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Northern Rockies Skies for October: Aquila, the Eagle

September 25, 2014

A monthly look at the night skies of the northern Rocky Mountains, written by astronomers Ron Canterna, University of Wyoming, and Jay Norris, Challis, Idaho Observatory.

Aquila, the eagle, lies on the celestial equator (the projection of the Earth’s equator onto the sky) and along the Milky Way. It is famous for being the southernmost part of the summer triangle, with its brightest star being Altair. In the autumn night skies, it is best seen immediately after sunset, prominently on the meridian.

In Greek mythology, Aquila carried Zeus’s thunderbolts and carried the young Trojan boy, Ganymede, to Olympus. Ganymede is represented by the nearby constellation Aquarius.

Altair, the 12th brightest star in the sky, is very close to the sun, nearly 17 light-years away. The Arabic name Altair means the flying eagle. Looking closely at Altair through binoculars, you can see Tarazed, the scale’s beam, to the northwest and Alshain, the falcon star, to the southeast.

October events and planet and meteor alert: A bloody-red total lunar eclipse is scheduled Oct. 8. The Draconid meteor shower peaks around Oct. 8-9 and the Orionids around Oct. 22-23.

Right after sunset on the southwestern horizon is Saturn; Mars is to the east of Saturn. Mercury and Venus are too close to the sun to be seen this month. Jupiter rises around 4 a.m.

October 2014 Interest: Interstellar Travel: Trips to the Nearest Stars

 (Best URL:  http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html)

Last month, we considered the time and energy costs that would be incurred in a somewhat fantasy-like trip to the center of our Milky Way Galaxy, a distance of about 27,000 light-years. This distance is a large fraction of the galaxy's diameter, and therefore interesting from the point of view of beginning a colonization of the galaxy. The time and energy involved for such a project are enormous, seemingly prohibitive. But the nearest stars are much closer, and shorter trips seem possibly within reach of future technologies.

For any practical interstellar journey, the spaceship accelerates at 1 G (the acceleration of gravity at Earth's surface) halfway to near light speed, and then similarly decelerates to arrive at zero velocity. At near the speed of light, some important effects of special relativity come into play -- time dilation and length contraction, making the elapsed time much shorter for the space travelers compared to the stay-at-home Earthlings. Consider Vega, the brightest star in the summer evening sky, at a distance of 25 light years.

Several sun-like stars are closer, some of which may be found to harbor Earth-like planets. Such a journey to Vega would take a little more than three years in the spaceship traveling frame, whereas about 13 years would elapse back on Earth -- less than a generational timescale. The required "fuel tank,” assuming 100 percent efficient conversion of mass to energy of propulsion (provided by a hypothetical matter/anti-matter annihilation machine), would be almost 800 times the mass of the travelers' space module.

Perhaps the more interesting challenges would be the kinetic ones: handling the heat generated by interstellar dust impinging on the spaceship bow at near light speed, plus the occasional small interstellar rock approaching at these relativistic speeds, which would obliterate the spaceship if not effectively diverted. A few amusing science fiction stories have envisioned constructing large enough interstellar spaceships to make these trips out of small asteroids.

Thus, it may not be an unimaginably difficult task to journey to the nearest stars, and back soon enough to see one's teenage son or daughter catch up with oneself in middle age. This conclusion, of course, presumes multiple advances in technology can be achieved. In the context of Fermi's Paradox (where are the space aliens from the nearest stars?), we may be still left wondering, since short interstellar trips may not be completely in the realm of fantasy.

To view this month’s sky chart, click here.


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