- 4406 - UNIVERSE - expanding at different rates? - James Webb telescope confirms there is something seriously wrong with our understanding of the universe. Depending on where we look, the universe is expanding at different rates. Now, scientists using space telescopes have confirmed that the observation is not down to a measurement error.
------------------------- 4406 - UNIVERSE - expanding at different 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 is known as the “Hubble
Tension” It 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) confirmed 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.
-
- With measurement errors negated, what
remains is the real and exciting possibility we have misunderstood the
universe. In 1998 there was the
discovery of “dark energy”, the mysterious force behind the universe's
accelerating expansion.
-
- Currently, there are two
"gold-standard" methods for figuring out the “Hubble constant” for
the universe 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 “46,200 mph
per million light-years, or 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 of 67 km/s/Mpc. 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.
-
- The tension at the heart of cosmology is
here to stay.
-
-
March 25, 2023 UNIVERSE -
expanding at different rates?
4406
------------------------------------------------------------------------------------------
-------- 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” -----------
--------------------- --- Wednesday, March 27,
2024
---------------------------------
No comments:
Post a Comment