785 research outputs found
Estimating the Hubble constant on a base of observed values of the Hubble parameter H(z) in a model without expansion
No full textIn the model of low-energy quantum gravity by the author, the
ratio H(z)/(1 + z) should be equal to the Hubble constant. Here, the
weighted average value of the Hubble constant has been found using
29 observed values of the Hubble parameter H(z): ±σ0 =
(64.40 ± 5.95) km s−1 Mpc−1
The impact of dust on Cepheid and Type Ia supernova distances
No full textMilky-Way and intergalactic dust extinction and reddening must be accounted for in measurements of distances throughout the universe. This work provides a comprehensive review of the various impacts of cosmic dust focusing specifically on its effects on two key distance indicators used in the distance ladder: Cepheid variable stars and Type Ia supernovae. We review the formalism used for computing and accounting for dust extinction and reddening as a function of wavelength. We also detail the current state of the art knowledge of dust properties in the Milky Way and in host galaxies. We discuss how dust has been accounted for in both the Cepheid and SN distance measurements. Finally, we show how current uncertainties on dust modeling impact the inferred luminosities and distances, but that measurements of the Hubble constant remain robust to these uncertainties.https://arxiv.org/pdf/2311.08253.pdfFirst author draf
Hubble Space Telescope - Scientific, Technological and Social Contributions to the Public Discourse on Science
No full textThe Hubble Space Telescope has unified the world with a sense of awe and wonder for 2 I years and is currently more scientifically powerful than ever. I will present highlights of discoveries made with the Hubble Space Telescope, including details of planetary weather, star formation, extra-solar planets, colliding galaxies, and a universe expanding with the acceleration of dark energy. I will also present the unique technical challenges and triumphs of this phenomenal observatory, and discuss how our discoveries in the cosmos affect our sense of human unity, significance, and wonder
2009 International Year of Astronomy (IYA2009)
No full text400 years ago, Galileo first turned a telescope to the sky, and to honor that historic moment, 2009 has been designated the International Year of Astronomy (IYA2009). This session will feature two scientists who have used the telescope to understand our solar system and well beyond to yield fantastic new discoveries. Jennifer Wiseman will share the work she does with NASA, presenting beautiful and tantalizing images from the Hubble Space Telescope and discussing how space astronomy can inspire all ages
Cosmic dust impacts on the Hubble Space Telescope
No full textExposure of the Hubble Space Telescope to space in low Earth orbit resulted in numerous hypervelocity impacts by cosmic dust (micrometeoroids) and anthropogenic particles (orbital debris) on the solar arrays and the radiator shield of the Wide Field and Planetary Camera 2, both subsequently returned to Earth. Solar cells preserve residues from smaller cosmic dust (and orbital debris) but give less reliable information from larger particles. Here, we present images and analyses from electron, ion and X-ray fluorescence microscopes for larger impact features (millimetre- to centimetre-scale) on the radiator shield. Validated by laboratory experiments, these allow interpretation of composition, probable origin and likely dimensions of the larger impactors. The majority (~90%) of impacts by grains greater than 50 μm in size were made by micrometeoroids, dominated by magnesium- and iron-rich silicates and iron sulfides, metallic iron-nickel and chromium-rich spinel similar to that in ordinary chondrite meteorites of asteroid origin. Our re-evaluation of the largest impact features shows substantially fewer large orbital debris impacts than reported by earlier authors. Mismatch to the NASA ORDEM and ESA MASTER models of particle populations in orbit may be partly due to model overestimation of orbital debris flux and underestimation of larger micrometeoroid numbers. This article is part of the theme issue ‘Dust in the Solar System and beyond’
Servicing Mission 4 and the Extraordinary Science of the Hubble Space Telescope
No full textJust two years ago, NASA astronauts performed a challenging and flawless final Space Shuttle servicing mission to the orbiting Hubble Space Telescope. With science instruments repaired on board and two new ones installed, the observatory. is more powerful now than ever before. I will show the dramatic highlights of the servicing mission and present some of the early scientific results from the refurbished telescope. Its high sensitivity and multi-wavelength capabilities are revealing the highest redshift galaxies ever seen, as well as details of the cosmic web of intergalactic medium, large scale structure formation, solar system bodies, and stellar evolution. Enlightening studies of dark matter, dark energy, and exoplanet atmospheres add to the profound contributions to astrophysics that are being made with Hubble, setting a critical stage for future observatories such as the James Webb Space Telescope
The Ever Changing Shape of the Universe: A Kuhnian Analysis of Edwin Hubble\u27s Discoveries
No full textThomas Kuhn, author of The Structure of Scientific Revolutions, sought to explain how science changes, functions, and advances. According to Kuhn, science periodically undergoes a paradigm-shift during which time the prevailing methodologies, theories, and commitments of normal-science are all thrown into question until a new dominant paradigm takes hold. However, as his career progressed and his critics railed against his new conception of scientific progress, Kuhn would emphasize the role of linguistic incommensurability in paradigm shifts over normal-science. In 1923, astronomer Edwin Hubble took the first steps toward the discovery of galaxies. In doing so, Hubble simultaneously drew upon the discoveries of his astronomical forbearers and utilized them in novel ways to expand the scope of scientific knowledge. Applying a Kuhnian analysis to Hubble\u27s discoveries suggests the staying power of Kuhn\u27s later writings and the weaknesses of his early analysis as Hubble both challenged and relied upon the larger astronomical communit
The Hubble Space Telescope: UV, Visible, and Near-Infrared Pursuits
No full textThe Hubble Space Telescope continues to push the limits on world-class astrophysics. Cameras including the Advanced Camera for Surveys and the new panchromatic Wide Field Camera 3 which was installed nu last year's successful servicing mission S2N4,o{fer imaging from near-infrared through ultraviolet wavelengths. Spectroscopic studies of sources from black holes to exoplanet atmospheres are making great advances through the versatile use of STIS, the Space Telescope Imaging Spectrograph. The new Cosmic Origins Spectrograph, also installed last year, is the most sensitive UV spectrograph to fly io space and is uniquely suited to address particular scientific questions on galaxy halos, the intergalactic medium, and the cosmic web. With these outstanding capabilities on HST come complex needs for laboratory astrophysics support including atomic and line identification data. I will provide an overview of Hubble's current capabilities and the scientific programs and goals that particularly benefit from the studies of laboratory astrophysics
Inflationary cosmology and the standard model Higgs with a small Hubble-induced mass
No full textAbstractWe study the dynamics of the standard model Higgs field in the inflationary cosmology. Since metastability of our vacuum is indicated by the current experimental data of the Higgs boson and top quark, inflation models with a large Hubble parameter may have a problem: In such models, the Higgs field rolls down towards the unwanted true vacuum due to the large fluctuation in the inflationary background. However, this problem can be relaxed by supposing an additional mass term for the Higgs field generated during and after inflation. We point out that it does not have to be larger than the Hubble parameter if the number of e-folds during inflation is not too large. We demonstrate that a high reheating temperature is favored in such a relatively small mass case and it can be checked by future gravitational wave observations. Such an induced mass can be generated by, e.g., a direct coupling to the inflaton field or nonminimal coupling to gravity
Astronomy from Space: The Hubble, Herschel and James Webb Space Telescopes
No full textSpace-based astronomy is going through a renaissance, with three Great Observatories currently flying: Hubble in the visible and ultraviolet, Spitzer in the infrared and Chandra in X-rays. The future looks equally bright. The final servicing mission to Hubble will take place in February 2009 and promises to make the observatory more capable than ever with two new cameras, and refurbishment that will allow it to last at least five years. The upcoming launch of the Herschel Space Telescope will open the far-infrared to explore the cool and dusty Universe. Finally, we look forward to the launch of the James Webb Space Telescope in 2013, which wil provide a successor to both Hubble and Spitzer. In this talk, the author discusses some of the highlights of scientific discovery in the last 10 years and reveals the promise to the next 10 years
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