Observations - news and views on astronomy from Sydney Observatory

Daily cosmobite: Fomalhaut’s dusty ring

Published by Andrew Jacob on November 21, 2014 No Comments

ALMA_Fomalhaut_01. ALMA/NASA/ESAThe brightest star in Piscis Austrinus is Fomalhaut. Images made by the Atacama Large Millimeter/submillimeter Array (ALMA) in 2012 revealed a narrow dusty ring probably constrained by a pair of unseen planets. That makes Fomalhaut one of about twenty naked-eye stars to host a multiple-planet system.


ALMA data, in orange, shows a dusty ring (partially imaged) around Fomalhaut. ALMA (ESO/NAOJ/NRAO). Visible light image in blue: the NASA/ESA Hubble Space Telescope



PiscisAustrinusPiscis Austrinus, the Southern Fish, is high overhead for southern hemisphere observers at present. It’s a challenge to discern the ‘fish’ shape but its brightest star, Fomalhaut, is easily seen with the naked eye.


Fomalhaut is the brightest star in Piscis Austrinus. Chart generated by TheSky6 © Software Bisque, Inc. www.bisque.com.




January 2015 is predicted to be hot, hot hot. So get out and about to Sydney Observatory and enjoy the evening telescope viewing, hearing amazing stories of the night sky and soaking up the atmosphere in one of the most important heritage and scientific sites in Australia. There are programs for families such as the Celestial Pizza nights, and romantic pre and post dinner programs for couples. Book before its too late.

Venus: goddess of love
23, 24, 25 Jan 6:30 to 8:15pm
Enjoy a glass of champagne and nibbles while observing the setting Sun and telescope viewing of Venus (weather permitting) whilst listening to live music in our gorgeous marquee.visitors
Cost: $35 per adult $32 concession and $30 members.

Telescope Express, viewing only
12, 14, 19, 22 Jan 9:30 to 10:30pm.
Telescope viewing only weather permitting, wet weather option is 3D Space Theatre and planetarium. Tickets are limited. This suits adults and high school students and older.
Cost: $50 family, $18 adult, $14 concession; Powerhouse members $43 family, $16 adult, $12 concession.

Dreamtime Astronomy : planetarium and telescope tours
7:30 to 8:30pm, Tuesdays, Fridays and Saturdays
Hear stories written across the Australian sky as out Aboriginal Guides share their cultural astronomy under the virtual night sky in the planetarium. Then view objects through the telescope.
Cost: $50 family, $18 adult, $12 child; Powerhouse Members $43 family, $16 adult, $11 child.
BOOK NOWRomantic sunset photo Geoff Wyatt

Celestial Night Tour
8:30 to 10pm. Bookings and prepayment required.
View Orion the Hunter, Taurus the Bull and Canis Major the Great Dog and, at the beginning of the month, the Moon (first week of Jan only), amongst other celestial features through telescopes and experience the new ‘Telescopes’ 3D Space Theatre program. Cost: $50 family, $18 adult, $12 child; Powerhouse Members $43 family, $16 adult, $11 child.BOOK NOW! or phone 02 9921 3485 during office hours (8:30am – 4:30pm) to avoid disappointment. Please read our conditions before booking a tour.

Celestial Pizza Nights
12, 14, 19, 22 Jan 7:30 to 8:15pm
These special nights of pizza, astronomy stories and telescope viewing (weather permitting) are especially for young families.
Cost: $30 adult, $27 concession, $25 child (4 years+), $85 family. MAAS members $25 adult, $22 conc, $20 child, $72 family

NASA.GSFC.dmr_4yr_cmb_stereoThe Cosmic Background Explorer (COBE) satellite was launched 25 years ago on 18 September, 1989. It showed that the cosmic microwave background, the cold afterglow of the Big Bang, was not completely uniform. Tiny temperature fluctuations visible in this “map” have grown into enormous galactic structures in the intervening 14 billion years.



COBE made this “map of the early universe” showing tiny variations in the cosmic microwave background. NASA/GSFC




CometSwift.HCR.JS. 1892Comets like C67P/Churyumov-Gerasimenko formed in the frozen outer regions of the solar system. Virtually unchanged for over 4.5 billion years they provide clues about the formation of the solar system.

In 1892 Henry Russell and James Short photographed Comet Swift from Sydney Observatory.





Daily cosmobite: Philae falls for comet 67P/Churyumov-Gerasimenko

Published by Andrew Jacob on November 12, 2014 1 Comment

Philae.on.67PIf all goes to plan the Rosetta spacecraft will release its comet lander Philae just after 8pm (AEDT) tonight. Philae will hopefully make the first ever landing on a comet (67P/Churyumov-Gerasimenko) in the early morning hours of Thursday November 13 AEDT. Follow the ESA landing webcast.


How Philae should look after it lands on comet 67P/Churyumov-Gerasimenko. Image © ESA.






Harry ponders the X3 flare from sunspot group AR12192

Published by Andrew Jacob on November 11, 2014 No Comments

x3flare_composite. HarryRobertsThe GOES X3.1 flare of October 24, 2014. Sketch and copyright Harry Roberts ©, all rights reserved.

       As AR12192 crossed the Sun in the second half of October, it not only grew unusually large, but it hosted six GOES class-X flares, the strongest class; the writer logged one of the six. As well, an M8.7 flare was logged on Oct. 21st. This is an account of the X3.1 flare of Oct.24th.

The writer aims to log as much detail as possible of the spot group hosting the flare, hoping to understand the context of these energetic events. Detail of the group’s umbrae and penumbrae and the heliocentric coordinates of major features are recorded. As well, Mt. Wilson’s daily magnetograph data is sampled and added to the sunspot sketch (Fig1). The writer’s sketch is made ~5 hours after Mt Wilson’s worker completes theirs (also in pencil), adding one more to their vast archive. Now mostly digitised, it may be browsed at leisure: a treasure trove! There you will find the biggest spot yet recorded, in April 1947, and twice the area of 12192; the second biggest was in late Jan. 1946. Yes, the biggest spots in 140 years are concentrated around the mid-20th century – but why?

X3.1 flare. With complex spots like 12192 it helps to have the WL sketch ready when a flare erupts: flare ribbons can then be mapped with some accuracy. Since flares change rapidly, transparent overlays record flare motions relative to the more-or-less ‘fixed’ sunspots. Other transients like surges and filaments can be similarly logged.

However, at times of high activity, flares may erupt before the WL sketch is done, thus the X3.1 peak went unnoticed (in H-alpha) and its initial stages missed. Fig 2 shows the flare ~40m after its peak when it had faded to X1.1 but was still large and bright, visual class 2b. This was the biggest of the six X-class flares.

  1. Big surges had been ejecting from the group’s dominant (f) spot (at –13,242) from the 22nd, and on the 23rd some reached a point 30º lat south of the group – before retracting to their start point –a distance of 370Mm! We noted that the surges emerged (as they do) from the margins of the big (f) spot– and magnetograph data show a curious ‘collar’ of opposite polarity around the big spot’s penumbra– this seemed to promote surging.

Flare geometry. The X3 flare did not much involve the big (f) spot but erupted mainly along a ~N-S line, from the tangle of ‘red’ (p) spots at -10,251, southwards to –25,247. The SDO HMI magnetogram was used to (roughly) plot the group’s inversion line – the boundary between unlike polarities. Its complex windings are mapped as blue lines x-x’ and y-y’. Note the cluster of opposite polarities within the big (f) spot on its west side – one of R18 polarity – line x-x’ winds around it (arrow). Minor flare ribbons traced the gaps between umbrae and the ‘light bridge’ of the big (f) spot (Fig2).

Perhaps the flare arose on the N and W margins of line y-y’ and, as events proceeded, spread away from there. The Oct. 21st M8.7 flare developed toward this region too, SW of the group – where surges also were targeted.

There seems no doubt that AR12192 reached its huge size by a fusion of multiple groups that began back in Sep. when the group was AR12172,  and when 12173 emerged nearby – and merged in some way during its far side transit. It has hosted some amazing H-alpha transients – and may well have more on its mid-November return.

Harry Roberts is a Sun and Moon observer, a regular contributor to the Sydney Observatory blog and a member of the Sydney City Skywatchers.

HWDomeDemolition1986.NLThe brick building under Harley Wood’s dome was demolished in 1986. The copper dome and Melbourne astrograph were intended by Macquarie University to continue their scientific work. However, this never came to be. The copper dome and astrograph were returned to the Powerhouse museum in 2008.


The demolition of Wood’s Melbourne astrograph building. Photo by Nick Lomb, ©MAAS.





HWDomeRemoval1986.NLHarley Wood was the NSW Government Astronomer from 1943 to 1974. The dome he constructed was removed in 1986. The dome and Melbourne astrograph (and many other items) were rescued by Alan Vaughan and Macquarie University.



Wood’s dome being removed in 1986. The Melbourne astrograph is revealed and awaits removal. Photo by Nick Lomb, ©MAAS.






Harry observes the emergence of a Great Sunspot AR12192

Published by Andrew Jacob on November 8, 2014 No Comments

Sunspot AR12192 copyright by Harry Roberts
Emergence of a Great Sunspot AR12192. Sketch and copyright Harry Roberts ©, all rights reserved.

What is it that causes some spots to grow very large? All are shaped by magnetic fields – stronger fields make bigger darker spots – but is this the sole reason? Why is the Sun’s magnetic flux so unevenly distributed?

Return of AR12172?  It seems that 2192 (shorter #) was the return of 2172: the coordinates of the two groups show that the (p) spot of 2172 was at –11,242 and the huge (f) spot of 2192 is in the same place, at –13, 242.

However, the polarities of the two spots are opposite: the former (p) spot was red 2400G (R24) and the huge (f) spot now at the same site was violet 2700G (V27). How to explain the changed polarities? It seems some curious sunspot motions have taken place and/or new flux has emerged within the remains of the old 2172 bipolar group. More study is needed.

Indeed, as 1272 transited the western hemisphere, back in late September, we saw new flux emerge ‘ahead’ and south of the (p) spot, peppering a vast area with minor spots. Was this the genesis of 2192?

In any event, Oct. 15 showed no sign of the old group yet, but GOES reported strong flares just behind the eastern limb at 10ºS. As well, in H-alpha there were sure signs of an active group approaching (Fig1) with surges and post flare loops above the limb.

12192 emergence. Oct. 17 (Fig2) saw a big new group rounding the limb and it seemed unusually ‘bulky’: Helio freeware gave the newcomer an unlikely area of 1700 units! Surely, I had made some mistake?

The new group seemed to have minor (p) spots scattered over a large area some 8º ahead of the dominant spot, the latter sited at –13,242. In H-alpha bright plage and dark surges on the disc with a few bits above the limb, were minor signs of activity.

Area. Next day the real bulk of the newcomer was obvious (Fig3): this time ‘helio’ gave the area as 1900 units. Again I doubted my maths as NOAA had it at just a few hundred units. However, by the 20th NOAA and I were in agreement with an area of just on 2000units. Clearly this was a giant sunspot (Figs 4 and 5) and its area peaked, it seems, at 2740 units on 23rd at 2400UT – followed by a slow decline as the penumbrae of the (p) spots began to fragment

12th Biggest? How does this group compare with earlier sunspots? According to the assiduous J. Janssens, this is the 12th largest sunspot since area records began in 1874: it’s really big!

Interestingly, his data show that the biggest sunspots for the period occurred in the mid 20thC and also that 2192 was bigger than any SC23 spots. (Caution: the data are sorted by Greenwich Area not NOAA Area.)

Delta  class. A very complex inversion line, the boundary between spots of opposite sign, is added in blue Fig4: source SDO.  The group is of Hale Delta class, with spots of opposite sign in the same penumbrae; a merging of multiple spot groups perhaps.

  1. Despite its apparent magnetic complexity it did not host record flares. GOES X-class flares began, it seems, with an X1.1 Oct. 19, 05:00UT, for a total of six during disc transit. The writer logged an M8.7 and an X3.1 (more on these shortly). Surprisingly it is reported that no CME’s resulted from any of these flares. Why?

Surges. These relatively ‘cool’ jets of material that emerge from dominant spots began to appear in numbers from the big (f) spot on the 22nd. Some reached enormous lengths (23rd) before recoiling back to their starting points. More on these when we examine the group’s transit of the Sun’s western hemisphere.

This group will return after its transit of the far side: anyone with a solar telescope should look for it at the Sun’s following (i.e. eastern) limb around November 12th. Clear skies!

Harry Roberts is a Sun and Moon observer, a regular contributor to the Sydney Observatory blog and a member of the Sydney City Skywatchers.



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