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:

earthstory:

Last week the Solar Dynamics Observatory (SDO) caught a glimpse of the Moon transiting the sun. Here is that sequence in a variety of wavelengths.

pbsdigitalstudios:

Behold: The Beauty of Solar Magnetism: http://youtu.be/9lshwKIQ29E

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

Failure Of The First Trident D5 Submarine-based Test Launch

In 1971, the US Navy issued a requirement for a submarine-launched, multiple warhead, ballistic missile with intercontinental range and a stellar-inertial navigation system. This would give the Navy capability against Soviet missile siloes and other hardened targets. Lockheed proposed a two-phase program. Trident C-4 would fit in launch tubes in existing submarines, with a range 50% greater than Poseidon. Trident II D-5 would have longer stages, requiring a new class of submarine to be built to accommodate it, but have the desired intercontinental range. Lockheed began development of the Trident II in October 1983. First launch was in January 1987, and first submerged launch in March 1989. This was a failure, revealing problems with the first-stage engine nozzle.

Failure Of The First Trident D5 Submarine-based Test Launch

In 1971, the US Navy issued a requirement for a submarine-launched, multiple warhead, ballistic missile with intercontinental range and a stellar-inertial navigation system. This would give the Navy capability against Soviet missile siloes and other hardened targets. Lockheed proposed a two-phase program. Trident C-4 would fit in launch tubes in existing submarines, with a range 50% greater than Poseidon. Trident II D-5 would have longer stages, requiring a new class of submarine to be built to accommodate it, but have the desired intercontinental range. Lockheed began development of the Trident II in October 1983. First launch was in January 1987, and first submerged launch in March 1989. This was a failure, revealing problems with the first-stage engine nozzle.

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)

blazepress:

Filming a rainbow when suddenly.

blazepress:

Filming a rainbow when suddenly.

xysciences:

A gif representing nuclear fusion and how it creates energy. 
[Click for more interesting science facts and gifs]

For those who don’t understand the GIF. It illustrates the Deuterium-Tritium fusion; a deuterium and tritium combine to form a helium-4. Most of the energy released is in the form of the high-energy neutron.
Nuclear fusion has the potential to generate power without the radioactive waste of nuclear fission (energy from splitting heavy atoms  into smaller atoms), but that depends on which atoms you decide to fuse. Hydrogen has three naturally occurring isotopes, sometimes denoted ¹H, ²H, and ³H. Deuterium (²H) - Tritium (³H) fusion (pictured above) appears to be the best and most effective way to produce energy. Atoms that have the same number of protons, but different numbers of neutrons are called isotopes (adding a proton makes a new element, but adding a neutron makes an isotope of the same atom). 
The three most stable isotopes of hydrogen: protium (no neutrons, just one proton, hence the name), deuterium (deuterium comes from the Greek word deuteros, which means “second”, this is in reference two the two particles, a proton and a neutron), and tritium (the name of this comes from the Greek word “tritos” meaning “third”, because guess what, it contains one proton and two neutrons). Here’s a diagram
Deuterium is abundant, it can be extracted from seawater, but tritium is a  radioactive isotope and must be either derived(bred) from lithium or obtained in the operation of the deuterium cycle. Tritium is also produced naturally in the upper atmosphere when cosmic rays strike nitrogen molecules in the air, but that’s extremely rare. It’s also a by product in reactors producing electricity (Fukushima Daiichi Nuclear Power Plant). Tritium is a low energy beta emitter (unable to penetrate the outer dead layer of human skin), it has a relatively long half life and short biological half life. It is not dangerous externally, however emissions from inhaled or ingested beta particle emitters pose a significant health risk.
During fusion (energy from combining light elements to form heavier ones), two atomic nuclei of the hydrogen isotopes deuterium and tritium must be brought so close together that they fuse in spite of the strongly repulsive electrostatic forces between the positively charged nuclei. So, in order to accomplish nuclear fusion, the two nuclei must first overcome the electric repulsion (coulomb barrier ) to get close enough for the attractive nuclear strong force (force that binds protons and neutrons together in atomic nuclei) to take over to fuse the particles. The D-T reaction is the easiest to bring about, it has the lowest energy requirement compared to energy release. The reaction products are helium-4 (the helium isotope) – also called the alpha particle, which carries 1/5 (3.5 MeV) of the total fusion energy in the form of kinetic energy, and a neutron, which carries 4/5 (14.1 MeV). Don’t be alarmed by the alpha particle, the particles are not dangerous in themselves, it is only because of the high speeds at which they are ejected from the nuclei that make them dangerous, but unlike beta or gamma radiation, they are stopped by a piece of paper.

xysciences:

A gif representing nuclear fusion and how it creates energy. 

[Click for more interesting science facts and gifs]

For those who don’t understand the GIF. It illustrates the Deuterium-Tritium fusion; a deuterium and tritium combine to form a helium-4. Most of the energy released is in the form of the high-energy neutron.

Nuclear fusion has the potential to generate power without the radioactive waste of nuclear fission (energy from splitting heavy atoms  into smaller atoms), but that depends on which atoms you decide to fuse. Hydrogen has three naturally occurring isotopes, sometimes denoted ¹H, ²H, and ³H. Deuterium (²H) - Tritium (³H) fusion (pictured above) appears to be the best and most effective way to produce energy. Atoms that have the same number of protons, but different numbers of neutrons are called isotopes (adding a proton makes a new element, but adding a neutron makes an isotope of the same atom). 

The three most stable isotopes of hydrogen: protium (no neutrons, just one proton, hence the name), deuterium (deuterium comes from the Greek word deuteros, which means “second”, this is in reference two the two particles, a proton and a neutron), and tritium (the name of this comes from the Greek word “tritos” meaning “third”, because guess what, it contains one proton and two neutrons). Here’s a diagram

Deuterium is abundant, it can be extracted from seawater, but tritium is a  radioactive isotope and must be either derived(bred) from lithium or obtained in the operation of the deuterium cycle. Tritium is also produced naturally in the upper atmosphere when cosmic rays strike nitrogen molecules in the air, but that’s extremely rare. It’s also a by product in reactors producing electricity (Fukushima Daiichi Nuclear Power Plant). Tritium is a low energy beta emitter (unable to penetrate the outer dead layer of human skin), it has a relatively long half life and short biological half life. It is not dangerous externally, however emissions from inhaled or ingested beta particle emitters pose a significant health risk.

During fusion (energy from combining light elements to form heavier ones), two atomic nuclei of the hydrogen isotopes deuterium and tritium must be brought so close together that they fuse in spite of the strongly repulsive electrostatic forces between the positively charged nuclei. So, in order to accomplish nuclear fusion, the two nuclei must first overcome the electric repulsion (coulomb barrier ) to get close enough for the attractive nuclear strong force (force that binds protons and neutrons together in atomic nuclei) to take over to fuse the particles. The D-T reaction is the easiest to bring about, it has the lowest energy requirement compared to energy release. The reaction products are helium-4 (the helium isotope) – also called the alpha particle, which carries 1/5 (3.5 MeV) of the total fusion energy in the form of kinetic energy, and a neutron, which carries 4/5 (14.1 MeV). Don’t be alarmed by the alpha particle, the particles are not dangerous in themselves, it is only because of the high speeds at which they are ejected from the nuclei that make them dangerous, but unlike beta or gamma radiation, they are stopped by a piece of paper.

mashable:

45 years ago today, Apollo 11 landed on the first humans on the moon. Neil Armstrong and Buzz Aldrin spent 21.5 hours on the lunar surface.

mashable:

45 years ago today, Apollo 11 landed on the first humans on the moon. Neil Armstrong and Buzz Aldrin spent 21.5 hours on the lunar surface.

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

July 20, 1969: One Giant Leap For Mankind

Astronaut Buzz Aldrin descending the ladder and stepping onto the Moon.  Neil Armstrong's “one small step” onto the lunar surface was actually a 3-foot jump down off the lunar module’s ladder to the ground.

Credit: NASA

July 20, 1969: One Giant Leap For Mankind

Astronaut Buzz Aldrin descending the ladder and stepping onto the Moon.  Neil Armstrong's “one small step” onto the lunar surface was actually a 3-foot jump down off the lunar module’s ladder to the ground.

Credit: NASA

nucleargearing:

Atlas D ICBM Launch
Vandenberg AFB, CA
c. 1960

nucleargearing:

Atlas D ICBM Launch

Vandenberg AFB, CA

c. 1960

amnhnyc:

Astronomers have long pondered the origins of enormous elliptical galaxies in the young Universe. An object 11 billion light-years away spotted by the Herschel mission may help unravel the mystery. 
Two massive spiral galaxies merged to create a giant elliptical galaxy, which were previously believed to form through the absorption of dwarf galaxies over time. 
Learn more about this finding in a Science Bulletin video. 

amnhnyc:

Astronomers have long pondered the origins of enormous elliptical galaxies in the young Universe. An object 11 billion light-years away spotted by the Herschel mission may help unravel the mystery. 

Two massive spiral galaxies merged to create a giant elliptical galaxy, which were previously believed to form through the absorption of dwarf galaxies over time. 

Learn more about this finding in a Science Bulletin video