In the early 1930′s, Bell Labs, the research division of AT&T, launched a project to use radio “short waves” to transmit telephone calls across the Atlantic. The technology to transmit signals via short waves was reasonably well understood. But engineers also needed to understand sources of noise that might interfere with radio communications signals. So the powers-that-were at Bell Labs tasked a young engineer to find sources of radio static that might interfere with transmissions. During his work, this young engineer, Karl Jansky, made an accidental discovery that revolutionized astronomy [Read more…] about The Mysterious Hiss from the Milky Way
Share This:Archives for July 2017
The Distances to the Galaxies
In our previous stop on our tour of celestial objects of cosmological importance, we looked at a handful of galaxies measured by the early 20th-century astronomer Vesto Slipher. The former Indiana farm boy wrestled with a modestly endowed telescope and a 450-pound spectrometer to make an astonishing discovery. He found the ‘spiral nebulae’ like Andromeda (M31) and the Sombrero (M104) were moving away from us at astonishing speeds, up to 1000 km/s and far faster than any nearby stars. The speeds of these spiral assemblies strongly suggested they lay outside our own group of stars, and were perhaps separate galaxies in their own right far outside our own.
But in science, a strong suggestion is not proof.
In the first years of the 20th century, astronomers had no way of knowing for sure the distance to these spiral assemblies. Indeed, a hundred years ago, they only could estimate the distances to a handful of nearby stars. The true scale of even our own galaxy was a complete mystery. No one knew whether the Milky Way was all there was to the universe, and whether it was a hundred light years across, or a thousand, or a trillion. Never mind the distances to the mysterious ‘spiral nebulae’, which may simply have been nearby star systems in the process of formation.
The key to the distance to the spiral nebulae, which we now know to be separate galaxies, and to the universe itself, lay unexpectedly in a class of unassuming stars, many of which you can see from your backyard with a pair of binoculars or without any optics at all [Read more…] about The Distances to the Galaxies
Share This:The Sky This Month – July 2017
1 July. First Quarter Moon, 00:51 UT
1 July. The first quarter Moon joins Jupiter and the bright star Spica in the southwestern sky. Jupiter is west of Spica and much brighter. This is more or less the last month to get a good view of the planet as it continues to fade, grow smaller, and appear lower in the southern or southwestern sky during July. It’s still brighter than any star and a beautiful sight in a small telescope.
3 July. Earth reaches aphelion, its furthest point from the Sun in its orbit. Today the planet lies 152,092,504 km (94,505,901 miles) from the Sun [Read more…] about The Sky This Month – July 2017
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