MRI imaging techniques increase understanding of the Sun's interior plasma motions and convection currents
Scientists from NYU's Courant Institute of Mathematical Sciences and its Department of Physics, Princeton University, the Max Planck Institute, and NASA, have come together to produce MRI images of the Sun's internal plasma motions which significantly increase our understanding of how convection currents progress from deep within its structure to the surface. As the Sun is opaque, this convection is not normally observable. It also poses significant questions regarding our understanding of sunspot formation and magnetic field generation.
The research, undertaken from images taken from a 16-million pixel camera, produced readings which seemed to show that "convective velocities are 20 - 100 times weaker than current theoretical estimates
." (1) This was done by deducing the motion of the hidden plasma currents beneath the surface of the Sun from the images of movements from its surface. Shravan Hanasoge, an associate research scholar in geosciences at Princeton University and a visiting scholar at NYU's Courant Institute of Mathematical Sciences, said the results that if they "are indeed that slow in the Sun, then the most widely accepted theory concerning the generation of solar magnetic field is broken, leaving us with no compelling theory to explain its generation of magnetic fields and the need to overhaul our understanding of the physics of the Sun's interior
For more information, click here
.(1) Anomalously Weak Solar Convection, Shravan M. Hanasoge and Thomas L. Duvall, Jr. and Katepalli R. Sreenivasan, 14/06/2012.
Dark matter structure observed for the first time as scientists discover a dark matter filament between two clusters of galaxies about 2.7 billion light-years away.
Jörg Dietrich: physicist
For something that makes up an estimated 84% of the universe (1), dark matter is a pretty elusive substance: until now, that is. Scientists have observed a filament of dark matter connecting galaxy clusters Abell 222 and Abell 223, almost 2.7 billion light-years away. The presence of dark matter has been detected by monitoring the way large clumps of it, located in galaxy clusters, bend light. This phenomenon is more difficult to observe with the filaments which are thought to connect the various clusters, much like a spider's web, as they have a much smaller mass.
The observation published in Nature Magazine this week - which was made by Jörg Dietrich
, a cosmologist at the University Observatory Munich in Germany, and his colleagues - was of a massive filament which was "oriented so that most of its mass lies along the line of sight to Earth
." (2) In the published Abstract
we are told that "[i]t is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments
." (3) Dietrich goes on to say that the discovery "'is the first time a dark matter filament has been convincingly detected
" and that it is "a resounding confirmation of the standard theory of structure formation of the universe...and a confirmation people didn't think was possible at this point.
" (4)(1) Wikipedia(2) Dark matter’s tendrils revealed, Nature Magazine, Zeeya Merali, 04/07/2012.
(3) A filament of dark matter between two clusters of galaxies, Nature Magazine, Jörg P. Dietrich, Norbert Werner, Douglas Clowe, Alexis Finoguenov, Tom Kitching, Lance Miller & Aurora Simionescu, 04/07/2012.
(4) The skeleton of the universe? Cosmic web of mysterious 'dark matter' detected holding two galaxy clusters together, Daily Mail, Rob Waugh, 05/07/2012
Picture showing the dark matter filament between two galaxy clusters
Transit of Venus 2012
Image (c) O. Toumilovitch
The May edition of Physics World
will lead with a fascinating story about the transit of the planet Venus across the disk of the Sun, which is to occur on the 5th or 6th (depending on your time zone) of June this year. Transits occur in pairs separated by eight years, with the gap between pairs of transits alternating between 105.5 and 121.5 years. The last transit, the first of the pair to occur in our lifetimes, was in 2004. The earliest recorded transit was in 1639. The following transits were recorded in pairs: 1761 and 1769, and 1874 and 1882. The pair of transits will not occur again until 2117 and 2125. The transit will take approximately six hours, and viewers will see a small black dot passing slowly across the face of the Sun. Venus has been the brightest star in the sky for most of March, and has been in a visible conjunction with Jupiter recently as well. In the picture below, Venus is to the left of the Moon, with Jupiter below it.
Conjunction of Moon, Venus & Jupiter with clouds © Steve Crane
Normally, when Venus passes between the Earth and the Sun, it does so either above or below the Sun, thus passing unnoticed. However, during these transits, Venus crosses the ecliptic, the plane the apparent path of the Sun across the celestial sphere as seen from the Earth. When this happens, an occultation of the Sun occurs - an occultation being the process where one object is hidden by another object by passing between the first object and the observer, much like the process of a solar eclipse. Eclipses, transits and occultations occur at times of syzygy, when three celestial bodies, such as the Sun, Earth and Venus, are configured in a straight line. In the case of a solar eclipse, the Moon, as seen from the Earth, is the same size as the Sun, and so totally obscures the Sun from the point of view of the Earth. In the case of the Sun's occultation by Venus, only a tiny part of the Sun's disk is obscured as Venus, though bigger than the Moon in reality, looks much smaller when viewed from the Earth.
The first person to predict a transit of Venus was the mathematician, astronomer and astrologer Johannes Kepler. In 1627 he made some predictions relating to transits that would occur in the 17th and 18th Centuries. His first prediction was for the 1631 transit. Unfortunately, as the tables he used to make the prediction contained inaccuracies, he did not realise that the transit would not be visable from mainland Europe. Because of this, the first transit of Venus to be predicted went unobserved. Kepler also predicted that there would be a "near miss," i.e. that Venus would pass close to the Sun without causing an occultation, in 1639.
In the early to mid 1630’s, astronomer Jeremiah Horrocks believed that Venus, instead of passing the Sun, would indeed make a transit. Horrocks believed there to be inaccuracies in the tables used by Kepler to predict the 1639 “near miss,” and had started to make observations of his own. He entered into correspondence with another English astronomer, William Crabtree, and the two of them became, on 4 December 1639, the first recorded people to observe a transit of Venus. For Horrocks, it was nearly a disaster, as the transit, due to start at 3pm, was obscured by cloud. It cleared at 3:15pm, allowing Horrocks to view it for a further half hour until sunset. Horrocks and Crabtree managed to view the transit by focusing the image of Sun through a telescope and projecting it onto a piece of card. They could then watch the little black dot that was Venus make its way across the card. Horrocks died only a couple of years later in 1641. He was only 22 years old.
Andrea Wulf, Author
The transit has also sparked, in more recent times, the imagination of the author Andrea Wulf whose book, called Chasing Venus: The Race to Measure the Heavens,
is now available. It is an "absorbing account
" of the 1761 and 1769 scientific expeditions to record the exact time and duration of the transits, which occurred all over the world. As Wulf says in an interview with The Wall Street Journal, "this heavenly rendezvous spurred the first international scientific collaboration, laying the foundation of modern science
." (1) Why did this happen? Well, it was all to do with measuring the distance between the Earth and the Sun.
To do this properly, readings had to be taken from both the Southern and Northern Hemispheres, in as many locations as possible. What is so amazing is that this occured during a period of global warfare: the Seven Years War
. "[H]undreds of astronomers from the belligerent nations joined together to plan expeditions to see the transit from India, the Arctic Circle, Siberia, Tahiti, Newfoundland, Baja California and many other places...
" (2) The planning of such a collaboration was all the more difficult as the means of communication available was much slower than today: "a letter posted in Philadelphia took two to three months to reach London
." (3) In the video below, Wulf discusses her book, and gives examples of the personal stories of the astronomers that took part, and also the world leaders, such as Catherine the Great of Russia, who's minds were captured by the idea of "Chasing Venus.
The 1761 transit also provided Russian polymath, scientist and writer, and founder of the University of Moscow, Mikhail Lomonosov, with the conditions to discover that Venus had an atmosphere. He made observations of the physical properties of the planet during the occultation, which were published in his paper The Appearance of Venus on Sun as It was Observed at the St Petersburg Emperor’s Academy of Sciences on May 26, 1761:
"I found a black indentation from the coming Venus, which replaced the former vague spot. I continued to look attentively how the trailing side of the planet approaches the Sun; suddenly, a hair-thin bright radiance (luminescence) between Venus’ trailed side and solar edge appeared that lasted only less than a second.
"Before the Venus ingress, when its front side approached the solar edge at about one tenth of the planet’s diameter, a bulge set up which progressively became more pronounced as Venus came to leave the Sun. Soon after that the bulge disappeared and instead, Venus appeared with no edge. Similar to the ingress phase, the last touch of the planet’s trailing side at the emergence was also accompanied by a small break and solar edge obscuration." (4)
As a result of these observations, Lomonosov concluded that "the planet Venus is surrounded by a distinguished air atmosphere similar (or even possibly larger) than that [which] is poured over our Earth." (5)
The Birth of Venus, Botticelli
The planet Venus has always fascinated us from earliest times. In Greek mythology Aphrodite, who later became Venus in Roman mythology, was a deity associated with beauty, pleasure and sexuality. In her common form, Aphrodite Pandemos, she was born of Zeus and Dione, and was the legendary beauty who provoked wars and constantly cuckolded her long-suffering husband, Hephaestus (Roman: Vulcan). However, in Hesiod's Theogony (circa 700BC), she was born when Cronous (Roman: Saturn) castrated his father, Ouranos (Roman: Uranus), and threw his severed genitals into the sea. From the foam these created, arose Aphrodite Ourania, the Heavenly Aphrodite, fully formed. In this version of the myth, she predates Zeus, and was contemporanious with the Titans. Hers was a more exalted cult, representing the love of body, mind and soul.
This idea of Venus as both a force of attraction, and as one of mind and soul, can be seen in the differing stances taken by exoteric and esoteric astrology. In exoteric astrology, Venus is the planet of love and relationships: "Venus is significator...of all expressions of love, and especially so when it comes to the romantic variety." (6) Here is Aphrodite Pandemos. While in esoteric astrology, the planet is linked to the principle of mind: “[t]hrough Venus [one] comes under the power of the mind, transmuted into wisdom through the instrumentality of love.” (7) Here we have Aphrodite Ourania.
It is perhaps appropriate that this planet, one to which we have ascribed the attributes of mind, relationships, and something deeper, should be the inspiration for science's first global collaboration. Andrea Wulf put's it so eloquently when she says that "[t]he most important result of this effort...was the successful collaboration of an international community of scientists—a precedent that has served humankind well. As we look skyward this June...we might pause for a moment to remember the hundreds of men who watched the exact same spectacle some 250 years ago." (8)
For further information about the transit, see the TransitofVenus.org website.
WARNING: Please remember, if you are interested in the transit:
"Never look at the sun directly, even when something exciting is happening, such as an eclipse. Doing so can cause irreversible damage to your eyesight and even lead to blindness. Several studies also suggest that sunlight exposure is a risk factor for cataracts." (9)
© James Edward Hughes 2012
The Cassini probe has discovered more interesting stuff about Saturn's Moon Titan
. The 3D image of the supposed "Ice Volcano" came from two separate flybys of the Cassini probe. The mountain causing all the excitement is Sotra Facula. It is a circular mountain about 40 miles (70 kilometres) across. These Ice volcanoes, or cryovolcanoes, are important for many reasons. First, they may explain the abundance of methane in Titan's atmosphere, as the volcanoes would release it into the atmosphere. This would replenish the methane lost to the sun, and keep Titan's atmosphere methane rich. Secondly, this source of methane would help fuel Titan's methane-ethane cycle, similar to the hydrologic cycle on Earth.
More info about Sotra Facula and other possible cryovolcanoes can be seen here:BBC NewsNew ScientistThe Daily GalaxyScience DailyNASANature News
Also, check out the video below for more info.
After a journey taking 33 years, and travelling nearly 11bn miles, the Voyager 1 probe is nearing the edge of the solar system. The Low-Energy Charged Particle Instrument has detected a change in the movement of the particles released from the Sun: rather than flowing outwards towards interstellar space, they are instead moving sideways, forming a phenomenon called the Heliosphere, the "bubble" surrounding our solar system. Edward Stone, a scientist on the Voyager project, said:
"We had no idea how far we would have to travel to get outside the Solar System. We now know that in roughly five years, we should be outside for the first time
For more details, please see the BBC article here
An interesting article from Nasa states that Jupiter's southern equitorial belt (SEB) - which interacts with the Great Red Spot - has disappeared!
This is not the first time the browny gas belt has disappeared. Glenn John Rogers, director of the British Astronomical Association's Jupiter Section, says that:"The SEB fades at irregular intervals, most recently in 1973-75, 1989-90, 1993, 2007, 2010. The 2007 fading was terminated rather early, but in the other years the SEB was almost absent, as at present."
The return of the SEB can be rather dramatic, and it's pot-luck as to who sees it first, given that it can be seen easily from earth.
See the full report from the NASA website here
One of the things which most fascinated me as a child was the moon of Saturn known as Titan. Back then, relatively little was know about Titan but, with the Cassini/Huygens mission, far more is known about this enigmatic moon.
Titan, a cold little place at -180C, has many interesting features which make this moon stand out from the crowd. It is bigger than Mercury and Pluto, and it's atmosphere is thcer than that of the Earth. It's core is rock, or possibly a rock and iron mix, its mantle and crust composed mainly of water, and ots surface a thin layer of hydrocarbons. Scientists think that, under the mantle, there may even be an ocean of water and ammonia.
On Earth, the stratosphere is composed of Ozone, and it is this which soaks up the solar radiation. On Titan, the stratosphere is composed of hydrocarbons. This haze, which characteristically surrounds the planet, was originally thought to be made up of lighter hydrocarbons, such as ethane. Since Huygens, however, we now know that there are much heavier compounds there, such as benzene.
This abundence of hydrocarbons is important because scientists now believe that methane plays the role of water on Titan. The temperature of Titan is close to the triple point of methane (the point where the solid, liquid and gaseous phases can co-exist) just as the temperature of Earth is close to the triple point of water.
There is also possibilities of a hydrologic cycle, though one far more extreme than that of Earth's, which has centuries of drought interspersed which massive downpours. Cassini observed areas ofthe surface of Titan darken after clouds passed over, suggesting rainfall. According to Ralph Lorenz and Christophe Sotin of Scientific American: "Titan is to the hydrologic cycle what Venus is to the greenhouse effect: a terrestrial process taken to extremes."
Quasars. When I was young I, along with millions of other kids, looked up at the sky in wonder, and wanted to know more about the universe in which our tiny planet resides. I learned about the solar system, about our galaxy, about stars an nebulae, and even about black holes. But the one thing which captured my imagination was the Quasar. Moving fantastically fast, astonishingly bright, and a long way from the Earth, the mystery of the Quasar was a thing of wonder to me.
More is known now about these illusive objects. Originally known as 'Quasi-steller Objects', Chinese-born US astrophysicist Hong-Yee Chiu shortened the name to the more manageable Quasar. Discovered in the late 1950's using radio telescopes, the first Quasars were thought to be stars. They were later discovered to something very different.
Current thought has it that Quasars have what are called 'Supermassive Black Holes' at their centres. The energy that escapes from the Quasars is generated beyond the event horizon, and is thus able to be expelled. Quasars are small, smaller than the orbit of Neptune, as they are able to shift luminosity levels quickly.
When, in 1963, Maarten Schmidt studied the spectrum of 3C 273 (the first Quasar to be discovered, which can be seen in Virgo) he saw that the spectral lines did not fit with any know substances. The reson for this, discovered some time later, was that there was a large red shift in the spectrum. The substances were actually Hydrogen. This red-shift, as described in the Doppler effect, that the object being observed is moving away from the observer. Given the size of the red shift, it was concluded that these objects must be moving very fast. In fact, 3C 273 was later shown to be over 2,000 milllion light years away, and moving at almost 48,000 km/s.
There are many types of Quasar known to scientists now, the two shown in the picture above fr example, and even double quasars have been seen. There aren't any Quasars near us, which, given what's inside them is probably a good thing! Hopefully more will be known about them, as they could hold clues to the nature of the early universe.