Quick Rosetta update:

This is the shape model of comet 67P/Churyumov-Gerasimenko. From the images taken on 14 July, the OSIRIS team has begun modelling the comet’s three-dimensional shape. The animated gif presented here covers one full rotation of the nucleus around its spin axis, to emphasise the lobate structure of the comet. This model will be refined as more data becomes available – it is still a preliminary shape model and some features may be artefacts.

More information: here
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Quick Rosetta update:

This is the shape model of comet 67P/Churyumov-Gerasimenko. From the images taken on 14 July, the OSIRIS team has begun modelling the comet’s three-dimensional shape. The animated gif presented here covers one full rotation of the nucleus around its spin axis, to emphasise the lobate structure of the comet. This model will be refined as more data becomes available – it is still a preliminary shape model and some features may be artefacts.

  • More information: here

Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Animations of Saturn’s aurorae

Earth isn’t the only planet in the solar system with spectacular light shows. Both Jupiter and Saturn have magnetic fields much stronger than Earth’s. Auroras also have been observed on the surfaces of Venus, Mars and even on moons (e.g. Io, Europa, and Ganymede). The auroras on Saturn are created when solar wind particles are channeled into the planet’s magnetic field toward its poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light. Aurora features on Saturn can also be caused by electromagnetic waves generated when its moons move through the plasma that fills the planet’s magnetosphere.  The main source is the small moon Enceladus, which ejects water vapor from the geysers on its south pole, a portion of which is ionized. The interaction between Saturn’s magnetosphere and the solar wind generates bright oval aurorae around the planet’s poles observed in visible, infrared and ultraviolet light. The aurorae of Saturn are highly variable. Their location and brightness strongly depends on the Solar wind pressure: the aurorae become brighter and move closer to the poles when the Solar wind pressure increases.

Credit: ESA/Hubble (M. Kornmesser & L. Calçada)

Stereoscopic View of the Lunar Surface

Apollo 11 carried a number of cameras for collecting data and recording various aspects of the mission, including a 35-mm surface close-up stereoscopic camera. It was designed for the highest possible resolution of a 3-inch square area with a flash illumination and fixed distance. Photography was accomplished by holding the camera on a walking stick against the object to be photographed. The camera was powered by four nickel-cadmium batteries that operated the motor-drive mechanism and an electronic flash strobe light.

There are many details seen in these pictures that were not known previously or that could not be seen with similar definition by astronauts Armstrong and Aldrin in their careful inspection of the lunar surface. The photographs taken on the mission with the close-up stereoscopic camera are of outstanding quality and show in detail the nature of the lunar surface material. From the photographs, information can be derived about the small-scale lunar surface geologic features and about processes occurring on the surface.

Image Credit: John Lloyd/NASA

Fundamental Studies in Droplet Combustion and FLame EXtinguishment in Microgravity (FLEX-2)

The Flame Extinguishment - 2 (FLEX-2) experiment is the second experiment to fly on the ISS which uses small droplets of fuel to study the special spherical characteristics of burning fuel droplets in space. The FLEX-2 experiment studies how quickly fuel burns, the conditions required for soot to form, and how mixtures of fuels evaporate before burning. Understanding how fuels burn in microgravity could improve the efficiency of fuel mixtures used for interplanetary missions by reducing cost and weight. It could also lead to improved safety measures for manned spacecraft.

  • More information: here

Credit: Reid Wiseman/NASA

(Source: youtube.com)

Tokamaks: the future of fusion energy

Fusion is the energy that powers our Sun and other stars.  It has been a goal of scientists around the world to harness this process by which the stars “burn” hydrogen into helium (i.e. nuclear fusion) for energy production on Earth since it was discovered in the 1940′s.

Nuclear fusion is the process by which light nuclei fuse together to create a single, heavier nucleus and release energy.  Given the correct conditions (such as those found in plasma), nuclei of light elements can smash into each other with enough energy to undergo fusion. The “easiest” (most energetically favorable) fusion reaction occurs between the hydrogen isotopes deuterium and tritium.  When the nucleus of a deuterium atom crashes into the nucleus of a tritium atom with sufficient energy, a fusion reaction occurs and a huge amount of energy is released, 17.6 million electron volts to be exact. 

Why fusion? To put this in terms of energy that we all experience; fusion generates more energy per reaction than any other energy source.  A single gram of deuterium/tritium fusion fuel can generate 350 million kJ of energy, nearly 10 million times more energy than from the same amount of fossil fuel!

Fusion power has the potential to provide sufficient energy to satisfy mounting demand, and to do so sustainably, with a relatively small impact on the environment. Nuclear fusion has many potential attractions. Firstly, its hydrogen isotope fuels are relatively abundant – one of the necessary isotopes, deuterium, can be extracted from seawater, while the other fuel, tritium, would be bred from a lithium blanket using neutrons produced in the fusion reaction itself. Furthermore, a fusion reactor would produce virtually no CO2 or atmospheric pollutants, and its other radioactive waste products would be very short-lived compared to those produced by conventional nuclear reactors.

Fusion reactions require so much energy that they must occur with the hydrogen isotopes in this plasma state. Plasma makes up all of the stars, and is the most common form of matter in the visible universe. Since plasmas are made of charged particles every particle can interact with every other particle, even over very long distances. The fact that 99% of the universe is made of plasmas makes studying them very important if we are to understand how the universe works.

How do we create fusion in a laboratory? This is where tokamaks come in. In order for nuclear fusion to occur, the nuclei inside of the plasma must first be extremely hot, like in a star. Unfortunately, no material on Earth can withstand these temperatures so in order to contain a plasma with such high temperatures, we have to be creative. One clever solution is to create a magnetic “bottle” using large magnet coils to capture the plasma and suspend it away from the container’s surfaces. The plasma follows along the magnetic field, suspended away from the walls. This complex combination of magnets used to confine the plasma and the chamber where the plasma is held is known as a tokamak. Tokamaks have a toroidal shape (i.e. they are shaped like a donut) so they have no open ends for plasma to escape. Tokamaks, like the ASDEX Upgrade (pictured above), create and contain the hottest materials in the solar system. The aim of ASDEX Upgrade, the “Axially Symmetric Divertor Experiment”, is to prepare the physics base for ITER.

ITER (International Thermonuclear Experimental Reactor and Latin for “the way” or “the road”) is an international nuclear fusion research and engineering project, which is currently building the world’s largest experimental tokamak nuclear fusion reactor. The ITER project aims to make the long-awaited transition from experimental studies of plasma physics to full-scale electricity-producing fusion power plants.

Further readings:

Titan’s Atmosphere

Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found

Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan’s polar regions.

The atmosphere is largely nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. Titan’s lower gravity means that its atmosphere is far more extended than Earth’s and about 1.19 times as massive. It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan’s surface features obscure. Atmospheric methane creates a greenhouse effect on Titan’s surface, without which Titan would be far colder. Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.

Titan’s clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.The findings of the Huygens probe indicate that Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface. Clouds typically cover 1% of Titan’s disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the southern summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only after the southern summer solstice but also during mid-spring.

Image Credit: NASA/JPL/Space Science Institute

Microwave Induced Plasma

This coaxial microwave plasma source (MPS) generates plasma without using a magnetic field. It works like an inverse luminescent tube excited by microwaves. The coaxial microwave plasma generator consists of a copper rod (antenna) as inner conductor surrounded by quartz tube filled with argon gas, the plasma is the outer conductor. The inside of the tube is at atmospheric pressure whereas the outside is at low pressure. The plasma formed around the quartz tube acts as an outer conductor in such a way that a spatially extended surface wave is created, just in an equivalent (‘inverse’) situation to that found in the Surfatron source (where the plasma is inside the tube instead of outside).
The microwave with a frequency of 2.45 GHz generated by two magnetrons is fed into the copper rods at both ends. On the outside of the tube, in the low pressure, the microwave fields ignite the plasma. The plasma represents a conductive medium so by increasing microwave power the plasma grows from both ends along the tube, and a homogeneous plasma is formed. The high power microwave breakdown at atmospheric pressure leads to the formation of filamentary structures. These striations or string-like structures, also known as birkeland currents, are seen in many plasmas, like the plasma ball, the aurora,lightning,electric arcs, solar flares, and even supernova remnants.

Microwave Induced Plasma

This coaxial microwave plasma source (MPS) generates plasma without using a magnetic field. It works like an inverse luminescent tube excited by microwaves. The coaxial microwave plasma generator consists of a copper rod (antenna) as inner conductor surrounded by quartz tube filled with argon gas, the plasma is the outer conductor. The inside of the tube is at atmospheric pressure whereas the outside is at low pressure. The plasma formed around the quartz tube acts as an outer conductor in such a way that a spatially extended surface wave is created, just in an equivalent (‘inverse’) situation to that found in the Surfatron source (where the plasma is inside the tube instead of outside).

The microwave with a frequency of 2.45 GHz generated by two magnetrons is fed into the copper rods at both ends. On the outside of the tube, in the low pressure, the microwave fields ignite the plasma. The plasma represents a conductive medium so by increasing microwave power the plasma grows from both ends along the tube, and a homogeneous plasma is formed. The high power microwave breakdown at atmospheric pressure leads to the formation of filamentary structures. These striations or string-like structures, also known as birkeland currents, are seen in many plasmas, like the plasma ball, the aurora,lightning,electric arcs, solar flares, and even supernova remnants.

Saturn’s Rings and Enceladus

Saturn’s most distinctive feature is the thousands of rings that orbit the planet. Despite the fact that the rings look like continuous hoops of matter encircling the giant planet, each ring is actually made of tiny individual particles. Saturn’s rings consist largely of water ice mixed with smaller amounts of dust and rocky matter. Data from the Cassini spacecraft indicate that the environment around the rings is like an atmosphere, composed principally of molecular oxygen.

The ring system is divided into 5 major components: the G, F, A, B, and C rings, listed from outside to inside (but in reality, these major divisions are subdivided into thousands of individual ringlets). The F and G rings are thin and difficult to see, while the A, B, and C rings are broad and easily visible. The large gap between the A ring and and the B ring is called the Cassini division. One of Saturn’s moons, namely; Enceladus is the source of Saturn’s E-ring. The moon’s geyser-like jets create a gigantic halo of ice, dust, and gas that helps feed Saturn’s E ring.

Enceladus has a profound effect on Saturn and its environment. It’s the only moon in our solar system known to substantially influence the chemical composition of its parent planet. The whole magnetic environment of Saturn is weighed down by the material spewing from Enceladus, which becomes plasma — a gas of electrically charged particles.  This plasma, which creates a donut-shaped cloud around Saturn, is then snatched by Saturn’s A-ring, which acts like a giant sponge where the plasma is absorbed. 

Credit: , NASA/JPL/SSI

The Saturn V rocket launches Apollo 11 on its historic journey to the Moon on 16 July, 1969.

Apollo 11 Saturn V Launch (HD) from Mark Gray on Vimeo.

Apollo 11 Saturn V Launch (HD) from Mark Gray on Vimeo.

Saturn’s Rings at Maximum Tilt

In March 2003, Saturn’s rings were at maximum tilt toward Earth, a special event occurring every 15 years. With the rings fully tilted, astronomers get the best views of the planet’s Southern Hemisphere. They took advantage of the rings’ unique alignment by using Hubble to capture some stunning images.

Credit: NASA, ESA, E. Karkoschka, G. Bacon (STScI)

Saturn’s Rings at Maximum Tilt

In March 2003, Saturn’s rings were at maximum tilt toward Earth, a special event occurring every 15 years. With the rings fully tilted, astronomers get the best views of the planet’s Southern Hemisphere. They took advantage of the rings’ unique alignment by using Hubble to capture some stunning images.

Credit: NASA, ESA, E. Karkoschka, G. Bacon (STScI)

Nikola Tesla in his office in 1916, demonstrating an electrical apparatus.

Nikola Tesla in his office in 1916, demonstrating an electrical apparatus.

"The scientific man does not aim at an immediate result. He does not expect that his advanced ideas will be readily taken up. His work is like that of the planter — for the future. His duty is to lay the foundation for those who are to come, and point the way. He lives and labors and hopes."

Nikola Tesla 

(Source: teslauniverse.com)

Spectroscopy and the Birth of Astrophysics

The 3D animation (above) depicts how the light of a distant star is studied by astronomers. The spectrum of the light provides vital information about the composition and history of stars. Now, let’s look into the history of stellar spectroscopy.

In 1802, William Wollaston noted that the spectrum of sunlight did not appear to be a continuous band of colours, but rather had a series of dark lines superimposed on it. Wollaston attributed the lines to natural boundaries between colours. Joseph Fraunhofer made a more careful set of observations of the solar spectrum in 1814 and found some 600 dark lines, and he specifically measured the wavelength of 324 of them. Many of the Fraunhofer lines in the solar spectrum retain the notations he created to designate them. In 1864, Sir William Huggins matched some of these dark lines in spectra from other stars with terrestrial substances, demonstrating that stars are made of the same materials of everyday material rather than exotic substances. This paved the way for modern spectroscopy.

Since even before the discovery of spectra, scientists had tried to find ways to categorize stars. By observing spectra, astronomers realized that large numbers of stars exhibit a small number of distinct patterns in their spectral lines. Classification by spectral features quickly proved to be a powerful tool for understanding stars.

The current spectral classification scheme was developed at Harvard Observatory in the early 20th century. Work was begun by Henry Draper who photographed the first spectrum of Vega in 1872. After his death, his wife donated the equipment and a sum of money to the Observatory to continue his work. The bulk of the classification work was done by Annie Jump Cannon from 1918 to 1924. The original scheme used capital letters running alphabetically, but subsequent revisions have reduced this as stellar evolution and typing has become better understood.

While the differences in spectra might seem to indicate different chemical compositions, in almost all instances, it actually reflects different surface temperatures. With some exceptions (e.g. the R, N, and S stellar types), material on the surface of stars is “primitive”: there is no significant chemical or nuclear processing of the gaseous outer envelope of a star once it has formed. Fusion at the core of the star results in fundamental compositional changes, but material does not generally mix between the visible surface of the star and its core. Ordered from highest temperature to lowest, the seven main stellar types are O, B, A, F, G, K, and M. Astronomers use one of several mnemonics to remember the order of the classification scheme. O, B, and A type stars are often referred to as early spectral types, while cool stars (G, K, and M) are known as late type stars.

Scientists assumed that the spectral classes represented a sequence of decreasing surface temperatures of the stars, but no one was able to demonstrate this quantitatively. Cecilia Payne, who studied the new science of quantum physics, knew that the pattern of features in the spectrum of any atom was determined by the configuration of its electrons. She showed that Cannon’s ordering of the stellar spectral classes was indeed a sequence of decreasing temperatures and she was able to calculate the temperatures.

  • More information: here

Credit: ESO, Jesse S. Allen

Dark Gamma Ray Bursts

An artist’s conception of the environment around GRB 020819B based on ALMA observations. The GRB occurred in an arm of a galaxy in the constellation of Pisces (The Fishes). GRBs are huge explosions of a star spouting high-speed jets in a direction toward the observer. In a complete surprise, less gas was observed than expected, and correspondingly much more dust, making some GRBs appear as “dark GRBs”.

Gamma-ray bursts (GRBs) are intense bursts of extremely high energy observed in distant galaxies — the brightest explosive phenomenon in the Universe. Bursts that last more than a couple of seconds are known as long-duration gamma-ray bursts (LGRBs) and are associated with supernova explosions — powerful detonations at the ends of the lives of massive stars.

In just a matter of seconds, a typical burst releases as much energy as the Sun will in its entire ten-billion-year lifetime. The explosion itself is often followed by a slowly fading emission, known as an afterglow, which is thought to be created by collisions between the ejected material and the surrounding gas. However, some gamma-ray bursts mysteriously seem to have no afterglow — they are referred to as dark bursts. One possible explanation is that clouds of dust absorb the afterglow radiation.

  • More information: here

Credit: Bunyo Hatsukade(NAOJ), ALMA (ESO/NAOJ/NRAO)