As we’re now well into the second half of summer in the Northern hemisphere and the number of hours available to us for stargazing are slowly but surely increasing again, the mild evenings make for some very comfortable viewings of some very special wonders in our night sky. So pull up a garden chair, a cool drink and a pair of binoculars…
Eagle 1
The proud eagle has long been recognized as a ruler of the skies and been a symbol of prestige and power so it’s no surprise to learn that it too has a place in Space. One eagle that is as tightly bound in the human psyche of ‘Space’ today as the word ‘Apollo’ evokes the Space Age and the Space Race is of course the 9.4 metre-wide Lander Module (LM) named ‘Eagle’ that brought Astronauts Neil Armstrong and Buzz Aldrin safely to and from the surface of the Moon in July 1969 (For a look inside, see this YouTube video by Jared Owen). Although the ascent stage (top half) of the module left the lunar surface decades ago, the bottom half or ‘descent stage’ of the Eagle still remains at the landing site of the Apollo 11 lunar mission which still captivates many as a fascinating observational target. The Apollo 11 crew landed in the ‘Sea of Tranquility’ – at the edge of one of the huge basalt-filled basins that were created by one of the largest asteroid impacts in the early history of Earth’s natural satellite.
Eagle LM landing site. Image Credit: Stellarium/Nick Parke
Although an amateur astronomer would need a very large telescope to spot even a 700m-wide object on the Moon from 384 400km away on Earth, it’s still exciting to know we are looking at the very part of the Moon that first saw mankind reaching out and actually touching something in Space for the first time. Perhaps the best opportunity this month for observing the landing site of NASA’s ‘Eagle’ spacecraft will be on the 12th of the month at 4am when the Moon is highest in the sky.
Eagle 2
The next ‘eagle’ in our August night sky is a star inextricably linked to the bird of prey, that bright star ‘Altair’. Human eyes aren’t too good at seeing in the dark so at a glance we often miss the fact that there are violet, blue, red, orange and yellow-tinted as well as white stars in the heavens. But Altair is one of the few that ‘does what it says on the tin’ or rather is just as it appears to the naked eye, as a it is a white main sequence star. The star’s name has an Arabian origin and means the “flying eagle”. It earns its name from being the ‘Alpha’ star or brightest star in the constellation of Aquila the Eagle and in Greek mythology Aquila was the pet eagle belonging to the king of the gods – Zeus, (if not Zeus himself, in disguise).With fewer stars of our star city being visible in the summer sky and with Altair having a magnitude less than +1.0 (which inversely makes it one of the brightest, in fact the 12th brightest star in the whole night sky) – it is easy for all levels of stargazer to spot as it really draws the eye.
Summer Triangle, Aquila, Altair. Image Credit: Stellarium/Nick Parke
You can easily confirm that you are observing the correct star as it marks the bottom point of the large asterism the ‘Summer Triangle’ which can still be viewed as we face south mid-month around 11pm. Finally, Altair’s association with the predatory bird is further secured by reaching farther back in time to Sumerian and Babylonian cultures when it was referred to as the ‘eagle star’. Eagles can move fast so it should be no surprise that the Eagle Star rotates much faster than our Sun. At it’s equator the Sun rotates at the speed of approximately 2km per second, but at its equator Altair spins at a staggering 286 kilometres per second! The speed of rotation is in fact so fast that it causes the star itself to change shape from a sphere of hot gas to something a little more like the shape of a skittle, being flattened at its poles. In terms of size, Altair – the brightest ‘eagle’ in our August night sky Altair measures 2.8 million km in diameter, 1.8 times the size of our local star.
Eagle 3
Eagle Nebula sculpture. Image Credit: AOP/Nick Parke
Our third and final eagle in Space is known as the Eagle Nebula. This ‘nebula’ –(Latin word for cloud) is an open cluster of stars that happens to be shaped like a mighty eagle in Space with wings outstretched. Known as ‘Messier 16’ or M16, it was observed and included in the 18th century French astronomer – Charles Messier’s 1774 celestial catalogue of deep sky objects known as the ‘Catalogue de Nebuleuses et des Amas d’Etoiles’ and in the Armagh Observatory’s New General Catalogue [NGC 6611]. Thanks to its enormous size and comparative brightness to other nebulae it is one of the most observed celestial wonders in the heavens by amateur astronomers.
Eagle Nebula sky location. Image Credit: Stellarium/Nick Parke
Looking like the talons beneath the great bird are the just-as-popular ‘Pillars of Creation’, towering structures 9.5 light years high that contain the important ingredients for future star systems and worlds. M16 sits right on the edge of naked eye observation with an apparent magnitude of +6.0 to +6.2, so a small pair of binoculars could be needed if you’d like to take a peek at the biggest eagle in Space. The deep sky object lies 7000 light years from Earth a little to the right of and beneath the constellation of Aquila, at the tail end of the stellar snake Serpens. Discovered by Jean-Philippe de Cheseaux in 1745, the wings of the magnificent cosmic eagle span 70 light years across (66.5 trillion kilometres), that’s a realm some 22 times the diameter of our entire Solar System!
Eagle Nebula. Image Credit: T.A.Rector (University of Alaska Anchorage, NRAO/AUI/NSF and NOAO/AURA/NSF) and B.A.Wolpa (NOAO/AURA/NSF)
0 Comments