OrbitalHub

Wikipedia dixit:

“A solar flare is a sudden flash of brightness observed near the Sun’s surface. It involves a very broad spectrum of emissions, an energy release of typically 1 × 10²⁰ joules of energy for a well-observed event. A major event can emit up to 1 × 10²⁵ joules (the latter is roughly the equivalent of 1 billion megatons of TNT, or over 400 times more energy than released from the impact of Comet Shoemaker–Levy 9 with Jupiter). Flares are often, but not always, accompanied by a coronal mass ejection. The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.

Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona), when the plasma medium is heated to tens of millions kelvins, while the cosmic-ray-like electrons, protons, and heavier ions are accelerated to near the speed of light. They produce radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays, although most of the energy is spread over frequencies outside the visual range and for this reason the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CME), although the relation between CMEs and flares is still not well established.

X-rays and UV radiation emitted by solar flares can affect Earth’s ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies.

Solar flares were first observed on the Sun by Richard Christopher Carrington and independently by Richard Hodgson in 1859 as localized visible brightenings of small areas within a sunspot group. Stellar flares can be inferred by looking at the lightcurves produced from the telescope or satellite data of variety of other stars.

The frequency of occurrence of solar flares varies, from several per day when the Sun is particularly “active” to less than one every week when the Sun is “quiet”, following the 11-year cycle (the solar cycle). Large flares are less frequent than smaller ones. On July 23, 2012, a massive, and potentially damaging, solar superstorm (solar flare, coronal mass ejection, solar EMP) barely missed Earth, according to NASA. According to NASA, there may be as much as a 12% chance of a similar event occurring between 2012 and 2022, although because this particular figure was based on an extreme extrapolation of the calculated frequency of future storms, the actual probability of this is quite uncertain.”

Video credit: NASA’s Goddard Space Flight Center/Genna Duberstein

Wikipedia dixit:

“A neutron star is the collapsed core of a large (10–29 solar masses) star. Neutron stars are the smallest and densest stars known to exist. Though neutron stars typically have a radius on the order of 10 kilometres (6.2 mi), they can have masses of about twice that of the Sun. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past the white dwarf star density to that of atomic nuclei. Most of the basic models for these objects imply that neutron stars are composed almost entirely of neutrons, which are subatomic particles with no net electrical charge and with slightly larger mass than protons. They are supported against further collapse by neutron degeneracy pressure, a phenomenon described by the Pauli exclusion principle. If the remnant has too great a density, something which occurs in excess of an upper limit of the size of neutron stars at 2–3 solar masses, it will continue collapsing to form a black hole.

Neutron stars that can be observed are very hot and typically have a surface temperature around 600000 K. They are so dense that a normal-sized matchbox containing neutron-star material would have a mass of approximately 3 billion tonnes, or a 0.5 cubic kilometre chunk of the Earth (a cube with edges of about 800 metres). Their magnetic fields are between 10⁸ and 10¹⁵ times as strong as that of the Earth. The gravitational field at the neutron star’s surface is about 2×10¹¹ times that of the Earth.

As the star’s core collapses, its rotation rate increases as a result of conservation of angular momentum, hence newly formed neutron stars rotate at up to several hundred times per second. Some neutron stars emit beams of electromagnetic radiation that make them detectable as pulsars. Indeed, the discovery of pulsars in 1967 was the first observational suggestion that neutron stars exist. The radiation from pulsars is thought to be primarily emitted from regions near their magnetic poles. If the magnetic poles do not coincide with the rotational axis of the neutron star, the emission beam will sweep the sky, and when seen from a distance, if the observer is somewhere in the path of the beam, it will appear as pulses of radiation coming from a fixed point in space (the so-called “lighthouse effect”). The fastest-spinning neutron star known is PSR J1748-2446ad, rotating at a rate of 716 times a second or 43,000 revolutions per minute, giving a linear speed at the surface on the order of 0.24 c (i.e. nearly a quarter the speed of light).

There are thought to be around 100 million neutron stars in the Milky Way, a figure obtained by estimating the number of stars that have undergone supernova explosions. However, most are old and cold, and neutron stars can only be easily detected in certain instances, such as if they are a pulsar or part of a binary system. Slow-rotating and non-accreting neutron stars are virtually undetectable; however, since the Hubble Space Telescope detection of RX J185635-3754, a few nearby neutron stars that appear to emit only thermal radiation have been detected. Soft gamma repeaters are conjectured to be a type of neutron star with very strong magnetic fields, known as magnetars, or alternatively, neutron stars with fossil disks around them.

Neutron stars in binary systems can undergo accretion which typically makes the system bright in x-rays while the material falling onto the neutron star can form hotspots that rotate in and out of view in identified X-ray pulsar systems. Additionally, such accretion can “recycle” old pulsars and potentially cause them to gain mass and spin-up to very fast rotation rates, forming the so-called millisecond pulsars. These binary systems will continue to evolve, and eventually the companions can become compact objects such as white dwarfs or neutron stars themselves, though other possibilities include a complete destruction of the companion through ablation or merger. The merger of binary neutron stars may be the source of short-duration gamma-ray bursts and are likely strong sources of gravitational waves. Though as of 2016 no direct detection of the gravitational waves from such an event has been made, gravitational waves have been indirectly detected in a system where two neutron stars orbit each other.”

Video credit: NASA Goddard

ESA dixit:

“Bricks have been 3D printed out of simulated moondust using concentrated sunlight. This ESA project took place at the DLR German Aerospace Center facility in Cologne, with a 3D printer table attached to a solar furnace, baking successive 0.1 mm layers of moondust at a temperature of 1000°C. A 20 x 10 x 3 cm brick for building can be completed in around five hours. DLR Cologne’s solar furnace has two working setups: as a baseline, it uses 147 curved mirror facets to focus either actual sunlight into a high temperature beam, employed to melt together the grains of regolith. But this mode is weather dependent, so a solar simulator was subsequently employed as well – based on an array of xenon lamps more typically found in cinema projectors.”

Video credit: ESA

Wikipedia dixit:

“As seen from the Earth, a solar eclipse is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks (“occults”) the Sun. This can happen only at new moon when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.

If the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every month. However, the Moon’s orbit is inclined (tilted) at more than 5 degrees to the Earth’s orbit around the Sun (see ecliptic), so its shadow at new moon usually misses Earth. Earth’s orbit is called the ecliptic plane as the Moon’s orbit must cross this plane in order for an eclipse (both solar as well as lunar) to occur. In addition, the Moon’s actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun totally. The orbital planes cross each other at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses. However, total solar eclipses are rare at any particular location because totality exists only along a narrow path on the Earth’s surface traced by the Moon’s shadow or umbra.

An eclipse is a natural phenomenon. Nevertheless, in some ancient and modern cultures, solar eclipses have been attributed to supernatural causes or regarded as bad omens. A total solar eclipse can be frightening to people who are unaware of its astronomical explanation, as the Sun seems to disappear during the day and the sky darkens in a matter of minutes.

Since looking directly at the Sun can lead to permanent eye damage or blindness, special eye protection or indirect viewing techniques are used when viewing a solar eclipse. It is technically safe to view only the total phase of a total solar eclipse with the unaided eye and without protection; however, this is a dangerous practice, as most people are not trained to recognize the phases of an eclipse, which can span over two hours while the total phase can only last a maximum of 7.5 minutes for any one location. People referred to as eclipse chasers or umbraphiles will travel to remote locations to observe or witness predicted central solar eclipses.”

Video credit: NASA Goddard

ESA dixit:

“Video, based on measurements by ESA’s Gaia and Hipparcos satellites, shows how our view of the Orion constellation will evolve over the next 450 000 years. Stars are not motionless in the sky: their positions change continuously as they move through our Galaxy, the Milky Way. These motions, too slow to be appreciated with the naked eye over a human lifetime, can be captured by high-precision observations like those performed by ESA’s billion-star surveyor, Gaia. By measuring their current movements, we can reconstruct the past trajectories of stars through the Milky Way to study the origins of our Galaxy, and even estimate stellar paths millions of years into the future. This video provides us with a glimpse over the coming 450 000 years, showing the expected evolution of a familiar patch of the sky, featuring the constellation of Orion, the Hunter.

The portion of the sky depicted in the video measures 40 x 20º – as a comparison, the diameter of the full Moon in the sky is about half a degree. Amid a myriad of drifting stars, the shape of Orion as defined by its brightest stars is slowly rearranged into a new pattern as time goes by, revealing how constellations are ephemeral. The red supergiant star Betelgeuse is visible at the centre towards the top of the frame at the beginning of the video (represented in a yellow–orange hue). According to its current motion, the star will move out of this field of view in about 100 000 years. The Universe has a much harsher fate in store for Betelgeuse, which is expected to explode as a supernova within the next million of years.

More of the stars shown in this view will have exploded as supernovas before the end of the video, while others might be still evolving towards that end, like Orion’s blue supergiant, Rigel, visible as the bright star in the lower left, or the red giant Aldebaran, which is part of the constellation Taurus, and can be seen crossing the lower part of the frame from right to left. Many new stars will also have been born from the Orion molecular cloud, a mixture of gas and dust that is not directly seen by Gaia – it can be identified as dark patches against the backdrop of stars – but shines brightly at infrared wavelengths. The birth and demise of stars are not shown in the video. The Hyades cluster, a group of stars that are physically bound together and are also part of the Taurus constellation, slowly makes its way from the lower right corner to the upper left.

The new video is based on data from the Tycho–Gaia Astrometric Solution, a resource that lists distances and motions for two million stars in common between Gaia’s first data release and the Tycho-2 Catalogue from the Hipparcos mission. Additional information from ground-based observations were included, as well as data from the Hipparcos catalogue for the brightest stars in the view.”

Video credit: ESA

Wikipedia dixit:

“The Larsen Ice Shelf is a long, fringing ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to the area just southward of Hearst Island. It is named for Captain Carl Anton Larsen, the master of the Norwegian whaling vessel Jason, who sailed along the ice front as far as 68°10′ South during December 1893. In finer detail, the Larsen Ice Shelf is a series of shelves that occupy (or occupied) distinct embayments along the coast. From north to south, the segments are called Larsen A (the smallest), Larsen B, and Larsen C (the largest) by researchers who work in the area. Further south, Larsen D and the much smaller Larsen E, F and G are also named. The breakup of the ice shelf since the mid 1990s has been widely reported, with the collapse of Larsen B in 2002 being particularly dramatic.

Larsen C is the fourth largest ice shelf in Antarctica, with an area of about 50,000 km2 (19,000 sq mi). In 2004, a report concluded that although the remaining Larsen C region appeared to be relatively stable, continued warming could lead to its breakup within the next decade. News reports in summer of 2016 suggested that this process has begun. On 10 November 2016 scientists photographed the growing rift running along the Larsen C ice shelf, showing it running about 110 kilometres (68 mi) long with a width of more than 91 m (299 ft), and a depth of 500 m (1,600 ft). By December 2016, the rift had extended another 21 km (13 mi) to the point where only 20 km (12 mi) of unbroken ice remained and calving was considered to be a certainty in 2017. This will cause the collapse of between nine and twelve percent of the ice shelf, 6,000 km2 (2,300 sq mi), an area greater than the size of the US state of Delaware. After calving, the broken fragment will be 350 m (1,150 ft) thick and have an area of about 5,000 km2 (1,900 sq mi). If it calves without breaking into small fragments, it will be among the largest icebergs ever recorded.

On 1 May 2017 members of the Antarctic research group Project MIDAS, a British Antarctic research project observing the ever-growing crack, reported that satellite images showed a new crack, around 9 miles long (15 kilometers), branching off the main crack approximately six miles behind the previous tip, heading toward the ice front. Scientists with Swansea University in the UK say the crack lengthened 11 miles from 25 May to 31 May, and that less than 8 miles of ice is all that prevents the birth of an enormous iceberg.

Since the ice shelf is already floating, its departure from Antartica would not affect global sea levels. But a number of glaciers discharge onto it from the lands behind the ice shelf, and therefore might flow faster if it breaks away from the continent. If all the ice that the Larsen C shelf currently holds back were to enter the sea, it is estimated that global waters would rise by 10 cm (4 in).”

Video credit: ESA