Saturday, 25 May 2013

Great flare in AR11748

AR11748 hosting an X3 flare - and its aftermath. The sketches show flare ribbons and flare loops ( the brightest parts of a flare arcade) the latter developing into an unusually compact cluster of post flare loops above the Sun's NE limb. Dates and times are UT. The spot group was, it seems, much reduced as a result of the weakened umbral fields of SC24. The event was sited at lat. +12, long. 290. A particularly elegant display though it rose only ~40Mm above the limb during the session.

Tuesday, 14 May 2013

Homunculus Nebula

Perhaps the strangest object in the night sky, the "Homunculus", contains the giant star Eta Carinae. This is a 'rough' sketch made with the 25" Mike Kerr Telescope at ASNSW's dark sky site, Wiruna. This is the raw sketch - though I have erased some notes etc. Key points of interest are the billows of cumulus-like gas at the right-lobe, and the central 'jet' of the left-lobe The latter has a dimmer cloud of ejecta. The right-lobe showed distinct gaps in places - and an equatorial 'jet' is seen below the star. A second 'jet' was suspected above the star. Magnification was 350. Many thanks to Chris Ross for pointing the huge 'scope at the target, I look forward to a longer session with, maybe, steadier 'seeing'. The prime spectrum of Eta Car clearly showed the hydrogen-alpha and beta lines in emission! I suspect it's the only object to do so with amateur telescopes.
     For complex reasons the bright emission points in this spectrum will soon disappear (~2014) when an unseen WR companion to Eta Car reaches periastron. "Watch this space" if, like us on the night, you have a diffraction grating in front of the 'scope's eyepiece; a rare event in practical astrophysics.

Tuesday, 7 May 2013

SPSP Challenge: IC2966 - can you see it?

Is IC2966 in fact Dunlop 266, 267?  He described two small hazy spots very near the Index Catalogue (IC) object. He was using a nine inch speculum - perhaps he did! IC2966 is one of the 'missing' Dunlop Objects that scholars do not credit to Dunlop. SPSP attendees might like to tackle the object with eight to ten inch telescopes. Report what you see to me (Harry) - I hope to be there. And the forecast is for clear-ish skies.

Where is IC2966? Its on the Musca/Centaurus border at 11h50m -64deg52min - overhead near the Southern Cross during the South Pacific Star Party. Good luck!
      Happy to report the two faint nebulae were fairly easy with the Mike Kerr 25" F5 telescope - pointed by Chris Ross. A 15m exposure by Joe Cauchi with his 16" reflector shows a pair of stars embedded in a blue reflection nebula - just as Dunlop described. How did he see it in a nine inch speculum: or was it then brighter?

Joe's great shot approximates the view in the 25". It seems the embedded stars are spectral type B or A as they excite no H-alpha emission - just a faint blue reflection nebula. Here's an idea: 180y ago the nebula was denser and scattered more light - but has now 'cleared' and little scattering occurs. Any thoughts?

Friday, 3 May 2013

AR11726 at the Limb

AR11726 was a large spot group of great complexity. When it reached the limb it revealed some fine H-alpha features. Here we see post flare loops after a GOES C5.7 flare at 22:25UT. The site showed no activity at 22:00, when white light viewing began. Returning to H-alpha at 23:03 showed these events. View 1: above the site we see the PFL ~40Mm high. Below are bright surges and some tiny  loops of the C5.7 flare. View2 shows the flare loops still present, now with larger surges - the latter are still strong in View3, while the PFL are fading. View4: crossing the flare loops are parts of a tall surge, in the process of recoiling back into the solar surface. Only the following spot of the active region was seen the time; the rest was concealed behind the limb