Combined observations by NASA’s NIRCam (Near Infrared Camera) and Hubble’s WFC3 (Wide Field Camera 3) show spiral galaxy NGC 5584 located 72 million light-years from Earth. Among the bright stars in NGC 5584 are pulsating stars called Cepheid variables and Type Ia supernovae, a special class of exploding stars. Astronomers use Cepheid variable stars and Type Ia supernovae as reliable distance markers to measure the rate of expansion of the universe. Credit: NASA, ESA, CSA, A. Riess (STScI)
The “Hubble tension” represents the difference between the observed expansion rate of the universe and the predicted expansion rate of the universe.of james webb space telescope Adjust previously made measurements. hubble space telescope. Despite advances, questions remain about the rapid expansion of the universe and the potential underlying cosmic phenomena.
The expansion rate of the universe, known as the Hubble constant, is one of the fundamental parameters for understanding the evolution and ultimate fate of the universe. However, constant values measured with a wide range of independent distance indicators and big bang afterglow.
NASAThe James Webb Space Telescope will provide new capabilities to probe and refine some of the strongest observational evidence for this tension. Nobel Prize winner Adam Riess of Johns Hopkins University and the Space Telescope Science Institute will present his and colleagues’ recent work using Webb observations to improve the accuracy of local measurements of the Hubble constant.
The challenge of space measurement
Have you ever had trouble seeing a beacon at the edge of your field of vision? What does it say? What does it mean? ” looks so small that we also struggle with it.
“The sign that cosmologists are trying to read is the cosmic speed limit sign, a number called the Hubble constant, which tells us how fast the universe is expanding. Our signature is written on stars in distant galaxies. The brightness of certain stars in those galaxies tells us how far away they are, and therefore how long this light took to reach us. Redshift tells us how much the universe has expanded in that time period. Expansion rate.
![Undense Cepheids observed in near-infrared light](https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-777x439.jpg 777w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-400x226.jpg 400w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-768x434.jpg 768w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-1536x867.jpg 1536w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-2048x1156.jpg 2048w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-180x101.jpg 180w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-260x146.jpg 260w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-373x210.jpg 373w,https://scitechdaily.com/images/Uncrowding-Cepheids-in-Near-Infrared-120x67.jpg 120w)
This figure shows the combined power of NASA’s Hubble and Webb Space Telescopes in determining the precise distances to a special class of variable stars used to calibrate the universe’s expansion rate. These Cepheid variable stars are found in dense star fields. Light contamination from surrounding stars can reduce the accuracy of Cepheid brightness measurements. As seen on the right side of the diagram, Webb’s sharper infrared vision allows him to more clearly separate Cepheid targets from surrounding stars. Webb’s data confirms the accuracy of his 30 years of Hubble observations of Cepheids, which are important in establishing the bottom rung of the cosmic distance ladder for measuring the rate of expansion of the universe. On the left, NGC 5584 is seen in a composite image from Webb’s NIRCam (Near Infrared Camera) and Hubble’s Wide Field Camera 3. Credits: NASA, ESA, A. Riess (STScI), W. Yuan (STScI)
“A particular type of star, the Cepheid variable star, has provided us with the most accurate distance measurements for more than a century because these stars are so bright. They are supergiants with brightness. Additionally, they pulsate (that is, expand and contract in size) over several weeks and exhibit relative brightness. The longer the period, the brighter they are intrinsically. These are the gold standard tools for measuring the distances of galaxies more than 100 million light-years away, a key step in determining the Hubble constant. Unfortunately, the stars in galaxies are far away from us. Because they are clustered together in a small space from our perspective, we often lack the resolution to separate them from the stars next to our line of sight.
Hubble’s Contribution and Web Advancement
“The main justification for building the Hubble Space Telescope was to solve this problem. Prior to Hubble’s launch in 1990 and subsequent Cepheid measurements, the rate of expansion of the Universe was highly uncertain; Astronomers weren’t sure whether the universe had been expanding for 10 billion years or 20 billion years. The faster the rate of expansion, the younger the universe. Because the slower the expansion rate, the older the Universe is. Hubble has better visible wavelength resolution than ground-based telescopes because it sits unaffected by the blurring of Earth’s atmosphere. It is now possible to identify individual Cepheid variable stars in galaxies more than 100 million light-years away and measure the time intervals over which their brightness changes.
“But to see light passing through the intervening dust intact, we need to see Cepheids in the near-infrared part of the spectrum as well. (Dust absorbs and scatters blue light, so distant objects Unfortunately, Hubble’s vision of red light is not as sharp as that of blue light, so the light of the Cepheid stars seen there is not as bright as that of other Cepheid stars in its field of view. It is mixed with stars. It can explain the average amount of blending. statisticallyIt’s the same method that doctors use to figure out your weight by subtracting the average weight of your clothes from the scale reading, but doing so adds noise to your measurements. Some people’s clothes are heavier than others.
“But sharp infrared vision is one of the James Webb Space Telescope’s superpowers. It has large mirrors and sensitive optics that allow it to separate Cepheid light from neighboring stars with little mixing. In the first year of Webb operations with the General Observer Program 1685, we combined observations of Cepheids discovered by Hubble in two steps along what is known as the cosmic distance ladder. The first step allows us to calibrate the true luminosity of a Cepheid by observing it within a galaxy at a known geometric distance. In our program, that galaxy is NGC 4258 The second step is to observe Cepheids in the host galaxy of recent Type Ia supernovae. The combination of the first two steps conveys information about the distance to the supernova and adjusts its true luminosity. Step 3 is to observe distant supernovae where the expansion of the universe is evident, and can be measured by comparing their brightness with the distance estimated from the redshift of the supernova’s host galaxy. The series of steps is known as a distance ladder.
“We recently obtained our first Webb measurements at steps 1 and 2, which complete the distance ladder and allow us to compare them with previous measurements from Hubble (see figure). The measurements have dramatically reduced the noise of Cepheid measurements thanks to the observatory’s resolution in near-infrared wavelengths. This kind of improvement is what astronomers dream of. In the first he observed over 320 Cepheids in two steps. Early Hubble Space Telescope measurements were noisy but proved accurate. We observed four additional supernova host stars in the Webb and found similar results for the entire sample.
![Comparison of the relationship between Cepheid period and luminosity](https://scitechdaily.com/images/Comparison-of-Cepheid-Period-Luminosity-Relations-777x694.jpg 777w,https://scitechdaily.com/images/Comparison-of-Cepheid-Period-Luminosity-Relations-400x357.jpg 400w,https://scitechdaily.com/images/Comparison-of-Cepheid-Period-Luminosity-Relations-768x686.jpg 768w,https://scitechdaily.com/images/Comparison-of-Cepheid-Period-Luminosity-Relations-1536x1373.jpg 1536w,https://scitechdaily.com/images/Comparison-of-Cepheid-Period-Luminosity-Relations-2048x1830.jpg 2048w)
A comparison of the relationship between the period and luminosity of Cepheids used to measure distance. The red dots are from NASA’s Webb and the gray dots are from NASA’s Hubble. The top panel is from NGC 5584, a type Ia supernova parent, and the inset shows image stamps of the same Cepheids observed with each telescope. The bottom panel is for NGC 4258, a galaxy with known geometric distance, and the inset shows the difference in distance coefficients between NGC 5584 and NGC 4258 as measured by each telescope. The two telescopes are in excellent agreement. Credit: NASA, ESA, A. Riess (STScI), G. Anand (STScI)
The enduring mystery of the Hubble tension
“What the results still don’t explain is why the universe appears to be expanding so rapidly. We can Predict Find out the expansion rate of the universe by observing pictures of babies. space microwave backgroundIt then takes the best models of how it grows over time to tell us how fast the universe is expanding today. The fact that current measurements of the expansion rate are significantly higher than predicted is a decade-old problem known as the “Hubble strain.” The most interesting possibility is that this tension is a clue about something we’re missing in our understanding of the universe.
“It could indicate the presence of exotic dark energy, exotic dark matter, a modification of our understanding of gravity, or unique particles or fields. A more mundane explanation is that multiple measurements This means that the errors are colluding in the same direction (astronomers used independent steps to rule out single errors), which is why it is highly recommended to redo the measurement with higher fidelity. Important: Webb’s confirmation of Hubble’s measurements provides the strongest evidence that systematic errors in Hubble’s Cepheid photometry do not play a significant role in the current Hubble tension. That leaves more interesting possibilities on the table and deepens the mystery of the tension.”
In this post, paper it was accepted by astrophysical journal.
Reference: “Crowded No More: The Accuracy of the Hubble Constant Tested with High Resolution Observations of Cepheids by JWST” by Adam G. Riess, Gagandeep S. Anand, Wenlong Yuan, Stefano Casertano, Andrew Dolphin, Lucas M. Macri, Louise Breuval), Dan Skolnick, Marshall Perrin, Richard I. Anderson, approved; astrophysical journal.
arXiv:2307.15806
Author: Adam Rees is the Bloomberg Distinguished Professor at Johns Hopkins University, the Thomas J. Barber Professor of Space Studies at the JHU Krieger School of Arts and Sciences, a Distinguished Astronomer at the Space Telescope Science Institute, and the recipient of the 2011 award . Nobel Prize in Physics.