Sunday, 5 November 2017

Polarity Inversion Line

Flares fascinate. How and why do these huge high-temperature events erupt? Close study of the polarity of sunspots suggests they occur along the boundary between spots of opposite sign. At least this GOES M4.2 did in AR12673 two months ago. The sketch (lhs) shows the spot group in WL and H-alpha (polarity line in BLUE). The polarity map from the (c)SDO satellite shows the polarity a few hours later. 

Friday, 15 September 2017

X8 Post flare loops

The X8 flare in AR12673 was not seen - with the group now just behind the limb. But the coronal loops acted as conduits for plasma condensing on them to reach the chromosphere. As the fields changed the loops evolved. "Elegant" was how Zirin ("Astrophysics of the Sun", 1986) described them. 

Sunday, 6 August 2017

LMC Blue Filaments (Dragon unbound!)

This sketch covers a bright field 2 deg. N of LMC centre. The fov is 3 full moons wide and 4 high. It's a big field! The two filaments alpha-alpha and beta-beta are, apparently, anonymous. They are very blue in H-beta. It's presumed they are distorted galactic blue-knots or arms of mainly OB stars. The named features are listed l.h.s. Why did the filaments take this strange shape? They are visible in small binoculars. The 'Dragon's Head' is the only thing with a common (and appropriate) name. The whole looks like an Oriental dragon!

Sunday, 18 June 2017

Nu Scorpii: the 'double double'

The writer has always enjoyed viewing double stars, particularly if they are ‘tight’ ones: that is, close pairs that are hard to separate. Although my ‘scopes are not dedicated to the task, ‘tricks’ like using aperture masks and simple orthoscopic eyepieces will often succeed, though the most important factor is steady seeing, that usually occurs later at night.

A favourite example is the ‘double-double’ Nu Scorpii, aka “Jabbah” (Arabic for the Scorpion’s forehead) close to bright star Beta Sco, refer to star maps (P82, Astron 2017). A ‘double-double’ is a quaternary system with two pairs of stars gravitationally bound in a four-star system. As Agnes Clerke wrote (1905): it is “perhaps the most beautiful quadruple group in the heavens.” 

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.