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Tag Archives: Hubble Space Telescope

From a press release of the Space Telescope Science Institute, January 26, 2017:

By using galaxies as giant gravitational lenses, an international group of astronomers using the Hubble Space Telescope have made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.

The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers used the Hubble Space Telescope and other telescopes in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant. This new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference.

However, the value measured by this team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.

Studied lensed quasars of H0LiCOW collaboration

Credit: ESA/Hubble, NASA, Suyu et al.

The targets of the new study were massive galaxies positioned between Earth and very distant quasars — incredibly luminous galaxy cores. The light from the more distant quasars is bent around the huge masses of the galaxies as a result of strong gravitational lensing. This creates multiple images of the background quasar, some smeared into extended arcs.

Because galaxies do not create perfectly spherical distortions in the fabric of space and the lensing galaxies and quasars are not perfectly aligned, the light from the different images of the background quasar follows paths which have slightly different lengths. Since the brightness of quasars changes over time, astronomers can see the different images flicker at different times, the delays between them depending on the lengths of the paths the light has taken. These delays are directly related to the value of the Hubble constant.

Links: the full STScI press release, including further figures and links to published papers.

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From a HST press release, September 24, 2015:

A stunning new set of images from Hubble’s Wide Field Camera 3 capture the scattered stellar remains in spectacular new detail and reveal its expansion over the years since HST last captured them, in 1997.

Credit: NASA, ESA, Hubble Heritage Team

Credit: NASA, ESA, Hubble Heritage Team

Deriving its name from its delicate, draped filamentary structures, the beautiful Veil Nebula is one of the best-known supernova remnants. It formed from the violent death of a star twenty times the mass of the Sun that exploded about 8000 years ago. Located roughly 2100 light-years from Earth in the constellation of Cygnus (The Swan), this brightly coloured cloud of glowing debris spans approximately 110 light-years.

Astronomers suspect that before the Veil Nebula’s source star exploded it expelled a strong stellar wind. This wind blew a large cavity into the surrounding interstellar gas. As the shock wave from the supernova expands outwards, it encounters the walls of this cavity — and forms the nebula’s distinctive structures. Bright filaments are produced as the shock wave interacts with a relatively dense cavity wall, whilst fainter structures are generated by regions nearly devoid of material. The Veil Nebula’s colorful appearance is generated by variations in the temperatures and densities of the chemical elements present; they do not represent the real colors of the nebula.

Links: Full press release and description; images for download and video.

The Astronomy Picture of the Day (APOD) on February 4, 2014, shows star birth in action: a bipolar particle beam is seen, forming what we call a Herbig-Haro object, named for astronomers George Herbig and Guillermo Haro (see Section 12.1b, pp. 314-316).

Credit: Hubble Legacy Archive, NASA, ESA – Processing: Judy Schmidt

The powerful jet likely contains electrons and protons moving hundreds of kilometers per second. The above image was taken by the Hubble Space Telescope in infrared light in order to better understand turbulent star forming regions known as Young Stellar Objects (YSOs). Frequently when a star forms, a disk of dust and gas circles the YSO causing a powerful central jets to appear. In this case, the energetic jets are creating, at each end, Herbig-Haro object 24 (HH 24), as they slam into the surrounding interstellar gas. The entire star forming region lies about 1,500 light years distant in the Orion B molecular cloud complex. Due to their rarity, jets like that forming HH 24 are estimated to last only a few thousand years.

Links: APOD, February 4, 2014.