they were seldom seen………..
then they turned up – both of them!………….
they were seldom seen………..
then they turned up – both of them!………….
Is a Silver Coin a Silver Dollar? Neither, it’s galaxy NGC 253.
Transit of Mercury
It Was Another Historical Astronomical Event
Mercury and The Sun
— NASA (@NASA) May 9, 2016
Before Galileo, it was thought that all bright objects in the sky were either the planets in the Solar System, moons, comets, or stars. Until the beginning of the twentieth century, astronomers did not know the size of the Universe, but speculated it to be about as big as the Milky Way.
In 1920, at the National Academy of Science, there was a big debate between Harlow Shapley and Heber D. Curtis on whether nebulae are small globular clusters surrounding the Milky Way, or separate galaxies located farther away. Nothing was resolved at the debate; neither side was able to provide conclusive evidence to prove their side correct over their opponent.
In 1923, Edwin Hubble resolved the matter with a photograph that he took of the Andromeda Galaxy. What he found in his photograph was a very bright light source pulsing at a certain rate, a Cepheid variable, located outside the Milky Way. This can be used to determine the distance to it.
Hubble proved that the Universe was full of galaxies, and disproved that the Milky Way was the extent of the Universe. There are many types of galaxies in the Universe, elliptical, barred spiral galaxies; they vary in shape and size, but on average spiral galaxies are the most abundant.
NGC 7479 (also known as Caldwell 44) is a barred spiral galaxy about 105 million light-years away in the constellation Pegasus. It was discovered by William Herschel in 1784. Supernovae SN 1990U and SN 2009jf occurred in NGC 7479. NGC 7479 is also recognized as a Seyfert galaxy and a Liner undergoing starburst activity not only on the nucleus and the outer arms, but also across the bar of the galaxy, where most of the stars were formed in the last 100 million years.
Polarization studies of this galaxy indicate that it recently underwent a minor merger and that it is unique in the radio continuum, with arms opening in a direction opposite to the optical arms. This feature, along with the asymmetrical arms of the galaxy and the intense star formation activity are attributed to a merger with a smaller galaxy.
In quantum mechanics, the Schrödinger equation is a partial differential equation that describes how the quantum state of a quantum system changes with time. It was formulated in late 1925, and published in 1926, by the Austrian physicist Erwin Schrödinger.
In classical mechanics Newton’s second law, (F = ma), is used to mathematically predict what a given system will do at any time after a known initial condition. In quantum mechanics, the analogue of Newton’s law is Schrödinger’s equation for a quantum system (usually atoms, molecules, and subatomic particles whether free, bound, or localized). It is not a simple algebraic equation, but in general a linearpartial differential equation, describing the time-evolution of the system’s wave function (also called a “state function”).
The concept of a wavefunction is a fundamental postulate of quantum mechanics. Although Schrödinger’s equation is often presented as a separate postulate, some authors show that some properties resulting from Schrödinger’s equation may be deduced just from symmetry principles alone, for example the commutation relations. Generally, “derivations” of the Schrödinger equation demonstrate its mathematical plausibility for describing wave-particle duality, but to date there are no universally accepted derivations of Schrödinger’s equation from appropriate axioms.
In the Copenhagen interpretation of quantum mechanics, the wave function is the most complete description that can be given of a physical system. Solutions to Schrödinger’s equation describe not only molecular, atomic, and subatomic systems, but also macroscopic systems, possibly even the whole universe. The Schrödinger equation, in its most general form, is consistent with both classical mechanics and special relativity, but the original formulation by Schrödinger himself was non-relativistic.
The Schrödinger equation is not the only way to make predictions in quantum mechanics—other formulations can be used, such as Werner Heisenberg‘s matrix mechanics, and Richard Feynman‘s path integral formulation.
Leo in the night sky unfounded again due to cloud mass
A dark nebula or absorption nebula is a type of interstellar cloud that is so dense it obscures the light from objects behind it, such as background stars and emission or reflection nebulae.
The Sun is a magnetically active star. It supports a strong, changing magnetic field that varies year-to-year and reverses direction about every eleven years around solar maximum.
The Sun’s magnetic field leads to many effects that are collectively called solar activity, including sunspots on the surface of the Sun, solar flares, and variations in solar wind that carry material through the Solar System.
The effects of solar activity on Earth include auroras at moderate to high latitudes and the disruption of radio communications and electric power. Solar activity is thought to have played a large role in the formation and evolution of the Solar System. Solar activity changes the structure of Earth’s outer atmosphere.
All matter in the Sun is in the form of gas and at high temperatures, plasma. This makes it possible for the Sun to rotate faster at its equator (about 25 days) than it does at higher latitudes (about 35 days near its poles). The differential rotation of the Sun’s latitudes causes its magnetic field lines to become twisted together over time, producing magnetic field loops to erupt from the Sun’s surface and trigger the formation of the Sun’s dramatic sunspots and solar prominences (see Magnetic reconnection).
This twisting action creates the solar dynamo and an 11-year solar cycle of magnetic activity as the Sun’s magnetic field reverses itself about every 11 years.
Matter should not be confused with mass, as the two are not quite the same in modern physics. For example, mass is a conserved quantity, which means that its value is unchanging through time, within closed systems.
However, matter is not conserved in such systems, although this is not obvious in ordinary conditions on Earth, where matter is approximately conserved.
Still, special relativity shows that matter may disappear by conversion into energy, even inside closed systems, and it can also be created from energy, within such systems.
However, because mass (like energy) can neither be created nor destroyed, the quantity of mass and the quantity of energy remain the same during a transformation of matter (which represents a certain amount of energy) into non-material (i.e., non-matter) energy. This is also true in the reverse transformation of energy into matter.
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun.
The duration of such transits is usually measured in hours (the transit of 2012 lasted 6 hours and 40 minutes). A transit is similar to a solar eclipse by the Moon. While the diameter of Venus is more than 3 times that of the Moon, Venus appears smaller, and travels more slowly across the face of the Sun, because it is much farther away from Earth.
Although reflection from the rings increases Saturn’s brightness, they are not visible from Earth with unaided vision.
In 1610, the year after Galileo Galilei first turned a telescope to the sky, he became the very first person to observe Saturn’s rings, though he could not see them well enough to discern their true nature.
A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disc containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters.
Edwin will never know Hubble
Just one month after boarding the International Space Station, Peake has completed his first Spacewalk with fellow astronaut Tim Kopra. It’s fair to say the UK was firmly gripped by “Spacewalk fever” on January 15 2015.
UK astronaut Tim Peake described his first walk in space as “exhilarating”, as he posted photos – including a selfie – of the feat on Twitter.It will “be etched in my memory forever – quite an incredible feeling,” said Peake, the first astronaut representing the UK to carry out a spacewalk.He and US colleague Tim Kopra were outside the International Space Station (ISS) for four hours and 43 minutes.But their spacewalk was cut short after water leaked into Col Kopra’s helmet.The pair had already replaced a failed electrical box, which was their main objective.
UK newspaper The Guardian had this to say…
The moment was hardly lost on him. As Tim Peake clambered out of the International Space Station he nodded to the union flag emblazoned on his shoulder. To wear the patch was, he said, “a huge privilege, and a proud moment”.
Britain’s first European Space Agency astronaut began his maiden spacewalk shortly before 1pm on Friday as the orbiting station soared 250 miles above Australia. By the time he returned inside, he had circled the planet at least three times and witnessed six stunning sunsets or sunrises.
Emerging from the Quest airlock into the darkness of Earth’s shadow, Peake joined Nasa’s Tim Kopra for more than four hours of challenging work. Under the direction of ground staff in Houston, the astronauts overcame snagged tethers, a brief carbon dioxide scare, and a torn glove before the day was done.
Flybys are a major element of Cassini’s tour. The spacecraft’s looping, elliptical path around Saturn is carefully designed to enable occasional visits to the many moons in the system. All flybys provide an opportunity to learn more about Saturn’s icy satellites, and encounters with giant Titan are actually used to navigate the spacecraft, changing its orbit or setting up future flybys.
Many of the most exciting encounters are “targeted” flybys, for which Cassini’s flight path is steered so the spacecraft will pass by a specific moon at a predetermined distance, referred to as “closest approach.” Cassini’s targeted flybys have yielded incredible close-up views and many groundbreaking science results. Visits to Dione and Hyperion, for example, as well as the daring Oct. 2008 dives through the Enceladus plume, have provided some of the great highlights of the mission.
This is going to start the very dull “politically correct ” taking over Christmas usual stuff we get every year. The Cinema chain didn’t want to show it because that would remind people christmas means consumerism – you are a commodity, if you believe in God or not.
They survey and sniff, analyze and scrutinize. And of course, they take stunning images in various visible spectra. The 12 science instruments onboard the Cassini spacecraft are seemingly capable of doing it all. Each instrument is designed to carry out sophisticated scientific studies of Saturn, from collecting data in multiple regions of the electromagnetic spectrum, to studying dust particles, to characterizing Saturn’s plasma environment and magnetosphere.
The instruments gather data for 27 diverse science investigations, providing scientists with an enormous amount of information on the most beautiful planet in our Solar System.
When the sky is clear – you can even see Lepus on the horizon
I can make out Lepus tonight with my naked eye. The best view so far this autumn. Of course, Orion looks glorious as it always does on a clear night, though I find it much harder to see Lepus in such detail usually.
Lepus is a constellation lying just south of the celestial equator, immediately south of Orion. Its name is Latin for hare. Although the hare does not represent any particular figure in Greek mythology, Lepus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is located below the constellation Orion (the hunter), and is sometimes represented as a hare being chased by Orion or, alternatively, by Orion’s hunting dogs.
Orion and Lepus clip
Quote is via Wiki
This constellation should not be confused with Lupus, the wolf.
William Herschel discovered the nebula on February 7, 1785, and cataloged it as H IV.27. John Herschel observed it from the Cape of Good Hope, South Africa, in the 1830s, and numbered it as h 3248, and included it in the 1864 General Catalogue as GC 2102; this became NGC 3242 in J. L. E. Dreyer’s New General Catalogue of 1888.
This planetary nebula is most frequently called the Ghost of Jupiter, or Jupiter’s Ghost due to its similar size to the planet, but it is also sometimes referred to as the Eye Nebula.
The nebula measures around two light years long from end to end, and contains a central white dwarf with an apparent magnitude of eleven. The inner layers of the nebula
were formed some 1,500 years ago.
The two ends of the nebula are marked by FLIERs, lobes of fasting moving gas often tinted red in false-color pictures. NGC 3242 can easily be observed with amateur telescopes, and appears bluish-green to most observers. Larger telescopes can distinguish the outer halo as well.
See more of Hubble here
Amateur astronomy is a hobby whose participants enjoy watching the sky, and the abundance of objects found in it with the unaided eye, binoculars, or telescopes. Even though scientific research is not their main goal, many amateur astronomers make a contribution to astronomy by monitoring variable stars, tracking asteroids and discovering transient objects, such as comets and novae.
The typical amateur astronomer is one who does not depend on the field of astronomy as a primary source of income or support, and does not have a professional degree or advanced academic training in the subject. Many amateurs are beginners or hobbyists, while others have a high degree of experience in astronomy and often assist and work alongside professional astronomers.
Amateur astronomy is usually associated with viewing the night sky when most celestial objects and events are visible, but sometimes amateur astronomers also operate during the day for events such as sunspots and solar eclipses. Amateur astronomers often look at the sky using nothing more than their eyes, but common tools for amateur astronomy include portable telescopes and binoculars.
People have studied the sky throughout history in an amateur framework, without any formal method of funding. It is only within about the past century, however, that amateur astronomy has become an activity clearly distinguished from professional astronomy, and other related activities.
Objects observed in deep space (extragalactic space, ~10 megaparsecs or more) are found to have a Doppler shift interpretable as relative velocity away from the Earth;
This Doppler-shift-measured velocity, of various galaxies receding from the Earth, is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away.
Hubble’s law is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big
Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow.
Although widely attributed to Edwin Hubble, the law was first derived from the general relativity equations by Georges Lemaître in a 1927 article where he proposed the expansion of the universe and suggested an estimated value of the rate of expansion, now called the Hubble constant.
Two years later Edwin Hubble confirmed the existence of that law and determined a more accurate value for the constant that now bears his name. Hubble inferred the recession velocity of the objects from their redshifts, many of which were earlier measured and related to velocity by Vesto Slipher in 1917.
The law is often expressed by the equation v = H0D, with H0 the constant of proportionality (Hubble constant) between the “proper distance” D to a galaxy (which can change over time, unlike the comoving distance) and its velocity v (i.e. the derivative of proper distance with respect to cosmological time coordinate; see Uses of the proper distance for some discussion of the subtleties of this definition of ‘velocity’). The SI unit of H0 is s−1 but it is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09×1019 km) away. The reciprocal of H0 is the Hubble time.
The ancient night sky was studied and defined by the dark patches seen – not by the stars seen, in ancient aboriginal astronomy.
Dark patches in the sky
Unlike Greek celestial tradition, which focuses almost exclusively on stars, Aboriginal astronomy focuses on the Milky Way and often incorporates the dark patches between stars.
The Emu in the Sky, a story common to many Aboriginal groups, is an example of this — its body is made up of the dark patches in the Milky Way. The Boorong people saw the
same dark patches as the smoke from the fires of Nurrumbunguttias, the old spirits. The Kaurna people saw the Milky Way — called Wodliparri or hut river — as a large river
where a Yura (monster) lives in the dark patches.
Serious Sunspots Study Started With Maunder…………
About the man…(12 April 1851 – 21 March 1928) was a British astronomer best remembered for his study of sunspots and the solar magnetic cycle that led to his identification of the period from 1645 to 1715 that is now known as the Maunder Minimum.
Edward Walter Maunder was born in 1851, in London, the youngest child of a minister of the Wesleyan Society. He attended King’s College London but never graduated. He took a job in a London bank to finance his studies.
In 1873 Maunder returned to the Royal Observatory, taking a position as a spectroscopic assistant. Shortly after, in 1875, he married Edith Hannah Bustin, who gave birth to six children, 3 sons, 2 daughters and a son who died in infancy. Following the death of Edith in 1888, he met Annie Scott Dill Russell (1868–1947) in 1890, a mathematician and astronomer with whom he collaborated for the remainder of his life. In 1895 Maunder and Russell married. In 1916 Annie Maunder became one of the first women accepted by the Royal Astronomical Society.
Part of Maunder’s job at the Observatory involved photographing and measuring sunspots, and in doing so he observed that the solar latitudes at which sunspots occur varies in a regular way over the course of the 11 year cycle. After 1891, he was assisted in his work by his second wife, Annie Scott Dill Maunder (née Russell), a mathematician educated at Girton College in Cambridge. She worked as a “lady computer” at the Observatory from 1890 to 1895. In 1904, he published their results in the form of the “butterfly” diagram.
After studying the work of Gustav Spörer, who examined old records from the different observatories archives looking for changes of the heliographic latitude of sunspots, Maunder announced Spörer’s conclusions in own paper edited in 1894. The period, recognised earlier by Spörer, now bears Maunder’s name.
He travelled extensively for observations going to places such as the West Indies, Lapland, India, Algiers, Mauritius. His last eclipse expedition was to Labrador for the Solar eclipse of 30 August 1905 at the invitation of the Canadian government.
Starting with the M.R.O.
Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory. The mission is managed by the California Institute of Technology, at the JPL, in La Cañada Flintridge, California, for the NASA Science Mission Directorate, Washington, D.C. It was launched August 12, 2005, and attained Martian orbit on March 10, 2006. In November 2006, after five months of aerobraking, it entered its final science orbit and began its primary science phase.
As MRO entered orbit, it joined five other active spacecraft which were either in orbit or on the planet’s surface:Mars Global Surveyor, Mars Express, 2001 Mars Odyssey, and the two Mars Exploration Rovers (Spirit and Opportunity); at the time, this set a record for the most operational spacecraft in the immediate vicinity of Mars. Mars Global Surveyor and the Spirit rover have since ceased to function; the remainder remain operational as of July 2015.
MRO contains a host of scientific instruments such as cameras, spectrometers, and radar, which are used to analyze the landforms, stratigraphy, minerals, and ice of Mars. It paves the way for future spacecraft by monitoring Mars’ daily weather and surface conditions, studying potential landing sites, and hosting a new telecommunications system. MRO’s telecommunications system will transfer more data back to Earth than all previous interplanetary missions combined, and MRO will serve as a highly capable relay satellite for future missions.
Super Moon – Lunar Eclipse Night
If you have a half decent camera, I hope you are trying to capture some of the amazing sights of the Moon.
Get some tips from the space website – it has a good short film that gives you times of the changing eclipse. Good to watch even for a non-photographer like me.
A lenticular galaxy is a type of galaxy which is intermediate between an elliptical galaxy and a spiral galaxy in galaxy morphological classification schemes. Lenticular galaxies are disc galaxies (like spiral galaxies) which have used up or lost most of their interstellar matter and therefore have very little ongoing star formation.
They may, however, retain significant dust in their disks. As a result, they consist mainly of aging stars (like elliptical galaxies). Because of their ill-defined spiral arms, if they are inclined face-on it is often difficult to distinguish between them and elliptical galaxies.
Despite the morphological differences, lenticular and elliptical galaxies share common properties like spectral features, scaling relations and both can be considered early type galaxies which are passively evolving, at least in the local universe.
A different astronomy and space science related image is featured each day, along with a brief explanation.
A gravitational lens refers to a distribution of matter (such as a cluster of galaxies) between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer. This effect is known as gravitational lensing and the amount of bending is one of the predictions of Albert Einstein‘s general theory of relativity. (Classical physics also predicts bending of light, but only half that of general relativity’s.)
Although Orest Chwolson (1924) or Frantisek Klin (1936) are sometimes credited as being the first ones to discuss the effect in print, the effect is more commonly associated with Einstein, who published a more famous article on the subject in 1936.
Fritz Zwicky posited in 1937 that the effect could allow galaxy clusters to act as gravitational lenses. It was not until 1979 that this effect was confirmed by observation of the so-called “Twin QSO” SBS 0957+561.
Unlike an optical lens, maximum ‘bending’ occurs closest to, and minimum ‘bending’ furthest from, the center of a gravitational lens. Consequently, a gravitational lens has no single focal point, but a focal line instead. If the (light) source, the massive lensing object, and the observer lie in a straight line, the original light source will appear as a ring around the massive lensing object. If there is any misalignment the observer will see an arc segment instead.
This phenomenon was first mentioned in 1924 by the St. Petersburg physicist Orest Chwolson, and quantified by Albert Einstein in 1936. It is usually referred to in the literature as an Einstein ring, since Chwolson did not concern himself with the flux or radius of the ring image. More commonly, where the lensing mass is complex (such as a galaxy group or cluster) and does not cause a spherical distortion of space–time, the source will resemble partial arcs scattered around the lens. The observer may then see multiple distorted images of the same source; the number and shape of these depending upon the relative positions of the source, lens, and observer, and the shape of the gravitational well of the lensing object.
The Orion Nebula
The nebula is visible with the naked eye even from areas affected by some light pollution. It is seen as the middle “star” in the sword of Orion, which are the three stars located south of Orion’s Belt. The star appears fuzzy to sharp-eyed observers, and the nebulosity is obvious through binoculars or a small telescope. The peak surface brightness of the central region is about 17 Mag/arcsec2 (about 14 millinits) and the outer bluish glow has a peak surface brightness of 21.3 Mag/arcsec2 (about 0.27 millinits). (In the photos shown here the brightness, or luminance, is enhanced by a large factor.)
The Orion Nebula contains a very young open cluster, known as the Trapezium due to the asterism of its primary four stars. Two of these can be resolved into their component binary systems on nights with good seeing, giving a total of six stars. The stars of the Trapezium, along with many other stars, are still in their early years. The Trapezium may be a component of the much larger Orion Nebula Cluster, an association of about 2,000 stars within a diameter of 20 light years. Two million years ago this cluster may have been the home of the runaway stars AE Aurigae, 53 Arietis, and Mu Columbae, which are currently moving away from the nebula at velocities greater than 100 km/s.
Not the easiset to see with the naked eye. When you look to the right or left of it, you can see it a bit better.
Locate the constellation of Taurus to find it.
See more about Pleiades by taking a look at this post I did a couple of years ago…
The California Nebula
NGC 1499 is an emission nebula located in the constellation Perseus. It is so named because it appears to resemble the outline of the US State of California on long exposure photographs. It is almost 2.5° long on the sky and, because of its very low surface brightness, it is extremely difficult to observe visually.
It can be observed with a Hβ filter (isolates the Hβ line at 486 nm) in a rich-field telescope under dark skies. It lies at a distance of about 1,000 light years from Earth. Its fluorescence is due to excitation of the Hβ line in the nebula by the nearby prodigiously energetic O7 star, xi Persei (also known as Menkib).
Stephan’s Quintet in the constellation Pegasus is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group was discovered by Édouard Stephan in 1877 at Marseille Observatory. The group is the most studied of all the compact galaxy groups. The brightest member of the visual grouping is NGC 7320 that is shown to have extensive H II regions, identified as red blobs, where active star formation is occurring.
These galaxies are of interest because of their violent collisions. Four of the five galaxies in Stephan’s Quintet form a physical association, Hickson Compact Group 92, and are involved in a cosmic dance that most likely will end with the galaxies merging. Radio observations in the early 1970s revealed a mysterious filament of emission which lies in inter-galactic space between the galaxies in the group.
This same region is also detected in the faint glow of ionized atomic hydrogen seen in the visible part of the spectrum as the magnificent green arc in the picture to the right. Two space telescopes have recently provided new insight into the nature of the strange filament, which is now believed to be a giant intergalactic shock-wave (similar to a sonic boom but traveling in intergalactic gas rather than air) caused by one galaxy (NGC 7318B) falling into the center of the group at several millions of miles per hour.
Perhaps even more unexpected is the discovery of very powerful molecular hydrogen signals from the shock wave, seen by the NASA Spitzer Space Telescope which detects infrared radiation. The molecular hydrogen emission, which is seen through infrared spectral analysis using the Spitzer Space Telescope is one of the most turbulent formations of molecular hydrogen ever seen, and the strongest emission originates near the center of the green area in the visible light picture discussed earlier.
This phenomenon was discovered by an international team led by scientists at the California Institute of Technology and includes scientists from Australia, Germany and China. The detection of molecular hydrogen from the collision was initially unexpected because the hydrogen molecule is very fragile and is easily destroyed in shock waves of the kind expected in Stephan’s Quintet.
However, one solution is that when a shock front moves through a cloudy medium like the center of the group, millions of smaller shocks are produced in a turbulent layer, and this can allow molecular hydrogen to survive. Most notable is the fact that this collision can help provide a view into what happened in the postulated beginning of the universe some 14 billion years ago, since shocked molecular hydrogen is likely to be present in the early universe.
Ziggy Boo Dude
This is a Supernova Remnant
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.
There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; or a white dwarf star may accumulate (accrete) material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion.
In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light, that is, about 30,000 km/s. These ejecta are highly supersonic: assuming a typical temperature of the interstellar medium of 10,000 K, the Mach number can initially be > 1000. Therefore, a strong shock wave forms ahead of the ejecta, that heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecsbefore its speed falls below the local sound speed.
One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was observed in February 1987. Other well-known supernova remnants include the Crab Nebula, Tycho, the remnant of SN 1572, named after Tycho Brahe who recorded the brightness of its original explosion, and Kepler, the remnant of SN 1604, named after Johannes Kepler. The youngest known remnant in our galaxy is G1.9+0.3, discovered in the galactic center.
Callisto is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede, and the largest object in the Solar System not to be properly differentiated. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1880000 km. It is not part of the orbital resonance that affects three inner Galilean satellites—Io, Europa and Ganymede—and thus does not experience appreciable tidal heating. Callisto’s rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward; Jupiter appears to stand nearly still in Callisto’s sky. It is less affected by Jupiter’s magnetosphere than the other inner satellites because of its more remote orbit, located just outside Jupiter’s main radiation belt.
Callisto is composed of approximately equal amounts of rock and ices, with a mean density of about 1.83 g/cm3, the lowest density and surface gravity of Jupiter’s major moons. Compounds detected spectroscopically on the surface include water ice, carbon dioxide, silicates, and organic compounds. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate core and possibly a subsurface ocean of liquid water at depths greater than 100 km.
The surface of Callisto is the oldest and most heavily cratered in the Solar System. It does not show any signatures of subsurface processes such as plate tectonics or volcanism, with no signs that geological activity in general has ever occurred, and is thought to have evolved predominantly under the influence of impacts. Prominent surface features include multi-ring structures, variously shaped impact craters, and chains of craters (catenae) and associated scarps, ridges and deposits. At a small scale, the surface is varied and made up of small, sparkly frost deposits at the tips of high spots, surrounded by a low-lying, smooth blanket of dark material. This is thought to result from the sublimation-driven degradation of small landforms, which is supported by the general deficit of small impact craters and the presence of numerous small knobs, considered to be their remnants. The absolute ages of the landforms are not known.
Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide and probably molecular oxygen as well as by a rather intense ionosphere. Callisto is thought to have formed by slow accretion from the disk of the gas and dust that surrounded Jupiter after its formation. Callisto’s gradual accretion and the lack of tidal heating meant that not enough heat was available for rapid differentiation. The slow convection in the interior of Callisto, which commenced soon after formation, led to partial differentiation and possibly to the formation of a subsurface ocean at a depth of 100–150 km and a small, rocky core.
The likely presence of an ocean within Callisto leaves open the possibility that it could harbor life. However, conditions are thought to be less favorable than on nearby Europa . Various space probes from Pioneers 10 and 11 to Galileo and Cassini have studied Callisto. Because of its low radiation levels, Callisto has long been considered the most suitable place for a human base for future exploration of the Jovian system.
Messier 13 (M13), also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster of about 300,000 stars in the constellation of Hercules.
M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764. It is located at right ascension 16h 41.7m and declination +36° 28′. With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes. Nearby is NGC 6207, a 12th magnitude edge-on galaxy that lies 28 arc minutes directly north east. A small galaxy, IC 4617, lies halfway between NGC 6207 and M13, north-northeast of the large globular cluster’s center.
M13 is about 145 light-years in diameter, and it is composed of several hundred thousand stars, the brightest of which is a red giant, the variable star V11, with an apparent visual magnitude of 11.95. M13 is 25,100 light-years away from Earth.
Centaurus contains several very bright stars because of its position in the Milky Way; in addition, its alpha and beta stars are used to find the constellation Crux. The constellation has 281 stars above magnitude 6.5, meaning that they are visible to the unaided eye, the most of any constellation. Alpha Centauri, the closest star to the Sun, has a high proper motion; it will be a mere half-degree from Beta Centauri in approximately 4000 years.
Alpha Centauri is a triple star system that contains Proxima Centauri, the nearest star to the Sun. Traditionally called Rigil Kentaurus or Toliman, meaning “foot of the centaur”, the system has an overall magnitude of -0.28 and is 4.4 light-years from Earth. The primary and secondary are both yellow-hued stars; the primary, is of magnitude -0.01 and the secondary is of magnitude 1.35. Proxima, the tertiary star, is a red dwarf of magnitude 11.0; it is almost 2 degrees away from the primary and secondary and has a period of approximately one million years. Also a flare star, Proxima has minutes-long outbursts where it brightens by over a magnitude. The primary and secondary have a period of 80 years and will be closest to each other as seen from Earth in 2037 and 2038.
In addition to Alpha Centauri (the 3rd brightest star in the sky), a second first magnitudestar, Beta Centauri, is part of Centaurus. Also called Hadar and Agena, Beta Centauri is a double star; the primary is a blue-hued giant star of magnitude 0.6, 525 light-years from Earth. The secondary is of magnitude 4.0 and has a very small separation. A bright binary star in Centaurus is Gamma Centauri, which appears to the naked eye at magnitude 2.2. The primary and secondary are both blue-white hued stars of magnitude 2.9; their period is 85 years.
Centaurus also has many dimmer double stars and binary stars. 3 Centauri is a double star with a blue-white hued primary of magnitude 4.6 and a secondary of magnitude 6.1. The primary is 298 light-years from Earth.
Centaurus is home to many variable stars. R Centauri is a Mira variable star with a minimum magnitude of 11.8 and a maximum magnitude of 5.3; it is 2100 light-years from Earth and has a period of 18 months. V810 Centauri is a semiregular variable.
BPM 37093 is a white dwarf star whose carbon atoms are thought to have formed a crystalline structure. Since diamond also consists of carbon arranged in a crystalline lattice (though of a different configuration), scientists have nicknamed this star “Lucy” after the Beatles song “Lucy in the Sky with Diamonds.”
The Cat’s Paw Nebula – is a vast region of star formation. NGC 6334 is one of the most active nurseries of massive stars in our galaxy and has been extensively studied by astronomers.