#astronomy #galaxies #stars #cepheids
An article published in "The Astrophysical Journal Letters" reports the results of a study of the Small Magellanic Cloud that shows how this dwarf galaxy is undergoing distortions in its shape due to various gravitational influences. Satoya Nakano and Kengo Tachihara of Nagoya University, Japan, used data collected by ESA's Gaia space probe together with information on Cepheid stars collected by the OGLE project.
High-precision #measurements challenge our understanding of #Cepheids
"Classical Cepheids" are a type of pulsating star that rhythmically brighten and dim over time. These pulsations help astronomers measure vast distances across space, which makes Cepheids crucial "standard candles" that help us understand the size and scale of our universe.
14-JUN-2024
High-precision measurements challenge our understanding of Cepheids
“Classical #Cepheids” are a type of pulsating star that rhythmically brightens and dims over time. These pulsations help astronomers measure vast distances across space, which makes Cepheids crucial “standard candles” that help us understand the size and scale of our #universe.
EPFL scientists, through the VELOCE project, have clocked the speed of Cepheid stars – “standard candles” that help us measure the size of the universe – with unprecedented precision, offering exciting new insights about them.
Improving the foundation of the cosmic distance ladder and reinforcing the possibility of physics beyond ΛCDM:
Small Magellanic Cloud Cepheids Observed with HST Provide a New Anchor for the SH0ES Distance Ladder
by Louise Breuval and co-authors
https://arxiv.org/abs/2404.08038
#cosmology #HubbleConstant #HubbleTension #Hubble #HST #spacetelescope #cepheids #SH0ES #astronomy #astrophysics #astrodon #space #science #research #news #arXiv
We present phase-corrected photometric measurements of 88 Cepheid variables in the core of the Small Magellanic Cloud (SMC), the first sample obtained with the Hubble Space Telescope's (HST) Wide Field Camera 3, in the same homogeneous photometric system as past measurements of all Cepheids on the SH0ES distance ladder. We limit the sample to the inner core and model the geometry to reduce errors in prior studies due to the nontrivial depth of this cloud. Without crowding present in ground-based studies, we obtain an unprecedentedly low dispersion of 0.102 mag for a period-luminosity (P-L) relation in the SMC, approaching the width of the Cepheid instability strip. The new geometric distance to 15 late-type detached eclipsing binaries in the SMC offers a rare opportunity to improve the foundation of the distance ladder, increasing the number of calibrating galaxies from three to four. With the SMC as the only anchor, we find H$_0\!=\!74.1 \pm 2.1$ km/s/Mpc. Combining these four geometric distances with our HST photometry of SMC Cepheids, we obtain H$_0\!=\!73.17 \pm 0.86$ km/s/Mpc. By including the SMC in the distance ladder, we also double the range where the metallicity ([Fe/H]) dependence of the Cepheid P-L relation can be calibrated, and we find $γ= -0.234 \pm 0.052$ mag/dex. Our local measurement of H$_0$ based on Cepheids and Type Ia supernovae shows a 5.8$σ$ tension with the value inferred from the cosmic microwave background assuming a Lambda cold dark matter ($Λ$CDM) cosmology, reinforcing the possibility of physics beyond $Λ$CDM.
#astronomy #cosmology #cepheids #JWST
An article accepted for publication in "The Astrophysical Journal" reports the results of calculating the universe's expansion rate based on the observation of Cepheids with the James Webb Space Telescope. In particular, a team of researchers led by Adam Riess used the NIRCam instrument to observe over 330 cepheids in the galaxies NGC 4258 and NGC 5584.
Massimo Luciani
Corrado
michael
शून्यता
Daniel Pomarède