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)

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

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)

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

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

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)

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

The Cassini spacecraft’s narrow angle camera captured Saturn’s moon Rhea as it gradually slipped into the planet’s shadow – an event known as “ingress”. 
Credit: NASA/JPL/Space Science Institute

The Cassini spacecraft’s narrow angle camera captured Saturn’s moon Rhea as it gradually slipped into the planet’s shadow – an event known as “ingress”.

Credit: NASA/JPL/Space Science Institute

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)

Rocky planets are thought to form through the random collision and sticking together of what are initially microscopic particles in the disc of material around a star. These tiny grains, known as cosmic dust, are similar to very fine soot or sand. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found that the outer region of a dusty disc encircling a brown dwarf — a star-like object, but one too small to shine brightly like a star — also contains millimetre-sized solid grains like those found in denser discs around newborn stars. The finding challenges theories of how rocky, Earth-scale planets form, and suggests that rocky planets may be even more common in the Universe than expected.

Credit: ALMA (ESO/NAOJ/NRAO)/L. Calçada (ESO)/M. Kornmesser, J. Freitag, S. Messenger

Our Two Faced Moon

Because the Moon is tidally locked, it was not until 1959 that the farside was first imaged by the Soviet Luna 3 spacecraft (hence the Russian names for prominent farside features, such as Mare Moscoviense). And what a surprise -­ unlike the widespread maria on the nearside, basaltic volcanism was restricted to a relatively few, smaller regions on the farside, and the battered highlands crust dominated. Of course the cause of the farside/nearside asymmetry is an interesting scientific question. Past studies have shown that the crust on the farside is thicker, but why is the farside crust thicker? This mystery is called the Lunar Farside Highlands Problem.
Now scientists may have solved the 55-year-old mystery. The general consensus on the moon’s origin is that it probably formed shortly after the Earth and was the result of a Mars-sized object hitting Earth with a glancing, but devastating impact. This Giant Impact Hypothesis suggests that the outer layers of the Earth and the object were flung into space and eventually formed the moon. The moon, being much smaller than Earth cooled more quickly. Because the Earth and the moon were tidally locked from the beginning, the still hot Earth — more than 2500 degrees Celsius — radiated towards the near side of the moon. The far side, away from the boiling Earth, slowly cooled, while the Earth-facing side was kept molten creating a temperature gradient between the two halves. This gradient was important for crustal formation on the moon. The moon’s crust has high concentrations of aluminum and calcium, elements that are very hard to vaporize.
Aluminum and calcium would have preferentially condensed in the atmosphere of the cold side of the moon because the nearside was still too hot. Thousands to millions of years later, these elements combined with silicates in the moon’s mantle to form plagioclase feldspars, which eventually moved to the surface and formed the moon’s crust. The farside crust had more of these minerals and is thicker.
The moon has now completely cooled and is not molten below the surface. Earlier in its history, large meteoroids struck the nearside of the moon and punched through the crust, releasing the vast lakes of basaltic lava that formed the nearside maria that make up the man in the moon. When meteoroids struck the farside of the moon, in most cases the crust was too thick and no magmatic basalt welled up, creating the dark side of the moon with valleys, craters and highlands, but almost no maria.

Credit: ESO/M. Kornmesser, Penn State/A’ndrea Elyse Messer

Our Two Faced Moon

Because the Moon is tidally locked, it was not until 1959 that the farside was first imaged by the Soviet Luna 3 spacecraft (hence the Russian names for prominent farside features, such as Mare Moscoviense). And what a surprise -­ unlike the widespread maria on the nearside, basaltic volcanism was restricted to a relatively few, smaller regions on the farside, and the battered highlands crust dominated. Of course the cause of the farside/nearside asymmetry is an interesting scientific question. Past studies have shown that the crust on the farside is thicker, but why is the farside crust thicker? This mystery is called the Lunar Farside Highlands Problem.

Now scientists may have solved the 55-year-old mystery. The general consensus on the moon’s origin is that it probably formed shortly after the Earth and was the result of a Mars-sized object hitting Earth with a glancing, but devastating impact. This Giant Impact Hypothesis suggests that the outer layers of the Earth and the object were flung into space and eventually formed the moon. The moon, being much smaller than Earth cooled more quickly. Because the Earth and the moon were tidally locked from the beginning, the still hot Earth — more than 2500 degrees Celsius — radiated towards the near side of the moon. The far side, away from the boiling Earth, slowly cooled, while the Earth-facing side was kept molten creating a temperature gradient between the two halves. This gradient was important for crustal formation on the moon. The moon’s crust has high concentrations of aluminum and calcium, elements that are very hard to vaporize.

Aluminum and calcium would have preferentially condensed in the atmosphere of the cold side of the moon because the nearside was still too hot. Thousands to millions of years later, these elements combined with silicates in the moon’s mantle to form plagioclase feldspars, which eventually moved to the surface and formed the moon’s crust. The farside crust had more of these minerals and is thicker.

The moon has now completely cooled and is not molten below the surface. Earlier in its history, large meteoroids struck the nearside of the moon and punched through the crust, releasing the vast lakes of basaltic lava that formed the nearside maria that make up the man in the moon. When meteoroids struck the farside of the moon, in most cases the crust was too thick and no magmatic basalt welled up, creating the dark side of the moon with valleys, craters and highlands, but almost no maria.

Credit: ESO/M. Kornmesser, Penn State/A’ndrea Elyse Messer

(Source: news.psu.edu)

ESO's Paranal Observatory projecting a laser into the night sky to create a sodium beacon guide star. Laser guide stars are an artificial star image created for use in astronomical adaptive optics imaging. The, by now classical approach, is to use a narrow-line laser emitting at a sodium resonance line wavelength to create a yellow artificial “star” in the ~ 95 km altitude sodium cloud around the Earth. When working with an Adaptive Optics system, this beacon provides a bright reference source to correct atmospheric turbulence in real time in fields devoid of bright enough natural stars; note however that a moderately bright natural star is still needed to correct global image motion in the field (see a short tutorial here)
There are two main types of laser guide star system, known as sodium and Rayleigh beacon guide stars:
Sodium beacons are created by using a laser specially tuned to 589.2 nanometers to energize a layer of sodium atoms which are naturally present in the mesosphere at an altitude of around 90 kilometers. The sodium atoms then re-emit the laser light, producing a glowing artificial star. The same atomic transition of sodium is used to create bright yellow street lights in many cities. Rayleigh beacons rely on the scattering of light by the molecules which make up the lower atmosphere.
In contrast to sodium beacons, Rayleigh beacons are a much simpler and less costly technology, but do not provide as good a wavefront reference as the artificial beacon is generated much lower in the atmosphere. The lasers are often pulsed, with measurement of the atmosphere being time-gated (taking place a few microseconds after the pulse has been launched so that scattered light at ground level is ignored and only light which has traveled for several microseconds high up into the atmosphere and back is actually detected).
Credit: ESO/Gianluca Lombardi (glphoto.it)

ESO's Paranal Observatory projecting a laser into the night sky to create a sodium beacon guide star. Laser guide stars are an artificial star image created for use in astronomical adaptive optics imaging. The, by now classical approach, is to use a narrow-line laser emitting at a sodium resonance line wavelength to create a yellow artificial “star” in the ~ 95 km altitude sodium cloud around the Earth. When working with an Adaptive Optics system, this beacon provides a bright reference source to correct atmospheric turbulence in real time in fields devoid of bright enough natural stars; note however that a moderately bright natural star is still needed to correct global image motion in the field (see a short tutorial here)

There are two main types of laser guide star system, known as sodium and Rayleigh beacon guide stars:

  1. Sodium beacons are created by using a laser specially tuned to 589.2 nanometers to energize a layer of sodium atoms which are naturally present in the mesosphere at an altitude of around 90 kilometers. The sodium atoms then re-emit the laser light, producing a glowing artificial star. The same atomic transition of sodium is used to create bright yellow street lights in many cities. Rayleigh beacons rely on the scattering of light by the molecules which make up the lower atmosphere.
  2. In contrast to sodium beacons, Rayleigh beacons are a much simpler and less costly technology, but do not provide as good a wavefront reference as the artificial beacon is generated much lower in the atmosphere. The lasers are often pulsed, with measurement of the atmosphere being time-gated (taking place a few microseconds after the pulse has been launched so that scattered light at ground level is ignored and only light which has traveled for several microseconds high up into the atmosphere and back is actually detected).

Credit: ESO/Gianluca Lombardi (glphoto.it)