MACS1423-z7p64, a ‘Special’ Average Galaxy in the Distant Universe

MACS1423-z7p64, a ‘Special’ Average Galaxy in the Distant Universe

MACS1423-z7p64 is an ultra-faint galaxy at a redshift of 7.6, that puts it about 13.1 billion years in the past. (The farther away an object is, the farther its light is shifted into the red end of the spectrum, due to the expansion of the universe.)

Astronomers- led by a graduate student at the University of California, Davis-
have discovered this galaxy, one of the most distant galaxies in the universe, and it’s nothing out of the ordinary.

Hence, what is so special about this one?

These ultradistant galaxies, seen as they were close to the beginning of the universe, are interesting to scientists because they fall within the “Epoch of Reionization,” a period about a billion years after the Big Bang when the universe became transparent.

After the Big Bang, the universe was a cloud of cold, atomic hydrogen, which blocks light. The first stars and galaxies condensed out of the cloud and started to emit light and ionizing radiation. This radiation melted away the atomic hydrogen like a hot sun clearing fog, and the first galaxies spread their light through the universe.

To find such faint, distant objects like MACS1423-z7p64, the astronomers took advantage of a giant lens in the sky.
As light passes by a massive object such as a galaxy cluster, its path gets bent by gravity, just as light gets bent passing through a lens. When the object is big enough, it can act as a lens that magnifies the image of objects behind it.

Scientists are surveying the sky around massive galaxy clusters that are the right size and distance away to focus light from very distant galaxies. While it is similar to millions of other galaxies of its time, z7p64 just happened to fall into the “sweet spot” behind a giant galaxy cluster that magnified its brightness tenfold and made it visible to the team, using the Hubble Space Telescope. They were then able to confirm its distance by analyzing its spectrum with the Keck Observatory telescopes in Hawaii.

► Learn more>> https://www.ucdavis.edu/news/long-ago-and-far-away-average-galaxy

► The study “Spectroscopic confirmation of an ultra-faint galaxy at the epoch of reionization”, published in _Nature Astronomy _>> https://www.nature.com/articles/s41550-017-0091

► Read the preprint vesrion of this study on arXiv>> https://arxiv.org/abs/1704.02970

Image explanation: Astronomers used the gravity of a massive galaxy cluster as a lens to spot an incredibly distant galaxy, about 13.1 billion years in the past. They used the Hubble Space Telescope to find the galaxy and confirmed its age and distance with instruments at the Keck Observatory in Hawaii.
Image credit: NASA/Keck/Austin Hoag/Marusa Bradac

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8 Real World Enceladus Science Facts | NASA JPL

8 Real World Enceladus Science Facts | NASA JPL
Note: Click on the image and select the “More” option at the top of the screen and then choose “Download Photo” to better view this high-res infographic.

NASA’s Cassini spacecraft sampled the ocean of Saturn’s moon Enceladus, today Wednesday, Oct. 28, after it flew through the moon’s plume of icy spray.

Cassini launched in 1997 and entered orbit around Saturn in 2004. Since then, it has been studying the huge planet, its rings and its magnetic field. Here are some things to know about the mission’s close flyby of Enceladus:

— Enceladus is an icy moon of Saturn. Early in its mission, Cassini discovered Enceladus has remarkable geologic activity, including a towering plume of ice, water vapor and organic molecules spraying from its south polar region. Cassini later determined the moon has a global ocean and likely hydrothermal activity, meaning it could have the ingredients needed to support simple life.

— The flyby is Cassini’s deepest-ever dive through the Enceladus plume, which is thought to come from the ocean below. The spacecraft has flown closer to the surface of Enceladus before, but never this low directly through the active plume.

— The flyby is not intended to detect life, but it will provide powerful new insights about how habitable the ocean environment is within Enceladus.

— Cassini scientists are hopeful the flyby will provide insights about how much hydrothermal activity—that is, chemistry involving rock and hot water—is occurring within Enceladus. This activity could have important implications for the potential habitability of the ocean for simple forms of life. The critical measurement for these questions is the detection of molecular hydrogen by the spacecraft.

— Scientists also expect to better understand the chemistry of the plume as a result of the flyby. The low altitude of the encounter is, in part, intended to afford Cassini greater sensitivity to heavier, more massive molecules, including organics, than the spacecraft has observed during previous, higher-altitude passes through the plume.

— The flyby will help solve the mystery of whether the plume is composed of column-like, individual jets, or sinuous, icy curtain eruptions—or a combination of both. The answer would make clearer how material is getting to the surface from the ocean below.

— Researchers are not sure how much icy material the plumes are actually spraying into space. The amount of activity has major implications for how long Enceladus might have been active.

Credit: NASA/JPL

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