解析天鹤座

https://sandandstars.co.za/2016/08/27/galaxies-galore-in-grus/

Galaxies Galore in Grus

27th Aug 2016

Susan

Stars

During the day the Kalahari is alive with birds, filling the air with their songs. I had a great treat this afternoon – I saw some vultures soaring effortlessly on a thermal, circling around and around, held aloft by those huge wings. Magnificent birds. Watching them in the binoculars brought to mind another bird that glides through the air on magnificent wings… Grus, the crane.

I think Grus is a constellation close to the hearts of most South African stargazers because the Blue Crane is South Africa’s national bird.

It is a beautiful, graceful bird with its long slender neck, long legs and elegant wing plumes which sweep to the ground.

It is the softest blue-grey colour and stands about one metre high. It is the world’s most range-restricted crane, being almost entirely restricted to South Africa in its distribution.

The celestial crane – the constellation Grus – is also a beautiful, graceful bird with its long slender neck, long legs and elegant wing plumes swept back in flight. (It’s one of the few constellations that to me looks exactly like what it is… a crane in flight.)

And apart from being a graceful constellation, it is also stuffed with galaxies and as galaxies flourish under dark, dark skies, I spent the evening searching some out. I began with that well-known and fave grouping –

DSS image

The Grus Quartet

I was once standing in a queue in a Fruit and Veg shop, when I noticed that the woman ahead of me in the queue had a pair of identical twin girls, I’m guessing around five or six years old. I made some comment on how unusual it is to see two little human beings absolutely identical to each other in every way, and she replied they weren’t twins… and she reached behind her skirt and pulled into view a third little girl – a fraternal triplet to the identical pair. A sort of ‘two plus one’ arrangement.

And that is exactly how I think of the Grus Quartet: ‘a three plus one’ arrangement. A quartet of interacting spiral galaxies – here you have three members of the quartet – NGCs 7582, 7590 and 7599 – all fitting beautifully into a moderately high power field of view… and over there, needing to be pulled from behind the skirt, NGC 7552.

I’ve looked at the quartet many a time, but they were a delight in these dark skies. (I observed all the galaxies using magnifications of 64x, 90x, 144x, 230x, 288x.)

DSS image

NGC 7582 Galaxy Type (R′)SB(s)ab

23h18m23.7s -44°22′08″ mag 10.6 diam 5.0′ x 2.1′

It is the brightest and most obvious of the galaxies, appearing as a relatively bright little 3′ oval-spindle, oriented north-northwest to south-southeast, with a bright little nucleus. With higher power the galaxy becomes very slightly patchy, with a very hazy edge, both of which suggest a spiral structure. It appears much larger and a little more patchy with averted vision, a shapely little galaxy.

DSS image

NGC 7590 Galaxy Type (R′)SB(s)bc II

23h18m55s -42°14′17″ mag 11.5 diam 2.7′ x 1.0′\

NGC 7599 Galaxy Type SA(s)c II-III

23h19m21.5s -42°15′25″ mag 11.5 diam 4.4′ x 1.3′

NGC 7590 is the smallest of the quartet but it stands out well. It appears as a relatively bright 2′ oval, oriented northeast to southwest, with a slightly brighter little core. A little 11th mag star on its northeastern tip.

NGC7599 appears the dimmest of the three, and displays an even surface brightness without a distinctive nucleus, elongated east-northeast to west-southwest.

DSS image

NGC 7552 Galaxy Type (R′)SB(s)ab II

23h16m10.9s -42°35′02″ mag 10.6 diam 3.4′ x 2.7′

This galaxy appears as a bright little 3’ spindle elongated east to west. It has a prominent and bright little stellar nucleus. Higher magnification expanded the hazy edges considerably, and with averted vision I could see an extremely faint outer halo.

DSS image

NGC 7462 Galaxy Type SB(s)bc? Sp II-III

23h02m47.1s -40°50′07″ mag 12 diam 4.2′ x 0.7′

This galaxy is a beautiful sight – a strikingly bright narrow sliver of light, elongated east-west. It has a uniform surface brightness, and there is an 11th mag star on its western tip.

DSS image

NGC 7424 Galaxy Type SA(s)bc pec II

22h57m18.2s -41°04′15″ mag 10.5 diam 9.5′ x 8.1′

This galaxy has a bright stellar nucleus with a small, very faint halo, but which expanded with averted vision, although the inner section didn’t seem to brighten much.

DSS image

NGC 7410 Galaxy Type SB(s)b I-II

22h55m00.9s -39°39′38″ mag 10.3 diam 5.2’ x 1.6’

This galaxy has a long bright 3′ lens shape, elongated northeast to southwest with a bright nucleus. High power and averted vision revealed the surface brightness is not even – not so much a mottling as more like an unevenness in the glow.

DSS image

NGC 7412 Galaxy Type SB(s)b I-II

22h55m46.4s -42°38′24″ mag 11.4 diam 3.9′ x 2.9′

Very faint roundish glow, and a slightly brighter nucleus. Averted vision brightened the glow up a tad, but not by much.

DSS image

IC 1459 Galaxy Type E2

22h57m10.4s -36°37′27″ mag 10 diam 5.2′ x 3.8′

IC 5264 Galaxy Type E2

22h56m52.7s -36°33′18″ mag 12.5 diam 2.5’ x 0.5’

IC 1459 is a pretty bright hazy little 2’ envelope of light, elongated northeast to southwest, with a bright little nucleus. Its companion, NGC 5264, about 8’ to the south is only visible with averted vision – a very faint and uniform little wisp of light.

And that was it for Grus’ galaxies; my eyes needed a break after all that straining to make out just a little more faint fuzzy in the faint fuzzies. But before departing faint fuzzies, a stopover at a nice little planetary nebula –

DSS image

NGC 5148/50 Planetary Nebula

21h59m35.2s -39°23′09″ mag 11 diam 132”

This PN is located in the slender neck of Grus, only 1.2° west from mag 4.4 Lambda Gruis. With the OIII filter, it appears as a very, very small ghostly round nebula, the tiniest little soft silky smooth pale grey glow with a just barely perceptible dark central region.

And then it was time for some doubles:

DSS image

Theta Gruis Double Star

23h06.9m -43°41’

Started off this Theta down there amongst all the galaxies. A binocular pair, the primary a lovely bright yellow star, its companion also a bright whitish-yellow separated by 159” at PA 292°.

Dun 249 Double Star

23h23.9m -53°49’

A pretty pair – wide, easy, off-white, and in a pretty star field; separation 25.5°, PA 212°.

H 5288 Double Star

21h42.5m – 37°56’

A lovely brightish, pale yellow star in a pretty deserted field with a pretty little greyish-white companion, separated by 19.5”, PA 60 °. Nice view in their somewhat starless neighbourhood.

Delta-1 & 2 Gruis Double Star

22h29.2m – 43 °30

A lovely sight! Delta 1 and 2 are an optical pair, lovely colours – Delta 1a bright yellow star, Delta 2 a bright orangey-yellow star. Optical doubles don’t really do much for me… but this pair does because Delta 2 has a small little white companion separated by 60”, a small little grey-white star, holding its own against the two bright stars.

Pi Gruis Double Star

*22h22.7m – 45**°*57’

Now here was a lovely sight… a bright crimson carbon star and a silvery-yellow companion. There is little as pretty to my eyes as a carbon star, the reddest of red, like tiny little embers.

Dun 246 Double Star

*23h07.2m -50 °**41’***

A pretty pair of pale yellow stars in a somewhat thin field, the primary marginally brighter; separated by 8.8”, PA 254 °. I enjoy doubles when they are in barren fields.

And that was pretty much it for my flight around Grus.

Copyright © Susan Young 2016