Cepheid Host Galaxy NGC 5468 | Webb & Hubble Space Telescopes

Cepheid Host Galaxy NGC 5468 | Webb & Hubble Space Telescopes

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 most distant 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.

The rate at which the Universe is expanding, known as the Hubble constant, is one of the fundamental parameters for understanding the evolution and ultimate fate of the cosmos. However, a persistent difference, called the Hubble Tension, is seen between the value of the constant measured with a wide range of independent distance indicators and its value predicted from the afterglow of the Big Bang. The NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope has confirmed that the Hubble Space Telescope’s keen eye was right all along, erasing any lingering doubt about Hubble’s measurements.

The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighboring stars at ever greater 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 through the dust and naturally isolates the Cepheids from neighboring stars because its vision is sharper than Hubble’s at infrared wavelengths.

“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. “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.

Image Description: A face-on spiral galaxy with four spiral arms that curve outward in a counterclockwise direction. The spiral arms are filled with young, blue stars and peppered with purplish star-forming regions that appear as small blobs. The middle of the galaxy is much brighter and more yellowish, and has a distinct narrow linear bar angled from 11 o’clock to 5 o’clock. Dozens of red background galaxies are scattered across the image. The background of space is black.

Image Credit: NASA, ESA, CSA, STScI, A. Riess (JHU/STScI)

Release Date: March 11, 2024

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