kristen McQuinn) photographed large nearby star groups, including numerous stars within the Wolf–Lundmark–Melotte (WLM) galaxy.
This has revealed some observations of the dwarf galaxy Wolf-Lundmark-Melotte (WLM), which demonstrates the extraordinary resolution of James Webb. A comparison with images from James Webb’s predecessor, the Spitzer Space Telescope, shows how much human astronomy has advanced in just 20 years. Although the Spitzer Space Telescope is widely used in general observation fields due to its relatively small aperture and narrow wavelength range, and has opened a new horizon for infrared astronomy, James Webb can see that it is much easier to observe more specific objects.
Comparison photos: Spitzer IRAC image (left) uses IRAC1 filter using 3.6 micrometer wavelength (shown in cyan) and IRAC2 filter using 4.5 micrometer wavelength (shown in orange), while Webb NIRCam image uses 0.9 micrometer wavelength (shown in blue), F150W filter using 1.5 micrometer wavelength (shown in cyan), F250M filter using 2.5 micrometer wavelength (shown in yellow), and F430M filter using 4.3 micrometer wavelength (shown in red). mark) was used. © Spitzer/NASA
spitzer space telescope with observation results compare
The image on the left was taken by the Spitzer Space Telescope’s IRAC instrument, and the right image was taken by the James Webb Space Telescope’s NIRCam instrument. As a result of observations with the Spitzer Space Telescope, many galaxies and stars appear blurry against a black background.
Most celestial bodies are white, but some are blue or red. However, since most of them show a resolution that is not completely resolved, accurate identification of celestial bodies is impossible. The Spitzer Space Telescope does not have good resolution due to its small primary mirror size (0.85 m in diameter), but it is an ideal telescope for identifying cold objects in the universe because its observation wavelength (3.6 ~ 160 micrometers) is infrared. In addition, although the expected lifespan was 6 years, it is a thankful telescope that has been stably observing the infrared universe for over 16 years and diligently digging into the mysteries of the universe.
However, James Webb’s resolution is not comparable to that of the Spitzer Space Telescope because the primary mirror is much larger and the observed wavelength is shorter (usually, shorter wavelengths and larger primary mirrors show good resolution). Observations with the Spitzer Space Telescope have completely resolved most of the unidentifiable objects, revealing thousands of objects that are clearly distinguishable in a variety of colors, sizes, shapes and brightness. Most of the celestial bodies are shown in dark orange, blue, and white, and these are the stars that make up the WLM galaxy.
In particular, considering that most of the celestial objects that can be seen in James Webb images are celestial objects that did not appear in the observation photos of the Spitzer Space Telescope, it seems that the James Webb Space Telescope can be evaluated as worthy of a huge amount of capital and effort. (Go to see high-resolution comparison photos)
dwarf galaxy WLMIs why would it be interesting?
The WLM is a dwarf galaxy in our galactic neighborhood. Although fairly close to our own galaxy (about 3 million light-years from Earth, a light-year is the distance that light travels in a year, approximately 9.46 trillion kilometers), it is a relatively isolated galaxy.
To date, the astronomy community has not considered the WLM to have interacted with other systems, making it an ideal object for testing theories of galaxy formation and evolution. Numerous other nearby galaxies, if not dwarf galaxies, show traces of evolution through interactions with nearby galaxies. (zoom in go watch video)
© NASA, ESA, CSA, STScI, Kristen McQuinn/Rutgers University, image processing: Alyssa Pagan, Zolt Levay/STScI
Another interesting point is that the gas that makes up the galaxy above is similar to the gas that made up the galaxy in the early universe. That is, elements heavier than hydrogen and helium are less abundant than in other galaxies. Perhaps this is because galaxies have lost many of these constituent elements to galactic winds.
Stars in the WLM formed relatively recently, and are predicted to be due to some material being expelled from smaller galaxies when nearby massive stars explode, such as supernovae. As a result, the WLM galaxy is an object that is expected to provide answers to the question of how stars formed and evolved in small galaxies in the distant past. (Go see high-resolution photos of JWST)
Low-mass stars usually boast lifetimes of billions of years or more. This suggests that some of the stars visible in WLM were formed in the early universe. By examining the lifespan and characteristics of these low-mass stars, we can gain insight into what happened in the very distant past. Particularly, looking at galaxies with very high redshifts that retain their appearance when they first formed can help fill in the puzzle of galaxies’ early formation.
Professor McQueen’s team has already observed the above galaxy through the Hubble Space Telescope. By comparing the two images above, we are developing a tool that can measure the brightness of stars with higher accuracy. Through this, the stellar evolution model is expected to be further supplemented.
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