Planets of Our Solar System

Our solar system officially has eight planets and one star: the Sun. The discovery of an object larger than Pluto in 2005 rekindled the debate over whether such objects, belonging to the Kuiper Belt – a collection of icy bodies located beyond Neptune – should be called planets. Pluto and other large members of the Kuiper Belt are now considered “dwarf planets.”

Planet facts: space-facts.com

Our Sun constantly emits plasma which moves out in all directions at very high speeds and fills the entire solar system. The complex interaction between the Sun’s plasma atmosphere and its magnetic field gives rise to a wide range of fascinating and spectacular phenomena. The fluctuation of the sun’s magnetic fields can cause a large portion of the outer atmosphere to expand rapidly, spewing a tremendous amount of particles into space. These large eruptions of magnetized plasma are called coronal mass ejections. CMEs are the most spectacular and potentially harmful manifestations of solar activity. Some of these eruptive events accelerate particles to very high energies, high enough to penetrate a space suit or the hull of a spacecraft and can cause severe disturbances in the geospace environment when they encounter Earth’s magnetic field. However, only about 1% of the CMEs produce strong SEP (solar energetic particles) events. 

Credit: NASA/SDO/Duberstein

Propylene on Titan

With a thick atmosphere, clouds, a rain cycle and giant lakes, Saturn’s large moon Titan is a surprisingly Earthlike place. But unlike on Earth, Titan’s surface is far too cold for liquid water - instead, Titan’s clouds, rain, and lakes consist of liquid hydrocarbons like methane and ethane (which exist as gases here on Earth). When these hydrocarbons evaporate and encounter ultraviolet radiation in Titan’s upper atmosphere, some of the molecules are broken apart and reassembled into longer hydrocarbons like ethylene and propane.

NASA’s Voyager 1 spacecraft first revealed the presence of several species of atmospheric hydrocarbons when it flew by Titan in 1980, but one molecule was curiously missing - propylene, the main ingredient in plastic number 5. Now, thanks to NASA’s Cassini spacecraft, scientists have detected propylene on Titan for the first time, solving a long-standing mystery about the solar system’s most Earthlike moon.

NASA PlanetaryScientist Conor Nixon explains his discovery of propylene on Titan, Saturn’s largest moon. Scientists have known about the presence of atmospheric hydrocarbons on Titan since Voyager 1 flew by in 1980, but one molecule, propylene, was curiously missing. Now, thanks to new data from NASA’s Cassini spacecraft, propylene has been detected for the first time on Titan.

Credit: NASA’s Goddard Space Flight Center

Millisecond Pulsars

As the name suggestions, millisecond pulsars have pulse periods that are in the range from one to ten milliseconds. Most such millisecond pulsars are found in binary systems, typically with white-dwarf companions. These pulsars are highly magnetized, old neutron stars in binary systems which have been spun up to high rotational frequencies by accumulating mass and angular momentum from a companion star. Neutron stars form when a massive star explodes at the end of its life and leaves behind a super-dense, spinning ball of neutrons. A pulsar is the same thing as a neutron star, but with one added feature. Pulsars emit lighthouse-like beams of x-ray and radio waves that rapidly sweep through space as the object spins on its axis. Most pulsars rotate just a few times per second, but some spin hundreds of times faster. These millisecond pulsars are the fastest-rotating stars we know of.

  • To hear the sound of a pulsar, click here

Credit: NASA

Soft X-ray Emissions from Charge Exchange in the Heliosphere

The solar wind originates in the sun’s corona, the hottest part of its atmosphere, so its atoms have been ionized, stripped of many of their electrons. When these particles collide with a neutral atom, one of its electrons often jumps to the solar wind ion. Once captured, the electron briefly remains in an excited state, then emits a soft X-ray and settles down at a lower energy. X-rays with photon energies above 5–10 keV (below 0.2–0.1 nm wavelength) are called hard X-rays, while those with lower energy are called soft X-rays.

Credit: NASA’s Goddard Space Flight Center

Helioseismology: seismology of the Sun

The Sun oscillates and vibrates at many frequencies, like an ocean surface or …like a bell. Certain frequencies are amplified by constructive interference(wave propagation) and the turbulence “rings” the sun like a bell. Unfortunately, sound does not carry through the vacuum between the Sun and the earth, so we have to “listen" to the oscillations by looking at the motions of material on the surface of the Sun. With the right instruments, scientists can "hear" this ringing or pulsations from the Sun. To do this, they use an instrument called a Michelson Doppler Imager (MDI), mounted on the SOHO spacecraft and the Helioseismic and Magnetic Imager (HMI), one of the three instruments that make up the Solar Dynamics Observatory (SDO).

Although direct study of its interior is impossible —mostly because the Sun is nearly opaque to electromagnetic energy, insights into the conditions within the Sun may be gained by observing oscillating waves, rhythmic inward and outward motions of its visible surface. These oscillations on the surface are due to sound waves generated and trapped inside the sun. Sound waves are produced by pressure fluctuations in the turbulent convective motions of the sun’s interior. These trapped sound waves set the sun vibrating in millions of different patterns or modes. Using this acoustic energy, we can “see into the Sun”, just as geologists use seismic waves to study the structure of the Earth, the discipline of helioseismology makes use of acoustic pressure waves (infrasound) traversing the Sun’s interior. These oscillations are seen as volumes of gas called granules near the Sun’s surface that rise and fall with a particular frequency. It is like seeing the rolling motions of convection cells on the surface of  boiling water. This happens very close to the surface where the flow of energy that started in the nuclear reactions in the core reaches the surface and suddenly escapes. The sound from the convection is then trapped and filtered inside the sun to produce the solar music

Helioseismologists can use the properties of these waves to determine the temperature, density, composition, and motion of the interior of the sun. The spectral lines emitted from gas moving upwards will be slightly Doppler-shifted to the blue; spectral lines from gas moving downwards will be slightly Doppler-shifted to the red. In this way the rolling motions of convection near the Sun’s surface can be mapped out. There are three types of oscillations. Pressure modes (p-modes) are sound waves trapped in the temperature gradient (like an echo bouncing around inside a cavern). Fundamental modes (f-modes) or surface gravity waves are caused by gravitational interactions with the sun’s surface and resemble ocean waves. Gravity modes (g-modes) are not completely understood, but they are believed to be the result of buoyancy effects. All the known pressure and fundamental modes (some 10 million) have oscillation periods of less than 18 minutes, and most are around 5 minutes. The gravity modes are not known conclusively to exist, but they are predicted to have periods of 40 minutes or longer (160-min).

Further readings:

As Seen by STEREO-A: The Carrington-Class CME of 2012

STEREO (Solar TErrestrial RElations Observatory) is a solar observation mission, it consists of two space-based observatories - one ahead of Earth in its orbit (STEREO-A), the other trailing behind (STEREO-B). The two nearly identical spacecraft were launched in 2006 into orbits around the Sun that cause them to respectively pull farther ahead of and fall gradually behind the Earth. This enables stereoscopic imaging of the Sun and solar phenomena, such as coronal mass ejections.

STEREO-A, at a position along Earth’s orbit where it has an unobstructed view of the far side of the Sun, could clearly observe possibly the most powerful coronal mass ejection (CME) of solar cyle 24 on July 23, 2012. The flare erupted in the lower right quadrant of the solar disk from a large active region. The material launched into space in a direction towards STEREO-A. This created the ring-like ‘halo’ CME visible in the STEREO-A coronagraph, COR-2 (blue circular image). As the CME expanded beyond the field of view of the COR-2 imager, the high energy particles reached STEREO-A, and caused the snow-like noise in the image. Researchers have been analyzing the data ever since, and they have concluded that the storm was one of the strongest in recorded history. It might have been stronger than the Carrington Event itself.

The solar storm of 1859, also known as the Carrington Event, was a powerful geomagnetic solar storm in 1859 during solar cycle 10. A solar flare or coronal mass ejection hit Earth’s magnetosphere and induced the largest known solar storm, which was observed and recorded by Richard C. Carrington. The intense geomagnetic storm caused global telegraph lines to spark, setting fire to some telegraph offices and disabling the ‘Victorian Internet.” A similar storm today could have a catastrophic effect on modern power grids and telecommunication networks.

Credit: NASA’s Scientific Visualization Studio

Jupiter’s Irregular Satellites

The planet Jupiter has 67 confirmed moons. This gives it the largest retinue of moons with “reasonably secure” orbits of any planet in the Solar System. In fact, Jupiter and its moons are like a miniature solar system with the inner moons orbiting faster than the others. Eight of Jupiter’s moons are regular satellites, with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter’s equatorial plane. The remainder of Jupiter’s moons are irregular satellites, whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. There are 17 recently discovered irregular satellites that have not yet been named.

Image Credit: NASA/ESA/Lowell Observatory/J. Spencer/JHU-APL

Jupiter’s Irregular Satellites

The planet Jupiter has 67 confirmed moons. This gives it the largest retinue of moons with “reasonably secure” orbits of any planet in the Solar System. In fact, Jupiter and its moons are like a miniature solar system with the inner moons orbiting faster than the others. Eight of Jupiter’s moons are regular satellites, with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter’s equatorial plane. The remainder of Jupiter’s moons are irregular satellites, whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. There are 17 recently discovered irregular satellites that have not yet been named.

Image Credit: NASA/ESA/Lowell Observatory/J. Spencer/JHU-APL

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.