Archive for 2014

Harry watches and ponders a long-lived filament on the Sun

Published by Nick Lomb on September 2, 2014 No Comments

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A long-lived filament progressing across the Sun. Sketch and copyright Harry Roberts ©, all rights reserved

While a ‘prominence’ is “a bright feature seen above the Sun’s limb in a strong chromospheric spectral line” (H-alpha in our case)”,…a filament is a similar feature projected as a dark, usually elongated structure on the disc”.

“The filament-prominence configuration contains relatively dense and cool (5,000

These quotes are from Solar and Stellar Magnetic Activity by Schrijver and Zwaan (2008), page 196 – a valuable text for students of our star.

They add: “all filaments reside over zones of polarity inversion, between two strips of (dominant) opposite polarity”, the filament channel.

The Sun has two kinds of filament: those within active regions like sunspot groups; and those in quiet regions: “over polarity inversion zones between weak magnetic network” (P197). The latter are called quiet region filaments (QRF) from Zirin’s usage in Astrophysics of the Sun. The fields that form QRF are ‘weak’, about 5 – 10G or <1% of sunspot umbral fields. Yet these weak fields are able to form long-lived filaments of great length.

We know that the Sun’s radiative zone rotates as a solid body (Zirker et al), while the convection zone, the upper third of the solar radius, rotates differentially. The magnetic shears or twists of this zone cause not only sunspots but also the streaks or plumes of ‘old’ magnetic flux in the wake (i.e. eastwards) of sunspot groups. It is there, that the inversion boundaries between flux of opposite ‘sign’ give rise to the QRF. Yet not all such boundaries (or channels) host a filament: for unknown reasons.

What is the role of filaments? Schrijver and Zwaan suggest that: ”filaments probably indicate zones that are important in the flux removal from the solar atmosphere and in processes in the solar dynamo mechanism”. P198.

Filaments as markers. “Filaments are a good way to measure the rotation (of the Sun) because they are long-lived (my emphasis). However, it is difficult to measure their position when they are not on the meridian because we do not (accurately) know their height” Zirin: P116.

Currently most filaments seem faint and indistinct in comparison with those of SC23. Positional timings of a given filament can be made only if it has a well-defined point that can be timed.

On July 31 a dark QRF at the sun’s NE limb was logged, and on August 1 its preceding (p) end was used for a timing. Helio freeware sited that point at +10,229(Fig).

This filament proved to be long-lived, and was logged several times until it was no longer visible on Aug 8, when about 55ºW of the central meridian (CM). However, it survived, to become a tall prominence at the western limb on Aug 10 (Fig, rhs). The Figure shows some of the timed logs as well as the ‘untimed’ one of July 31; all other detail is omitted for clarity.

Zirin’s caution (above) applies, it seems, to the logs of Aug 6 and 7. In both cases the filament is inclined to our line-of-sight by >40º and it seems that the darker upper parts of the filament were logged, rather than the ‘foot-points’ at the surface. Perhaps only the logs between ±30º of the CM are reliable.

Filament’s Return! On Aug 24 it was good to see, after the filament’s two weeks behind the Sun, that the foot-points of a big prominence at the eastern limb agreed closely with those of the filament three weeks earlier (Fig).

At the west limb on the 10th and the east on the 24th, we see the filament projected against the darkness of space: as a prominence. The longitudes of the ‘foot-points’ are in fact those of the limbs, not the filament; the full longitude extent of the filament is actually >20 degrees.

Rain prevented views of the returned filament on the disc until Aug 30UT, when its west and east foot-points showed it remained at the same longitude (Fig, in red) as its earlier rotation, but had migrated somewhat to the north. Various authors note the slow migration of QRF’s towards the relevant pole, citing the meridional current as the cause.

Will the long-lived filament complete another transit of the Sun? We hope to find out soon, clear skies permitting!

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

2_Tarantula_X-ray_optical_infrared_NASAA group of astronomers suggest that a star in a cluster of stars inside the Tarantula Nebula is the most massive known. The star, R136a1, weighs in at 265 times the mass of our Sun.

A composite image of the Tarantula Nebula. Courtesy X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al

I was fortunate enough to attend this year’s Women in Astronomy workshop (WiA2014) held in Canberra at the ANU and themed ‘We are all made of stars’. Professor Brian Schmidt, Nobel prize winner, and one of Australia’s most distinguished astronomers, set the scene with the aim of the conference to ‘ensure astronomy is a vibrant field in Australia’ which he described as engaging a diverse range of the population in STEM (Science, Technology, Engineering, Maths). Senator Michaela Cash, Minister Assisting the Prime Minister for Women, was enthused about astronomy following a Queen concert where guitarist Brian May presented astronomy, as well as ‘We will Rock You’. Cash launched the conference committing to an educational focus on STEM subjects. There were 100 of the leading male and female astronomers working in Australia at the workshop. Concern about the declining percentage of students, and specifically girls, who take ‘hard science’ subjects at school is why this conference/workshop is particularly relevant. The full program is available online. Many of the presentations were inspiring, in this blog I have recounted just a few.

The Astronomical Society of Australia (ASA) is pro-active in pursuing diversity and gender equality in astronomy and in 2011 the Women in Astronomy Chapter instigated what has now become an annual workshop to examine the root cause of the problem and devise ways of dealing with it. Professor of Astrophysics at Swinburne University, Sarah Maddison, demonstrated current statistics which show that in Australia 74% of ASA members (predominantly astronomers) are men. The most senior levels of astronomy in Australia are dominated by males. Some actions have already been instigated to provide more role models to inspire young women to not only begin, but to pursue physics and astronomy. At the conference Dr Renu Sharma of announced one of these actions, the ICRAAR Visiting fellowship for Senior Women in Astronomy, which has been awarded to astrophysicist Dr Andreea Font.

Dr. Andreea Font

Dr. Andreea Font, recently awarded the ICRAR Visiting Fellowship for senior women in astronomy.

Many of Australia’s leading astronomers, male and female, were at this conference and they are all in agreement that change is required to make astronomy more gender inclusive. They see 74% of the solutions as coming from men. Breaking down the culture of difference was the essence of the moving and very pertinent inspirational personal story presented by Dr. Minh Huynh. Huynh described how Australia’s demographics had changed over the past century, and  the recent greatest increase in immigrants is from India and China. Huynh described the micro-inequities she had experienced since arriving in Australia in 1978 at the age of 8 with her parents as a refugee after travelling by boat from Vietnam to Indonesia. Growing up in Western Australia, Huynh completed her doctorate and then worked in the US at Caltech’s Planck Observatory and is now the Deputy International Square Kilometre Array Project Scientist at UWA. Huynh quoted American children’s rights activist Marian Wright Edelman: “You can’t be what you can’t see” and her presentation encouraged discussion about representation of women and different cultures, at all levels and in many forms.

Dr. Minh Huyh

Dr. Minh Huyh, ICRAR, University of Western Australia.

Later Malcolm Fiahlo, Equity and Diversity Officer for UWA, described race bias as the ‘Bamboo Ceiling’ and that in Australia accent and skin colour were key determinates which create cultural distance, which we must recognise and combat. His ‘Citizens of the Globe’ construct has had impact on UWA culture at all levels of the organization. He advocated ‘Courageous Conversations’ to create cultural competence citing Chinese proverb: A fish is the last one to know what water is. You can download his powerpoint.

Dr Cordelia Fine  described how neurosexism (the determined effort to find evidence for undermining the intellectual powers and abilities of women) has influenced what we perceive women are good at and why.  Fine quoted George Romanes, who in 1887 submitted a paper about the differences between male and female brains.  She critiqued and disproved his arguments, and very recent studies since, as fundamentally flawed. The only achievements of these unscientific studies, according to Fine, were to further encourage stereotyping. Fine’s position was that so far there are remarkably few proven differences between the male and female brain and that environmental forces such as the influence of role models, and stereotyping, have far greater impact.

The issues discussed extended beyond the male female divide and race discrimination to include LGBTIE.  An inspirational story was presented by Dr. Lisa Harvey-Smith, Project Scientist for the SKA pathfinder telescope and research astronomer at CSIRO’s Astronomy and Space Science Division in Sydney. Harvey-Smith’s presentation titled ‘Prop open that closet door’, chartered her childhood where she felt ‘one of the pack’ through to teenage years and adulthood, when prejudices took many forms, were hurtful and isolated her.  She described many ‘horrible’ comments made by adults and the impact of news-media, mainly tabloid, language. Jokes and other popular culture forms had proliferated stereotypes and prejudices.  One of the points Harvey-Smith highlighted was the importance of allies, people who did not tolerate homophobic behaviour, and how important it was to have someone to look up to, or follow and who you can relate to. Role models emerged as very important.

Photo: Philip Gostelow.

Dr. Lisa Harvey-Smith at CSIRO’s ASKAP radio telescope. Photo: Philip Gostelow.

There were many workshops on the second day to explore how we can think differently to encompass differences as the norm and encourage flexibility.  Dr. Natalie McDonagh, presented activities, which were focused on mindfulness and cultural change, and really opened up discussion about how to instigate change through creating new narratives.   Elizabeth Broderick, Sex Discrimination Commissioner,  told compelling and atrocious stories of discrimination. Her message was that change must come from the top.  The close of the proceedings by Professor Matthew Colless, Director of the Research School of Astronomy and Astrophysics at ANU, encouraged the participants to come up with real solutions which could be implemented or at least further explored.  Ideas included greater flexibility in terms of the number of papers expected per year during child-rearing periods and targets for employers to get rewards or penalties.

One of the ideas now realised from a previous WiA workshop is the Pleiades Awards for organisations which take steps to further the participation of women and women’s career advancement in organisations. Dr Harvey-Smith launched this program at the close of the WiA2014 workshop.

Vanessa Moss

PhD candidate and Sydney Observatory Guide Vanessa Moss gives ‘thumbs up’ to the 2014 WiA conference.

 

 

 

Daily cosmobite: spring is here!

Published by Nick Lomb on No Comments

1_Spring_Nick LombToday we say good bye to winter and welcome the start of spring. In some countries the tradition is that spring begins at the equinox, which is on 23 September this year. The choice of when to begin the seasons is completely arbitrary and having spring run through September, October and November matches the Australian climate.

Trees wake up and flower in spring. Photo Nick Lomb

Daily cosmobite: Saturn and the Moon

Published by Nick Lomb on August 31, 2014 No Comments

31_Saturn and the MoonAfter dusk each evening we can see the ringed planet Saturn in the north-west sky. After its close approach on Monday and Tuesday evenings the red planet Mars is still above and close by. Tonight the crescent Moon is below and to the left or west of Saturn and so we have an interesting configuration in the sky with two planets and the Moon.

Saturn and the Moon on the evening of 31 August 2014. Chart Nick Lomb

Daily cosmobite: what is the Universe made of?

Published by Nick Lomb on August 29, 2014 1 Comment

29_Ingredients of the Universe after Planck_ESAScientists studying the microwaves left over from the Big Bang have worked out the makeup of the Universe. Only five per cent is ordinary matter like the matter in people, bricks and air. The rest of the Universe is mysterious dark matter or even more mysterious dark energy.

The ingredients of the Universe after Planck. Courtesy ESA and the Planck Collaboration

Daily cosmobite: viewing the Big Bang

Published by Nick Lomb on August 28, 2014 No Comments

28_Planck map of Universe_ESAWe cannot see the origin of the Universe at the Big Bang, but scientists can study its afterglow dating from only a few hundred thousand years after the event. To do so they are using the European Space Agency’s Planck spacecraft that circles the Sun at a distance of 1.5 million km from Earth.

Planck’s map of the Universe. Courtesy ESA and the Planck Collaboration

Daily cosmobite: Mercury and the new Moon

Published by Nick Lomb on August 27, 2014 No Comments

27_Mercury and the new MoonOver the last few evenings the elusive planet Mercury has become visible low in the west after dusk. Tonight a very thin crescent Moon can be seen above and to the left or south of the planet. This is the first opportunity to see the crescent after the instant of new Moon that occurred just after midnight on Tuesday morning.

Mercury and a thin crescent Moon on the evening of 27 August 2014. Chart Nick Lomb

To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month. This month’s guide is presented by Geoffrey Wyatt, Sydney Observatory’s Senior Astronomy Educator.

Geoff fascinates us with his guide to the stars and constellations to look out for in September and also with insight into how astronomy was important to the ancient people of Mesopotamia, Greece and Rome.

Geoff tells us where and when to look out at night for the planets Mercury, Mars, Saturn in September. And he points out his highlight for the month, on 1st September when, shortly after sunset, Saturn, the Moon and Mars will all be in the constellation of Libra, with the Moon and Saturn just five degrees (or five pinkie widths) apart.

Listen to the September 2014 night sky guide audio, or read the transcript below.

HEAR THE AUDIO
You can subscribe with iTunes or upload the (34 mins) audio to your iPod or mp3 player, or listen to it on your computer.

SEE THE SKY CHART
We provide an embedded sky map (below) and a September 2014 night sky chart (PDF) which shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.

September 2014 night sky chart

BUY THE BOOK
Our annual book, ‘The 2014 Australasian sky guide’, by Dr Nick Lomb has more information and star maps for months from December 2013 until December 2015 inclusive (or wait till November when you can purchase the 2015 book), plus information about the Sun, twilight, the Moon and tides, and a host of other fascinating astronomical information. You can purchase it ($16.95) at Sydney Observatory and Powerhouse Museum shops or other good bookshops, or online through Powerhouse Publishing (additional packing/postage costs apply).

READ THE TRANSCRIPT (after the jump)

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Daily cosmobite: a famous cluster

Published by Nick Lomb on August 26, 2014 No Comments

26_Core of Omeg Centauri_HubbleThe constellation of Centaurus the Centaur contains the two pointer stars to the Southern Cross as well as Omega Centauri, a famous cluster of a million or so stars. From a dark sky the cluster is easily visible to the naked eye, while through binoculars it looks like a fuzzy blob.

Hubble Space Telescope image of the central parts of Omega Centauri. Photo courtesy NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

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