Aquila the Eagle is supposed to represent a bird figured on a Euphratean uranographic or star map from about 1200 BCE. It is one of the original 48 constellations still used today. The constellation as often associated with Zeus and often carried his thunderbolts.
Most ancient civilisations seem to associate Aquila as
either an eagle or bird of some kind. Some mythologies associate the bird as a
vulture rather than an eagle, the Romans and the Mongols did. Old stories talk
about the eagle carrying the shepherd boy Ganymede to Zeus.
Aquila is a summer constellation and its brightest star Altair which means flying eagle is part of a very familiar group of stars in the summer sky known as the Summer Triangle. It is the closest of those three stars being only 17 lightyears away, while Vega in the constellation of Lyra the Lyre is 25 light years away and Deneb in Cygnus the swan a massive 2200 light years away are the other two stars in the triangle.
Altair is magnitude zero star and is an A class star making it hotter than our Sun. It is a star that rotates very quickly meaning that it is not spherical in shape because it is flattened at the poles due its high rate of rotation.
Altair and the two stars that are either side of it beta and
gamma were known as the family of Aquila while the Chinese knew this little
group as Ho Koo a River Drum.
For any fans of the film Ben Hur one of the horses in the
great chariot race at Antioch one of them was Aquila.
Gamma or Tarazed which means the balance is the next
brightest star in Aquila, it is the brighter of the two stars that flank
Altair. The star is 395 light years away and is a K class giant star. It is
cooler than the Sun with a surface temperature of around 4,000 degrees. It’s a
young star only around 270 million year old and although it is more massive than the Sun it will not destroy
itself in a supernova explosion it will simply expel its outer layers of gas into
space, become a planetary nebula and then ultimately a small white dwarf star
as it reaches the end of its life.
Zeta also known by its Arabic name as Deneb el Okab which
means the tail of the eagle has a brightness of magnitude of 3 and is a double
star and is around 83 light years away . Its an A class star meaning its hotter
than our Sun.
Delta Aquilae is slightly fainter than zeta ay mag 3.3 it’s
an F class star slightly hotter than the Sun, and lies about 50ly .
If you have wondered what has happened to Beta Aquila well
it’s here its name is Alshain which
like gamma also means balance is the other star flanking Altair. It should
according to the Bayer system using the letters of the Greek alphabet be the
second brightest star in Aquila in fact it comes in as the 5th. I
have no idea why. Alshain is a G type star slightly cooler than
the Sun and is located 45 light-years from Earth. To the eye it is a single
star however it is in fact a triple star system.
Eta Aquilae is a variable star discovered by Edward Piggot
on September 10th 1784 in York, this was a
night to remember in York , as the deaf astronomer John Goodricke
discovered the variability of the star Beta Lyra. I christened Goodricke and
Pigoiott as the Fathers of Variable Star Astronomy for all the work they
undertook in that field of astronomy. Eta is a cepheid type variable the first
Cepheid was of course discovered by Goodricke from York!!
A cepheid variable star is a distance marker in the galaxy.
Cepheid variable are a class of variable
stars whose periods of variation are closely related to their luminosity and
that are therefore useful in measuring interstellar and intergalactic
distances. Most are spectral type F (moderately hot) at maximum luminosity and
type G (cooler, Sun-like) at minimum. In
1912 Miss Henrietta Leavitt of Harvard Observatory discovered the
period-luminosity relationship of the Cepheids in the Large Magellanic Cloud
and the Small Magellanic Cloud. These are two satellites galaxies to our own
Milky Way Galaxy. This work helped show that these nebulous patches in the sky
were not in our galaxy but were galaxies in their own right. Today we know they
are around 160-170,000ly.
A bright nova appears over the Western Front during World
War 1. Nova Aquilae 1918 was, first seen June 8th, 1918. First seen by the
Polish medical professor and amateur astronomer Zygmunt Laskowski it was
confirmed Britain by the amateur
astronomer Grace Cook. Nova Aquila was
the brightest novae seen during the last 300 years reaching a mag of -0.5.
Because the milky way passes through Aquila 9 nova have been seen in the last
120 years, most have been faint but you never know a bright one might be coming
in the near future is it is always worthwhile looking at this part of the sky.
There are no Messier objects in Aquila which is surprising,
since the constellation lies along the northern Milky Way between the rich star
clouds of Cygnus and the galactic opulence of Sagittarius.
Perhaps the finest
open cluster in Aquila is NGC 6709. Open
clusters are groups of young stars. This cluster is believed to be around 300
million years old. It’s a sprawling irregular group of stars which, to some
stargazers, looks like a sparkling unicorn. NGC 6709 is about 3,900 light years
away and spans about 17 light years.
The constellation is also home to NGC 6751, a planetary
nebula. that is also known as the Glowing Eye. The nebula is estimated to be
around 0.8 light-years in diameter and is estimated to be roughly 6,500
light-years away from Earth. It was formed when a star collapsed and threw off
its outer layer of gas several thousand years ago.
The word "nebula" is Latin for mist or cloud and
the term "planetary nebula" is a misnomer that originated in the
1780s with astronomer William Herschel because when viewed through his
telescope, these objects resemble the rounded shapes of planets. Herschel's
name for these objects was popularly adopted and has not been changed.
They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.
And finally NASA's Pioneer 11 space probe, which flew by
Jupiter and Saturn in the 1970s, is expected to pass near the star Lambda Aquila in about 4 million years.
www.theramblingastronomer.co.uk
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