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    • By NASA
      6 min read
      NASA’s Webb, Hubble Telescopes Affirm Universe’s Expansion Rate, Puzzle Persists
      When you are trying to solve one of the biggest conundrums in cosmology, you should triple check your homework. The puzzle, called the “Hubble Tension,” is that the current rate of the expansion of the universe is faster than what astronomers expect it to be, based on the universe’s initial conditions and our present understanding of the universe’s evolution.
      Scientists using NASA’s Hubble Space Telescope and many other telescopes consistently find a number that does not match predictions based on observations from ESA’s (European Space Agency’s) Planck mission. Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?
      This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. This is the farthest galaxy in which Hubble has identified Cepheid variable stars. These are important milepost markers for measuring the expansion rate of the universe. The distance calculated from Cepheids has been cross-correlated with a type Ia supernova in the galaxy. Type Ia supernovae are so bright they are used to measure cosmic distances far beyond the range of the Cepheids, extending measurements of the universe’s expansion rate deeper into space.
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      Hubble has been measuring the current rate of the universe’s expansion for 30 years, and astronomers want to eliminate any lingering doubt about its accuracy. Now, Hubble and NASA’s James Webb Space Telescope have tag-teamed to produce definitive measurements, furthering the case that something else – not measurement errors – is influencing the expansion rate.
      “With measurement errors negated, what remains is the real and exciting possibility we have misunderstood the universe,” said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess holds a Nobel Prize for co-discovering the fact that the universe’s expansion is accelerating, due to a mysterious phenomenon now called “dark energy.”
      As a crosscheck, an initial Webb observation in 2023 confirmed that Hubble measurements of the expanding universe were accurate. However, hoping to relieve the Hubble Tension, some scientists speculated that unseen errors in the measurement may grow and become visible as we look deeper into the universe. In particular, stellar crowding could affect brightness measurements of more distant stars in a systematic way.
      The SH0ES (Supernova H0 for the Equation of State of Dark Energy) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic milepost markers, known as Cepheid variable stars, which now can be correlated with the Hubble data.
      “We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” Riess said.
      The team’s first few Webb observations in 2023 were successful in showing Hubble was on the right track in firmly establishing the fidelity of the first rungs of the so-called cosmic distance ladder.
      Astronomers use various methods to measure relative distances in the universe, depending upon the object being observed. Collectively these techniques are known as the cosmic distance ladder – each rung or measurement technique relies upon the previous step for calibration.
      But some astronomers suggested that, moving outward along the “second rung,” the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance. Such inaccuracies could occur because the light of a Cepheid could blend with that of an adjacent star – an effect that could become more pronounced with distance as stars crowd together and become harder to distinguish from one another.
      The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighboring stars at ever farther distances between us and their host galaxies, requiring careful accounting for this effect. Intervening dust further complicates the certainty of the measurements in visible light. Webb slices though the dust and naturally isolates the Cepheids from neighboring stars because its vision is sharper than Hubble’s at infrared wavelengths.
      At the center of these side-by-side images is a special class of star used as a milepost marker for measuring the universe’s rate of expansion – a Cepheid variable star. The two images are very pixelated because they are a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the universe’s expansion rate and age. NASA, ESA, CSA, STScI, Adam G. Riess (JHU, STScI)
      Download this Image

      “Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder,” said Riess.
      The new Webb observations include five host galaxies of eight Type Ia supernovae containing a total of 1,000 Cepheids, and reach out to the farthest galaxy where Cepheids have been well measured – NGC 5468 – at a distance of 130 million light-years. “This spans the full range where we made measurements with Hubble. So, we’ve gone to the end of the second rung of the cosmic distance ladder,” said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble telescopes for NASA.
      Hubble and Webb’s further confirmation of the Hubble Tension sets up other observatories to possibly settle the mystery. NASA’s upcoming Nancy Grace Roman Space Telescope will do wide celestial surveys to study the influence of dark energy, the mysterious energy that is causing the expansion of the universe to accelerate. ESA’s Euclid observatory, with NASA contributions, is pursuing a similar task.
      At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the big bang observed by Planck’s measurement from the beginning of the universe is set firmly on the other side. How the universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed. “We need to find out if we are missing something on how to connect the beginning of the universe and the present day,” said Riess.
      These finding were published in the February 6, 2024 issue of The Astrophysical Journal Letters.
      The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. Goddard also conducts mission operations with Lockheed Martin Space in Denver, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations for NASA.
      The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
      More Webb News: https://science.nasa.gov/mission/webb/latestnews/
      More Hubble News: https://science.nasa.gov/mission/hubble/hubble-news/
      More Webb Images: https://science.nasa.gov/mission/webb/multimedia/images/
      More Hubble Images: https://science.nasa.gov/mission/hubble/multimedia/hubble-images/
      Webb Mission Page: https://science.nasa.gov/mission/webb/
      Hubble Mission Page: https://science.nasa.gov/mission/hubble/
      Learn More

      Hubble Reaches New Milestone in Mystery of Universe’s Expansion Rate


      Mystery of the Universe’s Expansion Rate Widens With New Hubble Data


      NASA’s Hubble Extends Stellar Tape Measure 10 Times Farther Into Space


      Discovering the Runaway Universe

      Media Contacts:
      Claire Andreoli – claire.andreoli@nasa.gov
      Laura Betz – laura.e.betz@nasa.gov
      NASA’s Goddard Space Flight Center, Greenbelt, MD
      Ray Villard, Christine Pulliam
      Space Telescope Science Institute, Baltimore, MD
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      Details
      Last Updated Mar 11, 2024 Editor Andrea Gianopoulos Location Goddard Space Flight Center Related Terms
      Astrophysics Astrophysics Division Goddard Space Flight Center Hubble Space Telescope James Webb Space Telescope (JWST) Missions Keep Exploring Discover More Topics From NASA
      Hubble Space Telescope


      Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.


      James Webb Space Telescope


      Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…


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      View the full article
    • By European Space Agency
      Image: NGC 5468 – Cepheid host galaxy View the full article
    • By European Space Agency
      Further embracing the New Space era, ESA is to develop two new Scout satellites: NanoMagSat and Tango. NanoMagSat will measure Earth’s magnetic field to help assess space weather hazards and continue on from ESA’s current Swarm mission. Tango will measure greenhouse-gas emissions from human activity and complements the upcoming Copernicus Carbon Dioxide Monitoring mission and the Sentinel-5 mission, as well as the current Sentinel-5P mission.
      View the full article
    • By NASA
      This Hubble Space Telescope image shows the powerful gravity of a galaxy embedded in a massive cluster of galaxies producing multiple images of a single distant supernova far behind it. The image shows the galaxy’s location within a large cluster of galaxies called MACS J1149.6+2223, located more than 5 billion light-years away. In the enlarged inset view of the galaxy, the arrows point to the multiple copies of an exploding star, named Supernova Refsdal, located 9.3 billion light-years from Earth.Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI) Astronomers investigating one of the most pressing mysteries of the cosmos – the rate at which the universe is expanding – are readying themselves to study this puzzle in a new way using NASA’s Nancy Grace Roman Space Telescope. Once it launches by May 2027, astronomers will mine Roman’s wide swaths of images for gravitationally lensed supernovae, which can be used to measure the expansion rate of the universe.
      There are multiple independent ways astronomers can measure the present expansion rate of the universe, known as the Hubble constant.  Different techniques have yielded different values, referred to as the Hubble tension. Much of Roman’s cosmological investigations will be into elusive dark energy, which affects how the universe is expanding over time. One primary tool for these investigations is a fairly traditional method, which compares the intrinsic brightness of objects like type Ia supernovae to their perceived brightness to determine distances. Alternatively, astronomers could use Roman to examine gravitationally lensed supernovae. This method of exploring the Hubble constant is unique from traditional methods because it’s based on geometric methods, and not brightness.
      “Roman is the ideal tool to let the study of gravitationally lensed supernovae take off,” said Lou Strolger of the Space Telescope Science Institute (STScI) in Baltimore, co-lead of the team preparing for Roman’s study of these objects. “They are rare, and very hard to find. We have had to get lucky in detecting a few of them early enough. Roman’s extensive field of view and repeated imaging in high resolution will help those chances.”
      Using various observatories like NASA’s Hubble Space Telescope and James Webb Space Telescope, astronomers have discovered just eight gravitationally lensed supernovae in the universe. However, only two of those eight have been viable candidates to measure the Hubble constant due to the type of supernovae they are and the duration of their time-delayed imaging.
      Gravitational lensing occurs when the light from an object like a stellar explosion, on its way to Earth, passes through a galaxy or galaxy cluster and gets deflected by the immense gravitational field. The light splits along different paths and forms multiple images of the supernova on the sky as we see it. Depending on the differences between the paths, the supernova images appear delayed by hours to months, or even years. Precisely measuring this difference in arrival times between the multiple images leads to a combination of distances that constrain the Hubble constant.
      “Probing these distances in a fundamentally different way than more common methods, with the same observatory in this case, can help shed light on why various measurement techniques have yielded different results,” added Justin Pierel of STScI, Strolger’s co-lead on the program.
      This illustration, using Hubble Space Telescope images of Supernova Refsdal, shows how the gravity of massive galaxy cluster MACS J1149.6+2223 bends and focuses the light from the supernova behind it, resulting in multiple images of the exploding star. The upper graphic shows that when the star explodes, its light travels through space and encounters the foreground galaxy cluster. The light paths are bent by the cluster’s gravity and redirected onto new paths, several of which are pointed at Earth. Astronomers, therefore, see multiple images of the exploding star, each one corresponding to one of those altered light paths. Each image takes a different route through the cluster and arrives at a different time. In the lower graphic, the redirected light passes through a giant elliptical galaxy within the cluster. This galaxy adds another layer of lensing.Credit: Illustration: NASA, ESA, A. Fields (STScI), and J. DePasquale (STScI). Science: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI) Finding the Needle in the Haystack
      Roman’s extensive surveys will be able to map the universe much faster than Hubble can, with the telescope “seeing” more than 100 times the area of Hubble in a single image.
      “Rather than gathering several pictures of trees, this new telescope will allow us to see the entire forest in a single snapshot,” Pierel explained.
      In particular, the High Latitude Time Domain Survey will observe the same area of sky repeatedly, which will allow astronomers to study targets that change over time. This means there will be an extraordinary amount of data – over 5 billion pixels each time – to sift through in order to find these very rare events.
      A team led by Strolger and Pierel at STScI is laying the groundwork for finding gravitationally lensed supernovae in Roman data through a project funded by NASA’s Research Opportunities in Space and Earth Science (ROSES) Nancy Grace Roman Space Telescope Research and Support Participation Opportunities program.
      “Because these are rare, leveraging the full potential of gravitationally lensed supernovae depends on a high level of preparation,” said Pierel. “We want to make all the tools for finding these supernovae ready upfront so we don’t waste any time sifting through terabytes of data when it arrives.”
      The project will be carried out by a team of researchers from various NASA centers and universities around the country.
      The preparation will occur in several stages. The team will create data reduction pipelines designed to automatically detect gravitationally lensed supernovae in Roman imaging. To train those pipelines, the researchers will also create simulated imaging: 50,000 simulated lenses are needed, and there are only 10,000 actual lenses currently known.
      The data reduction pipelines created by Strolger and Pierel’s team will complement pipelines being created to study dark energy with Type Ia supernovae.
      “Roman is truly the first opportunity to create a gold-standard sample of gravitationally lensed supernovae,” concluded Strolger. “All our preparations now will produce all the components needed to ensure we can effectively leverage the enormous potential for cosmology.”
      The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are Ball Aerospace and Technologies Corporation in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
      By Hannah Braun
      Space Telescope Science Institute, Baltimore, Md.
      ​​Media Contact:
      Claire Andreoli
      NASA’s Goddard Space Flight Center, Greenbelt, Md.
      301-286-1940
      Christine Pulliam
      Space Telescope Science Institute, Baltimore, Md.
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      Details
      Last Updated Feb 07, 2024 LocationGoddard Space Flight Center Related Terms
      Nancy Grace Roman Space Telescope Dark Energy Galaxies, Stars, & Black Holes Goddard Space Flight Center Missions Stars Supernovae The Universe View the full article
    • By European Space Agency
      Today, ESA’s Science Programme Committee approved the Laser Interferometer Space Antenna (LISA) mission, the first scientific endeavour to detect and study gravitational waves from space.
      View the full article
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