Saturday, 7 January 2017

LMC: The Tarantula Nebula and its clusters

A first 'shot' at this most complex of all nebulae: it showed wonderful detail despite 8 day Moon. The Lucke-Hodge Catalogue numbers are used for two of its clusters _ and the NGC has three numbers for the major nebulae components. When a darker night offers, I hope to develop the fainter detail of the vast extensions. The bright star in LH100 is 30 Dor. The 'little' cluster TM5 is 'anonymous': I guess not catalogued. Who is TM? The brighter bits drawn here are about 800ly across. Fainter outliers extend the whole to almost 2000ly diameter. Hubble views 30Dor and environs! -

Sunday, 13 November 2016

LMC nebula N11: Mega-bubble!

 NGC1760 to 1769 is a grouping sited NW of the LMC’s densest parts at 4h57m, -66°32’. Bino’s showed a featureless round glow at the site – but the 10in ‘scope told another story! N11dissected. The biggest single unit of N11 is N11B on the west side (Fig). It is a bean-shaped bright nebula ‘excited’ by some twenty O-type stars in chains, at least 10 are sketched. The stars of N11B are stellar assembly LH10.  N11C, the second brightest part of the complex, is round with a dark notch or two on its east side. I saw only two stars in this part, but research shows at least 10 O-types here. To the SW is N11E with two or more O stars: ‘deep’ images show six. To the northeast N11F completes the circle – a faint nebula with still more O-stars. The whole thing is 1100ly across, about 14 times the size of M42!

Friday, 21 October 2016

Thanks Karen!


Thanks for the great talk Karen! Shoalhaven Astronomers were treated to a feast of solar animations on 21st Oct 2016. The challenges in getting time-lapse of solar transients can be daunting: but Karen succeeded. We watched hard-to-see events unfold in amazement, as 'roos grazed the lawns outside. The low density solar chromosphere is dominated by magnetic fields: matter flows sedately - then abruptly plunges to the surface or 'pops' into space without warning. Incredible physics! A great night.

Sunday, 16 October 2016

NGC1532 'Woomera'

Most galaxies are ‘poker-faced’ – giving little away: featureless ovals with faint nuclei; but some offer a glimpse of a more dramatic existence –when galaxies collide.  One such is N1532 (Dunlop 600) in the constellation of Eridanus, the River.
On first impression this is a big edge-on spiral with, seemingly, two nuclei! Higher power shows a small bright elliptical ‘object’ almost in contact with the edge-on’s nucleus. Are these interacting galaxies? References suggest they are: although there is no extended disc to be seen around the small galaxy, NGC1531. The common name for this galaxy pair is ‘Woomera’, the long thin Aboriginal spear-thrower.
In fact, this object seems to still have the ‘spear’ attached! Repeat viewings showed a thin strand of galaxy ‘arm’- aimed at a nearby field star. The whole scene was much like a ‘Mimi’ art figure from Arnhem Land in Australia’s north (Fig). 

Saturday, 1 October 2016

Enigma: NGC55

This is a large member of the Sculptor Group of galaxies; but what are we seeing? Apparently, an edge-on view, but with the bright core to the W and only a fainter arm to the E? A Gendler image suggests the bright 'cigar' is the central core seen through an outer arm of blue stars. Several small 'knots' are likely OB clusters of activity. A possible stellar central nucleus is arrowed. Reference stars are noted in case we see a super nova! This galaxy is seen well in a 4in 'scope. Is NGC55 a barred spiral with only the E arm visible - the W one hidden from view?

Monday, 29 August 2016

N7009: 'planetary' puzzles

Puzzling things planetaries. They mainly emit H-alpha, OIII and H-beta light: i.e. they are almost pure LRGB sources. Here we contrast a superb HST(c) image with the same image made with zero RED and 50% GREEN. This 'recipe' approximates human visual sensitivity. The result is close to what we in fact see in a 10 inch 'scope. Why cant we see red H-alpha in deep-sky objects? Because our Sun emits little in that band and H-alpha is close to the limit of our sensitivity, while we see blue and green quite well. This is why many planetaries look nothing like their big-scope images. 
The central star (inset) was finally seen by 'blinking' with an orange (i.e. minus blue-green) filter, fully blocking the bright nebula but showing the 11.5 mag star.

Saturday, 30 July 2016

AR12565 and 67: Odd Couple

Two spot groups unusually close together. A fine prominence was seen at the limb on Jul22 with AR’s 12565 and 12567 still 20° from the limb. That prominence was likely the filament recorded 20°W of the groups during their disc transit. While very bright plage was seen sandwiched between the two dominant (p) spots and some arf – no flares were logged; flaring was then steady at GOES B2.

More M-flares! A gale cut short the Jul22/23 session, but M5 and M7 flares erupted just 2hrs and 5hrs later! The latter, a twin peaked event, hosted a rare spray of ejecta, apparently from AR12565(Fig SDO log). The spot duo had attained high activity levels while rounding the limb. A 3hr patrol on Jul23/24 with the duo on the W limb only showed plage, some surges, arf and fragments of a flare loop; but an M2 flare erupted just 4hr later at local sunset, again unseen! 
(Zirin, H "Astrophysics of the Sun" (1986) defines a spray as "the ejecta of flares...spray velocities can be huge, up ro 2000km/sec" . . " as from the muzzle of a gun" p270, 280 298 etc)