-
-------------------------
------------------------- 4392 -
JAMES WEBB -
discover Universe Expansion rates?
-
- Astronomers have used the James Webb and
Hubble space telescopes to confirm one of the most troubling conundrums in all
of physics that the universe appears to be expanding at bafflingly different
speeds depending on where we look.
-
- This problem, known as the “Hubble Tension”,
has the potential to alter or even upend cosmology altogether. In 2019,
measurements by the Hubble Space Telescope confirmed the puzzle was real; in
2023, even more precise measurements from the James Webb Space Telescope (JWST)
cemented the discrepancy.
-
- Now, a triple-check by both telescopes
working together appears to have put the possibility of any measurement error
to bed for good. The study, published February 6, 2024, suggests that there may
be something seriously wrong with our understanding of the universe.
-
- Currently, there are two
"gold-standard" methods for figuring out the Hubble constant of the
Universe's expansion rate. The first involves poring over tiny fluctuations in
the cosmic microwave background (CMB), an ancient relic of the universe's first
light produced just 380,000 years after the Big Bang.
-
- Between 2009 and 2013, astronomers mapped
out this microwave fuzz using the European Space Agency's Planck satellite to
infer a Hubble constant of roughly 46,200 mph per million light-years, or
roughly 67 kilometers per second per megaparsec (km/s/Mpc).
-
- The second method uses pulsating stars
called Cepheid variables. Cepheid stars are dying, and their outer layers of
helium gas grow and shrink as they absorb and release the star's radiation,
making them periodically flicker like distant signal lamps.
-
- As Cepheids get brighter, they pulsate more
slowly, giving astronomers a means to measure their absolute brightness. By
comparing this brightness to their observed brightness, astronomers can chain
Cepheids into a "cosmic distance ladder" to peer ever deeper into the
universe's past. With this ladder in place, astronomers can find a precise
number for its expansion from how the Cepheids' light has been stretched out,
or red-shifted.
-
- But this is where the mystery begins.
According to Cepheid variable measurements the universe's expansion rate is
around 74 km/s/Mpc: an impossibly high value when compared to Planck's
measurements. Cosmology had been hurled into uncharted territory.
-
- Initially, some scientists thought that the
disparity could be a result of a measurement error caused by the blending of
Cepheids with other stars in Hubble's aperture. But in 2023, the researchers
used the more accurate JWST to confirm that, for the first few
"rungs" of the cosmic ladder, their Hubble measurements were right.
Nevertheless, the possibility of crowding further back in the universe's past
remained.
-
- To resolve this issue, astronomers built on
their previous measurements, observing 1,000 more Cepheid stars in five host
galaxies as remote as 130 million light-years from Earth. After comparing their data to Hubble's, the
astronomers confirmed their past measurements of the Hubble constant.
-
- 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.
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.
-
- In other words: the tension at the heart of
cosmology is here to stay.
-
-
March 17, 2023 JAMES
WEBB - discover Universe Expansion rates? 4392
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Monday, March 18, 2024
---------------------------------
-
- Astronomers have used the James Webb and
Hubble space telescopes to confirm one of the most troubling conundrums in all
of physics that the universe appears to be expanding at bafflingly different
speeds depending on where we look.
-
- This problem, known as the “Hubble Tension”,
has the potential to alter or even upend cosmology altogether. In 2019,
measurements by the Hubble Space Telescope confirmed the puzzle was real; in
2023, even more precise measurements from the James Webb Space Telescope (JWST)
cemented the discrepancy.
-
- Now, a triple-check by both telescopes
working together appears to have put the possibility of any measurement error
to bed for good. The study, published February 6, 2024, suggests that there may
be something seriously wrong with our understanding of the universe.
-
- Currently, there are two
"gold-standard" methods for figuring out the Hubble constant of the
Universe's expansion rate. The first involves poring over tiny fluctuations in
the cosmic microwave background (CMB), an ancient relic of the universe's first
light produced just 380,000 years after the Big Bang.
-
- Between 2009 and 2013, astronomers mapped
out this microwave fuzz using the European Space Agency's Planck satellite to
infer a Hubble constant of roughly 46,200 mph per million light-years, or
roughly 67 kilometers per second per megaparsec (km/s/Mpc).
-
- The second method uses pulsating stars
called Cepheid variables. Cepheid stars are dying, and their outer layers of
helium gas grow and shrink as they absorb and release the star's radiation,
making them periodically flicker like distant signal lamps.
-
- As Cepheids get brighter, they pulsate more
slowly, giving astronomers a means to measure their absolute brightness. By
comparing this brightness to their observed brightness, astronomers can chain
Cepheids into a "cosmic distance ladder" to peer ever deeper into the
universe's past. With this ladder in place, astronomers can find a precise
number for its expansion from how the Cepheids' light has been stretched out,
or red-shifted.
-
- But this is where the mystery begins.
According to Cepheid variable measurements the universe's expansion rate is
around 74 km/s/Mpc: an impossibly high value when compared to Planck's
measurements. Cosmology had been hurled into uncharted territory.
-
- Initially, some scientists thought that the
disparity could be a result of a measurement error caused by the blending of
Cepheids with other stars in Hubble's aperture. But in 2023, the researchers
used the more accurate JWST to confirm that, for the first few
"rungs" of the cosmic ladder, their Hubble measurements were right.
Nevertheless, the possibility of crowding further back in the universe's past
remained.
-
- To resolve this issue, astronomers built on
their previous measurements, observing 1,000 more Cepheid stars in five host
galaxies as remote as 130 million light-years from Earth. After comparing their data to Hubble's, the
astronomers confirmed their past measurements of the Hubble constant.
-
- 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.
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.
-
- In other words: the tension at the heart of
cosmology is here to stay.
-
-
March 17, 2023 JAMES
WEBB - discover Universe Expansion rates? 4392
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Monday, March 18, 2024
---------------------------------
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