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)

Friday, 1 July 2016

N6397: plan ahead!

This globular has impressive stats: second nearest, fourth in Skiff’s list of brightest globulars and has the brightest members. Yet it is unimpressive when first viewed. This may be due to the small bright central cluster of stars, and the fact that the vast halo of 12/13mag stars is hard to see in small scopes. Full resolution seems to need a 12” scope or larger: the halo of faint stars is nearly 30min  arc dia.  It’s huge- almost the Moon’s apparent size: third largest after southern ‘giants’ Omega Cen and 47 Tuc. The sketch overflowed the page as more of the halo came into view! Plan Ahead!

A recent view in Bob S.'s 12" Dob showed what a spectacular thing N6397 is. Extra aperture makes a big difference.