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Astronomy

Astronomy December 2016

The world's best-selling astronomy magazine offers you the most exciting, visually stunning, and timely coverage of the heavens above. Each monthly issue includes expert science reporting, vivid color photography, complete sky coverage, spot-on observing tips, informative telescope reviews, and much more! All this in a user-friendly style that's perfect for astronomers at any level.

País:
United States
Língua:
English
Editora:
Kalmbach Publishing Co. - Magazines
Periodicidade:
Monthly
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US$ 42,99
12 Edições

nesta edição

3 minutos
one frame in the cosmic movie

Although none of us knew what a galaxy was until 1923, when Edwin Hubble came along, we now know the universe is filled with them. Estimates from the Hubble Space Telescope and other survey data suggest the cosmos contains at least 100 billion galaxies, each a magnificent system of stars, gas, and dust. Some galaxies are large, like the mammoth elliptical systems that lie at the hearts of huge galaxy clusters. Others are moderately sized, like our own Milky Way, a majestic barred spiral that contains on the order of 400 billion stars including our Sun. But numerous galaxies are small — dwarfs that have a fraction of the Milky Way’s size and are always imperiled, dodging the odds of being swallowed by more massive systems that lurk nearby. For the past…

2 minutos
qg quantum gravity

HOT BYTES >> TRENDING TO THE TOP SPITZER BEYOND NASA celebrated the Spitzer Space Telescope’s 13th birthday on August 25, and granted it a two-and-ahalf-year extension. GASSY STATES he ALMA radio observatory reveals that some large stars keep large amounts of carbon monoxide gas in their debris disks. GROOVY PHOBOS Odd grooves on Mars’ moon Phobos were caused by debris knocked loose from impacts that then fell back to the moon’s surface. SNAPSHOT Why do spiral galaxies spiral? Some 30 percent of galaxies in the cosmos are spirals. What makes their beautiful arms go? Today we’re going to a time and place no one has yet witnessed. Early in the history of the universe, astronomers believe, gravitational instabilities between bright and dark matter formed galaxies. Spiral galaxies were born with a high angular momentum; the material that came together to make…

16 minutos
astronews

IO’S ATMOSPHERE PERIODICALLY COLLAPSES Jupiter’s moon Io is known for its volcanoes, but a new discovery suggests an even more complex world than once known. In research published August 3 in the Journal of Geophysical Research: Planets, a group of scientists discovered that Io has an atmosphere, but only when it’s in sunlight. Using the Gemini North Telescope’s Texas Echelon Cross Echelle Spectrograph (TEXES), a group of scientists at the Southwest Research Institute documented unique atmospheric changes on Io. They found that Io’s thin atmosphere, which is mostly sulfur dioxide gas vented from volcanoes, collapses and freezes onto the surface when shaded by Jupiter. When temperatures on the moon drop below –235° F during its “nighttime,” Io’s atmosphere appears to deflate. These periods occur fairly frequently; two hours of every Io orbit (once…

1 minutos
from our inbox

Observing sunspots, now and later I’m a solar observer from the Midwest who recently read with interest Steve O’Meara’s column in the September issue, regarding naked-eye sunspot observing. It was very well done, like all his columns I’ve read! Anyway, O’Meara’s piece made me think of the brief section I wrote for my book, Observing the Sun: A Pocket Field Guide (Springer, 2013), about this same topic. I’ve always found it fun to try to sight any large umbra that develop but never thought to find a minimal size for my eyes. I just appreciate the novelty of catching a glimpse. I reference Dawes’ Limit as a factor in determining sunspot visibility. In retrospect, that might be in error. The other issues mentioned may be of greater importance. To answer O’Meara’s question about…

4 minutos
just an arcsecond!

How well we see is central to our observations. And sometimes, normal (20/20) vision isn’t quite enough. If we can read the eighth line of the Snellen eye chart, the examiner will say that our eyesight is fine. At 20 feet, each of those little letters appears to be 1/6th the width of the Moon. In both breadth and height, they displace an angle of 5'. But distinguishing between the letters C, G, and O, or between E and F, demands we resolve gaps and lines within each letter. This requires that our eyes see features just onefifth that large, or 1'. Thus, 20/20 vision is defined as having one arcminute of resolution. A single arcminute is 1/30th the width of the Moon. This distance is quite tiny, since the Moon is…

4 minutos
in a shark’s eye

Seen from above, the Bahama Banks are a spectacular sight. As I write this, I’m looking out the window of an airplane and taking it in. Ripples of color paint the ocean for miles on end. Bands of light green and blue give way to deeper turquoise. Beneath crystal clear water, undersea sand dunes formed by ocean currents stretch across vast expanses of flatbottomed shallows. The Bahama Banks are the submerged top of the Bahama Archipelago, limestone grown by corals millimeters at a time over the past 100 million years or so. But suddenly, the pastels give way to sharp-edged, soul-swallowing blue as dark as any the seas have to offer. This is the Tongue of the Ocean, a trench that drops as much as 14,000 feet to the ocean floor. The…