Of the many fascinating phenomena associated with the Sun, solar prominences rate amongst the most spectacular of the observed features. These relatively cool and dense ribbons of plasma are anchored to the Sun’s surface in the photosphere and extend outwards into the Sun’s corona. From their structures and pattern of motion of material, several different types of prominences can be identified: a quiescent prominence may evolve into an active or eruptive prominence and merge into space with violent velocities. This particular prominence rose high into the corona for about 3 hours on December 31, 2012. 
Credit: NASA/SDO

Of the many fascinating phenomena associated with the Sun, solar prominences rate amongst the most spectacular of the observed features. These relatively cool and dense ribbons of plasma are anchored to the Sun’s surface in the photosphere and extend outwards into the Sun’s corona. From their structures and pattern of motion of material, several different types of prominences can be identified: a quiescent prominence may evolve into an active or eruptive prominence and merge into space with violent velocities. This particular prominence rose high into the corona for about 3 hours on December 31, 2012. 

Credit: NASA/SDO

Comet ‘Siding Spring’ headed for close encounter with Mars

Mars is about to dodge a cosmic snowball on this Sunday. On October 19, Comet Siding Spring will pass within 88,000 miles of Mars – just one third of the distance from the Earth to the Moon! Traveling at 33 miles per second and weighing as much as a small mountain, the comet hails from the outer fringes of our solar system, originating in a region of icy debris known as the Oort cloud.

Comets from the Oort cloud are both ancient and rare. Since this is Comet Siding Spring’s first trip through the inner solar system, scientists are excited to learn more about its composition and the effects of its gas and dust on the Mars upper atmosphere. NASA will be watching closely before, during, and after the flyby with its entire fleet of Mars orbiters and rovers, along with the Hubble Space Telescope and dozens of instruments on Earth. The encounter is certain to teach us more about Oort cloud comets, the Martian atmosphere, and the solar system’s earliest ingredients.

  • For more information, click here

Credit: NASA/GSFC

(Source: youtu.be)

Solar wind and Mars’ Atmosphere

Mars does not have a single unified magnetic field like Earth. It has smaller, more fractured fields which cover the planet and have different intensities and polarities. The absence of magnetic protection allows the supersonic solar wind flow to directly interact with the Martian ionosphere.

The Sun constantly emits high-energy photons (gamma rays) and when one of these photons enters the atmosphere of Mars, it can crash into a molecule, knocking loose an electron and turning it into an ion. These ions can then crash into other molecules and fling atoms everywhere. Some of these atoms can be knocked, or sputtered, into space, causing atmospheric loss. The amount of ionization in the ionosphere varies greatly with the amount of radiation received from the Sun. When the velocity of the solar wind increases, the Martian ionosphere is compressed and the ionopause (a boundary layer between the ionosphere and the solar wind) is displaced to lower altitudes.

Further Reading:

Credit: Chris Smith (HTSI), NASA/Nagoya University

(Source: youtube.com)

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

Time lapse of the Milky Way rising behind the South African Large Telescope (SALT)
Credit: Anthony Koeslag

Time lapse of the Milky Way rising behind the South African Large Telescope (SALT)

Credit: Anthony Koeslag

Mars Orbiters ‘Duck and Cover’ for Comet Siding Spring Encounter

NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data, as Comet C/2013 A1 Siding Spring heads toward a close flyby of Mars on Oct. 19.

The comet’s nucleus will miss Mars by about 82,000 miles (132,000 kilometers), shedding material hurtling at about 35 miles (56 kilometers) per second, relative to Mars and Mars-orbiting spacecraft. At that velocity, even the smallest particle — estimated to be about one-fiftieth of an inch (half a millimeter) across — could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, with a third on its way and expected to arrive in Martian orbit just a month before the comet flyby. Teams operating the orbiters plan to have all spacecraft positioned on the opposite side of the Red Planet when the comet is most likely to pass by.

The European Space Agency is taking similar precautions to protect its Mars Express (MEX) orbiter.
  • For more information about the Mars flyby of comet Siding Spring, click here.
Credit: NASA/JPL-Caltech
The Formation and Dynamics of Super-Earth Planets

Super-Earths, objects slightly larger than Earth and slightly smaller than Uranus, have found a special place in exoplanetary science. As a new class of planetary bodies, these objects have challenged models of planet formation at both ends of the spectrum and have triggered a great deal of research on the composition and interior dynamics of rocky planets in connection to their masses and radii.
Being relatively easier to detect than an Earth-sized planet at 1 AU around a G star, super-Earths have become the focus of worldwide observational campaigns to search for habitable planets. With a range of masses that allows these objects to retain moderate atmospheres and perhaps even plate tectonics, super-earths may be habitable if they maintain long-term orbits in the habitable zones of their host stars. Given that in the past two years a few such potentially habitable super-Earths have in fact been discovered, it is necessary to develop a deep understanding of the formation and dynamical evolution of these objects.
This article reviews the current state of research on the formation of super-Earths and discusses different models of their formation and dynamical evolution.

Image Credit: ESO/M. Kornmesser

The Formation and Dynamics of Super-Earth Planets

Super-Earths, objects slightly larger than Earth and slightly smaller than Uranus, have found a special place in exoplanetary science. As a new class of planetary bodies, these objects have challenged models of planet formation at both ends of the spectrum and have triggered a great deal of research on the composition and interior dynamics of rocky planets in connection to their masses and radii.

Being relatively easier to detect than an Earth-sized planet at 1 AU around a G star, super-Earths have become the focus of worldwide observational campaigns to search for habitable planets. With a range of masses that allows these objects to retain moderate atmospheres and perhaps even plate tectonics, super-earths may be habitable if they maintain long-term orbits in the habitable zones of their host stars. Given that in the past two years a few such potentially habitable super-Earths have in fact been discovered, it is necessary to develop a deep understanding of the formation and dynamical evolution of these objects.

This article reviews the current state of research on the formation of super-Earths and discusses different models of their formation and dynamical evolution.

Image Credit: ESO/M. Kornmesser

(Source: eso.org)

Total Lunar Eclipse

A total lunar eclipse will take place on October 8, 2014. It is the latter of two total lunar eclipses in 2014, and the second in a tetrad (four total lunar eclipses in series).

Lunar eclipses occur when the Moon passes through the Earth’s shadow, however, for a total lunar eclipse to occur, the Moon and Earth have to be on the same orbital plane with the Sun — this is known as a syzygy. During a total lunar eclipse, the Moon travels completely into the Earth’s shadow (umbra). Even though the Moon is immersed in the Earth’s shadow, indirect sunlight will still reach the Moon. As sunlight passes through Earth’s atmosphere it gets absorbed and then radiated out (scattered). The atmosphere filters out most of the blue-colored light. What’s left over is the orange- and red-colored light. From the Moon’s perspective the Earth’s edge appears to glow bright orange or red. This red-colored light passes through our atmosphere without getting scattered, projecting indirect, reddish light onto the Moon.

For more information:

Credit: NASA/SVS



This M7.3-class flare erupted on the right side of the sun on Oct. 2, 2014. M-class flares are one-tenth as powerful as the most powerful flares, which are designated X-class flares. 




Image Credit: NASA/SDO/ Wiessinger
This M7.3-class flare erupted on the right side of the sun on Oct. 2, 2014. M-class flares are one-tenth as powerful as the most powerful flares, which are designated X-class flares. 
Image Credit: NASA/SDO/ Wiessinger

(Source: nasa.gov)

NASA’s Solar Dynamics Observatory (SDO) captured an incredible view of a powerful solar flare on Thursday (Oct. 2). The flare reached its peak at 3:01 p.m. EDT (1901 GMT) on Tuesday. While the M7.3-class flare did cause a coronal mass ejection — an explosion of super-hot solar plasma — the eruption was not directed at Earth, and should not pose a concern for satellites in orbit or the planet.

  • For more information click here

Credit: NASA/SDO

Moon Phase and Libration

Lunar Reconnaissance Orbiter (LRO) has been in orbit around the Moon since the summer of 2009. Its laser altimeter (LOLA) and camera (LROC) are recording the rugged, airless lunar terrain in exceptional detail, making it possible to visualize the Moon with unprecedented fidelity.

Watch the video
 Credit: NASA/GSFC/Ernie Wright (USRA)

Moon Phase and Libration

Lunar Reconnaissance Orbiter (LRO) has been in orbit around the Moon since the summer of 2009. Its laser altimeter (LOLA) and camera (LROC) are recording the rugged, airless lunar terrain in exceptional detail, making it possible to visualize the Moon with unprecedented fidelity.

Credit: NASA/GSFC/Ernie Wright (USRA)

Sunspots

Our Sun is a main sequence star which actively fuses hydrogen into helium in its core. In certain regions of the Sun, the energy created by the hydrogen “burning” is carried to its surface by convection. However, intense magnetic fields in sunspots strangle the normal up-flow of energy from the interior, so energy is unable to reach the surface in these areas leaving the sunspot cooler and therefore darker than its surroundings. The strong magnetic fields in these convection zones promote cooling, thus the hot gas near the Sun’s surface contracts and sinks at speeds of up to 4,000 kilometers per hour. This drives an inward flow, like a planet-sized whirlpool. Of course, seeing behind the scenes in sunspots is not easy; the Sun below the photosphere is opaque and hidden. The only way to investigate the morphology and the structure of sunspots is through helioseismology. Using the Helioseismic and Magnetic Imager (HMI) on SDO, we can explore the solar interior by detecting natural sound waves on the Sun’s surface.

For more information:

Image Credit: NASA/SOHO/MDI/Alexander Kosovichev/Tom Bridgman

(Source: youtu.be)

The sun is a huge thermo-nuclear reactor, fusing hydrogen atoms into helium and producing million degree temperatures and intense magnetic fields. The outer layer of the sun near its surface is like a pot of boiling water, with bubbles of hot, electrified gas—electrons and protons in a fourth state of matter known as plasma—circulating up from the interior and bursting out into space. The steady stream of particles blowing away from the sun is known as the solar wind.

  • For more information click here.

Credit: NASA/SDO

No matter when or where you look, the Sun is always doing something interesting.

  • Image credit: NASA’s Goddard Space Flight Center/SDO

Henrietta Swan Leavitt

The parallax method used to measure the distances to nearby stars, pioneered by Bessel and others could only be used on stars closer than 100 light years away.  But most stars and other galaxies are far beyond that distance. The key for finding the distance to stars much further away was discovered by Henrietta Swan Leavitt who worked at Harvard College Observatory as a “computer,” one of several women paid 25 to 30 cents per hour to extract data from thousands of photographic plates.

Unfortunately stars are not the same intrinsic brightness (or luminosity), so it is impossible to tell if a star appears dim because it’s far away, or because it doesn’t put out much light. The key for finding the distance to stars was discovered by Henrietta Swan Leavitt who worked at Harvard College Observatory as a “computer,” one of several women paid 25 to 30 cents per hour to take data from thousands of photographic plates.

Leavitt’s assignment was to identify variable stars, which are stars that change in brightness over a few hours, days, or weeks. To do this she would compare two photos of a star field taken a few days or weeks apart. She used an instrument called a blink comparator that flips back and forth quickly between the two images so that a variable star shows up as a flashing spot. With this method she found more than 2,400 variable stars.

Leavitt became curious about whether there might be a relationship between the brightness of a variable star and the length of its period (how long it takes for the star to get brighter, dimmer, then brighter again). That was difficult because she did not know the intrinsic brightness of any given variable. She solved the problem by restricting her search to a particular kind of variable star known as Cepheid variables that reside in the Small Magellanic Cloud—a distant star cluster. She reasoned that all stars in the cluster must be approximately the same distance from Earth.

Her hunch paid off. Leavitt discovered 25 Cepheid variables in the cluster and created a graph showing the maximum brightness of each star and the length of its period. As she suspected, there was a clear relationship. Brighter stars had longer periods. All that was needed to find actual distances was to find the distance to just one nearby Cepheid variable. A few years later a team of astronomers did just that, making it possible to measure the distance to any Cepheid.

Image Credit: Dana Berry/NASA