The Sun and auroras for beginners

22/01/2012

Pick of the pics

Our Explosive Sun by Pål Brekke

In “Our Explosive Sun”, the picture has this caption. “A unique image of the planets close to the Sun observed with the LASCO telescope on SOHO. An occulting disk inside the telescope blocks the bright light from the solar disk creating an artificial solar eclipse. Mercury, Venus, Jupiter, Saturn, and the Pleiades are visible. Just outside the occulting disk one can see enormous ejections of gas from the hidden Sun. The horizontal streaks from the planets are artifacts from the digital camera (ESA/NASA).”

It’s one of my favourite images from the Space Age. The Large Angle and Spectrometric Coronagraph (LASCO) took it on 15 May 2000. Four planets and the Pleiades star cluster were almost in line with the Sun – which chose this theatrical moment to blast off a huge puff of gas in a coronal mass ejection (CME). So I’m not surprised to find the picture in Our Explosive Sun by Pål Brekke, a colourful book that’s just been published by Springer.

Pål Brekke (NRS)

Pål (pronounced Paul) is a Norwegian solar physicist who worked in the SOHO team for more than a decade, latterly as Deputy Project Scientist. We’ve known each other well from the time when I was writing a lot for the European Space Agency. Pål’s now a Senior Advisor at the Norwegian Space Centre.

Let’s be clear that Our Explosive Sun is a book for beginners, be they amateur astronomers, aurora watchers, high school students, or interested non-experts of any description. There’s plenty of elementary information about our mother star and the Solar System, and about how to observe the Sun safely or photograph the Northern Lights. Making the book distinctive are a mass of extraordinarily vivid and up to date illustrations, plus the occasional insights you get only from a true expert.

For example, in warning of the dangers that solar explosions will pose to astronauts flying to the Moon or Mars, Pål reminds us that the lunar flights of Apollos 16 and 17, in April and December 1972, were lucky to miss a big burst of deadly solar protons in August of that year. And in explaining the distances of stars, he notes that in about 40 years time an astronomer with a supertelescope on a planet in the Pleiades star cluster might in principle see Galileo turning his own telescope on the Pleaides for the first time, from a distance of 440 light-years.

It’s a pity perhaps that Pål doesn’t mention cosmic rays, which provide one of the great markers of solar variations both currently and in the past. And his remarks on solar activity and climate change are brief and rather cautious, e.g.: One thousand years ago, it was warmer on Greenland than today. … Human-driven climate change will work in addition to natural climate variability mainly caused by the Sun.

References

Pål Brekke, Our Explosive Sun: A Visual Feast of Our Source of Light and Life, Springer 2012. [Hardcover]

Amazon UK: http://www.amazon.co.uk/Our-Explosive-Sun-Visual-Source/dp/146140570X


Kennelful of Pluto puppies

13/09/2010

Pick of the Pics and Updating Magic Universe

A kennelful of Pluto puppies

Three successive images from the Hubble Space Telescope show two remote objects in the Solar System inching across the sky in front of a distant galaxy (bottom left of each image). The near-vertical streaks are due to the objects moving while Hubble was watching. They are small “trans-Neptunian” objects – comets or asteroids – orbiting the Sun at about 43 times farther out than the Earth. They appear to be companions, at about half the separation of the Earth and Moon. Credits: a negative version of part of Fig. 3 in Fuentes et al., Astrophysical Journal (see references); imagery from HST/ACS/WFC

Soon to be published is the discovery of 14 new members of the Solar System in the so-called Kuiper Belt beyond the most distant “real” planet, Neptune. They are 40-100 km leftover scraps from the building of the Sun’s family of planets. To find them, a team from the Harvard-Smithsonian Center for Astrophysics and Northern Arizona University, led by Carlos Fuentes, trawled through existing images from the Hubble Space Telescope.

As Halley’s Comet and 15 other regular visitors came from the trans-Neptunian Kuiper Belt, I suppose I should be updating my Comets book, but although it mentions “Halley-class” comets orbiting not far beyond Neptune, it doesn’t name the Kuiper Belt. That important feature figures in Magic Universe, which was written two decades later and is more receptive to updating on this point. Here’s the most relevant section in the story called “Comets and asteroids: snowy dirtballs and their rocky cousins”.

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superatomic circus

18/08/2010

Pick of the pics and Updating Einstein’s Universe & Magic Universe

Seeing the superatomic circus

When ultra-cold rubidium atoms club together in the superatoms called Bose-Einstein condensates, they usually make untidy crowds, as on the left. But a team led by Stefan Kuhr and Immanuel Bloch at the Max-Planck-Institut für Quantenoptik in Garching, Germany, brings them to order in a neater pattern, as seen in the middle picture. With more rubidium atoms the superatom grows wider (right). Criss-cross laser beams create a lattice-like pattern of pools of light where the atoms like to congregate. When the laser light’s electric field is relatively weak, the atoms jump (by quantum tunnelling) from one pool to another, creating the usual disorder. A stronger field, as in the central and right-hand images, fixes them in the novel state of matter called a Mott insulator. But atoms can be lost from the condensate, which explains the ring-like appearance on the right. Images from MPQ.

[You're recommended to click on the images for a better view]

Single atoms are located at the sites indicated by circles. Fig. 3 in Nature paper, Sherson et al. see ref.

What’s new here, in an advance online publication in Nature,  is not the creation of these kinds of  superatoms but the German team’s success in imaging them, with a specially developed microscope that picks up fluorescence from the atoms caused by the cooling process. In the image on the right individual atoms are pinpointed.

It’s exciting stuff, because we’re probably seeing the dawn of a new technology – after electronics comes “atomics”. If individual atoms in a superatom can be manipulated, they might be used to carry “addressable” information in an atomic computer.

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Misleading meteor photo

14/08/2010

Pick of the pics

Misleading use of a meteor photo

British newspapers today print a Reuters photo of Stonehenge that includes a single meteor from Thursday night’s Perseid shower. Some papers convey the impression that every streak in the photo is a meteor, when in fact all bar one near-vertical streak are just stars inching across the sky as the Earth turns during a long exposure of the camera.

As the photo is copyrighted I’ll not post it here, but you can see a typical offender at http://www.mirror.co.uk/news/weird-world/2010/08/14/stone-me-what-a-weird-shower-115875-22486527/

The Guardian has it correctly captioned at http://www.guardian.co.uk/science/gallery/2010/aug/13/perseid-meteor-shower#/?picture=365714247&index=5

A big meteor shower is well worth watching, and it’s nice to know you’re flying through the dust trail of a comet – Comet Swift-Tuttle in the case of the Perseids. The best I saw was from a small boat at sea — again the Perseids, which come conveniently in the summer sailing season. But you’re lucky if you spot one or two shooting stars every few minutes. Journalistic hyperbole can leave non-astronomers feeling disappointed.


Pretty magnetic monopoles

05/08/2010

Pick of the pics

A pretty magnetic pattern is pretty surprising too

Against the rules, triplets of magnetic north poles (bright points) and south poles (dark points) chum together with amazing regularity on small islands etched in a honeycomb pattern on an iron surface, using an electron beam. Hartmut Zabel at the Ruhr-Universität Bochum calls it a new magnetic order. The polarities are revealed by a magnetic force microscope, and the 20-micrometre scale line tells us that the width of the picture is about the average thickness of a human hair. Credit: RUB

Who’d have thought it? In kindergarten science you learn that like magnetic poles repel each other. Yet here we see energetically unfavourable triplets of poles occurring not just once or twice by mistake but all across a specially prepared iron surface, when subjected to a magnetic field.

The so-called “magnetic monopoles” created in this pattern are not to be confused with hypothetical fundamental particles of that name. And be wary of attempts to explain the phenomenon to you by reference to “spin ice”, and an analogy with water ice. They may be helpful for experts but can baffle non-physicists. All you really need to know is that the exposed north or south poles belong to atoms that can face one way or the other on the lattice surface.

Watch out for novel information-storage devices exploiting this “new magnetic order”. Prof. Zabel points out that “each node point has eight possible dipole constellations – far more than with conventional storage techniques based on two states”. The islands in the experiments were 3 micrometres long, but they might be made ten times smaller.

References

Alexandra Schumann, Björn Sothmann, Philipp Szary and Hartmut Zabel, “Charge ordering of magnetic dipoles in artificial honeycomb lattices,” Applied Physics Letters, Vol. 97, 022509 (2010). doi:10.1063/1.3463482

RUB press release: http://www.alphagalileo.org/ViewItem.aspx?ItemId=82499&CultureCode=en

For a relevant report last year from Helmholtz-Zentrum Berlin für Materialien und Energie see http://www.sciencedaily.com/releases/2009/09/090903163725.htm


Greenland bedrock

04/08/2010

Pick of the Pics and Climate Change: News and Comments

A drill reaches bedrock under the Greenland Ice Sheet

Dorthe Dahl-Jensen of the Niels Bohr Institute in Copenhagen holds up in triumph the last ice core drilled to a depth of 2537.36 metres at the deep drilling site NEEM on the Greenland Ice Sheet. The core contains rocky debris from a land surface corresponding with the Eemian interglacial period, which was warmer than now about 120,000 years ago. Clues in the ice and the bedrock are expected to give new information about climate change during that warm time, the extent of the residual ice sheet, and in the onset of cold conditions that led to the growth of the present ice sheet. The bedrock material may also include traces of much older life and associated climatic events. Credit: NEEM

Bedrock was reached on 27July, but in company with the American media I’ve just caught up with the news today. Under Danish-US leadership, the North Greenland Eemian Ice Drilling project, NEEM, has kept 300 scientists from 14 countries busy over the past five years. The drilling itself started in June 2009 and proceeded rapidly to its conclusion. It’s striking that they know the depth to within a centimetre.

The first results may be published later this year. Meanwhile you can see more pictures and information at http://neem.nbi.ku.dk/


Mirror image molecules in Orion

31/07/2010

Pick of the Pics and Updating Magic Universe

Mirror-image molecules sorted in the Orion Nebula

But Pasteur’s hope for a cosmic driver comes true only locally

A predominance of either left-handed or right-handed versions of molecules is likely within huge dust clouds imaged by Japanese astronomers. The electric field of light rays coming from the clouds corkscrews to the left or corkscrews to the right, with “circular polarization”. The different kinds of clouds are clearly distinguishable in a massive star-forming region within the Orion Nebula, called BN/KL. Yellow denotes left-handed light, and red, right-handed. The largest yellow and red features are about 100 times wider than the Solar System, and the astronomers suggest that the polarized light will favour the formation of left-handed or right-handed molecules. The conspicuous dots left of centre near the bottom are bright young stars of the Trapezium group — strong winds  from which have helped the astronomers by blowing away dust that otherwise would obscure the BN/KL region of interest. Credit: Near-infrared (2.14 μm) image with the SIRPOL polarization instrument, NAOJ.

On seeing this report by Tsubasa Fukue and Motohide Tamura of the National Astronomical Observatory of Japan (with colleagues in Japan, UK, Australia and USA) my mind went straight back to Louis Pasteur.

Alanine, an amino acid, has mirror-image forms. L (laevo) rotates the electric field of light to the left and and D (dextro) to the right. Image NAOJ.

Although immortalized for the germ theory of disease, Pasteur’s initial claim to fame came from a discovery he made as a young student – namely that molecules from living sources have effects on the polarization of light, but the same molecules made synthetically do not. This is the phenomenon of chirality, or handedness. Chemists had to learn to think three-dimensionally about versions of molecules that are mirror images of each other. In the example shown here, every amino acid molecule in living things on Earth is of the left-handed (L) kind.

Molecular handedness is a fundamental feature of life and Pasteur suspected that some fundamental feature of the Universe was responsible for it. The phenomenon has been both a puzzle and a spur for investigators of the origin of life. The fact that carbon compounds in meteorites show the same bias in handedness as that seen on Earth suggests that some physical process was at work throughout the Solar System, at least.

The astronomers now offer an answer. Circularly polarized light pervading the dust cloud in which the Sun and its planets were born would have prompted our molecular bias. The scenario is made convincing by the sheer size of the clouds in Orion possessing one polarity or the other. But it ‘s not the Universe-wide mechanism that Pasteur expected. It seems that if the Solar System had originated in a cloud with the opposite kind of circularly polarized light, all our amino acids would be dextro.

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