APOD 4.2

The 2015 solar eclipse over the upper part of the planet has generated tremendous popularity lately, despite its passing over few population centers able to actually see it considering weather conditions. This composite image of 29 telescopic images displays the brilliant corona of the sun in all its glory, only able to be seen well considering the entire rest of the sun is blocked out by the moon. These pictures were taken on March 20th, the day of the eclipse. Pink solar prominences are visible along the edge of the moon, as well as the specific surface features of the dark side of the moon surprisingly, illuminated by sunlight reflecting off of Earth.

APOD 4.1

This picture shows what used to be a faint light to one of the brightest stars in Sagittarius, although now it is fading. This is due to a nova. A nova is caused by the accretion of hydrogen onto the surface of the star, commencing a runaway fusion reaction. This produces a large amount of light, even enough to see it from earth. This specific nova was the brightest that we have been able to see from earth in over a year. This light is so bright that for weeks we will still be able to see it with binoculars.

Observation 6

http://www.astronomycast.com/2012/06/ep-262-solar-sails/

Solar sails (also called light sails or photon sails) are a form of spacecraft propulsion using the radiation pressure (also called solar pressure) from stars to push large ultra-thin mirrors to high speeds. Light sails could also be driven by energy beams to extend their range of operations, which is strictly beam sailing rather than solar sailing. Solar sail craft offer the possibility of low-cost operations combined with long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for delivery of payloads. Solar sails use a phenomenon that has a proven, measured effect on spacecraft. Solar pressure affects all spacecraft, whether in interplanetary space or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced by thousands of kilometres by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the attitude of a craft, a factor that must be included in spacecraft design. The total force exerted on an 800 by 800 meter solar sail, for example, is about 5 newtons at Earth's distance from Sol, making it a low-thrust propulsion system, similar to spacecraft propelled by electric engines.

Observation 5

http://www.astronomycast.com/2013/04/ep-292-the-oort-cloud/

The Oort cloud or Öpik–Oort cloud, named after Dutch astronomer Jan Oort and Estonian astronomer Ernst Öpik, is a spherical cloud of predominantly icy planetesimals believed to surround the Sun at a distance of up to around 100,000 AU (2 ly). This places it at half of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud. The outer limit of the Oort cloud defines the cosmographical boundary of the Solar System and the region of the Sun's gravitational dominance. The Oort cloud is thought to comprise two regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers conjecture that the matter composing the Oort cloud formed closer to the Sun and was scattered far into space by the gravitational effects of the giant planets early in the Solar System's evolution. Although no confirmed direct observations of the Oort cloud have been made, it may be the source of all long-period and Halley-type comets entering the inner Solar System, and many of the centaurs and Jupiter-family comets as well. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud.

Observation 4

http://www.astronomycast.com/2013/11/ep-322-soho/

The Solar and Heliospheric Observatory (SOHO) is a spacecraft built by a European industrial consortium led by Matra Marconi Space (now Astrium) that was launched on a Lockheed Martin Atlas II AS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2700 comets. It began normal operations in May 1996. It is a joint project of international cooperation between the European Space Agency (ESA) and NASA. Originally planned as a two-year mission, SOHO continues to operate after over 18 years in space. In June 2013, a mission extension lasting until December 2016 was approved. In addition to its scientific mission, it is the main source of near-real-time solar data for space weather prediction. Along with the GGS Wind and Advanced Composition Explorer (ACE) (and DSCOVR in 2015), SOHO is one of three spacecraft in the vicinity of the Earth–Sun L1 point, a point of gravitational balance located approximately 0.99 astronomical unit (AU)s from the Sun and 0.01 AU from the Earth. In addition to its scientific contributions, SOHO is distinguished by being the first three-axis-stabilized spacecraft to use its reaction wheels as a kind of virtual gyroscope; the technique was adopted after an on-board emergency in 1998 that nearly resulted in the loss of the spacecraft.

Observation 3

http://www.astronomycast.com/2013/12/ep-325-cold-fusion/

Cold fusion is a hypothetical type of nuclear reaction that would occur at, or near, room temperature, compared with temperatures in the millions of degrees that are required for "hot" fusion, which takes place naturally within stars. There is currently no accepted theoretical model which would allow cold fusion to occur. In 1989 Martin Fleischmann (then one of the world's leading electrochemists) and Stanley Pons reported that their apparatus had produced anomalous heat ("excess heat"), of a magnitude they asserted would defy explanation except in terms of nuclear processes. They further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium. The small tabletop experiment involved electrolysis of heavy water on the surface of a palladium (Pd) electrode. The reported results received wide media attention, and raised hopes of a cheap and abundant source of energy. Many scientists tried to replicate the experiment with the few details available. Hopes fell with the large number of negative replications, the withdrawal of many positive replications, the discovery of flaws and sources of experimental error in the original experiment, and finally the discovery that Fleischmann and Pons had not actually detected nuclear reaction byproducts. By late 1989, most scientists considered cold fusion claims dead, and cold fusion subsequently gained a reputation as pathological science. In 1989, a review panel organized by the United States Department of Energy (DOE) found that the evidence for the discovery of a new nuclear process was not persuasive enough to start a special program, but was "sympathetic toward modest support" for experiments "within the present funding system." A second DOE review, convened in 2004 to look at new research, reached conclusions similar to the first. Support within the then-present funding system did not occur.

Observation 2

http://www.astronomycast.com/2015/03/ep-369-the-fizeau-experiment/

The Fizeau experiment was carried out by Hippolyte Fizeau in 1851 to measure the relative speeds of light in moving water. Fizeau used a special interferometer arrangement to measure the effect of movement of a medium upon the speed of light. According to the theories prevailing at the time, light traveling through a moving medium would be dragged along by the medium, so that the measured speed of the light would be a simple sum of its speed through the medium plus the speed of the medium. Fizeau indeed detected a dragging effect, but the magnitude of the effect that he observed was far lower than expected. His results seemingly supported the partial aether-drag hypothesis of Fresnel, a situation that was disconcerting to most physicists. Over half a century passed before a satisfactory explanation of Fizeau's unexpected measurement was developed with the advent of Albert Einstein's theory of special relativity. Einstein later pointed out the importance of the experiment for special relativity.