- 4563 -
HUBBLE TENSION - The
universe is expanding? - Astronomers have used the James Webb and
Hubble space telescopes to confirm one of the most troubling conundrums in all
of physics. The universe appears to be expanding
at bafflingly different speeds depending on where we look.
-
-------------------------------- 4563
- HUBBLE TENSION
- The universe is expanding?
-
- 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)
repeated 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. There may be something seriously wrong with our understanding
of the universe.
-
- With measurement errors negated, what
remains is the real and exciting possibility we have misunderstood the
universe. Currently, there are two
"gold-standard" methods for figuring out the Hubble constant, a value
that describes the expansion rate of the universe.
-
- The first involves poring over tiny
fluctuations in the cosmic microwave background (CMB). Tne CMB is 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.
-
- 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.
-
- 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.
-
- They 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
-
-
September 24, 2024 HUBBLE
TENSION - The universe is expanding? 4563
------------------------------------------------------------------------------------------
-------- 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” -----------
--------------------- --- Thursday, September 26,
2024
---------------------------------
No comments:
Post a Comment