Objects for July, August and September

Aquila

Figure above shows "The Balance"

Altair

Distance: 16.7 light-years [Karkoschka p98].  Altair rotates at an angle of 64° to our line of sight [7]. Altair’s radius is 1.8 times larger than our Sun’s and it turns quickly around its axis every 8.9 hours [8]. This leads to the star having a distorted shape, with its equator diameter 25% larger than its polar diameter [8]. Altair is rotating at 90% of its breakup velocity [7].

Cygnus

“… offers the finest star-fields to be from from British latitudes” [Muirden, p121]. Click  and  for photos.

“The Milky Way flows through Cygnus, and this is one of the richest areas in the sky, so that it is well worth sweeping; note the dark rifts which indicate the presence of obscuring material” (Moore, Binoculars, p86]

“The Cygnus Star Cloud is the most conspicuous Milky Way cloud north of the celestial equator” [Crossen, p140]

Deneb – Distance: 2500 light-years [Karkoschka p46]. Deneb, of course. is famous as one of the stars of the Summer Triangle. A depiction of this triangle may have been painted onto the walls of Lascaux (in the Shaft of the Dead Man) 16500 years ago [1]. According to Kaler if "...placed at the distance of Vega, Deneb would shine ... 15 times more brightly than Venus at her best, be as bright as a well-developed crescent Moon, cast shadows on the ground, and easily be visible in broad daylight. Deneb is a true supergiant ... its diameter ... is 108 times that of the Sun, half the size of Earth's orbit ...With a rotation velocity of at least 30 kilometers per second, Deneb might take as long as half a year to make a full rotation" [12].

Sadr - Distance: 1800 light-years [Karkoschka p46].

Albireo - Distance: 395 light-years [Karkoschka p44].

Omicron 1 – “a mag. 4.0 yellow star showing brilliant contrast with its wide, blue mag. 5.0 companion ...one of the most colourful binocular doubles of all” [Muirden, p121]. Speaking personally I believe this beautiful coloured pair makes a convincing binocular substitute for the telescopic Albireo if you don’t have access to a telescope!

The North America Nebula “is dimly visible with the naked eye in the guise of a slightly brighter section of the Milky Way, and binoculars show it clearly as a larger region of diffuse nebulosity…. The nebula is nearly 50 light-years in diameter, and may owe much of its illumination to Deneb [Moore, Binoculars, p86]

Delphinus

Nicolaus Venator reversed his name and gave it to constellation stars Sualocin and Rotanev [Moore, Binoculars p87].  According to Karkoschka [p98] Sualocin lies at a distance of 240 light-years and Rotanev 100. Delphinus hosts two interesting red variables, U and EU [Moore, Binoculars p87].
 

Hercules

Globular Cluster M13

Distance:  23,000 light-years [Karkoschka p40]. In 1974 a three minute binary message was broadcast from the Arecibo radio telescope towards M13, the earliest we can expect a reply back from the globular cluster is in approximately 50,000 years time! [9].

Globular Cluster M92

Distance:  27,000 light-years [Karkoschka p40]. " M92 is also one of the oldest known globulars in the Milky Way, made up of stars between 12 billion and 13 billion years old" [19].

Rasalgethi

Distance: 360 light-years [Karkoschka p94].

Lyra

Vega

Distance: 25 light-years [Karkoschka p44]. Vega will be the Pole Star again in 13,700 AD [1]. Vega is approximately twice as massive as our sun, and has 2.5 times its diameter [2]. The star turns on its axis every 12.5 hours, leading to it having a flattened oblate spheroid shape. We are looking down at its pole which is brighter than its equator due to its shape and fast rotation [1]. Vega is 23 percent wider at its equator than at its poles [4]. Vega is rotating at 90% of its angular break-up rate with an equatorial velocity of 275 km/s with its pole inclined at 5 degrees relative to earth [3].

 

Vega sits in the middle of a 160 billion kilometre dust disk which appears to be remarkably smooth with no clear signs of any planet formation [5]. "Given the physical similarity between the stars of Vega and Fomalhaut, why does Fomalhaut seem to have been able to form planets and Vega didn’t?" George Rieke [10].

Castor, Vega and Fomalhaut are all members of the Castor Moving Group and as such probably have a common origin [6].

The Delta Twins

Delta1 Distance: 1080 light years [22]. Delta2 Distance: 750 light-years [Karkoschka p94]. "... a wide amazing color contrast pair" [20]. Split in even the smallest pocket binoculars, Delta-2 looks orangish, while Delta-1 is bluish-white. Both stars are members of the Stephenson 1 cluster but they are not a true binary system [21].

Epsilon Lyrae - The Double-double

Distance: 170 light-years [Karkoschka p44]. "Through binoculars, what appears as one star to the unaided eye resolves into two. Through a telescope, each star in that pair resolves into two again, making four stars" [23].

T Lyrae
 
Distance: 2400 light-years [25]. "The sky is full of small cold, red gems ... such as the very red star T Lyrae ... Spectroscopic analysis of T Lyrae and similar stars show the marked signature of carbon, and for this reason, they’re referred to as carbon stars" [24]. "T Lyrae is a deep red carbon star that is quite visible with binoculars (but is) below naked-eye visibility .... Carbon stars are the source of much if not most of the carbon in the Universe" [25]. The star is an irregular variable with a range between magnitudes 7.5 and 9.8 [25]. As a rough guide it is reasonable to assume that the faintest star visible in 10 x 50 binoculars is 9.5 [26].

Scorpius

Antares

Distance: 550 light-years [Karkoschka p90]. A red supergiant star shining opposite to Betelgeuse [15]. According to Moore (Stargazing, p84) Antares is easy to spot low in the south during July, there are no comparably bright stars near it but Deneb and Vega provide a rough line to it.

Scutum

Wild Duck Cluster M11

Distance: 6000 light-years [Karkoschka p94]. "... well seen even with binoculars, which begin to resolve it; it lies at the nucleus of a superb Milky Way region" [Muirden p135]. A "bright glow in binoculars" [Karkoschka p94]. Containing over 2,900 stars, it appears as a triangular patch of light through a pair of binoculars [14].

Astronomers refer to it as a metal-rich cluster because a nearby supernova likely seeded its molecular cloud complex with heavier elements [13].

Vulpecula

Dumb-bell Nebula M27

Distance: 1200 light-years [Karkoschka p98]. " ... a fine planetary nebula ... the present diameter is of the order of  2.5 light-years" [Moore, Binoculars p 147].

"Planetary nebulae are produced when a Sun-like star begins to reach the end of its life and starts shedding its outer layers into space." [16]. (M27) is "... the type of nebula our Sun will produce when nuclear fusion stops in its core" "... many things remain mysterious about bipolar planetary nebula like M27, including the physical mechanism that expels a low-mass star’s gaseous outer-envelope, leaving an X-ray hot white dwarf" [17]. "That the nebula is so much brighter than the star shows that the star emits primarily highly energetic radiation of the non-visible part of the electro-magnetic spectrum, which is absorbed by exciting the nebula's gas, and re-emitted by the nebula, at last to a good part in the visible light. Actually, as for almost all planetary nebulae, most of the visible light is even emitted in one spectral line only, in the green light at 5007 Angstrom" [18].

Asterism Collinder 399 - The Coathanger

 

I can remember looking at the Coathanger from the roof of the Charterhouse Science Block with 10x50s back in the day. Brian Skiff, in his 1998 Sky & Telescope article, used Hipparchos satellite date to show that the Coathanger is a chance line-of-sight noncluster, not a real group of associated stars at all. Pretty to look at anyway!