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Northern Sky: April 14 - 27, 2018

April Sky
April Sky

Northern Sky by Deane Morrison for  April 14-27 2018
 
If April can just let up on the rain and snow a bit, there are bright planets in both morning and evening for us to enjoy.
 
In the evening, we have Venus, the brightest of planets. It’s hard to miss—a real beacon in the west after sunset. But its beauty obscures a rather different reality. Venus has a thick atmosphere that’s mostly carbon dioxide. The planet owes its brightness to very reflective clouds of sulfuric acid droplets and crystals. Its surface atmospheric pressure is more than 90 times that of Earth’—as high as the pressure 3,000 feet down in the ocean. And its surface temperature hovers above 850 degrees Fahrenheit. In short, Venus is a hellish place with a heavenly face.
 
For an even more heavenly sight, have a look on Tuesday, April 17, when the moon pays a visit. On that evening Venus and a young fingernail crescent moon will make a lovely pair.
 
If you go outside on or before the 17th, before the moon gets bright enough to interfere, try comparing Venus to Sirius, the brightest of stars, which will be rather low in the southwest. Spoiler alert: It's no contest; Venus easily outshines Sirius.
 
Sirius and the other winter stars are busy exiting the sky to the west. In their place is the spring constellation Leo the lion. It’s now high in the south during prime evening viewing hours. Look for a backward question mark of stars with a bright one--namely, Regulus--at the base. That question mark is known as the Sickle, and its stars represent Leo's head and heart. The hindquarters and tail are a triangle of stars just east of the Sickle.
 
In the morning sky, the best thing to see is Mars because it's getting really bright now as Earth gets closer and closer. It appears as a red dot low in the southeast for a couple of hours before dawn. West of Mars is Saturn, and even farther west is brilliant Jupiter.
 
In astronomy news, a University of Minnesota researcher--formerly at UC Berkeley--led a team that found the most distant individual star ever observed. Its light took nine billion years to reach Earth--or, more exactly, the Hubble Space Telescope. It's a large blue star, but it could never have been seen from, as NASA puts it, more than halfway across the universe if nature hadn't given us a cosmic magnifying glass. That magnifying glass is a cluster of galaxies that are between us and the star, which the team named Icarus.
 
It works like this. Massive objects like stars, galaxies, and clusters of galaxies act like lenses. Their gravity is so strong, it bends the space all around them, and light bends with it. Icarus is behind that cluster of galaxies, but when light from the star got near the cluster, it was bent by the cluster's gravity and curved around the cluster, then continued on toward us. The bending focused and magnified Icarus’s light by about 600 times. But that wasn't enough; the researchers hypothesize that Icarus only became visible—briefly—when a sun-sized star in the cluster of galaxies moved in front of Icarus. Then, that star took the light from Icarus-- already magnified 600 times--and focused it again, resulting in a total magnification of 2,000 times. Enough for Hubble to pick up. This work gives astronomers a way to study stars in very distant galaxies. We see them as they existed billions of years ago, when the universe was much younger.
 
The team named the star Icarus because it had a brief, you might say, moment in the sun, just like its namesake from Greek mythology. He made wings of feathers, held together with wax, but he flew too near the sun. The wax melted, and that was it for Icarus.  
 

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