People look at the sky for many reasons. For the Astronomer it's a journey filled with endless possibilities. For the Cosmologist it's about creation and what lies beyond. There's mythology linked with the constellations, folklore, history, and archaeoastronomy that link humanity to the heavens, as if it is all connected by a sacred geometric stream of consciousness. Some love to relax and stargaze, finding it a healing tool. Pseudoscience takes us to Astrology, Ancient Alien Theory, or perhaps an inner knowing that our souls traveled here from a distant star to which we will one day return. Whatever the reason, since the beginning of time, stars have always set our galactic course, and now play a role in its final outcome.
A star is a massive, luminous ball of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible from Earth during the night when they are not outshone by the Sun or blocked by atmospheric phenomena.
Historically, the most prominent stars on the celestial sphere were grouped together into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.
For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen in its core releasing energy that traverses the star's interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium were created by stars, either via stellar nucleosynthesis during their lifetimes or by supernova nucleosynthesis when stars explode. Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space.
The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung-Russell diagram (H-R diagram), allows the age and evolutionary state of a star to be determined.
A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes.
The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, those stars having at least 0.4 times the mass of the Sun expand to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of the matter into the interstellar environment, where it will form a new generation of stars with a higher proportion of heavy elements.
Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a cluster or a galaxy.
Historically, stars have been important to civilizations throughout the world. They have been part of religious practices and used for celestial navigation and orientation. Many ancient astronomers believed that stars were permanently affixed to a heavenly sphere, and that they were immutable.
By convention, astronomers grouped stars into constellations and used them to track the motions of the planets and the inferred position of the Sun. The motion of the Sun against the background stars (and the horizon) was used to create calendars, which could be used to regulate agricultural practices. The Gregorian calendar, currently used nearly everywhere in the world, is a solar calendar based on the angle of the Earth's rotational axis relative to its local star, the Sun.
The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 BC.
The earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia in the late 2nd millennium BC, during the Kassite Period (ca. 1531-1155 BC).
The first star catalogue in Greek astronomy was created by Aristillus in approximately 300 BC, with the help of Timocharis.
The star catalog of Hipparchus (2nd century BC) included 1020 stars and was used to assemble Ptolemy's star catalogue. Hipparchus is known for the discovery of the first recorded nova (new star). Many of the constellations and star names in use today derive from Greek astronomy.
In spite of the apparent immutability of the heavens, Chinese astronomers were aware that new stars could appear.
In 185 AD, they were the first to observe and write about a supernova, now known as the SN 185.
The brightest stellar event in recorded history was the SN 1006 supernova, which was observed in 1006 and written about by the Egyptian astronomer Ali ibn Ridwan and several Chinese astronomers.
The SN 1054 supernova, which gave birth to the Crab Nebula, was also observed by Chinese and Islamic astronomers.
Medieval Islamic astronomers gave Arabic names to many stars that are still used today, and they invented numerous astronomical instruments that could compute the positions of the stars. They built the first large observatory research institutes, mainly for the purpose of producing Zij star catalogues.
Among these, the Book of Fixed Stars (964) was written by the Persian astronomer Abd al-Rahman al-Sufi, who discovered a number of stars, star clusters (including the Omicron Velorum and Brocchi's Clusters) and galaxies (including the Andromeda Galaxy).
In the 11th century, the Persian polymath scholar Abu Rayhan Biruni described the Milky Way galaxy as a multitude of fragments having the properties of nebulous stars, and also gave the latitudes of various stars during a lunar eclipse in 1019.
The Andalusian astronomer Ibn Bajjah proposed that the Milky Way was made up of many stars which almost touched one another and appeared to be a continuous image due to the effect of refraction from sublunary material, citing his observation of the conjunction of Jupiter and Mars on 500 AH (1106/1107 AD) as evidence.
Early European astronomers such as Tycho Brahe identified new stars in the night sky (later termed novae), suggesting that the heavens were not immutable.
In 1584 Giordano Bruno suggested that the stars were like the Sun, and may have other planets, possibly even Earth-like, in orbit around them, an idea that had been suggested earlier by the ancient Greek philosophers, Democritus and Epicurus, and by medieval Islamic cosmologists such as Fakhr al-Din al-Razi.
By the following century, the idea of the stars being the same as the Sun was reaching a consensus among astronomers. To explain why these stars exerted no net gravitational pull on the Solar System, Isaac Newton suggested that the stars were equally distributed in every direction, an idea prompted by the theologian Richard Bentley.
The Italian astronomer Geminiano Montanari recorded observing variations in luminosity of the star Algol in 1667.
Edmond Halley published the first measurements of the proper motion of a pair of nearby "fixed" stars, demonstrating that they had changed positions from the time of the ancient Greek astronomers Ptolemy and Hipparchus. The first direct measurement of the distance to a star (61 Cygni at 11.4 light-years) was made in 1838 by Friedrich Bessel using the parallax technique. Parallax measurements demonstrated the vast separation of the stars in the heavens.
William Herschel was the first astronomer to attempt to determine the distribution of stars in the sky. During the 1780s, he performed a series of gauges in 600 directions, and counted the stars observed along each line of sight. From this he deduced that the number of stars steadily increased toward one side of the sky, in the direction of the Milky Way core. His son John Herschel repeated this study in the southern hemisphere and found a corresponding increase in the same direction. In addition to his other accomplishments, William Herschel is also noted for his discovery that some stars do not merely lie along the same line of sight, but are also physical companions that form binary star systems.
The science of stellar spectroscopy was pioneered by Joseph von Fraunhofer and Angelo Secchi. By comparing the spectra of stars such as Sirius to the Sun, they found differences in the strength and number of their absorption lines - the dark lines in a stellar spectra due to the absorption of specific frequencies by the atmosphere.
In 1865 Secchi began classifying stars into spectral types. However, the modern version of the stellar classification scheme was developed by Annie J. Cannon during the 1900s.
Observation of double stars gained increasing importance during the 19th century. In 1834, Friedrich Bessel observed changes in the proper motion of the star Sirius, and inferred a hidden companion. Edward Pickering discovered the first spectroscopic binary in 1899 when he observed the periodic splitting of the spectral lines of the star Mizar in a 104 day period. Detailed observations of many binary star systems were collected by astronomers such as William Struve and S. W. Burnham, allowing the masses of stars to be determined from computation of the orbital elements. The first solution to the problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827.
The twentieth century saw increasingly rapid advances in the scientific study of stars. The photograph became a valuable astronomical tool. Karl Schwarzschild discovered that the color of a star, and hence its temperature, could be determined by comparing the visual magnitude against the photographic magnitude.
The development of the photoelectric photometer allowed very precise measurements of magnitude at multiple wavelength intervals. In 1921 Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope.
Important conceptual work on the physical basis of stars occurred during the first decades of the twentieth century.
In 1913, the Hertzsprung-Russell diagram was developed, propelling the astrophysical study of stars. Successful models were developed to explain the interiors of stars and stellar evolution. The spectra of stars were also successfully explained through advances in quantum physics. This allowed the chemical composition of the stellar atmosphere to be determined.
With the exception of supernovae, individual stars have primarily been observed in our Local Group of galaxies, and especially in the visible part of the Milky Way (as demonstrated by the detailed star catalogues available for our galaxy).
But some stars have been observed in the M100 galaxy of the Virgo Cluster, about 100 million light years from the Earth. In the Local Supercluster it is possible to see star clusters, and current telescopes could in principle observe faint individual stars in the Local Cluster - the most distant stars resolved have up to hundred million light years away.
However, outside the Local Supercluster of galaxies, neither individual stars nor clusters of stars have been observed. The only exception is a faint image of a large star cluster containing hundreds of thousands of stars located one billion light years away - ten times the distance of the most distant star cluster previously observed.
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. Historically, the term was also used to refer to a perceived pattern formed by prominent stars within apparent proximity to one another, and this practice is still common today.
The concept of the constellation was known to exist during the Babylonian period. Ancient sky watchers imagined that prominent arrangements of stars formed patterns, and they associated these with particular aspects of nature or their myths. Twelve of these formations lay along the band of the ecliptic and these became the basis of astrology. Many of the more prominent individual stars were also given names, particularly with Arabic or Latin designations.
As well as certain constellations and the Sun itself, stars as a whole have their own myths. To the Ancient Greeks, some "stars", known as planets, represented various important deities, from which the names of the planets Mercury, Venus, Mars, Jupiter and Saturn were taken. (Uranus and Neptune were also Greek and Roman gods, but neither planet was known in Antiquity because of their low brightness. Their names were assigned by later astronomers.)
Circa 1600, the names of the constellations were used to name the stars in the corresponding regions of the sky. The German astronomer Johann Bayer created a series of star maps and applied Greek letters as designations to the stars in each constellation. Later a numbering system based on the star's right ascension was invented and added to John Flamsteed's star catalogue in his book "Historia coelestis Britannica" (the 1712 edition), whereby this numbering system came to be called Flamsteed designation or Flamsteed numbering.
Under space law, the only internationally recognized authority for naming celestial bodies is the International Astronomical Union (IAU). A number of private companies sell names of stars, which the British Library calls an unregulated commercial enterprise. However, the IAU has disassociated itself from this commercial practice, and these names are neither recognized by the IAU nor used by them. One such star naming company is the International Star Registry, which, during the 1980s, was accused of deceptive practice for making it appear that the assigned name was official. This now-discontinued ISR practice was informally labeled a scam and a fraud, and the New York City Department of Consumer Affairs issued a violation against ISR for engaging in a deceptive trade practice.
As learned by star formation astronomers, stars are born in molecular clouds, large regions of slightly higher density of matter (though still less dense than the inside of an Earthly vacuum chamber), and form by gravitational instability inside those clouds triggered by shockwaves from supernovae.
High mass stars powerfully illuminate the clouds from which they formed. One example of such a nebula is the Orion Nebula.
Stars spend about 90% of their lifetime fusing hydrogen to produce helium in high-pressure reactions near the core. Such stars are said to be on the main sequence.
Small stars - called red dwarfs - burn their fuel very slowly and last tens to hundreds of billions of years, far longer than the time elapsed in the universe so far.
Red dwarfs are small stars that never really managed to get fired up. With masses of about 40% that of our sun, they are relatively cool, with a surface temperature of less than 3,200C, so they have a dimmer, reddish appearance. Red dwarfs collectively make up the vast majority of all stars in the universe. Stars that are smaller and dimmer still are known as brown dwarfs. These generally have a mass of less than 7% of our sun, making them too small to sustain hydrogen-burning fusion reactions at their core.
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type. They comprise the vast majority of stars and have a diameter and mass of less than one-third that of the Sun (down to 0.08 solar masses, which are brown dwarfs) and a surface temperature of less than 3,500 K. They emit little light, sometimes as little as 1/10,000th that of the sun. Due to the slow rate at which they burn hydrogen, red dwarfs have an enormous estimated lifespan; estimates range from tens of billions up to trillions of years.
Red dwarfs never initiate helium fusion and so cannot become red giants; the stars slowly contract and heat up until all the hydrogen is consumed. In any event, there has not been sufficient time since the Big Bang for red dwarfs to evolve off the main sequence.
The fact that red dwarfs remain on the main sequence while older stars have moved off the main sequence allows one to date star clusters by finding the mass at which the stars turn off the main sequence. In addition, the fact that no red dwarfs have evolved off the main sequence have been observed is evidence that the universe has a finite age.
One mystery which has not been solved as of 2004 is the lack of red dwarf stars with no metals (in astronomy a metal is any element other than hydrogen and helium). The Big Bang model predicts the first generation of stars should have only hydrogen, helium, and lithium. If such stars included red dwarfs, they should still be observable today, but are not. The conventional explanation is that without heavy elements, low mass stars cannot form and the first stars were extremely high mass population III stars which died quickly and produced the metals necessary for low mass stars to form later.
Red dwarf stars are believed to be the most common star type in the universe. Proxima Centauri, the nearest star to the Sun is a red dwarf, (Type M5, magnitude 11.0) as are twenty of the next thirty nearest. However, due to their low luminosity, few are known.
At the end of their lives, they simply become dimmer and dimmer, fading into black dwarfs - although none exist yet.
A black dwarf constitutes the remains of a Sun-sized star which has evolved to a black dwarf, or stellar remnant, subsequently cooled down such that it only emits black body radiation. None are known to exist in our universe, as the time taken for a white dwarf to cool to such a degree is hypothesized to be longer than the lifespan of the universe to date.
Even at the epoch when black dwarfs exist they will be extremely difficult to detect, emitting thermal radiation at a temperature not much above that of the cosmic microwave background radiation. One of the only ways to detect them may be through their gravitational influence.
Black dwarfs should not be confused with brown dwarfs, which are formed when gas contracts to form a star, but does not possess enough mass to initiate and sustain hydrogen nuclear fusion. (NB: what we now refer to as brown dwarfs were at times called black dwarfs in the 1960s.)
As most stars exhaust their supply of hydrogen, their outer layers expand and cool to form a red giant. In about 5 billion years, when the Sun is a red giant, it will subsume Mercury and Venus. Eventually the core is compressed enough to start helium fusion, and the star heats up and contracts. Larger stars will also fuse heavier elements, all the way to iron, which is the end point of the process.
An average-size star will then shed its outer layers as a planetary nebula. The core that remains will be a tiny ball of degenerate matter not massive enough for further fusion to take place, supported only by degeneracy pressure, called a white dwarf. It will fade into a black dwarf over very long stretches of time. In larger stars, fusion continues until collapse ends up causing the star to explode in a supernova.
This is the only cosmic process that happens on human timescales; historically, supernovae have been observed as "new stars" where none existed before. Most of the matter in a star is blown away in the explosion (forming nebulae such as the Crab Nebula) but what remains will collapse into a neutron star (a pulsar or X-ray burster) or, in the case of the largest stars, a black hole. The blown-off outer layers include heavy elements, which are often converted into new stars and/or planets. The outflow from supernovae and the stellar wind of large stars play an important part in shaping the interstellar medium.
Contaminated white dwarfs: Scientists solve riddle of celestial archaeology Science Daily - March 26, 2014
A decades old space mystery has been solved by an international team of astronomers. The team put forward a new theory for how collapsed stars become polluted - that points to the ominous fate that awaits planet Earth. Scientists investigated hot, young, white dwarfs - the super-dense remains of Sun-like stars that ran out of fuel and collapsed to about the size of the Earth. It has been known that many hot white dwarfs' atmospheres, essentially of pure hydrogen or pure helium, are contaminated by other elements -- like carbon, silicon and iron. What was not known, however, was the origins of these elements, known in astronomical terms as metals.
A white dwarf, also called a degenerate dwarf, is a stellar remnant composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun, and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored thermal energy. The nearest known white dwarf is Sirius B, 8.6 light years away, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910 by Henry Norris Russell, Edward Charles Pickering, and Williamina Fleming;, p. 1 the name white dwarf was coined by Willem Luyten in 1922.
White dwarfs are thought to be the final evolutionary state of all stars whose mass is not high enough to become a neutron star - over 97% of the stars in the Milky Way. After the hydrogen–fusing lifetime of a main-sequence star of low or medium mass ends, it will expand to a red giant which fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon, around 1 billion K, an inert mass of carbon and oxygen will build up at its center. After shedding its outer layers to form a planetary nebula, it will leave behind this core, which forms the remnant white dwarf. Usually, therefore, white dwarfs are composed of carbon and oxygen. If the mass of the progenitor is between 8 and 10.5 solar masses, the core temperature is sufficient to fuse carbon but not neon, in which case an oxygen-neon–magnesium white dwarf may be formed. Also, some helium white dwarfs appear to have been formed by mass loss in binary systems.
The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy, nor is it supported by the heat generated by fusion against gravitational collapse. It is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit - approximately 1.4 solar masses - beyond which it cannot be supported by electron degeneracy pressure. A carbon-oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may explode as a Type Ia supernova via a process known as carbon detonation. (SN 1006 is thought to be a famous example.)
A white dwarf is very hot when it is formed, but since it has no source of energy, it will gradually radiate away its energy and cool. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, a white dwarf will cool to temperatures at which it will no longer emit significant heat or light, and it will become a cold black dwarf. However, the length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the Universe (approximately 13.8 billion years), and since no white dwarf can be older than the age of the Universe, it is thought that no black dwarfs yet exist. The oldest white dwarfs still radiate at temperatures of a few thousand kelvins.
The interior of a stable star is in a state of hydrostatic equilibrium: the forces on any small volume almost exactly counterbalance each other. The balanced forces are inward gravitational force and an outward force due to the pressure gradient within the star. The pressure gradient is established by the temperature gradient of the plasma; the outer part of the star is cooler than the core. The temperature at the core of a main sequence or giant star is at least on the order of 107 K. The resulting temperature and pressure at the hydrogen-burning core of a main sequence star are sufficient for nuclear fusion to occur and for sufficient energy to be produced to prevent further collapse of the star.
As atomic nuclei are fused in the core, they emit energy in the form of gamma rays. These photons interact with the surrounding plasma, adding to the thermal energy at the core. Stars on the main sequence convert hydrogen into helium, creating a slowly but steadily increasing proportion of helium in the core. Eventually the helium content becomes predominant and energy production ceases at the core. Instead, for stars of more than 0.4 solar masses, fusion occurs in a slowly expanding shell around the degenerate helium core.
In addition to hydrostatic equilibrium, the interior of a stable star will also maintain an energy balance of thermal equilibrium. There is a radial temperature gradient throughout the interior that results in a flux of energy flowing toward the exterior. The outgoing flux of energy leaving any layer within the star will exactly match the incoming flux from below.
Most stars are identified only by catalogue numbers; only a few have names as such. The names are either traditional names (mostly from Arabic), Flamsteed designations, or Bayer designations.
The only body which has been recognized by the scientific community as having competence to name stars or other celestial bodies is the International Astronomical Union (IAU).
A number of private companies (e.g. the "International Star Registry") purport to sell names to stars; however, these names are not recognized by the scientific community, nor used by them, and many in the astronomy community view these organizations as frauds preying on people ignorant of how stars are in fact named. Read more Wikipedia
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and a slightly larger mass than protons. Neutron stars are very hot and are supported against further collapse because of the Pauli exclusion principle. This principle states that no two neutrons (or any other fermionic particle) can occupy the same place and quantum state simultaneously.
Astronomers discover most massive neutron star yet known PhysOrg - October 27, 2010
... a discovery with strong and wide-ranging impacts across several fields of physics and astrophysics. This neutron star is twice as massive as our Sun.
Team records 'music' from stars BBC - October 23, 2008
Scientists have recorded the sound of three stars similar to our Sun using France's Corot space telescope. A team writing in Science journal says the sounds have enabled them to get information about processes deep within stars for the first time. If you listen closely to the sounds of each star - by clicking on the media in this page - you'll hear a regular repeating pattern.These indicate that the entire star is pulsating. You'll also note that the sound of one star is very slightly different to the other. That's because the sound they make depends on their age, size and chemical composition. The technique, called "stellar seismology", is becoming increasingly popular among astronomers because the sounds give an indication of what is going on in the stars' interior.
Spots on supergiant star drive spirals in stellar wind PhysOrg - October 24, 2017
Massive stars are responsible for producing the heavy elements that make up all life on Earth. At the end of their lives they scatter the material into interstellar space in catastrophic explosions called supernovae - without these dramatic events, our solar system would never have formed. Zeta Puppis is an evolved massive star known as a 'supergiant'. It is about sixty times more massive than our sun, and seven times hotter at the surface. Massive stars are rare, and usually found in pairs called 'binary systems' or small groups known as 'multiple systems'. Zeta Puppis is special however, because it is a single massive star, moving through space alone, at a velocity of about 60 kilometers per second. "Imagine an object about sixty times the mass of the Sun, traveling about sixty times faster than a speeding bullet!" the investigators say.
Stellar 'Circle of Life' Captured in New NASA Photo Live Science - December 2, 2016
Rare system of five stars discovered BBC - July 8, 2015
The quintuplet consists of a pair of closely linked stars - binaries - one of which has a lone companion; it is the first known system of its kind. The pair of stars orbit around a mutual centre of gravity, but are separated by more than the distance of Pluto's orbit around the Sun.
Scientists discover brightest early galaxy and likely first generation stars PhysOrg - June 17, 2015
Astronomers using several of the largest telescopes on Earth and space have discovered the brightest galaxy yet found in the early Universe and have strong evidence that examples of the first generation of stars lurk within it. Astronomers have long theorized the existence of a first generation of stars known as Population III stars that were born out of the primordial material from the Big Bang. All the heavier chemical elements essential to life - including oxygen, nitrogen, carbon and iron - were forged in the bellies of stars. This means the first stars must have formed out of the only elements to exist prior to stars: hydrogen, helium and trace amounts of lithium.
Closest known flyby of star to our solar system: Dim star passed through Oort Cloud 70,000 years ago Science Daily - February 17, 2015
Astronomers from the US, Europe, Chile and South Africa have determined that 70,000 years ago a recently discovered dim star is likely to have passed through the solar system's distant cloud of comets, the Oort Cloud. No other star is known to have ever approached our solar system this close -- five times closer than the current closest star, Proxima Centauri. They analyzed the velocity and trajectory of a low-mass star system nicknamed "Scholz's star."
Researchers find evidence of fractal behavior in pulsating stars PhysOrg - February 4, 2015
A team of researchers working at the University of Hawaii using data from the Kepler space telescope, has found that the oscillations made by a star conform closely to the golden mean further study showed that it also behaves in a fractal pattern. In studying the Kepler data, the team was able to track the pulses that emanated from the star over a period of four years taken at 30 minute intervals. They found that two of star KIC 5520878's pulsating frequencies occurred at 4.05 and a 6.41 hour cycles - which the team noted had a ratio of 1.58, which is close to 1.618, aka the Golden Ratio -famously found in nature and sometimes artistic renderings. Intrigued, they looked deeper and found that the frequencies conformed to fractal patterns separating the oscillations into their constituent parts revealed additional weaker frequencies, similar to the way, the team points out, that images of shorelines display craggy lines regardless of how close or far away they are viewed from.
Planck telescope puts new datestamp on first stars BBC - February 5, 2015
The first stars in the Universe lit up later than was previously thought. That is the conclusion of scientists working on Europe's Planck satellite, which has made the most precise map of the "oldest light" in the cosmos. Earlier observations of this radiation had suggested that the first generation of stars burst into life about 420 million years after the Big Bang. The new Planck data now indicates they fired up around 560 million years after the Universe got going.
The oldest star in the universe? Maybe, maybe not PhysOrg - February 14, 2014
This week, the international media has trumpeted the discovery by Australian scientists of the oldest star in the universe, with the catchy name SMSS J031300.36-670839.3, formed in the almost pristine gas soon after the Big Bang. This would mean the star has been slowly burning away for almost 13.7 billion years. But this story may leave those that follow the scientific media scratching their heads slightly, as only six months ago the media telling us about HD 140283, the Methuselah Star, whose best-estimated age is almost 14.5 billion years. This formally makes HD 140283 older than the universe itself, but the uncertainty in the age, by about 800,000 years, could bring it back into line with our cosmological measurements for the universe's age.
'Oldest star' found from iron fingerprint PhysOrg - February 10, 2014
A team of astronomers has discovered the oldest known star in the Universe, which formed shortly after the Big Bang 13.7 billion years ago. The discovery has allowed astronomers for the first time to study the chemistry of the first stars, giving scientists a clearer idea of what the Universe was like in its infancy. As the Big Bang's name suggests, the universe burst into formation from an immense explosion, creating a vast soup of particles. Gigantic clouds of primordial soup, made mainly of hydrogen and helium, eventually collapsed to form the first stars - massive, luminous, short-lived objects that exploded as supernovae soon after. In the wake of such explosions, gas clouds gave rise to a second generation of stars that telescopes can still pick out today. Scientists have thought that the first stars in the universe burst with tremendous energy, spewing out the first heavy elements, such as carbon, iron, and oxygen. But according to new research from MIT, not all of these first stars may have been forceful exploders.
First Black Hole Orbiting a 'Spinning' Star Science Daily - January 16, 2014
Scientists have discovered the first binary system ever known to consist of a black hole and a 'spinning' star -- or more accurately, a Be-type star. Although predicted by theory, none had previously been found. Be-type stars are quite common across the Universe. In our Galaxy alone more than 80 of them are known in binary systems together with neutron stars. 'Their distinctive property is their strong centrifugal force: they rotate very fast, close to their break-up speed. It's like they were cosmic spinning tops.
Mystery Alignment of Dying Stars Puzzles Scientists Live Science - September 5, 2013
Dying stars that are among the most beautiful objects in the universe tend to line up across the night sky, and astronomers aren't sure why. These "cosmic butterflies" - actually a certain type of planetary nebula - all have their own formation histories, and they don't interact with each other. But something is apparently making them dance in step.
Earth's Gold Came from Colliding Dead Stars Science Daily - July 17, 2013
This artist's conception portrays two neutron stars at the moment of collision. New observations confirm that colliding neutron stars produce short gamma-ray bursts. Such collisions produce rare heavy elements, including gold. All Earth's gold likely came from colliding neutron stars. Gold is rare on Earth in part because it's also rare in the universe. Unlike elements like carbon or iron, it cannot be created within a star. Instead, it must be born in a more cataclysmic event -- like one that occurred last month known as a short gamma-ray burst (GRB). Observations of this GRB provide evidence that it resulted from the collision of two neutron stars -- the dead cores of stars that previously exploded as supernovae. Moreover, a unique glow that persisted for days at the GRB location potentially signifies the creation of substantial amounts of heavy elements -- including gold.
How the universe got its stars: An astronomical puzzle MSNBC - June 27, 2013
How star formation began is very much a controversial question. Astronomers have come a long way in understanding how stars form today, but the question of how the universe's first stars formed is an enduring mystery. While the topic remains complex and confusing, researchers say they hope to make strides in the near future with new and improved computer models and telescopes.
Weird Spinning Star Defies Explanation Live Science - January 25, 2013
Scientists have discovered a puzzling spinning star that is spontaneously switching between two very different personalities, flipping between emitting strong X-rays and emitting intense radio waves. While radio frequencies are known to vary as the star changes personalities, the newfound star is the first time example of variability in X-rays as well. The star, called a pulsar because it appears to pulse, has astronomers perplexed. The researchers say the pulsar's quick switching between radio and X-ray brightness implies large changes in the magnetosphere. But what drives these changes is not known.
Impossible Star Defies Astronomers' Theories Live Science - September 1, 2011
A primordial star at the outer edges of our Milky Way galaxy may upset current theories of star formation in the universe. The star simply shouldn't exist since it lacks the materials astronomers have long thought necessary for low-mass stars to form, scientists say. The star, with the somewhat cumbersome name of SDS J102915+172927, hails from the beginning of the universe. At 13 billion years old, it formed from the death of the first generation of stars. (The universe itself is estimated to be about 13.7 billion years old.) An analysis of the star's makeup reveals that it formed relatively quickly after the supernova-explosion deaths of a few of the short-lived original stars.
Hubble views the star that changed the universe PhysOrg - May 24, 2011
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view. The star goes by the inauspicious name of Hubble variable number one, or V1, and resides in the outer regions of the neighboring Andromeda galaxy, or M31. But in the early 1900s, most astronomers considered the Milky Way a single "island universe" of stars, with nothing observable beyond its boundaries. Andromeda was cataloged as just one of many faint, fuzzy patches of light astronomers called "spiral nebulae."
Two dying stars reborn as one PhysOrg - April 6, 2011
White dwarfs are dead stars that pack a Sun's-worth of matter into an Earth-sized ball. Astronomers have just discovered an amazing pair of white dwarfs whirling around each other once every 39 minutes. This is the shortest-period pair of white dwarfs now known. Moreover, in a few million years they will collide and merge to create a single star.
Seeing a Stellar Explosion in 3D PhysOrg - August 4, 2010
Astronomers using ESO's Very Large Telescope have for the first time obtained a three-dimensional view of the distribution of the innermost material expelled by a recently exploded star. The original blast was not only powerful, according to the new results. It was also more concentrated in one particular direction. This is a strong indication that the supernova must have been very turbulent, supporting the most recent computer models.
Scientists find most massive star ever discovered PhysOrg - July 21, 2010
Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters -- millions of times more luminous than the sun, losing weight through very powerful winds -- may provide an answer to the question, "how massive can stars be?"
Astronomers detect 'monster star' BBC - July 21, 2010
They are among the true monsters of space - colossal stars whose size and brightness go well beyond what many scientists thought was even possible. One of the objects, known simply as R136a1, is the most massive ever found. The star is seen to have a mass about 265 times that of our own Sun; but the latest modelling work suggests at birth it could have been bigger, still. Perhaps as much as 320 times that of the Sun, says Professor Paul Crowther from Sheffield University, UK. "If it replaced the Sun in our Solar System, it would outshine it by as much as the Sun currently outshines the full Moon," the astronomer told BBC News. The stars were identified by Crowther's team using a combination of new observations on the Very Large Telescope facility in Chile and data gathered previously with the Hubble Space Telescope.
Stars Just Got Bigger: A 300-Solar-Mass Star Uncovered Science Daily - July 21, 2010
The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun.
Unravelling the Mystery of Massive Star Birth: All Stars are Born the Same Way PhysOrg - July 14, 2010
Astronomers have obtained the first image of a dusty disc closely encircling a massive baby star, providing direct evidence that massive stars form in the same way as their smaller brethren. This discovery, made thanks to a combination of ESO's telescopes, is described in an article in this week's issue of Nature.
Astronomers Witness a Star Being Born PhysOrg - June 17, 2010
Astronomers have glimpsed what could be the youngest known star at the very moment it is being born. Not yet fully developed into a true star, the object is in the earliest stages of star formation and has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study that appears in the current issue of the Astrophysical Journal.
Unique eclipsing binary star system discovered PhysOrg - May 20, 2010
Astrophysicists at UC Santa Barbara are the first scientists to identify two white dwarf stars in an eclipsing binary system, allowing for the first direct radius measurement of a rare white dwarf composed of pure helium. The results will be published in the Astrophysical Journal Letters. These observations are the first to confirm a theory about a certain type of white dwarf star.
Mystery Disk Eclipses Star PhysOrg - April 8, 2010
This is the first close-up image of an eclipse beyond the solar system to be captured on camera by scientists.
Binary Superfast Stars Have Fast 5.4 Minute Orbits National Geographic - March 13, 2010
Newly discovered star one of hottest in Galaxy PhysOrg - December 2, 2009
Stellar blast is record-breaker BBC - October 29, 2009
...a gamma-ray burst from a star that died 13.1 billion light-years away.
Most Distant Object Found; Light Pierced "Dark Age" Fog National Geographic - October 28, 2009
The most distant object yet spied in the universe is the remnant of a star about 13 billion light-years from Earth that sheds new light on the earliest days of the universe.
Universe's first stars may have been twins New Scientist - July 9, 2009
A good fraction of the universe's first stars may have been born in pairs, a new study suggests. Since each star in a pair is likely to be smaller than a single star created from the same natal material, the work may help explain why so far no evidence has been found for exotic physical processes thought to occur in super-heavy stars from the early universe. It may also mean the star pairs could be detected by the gravitational waves they would emit at the end of their lives. Not much is known about the universe's first stars. It is theoretically possible to see them with telescopes by looking for objects that are extremely far away, since their light takes billions of years to reach Earth. But today's telescopes are not powerful enough to see the dim objects. Computer simulations suggest the ancient beacons, called population III stars, were extraordinarily massive, ranging from 30 to 300 times the mass of the sun. By contrast, the average Milky Way star is just 0.8 times the sun's mass.
Rare Magnetar Discovered: Giant Eruption Reveals 'Dead' Star Science Daily - June 16, 2009
Giant Eruption Reveals 'Dead' Star Space Daily - June 18, 2009
An enormous eruption has found its way to Earth after
traveling for many thousands of years across space.
... the dead star belonging to a rare group: the magnetars.
Dead Exploded Star Resurrected in 3-D Space.com - January 9, 2009
The dying remains of an exploded star have been resurrected in a new three-dimensional film that flies through the ancient supernova. At center stage in the new movie is Cassiopeia A, a dead star that exploded about 330 years ago to forge one of the youngest supernova graves in the Milky Way galaxy. Astronomers used observations from several ground- and space-based telescopes to build the 3-D voyage through the supernova, which starts at the remnant?s neutron star core. The movie then pulls back to reveal the wispy, gaseous remains of Cassiopeia A in hues of red, green, yellow and blue to mark materials seen in different wavelengths.
Photo: Star Portrait Reveals "Family Tree" National Geographic - August 22, 2008
Several generations of stars "pose" for a family portrait amid curtains of clouds in the star-forming region called W5, about 6,500 light-years away. The composite image was released today to mark the upcoming five-year anniversary of the Spitzer Space Telescope, which lifted off from Cape Canaveral Air Force Station in Florida on August 25, 2003. Since its launch, Spitzer's infrared images have been helping astronomers peer through gases and dust that can block visible light, revealing distant cosmic objects in high detail. The latest image of W5 uncovered a stellar family tree that offers scientists new evidence for the theory of triggered star formation. This is when powerful winds from massive stars carve out cavities inside nebulae, compressing gases along the rims of the cavities and spawning new stars.
How stars form amid black hole chaos MSNBC - August 21, 2008
Deep in the center of our galaxy, circling suspiciously close to the giant black hole lurking there, is a group of massive stars. Now scientists have designed a model that shows for the first time how these stars might have formed in such an extreme environment. Astronomers have long puzzled how these massive stars came to be in the vicinity of a huge black hole. They couldn't have formed as most stars do, from a tenuous cloud of gas, because this cloud would have been ripped apart by the savage gravitational forces from the black hole nearby. One guess was that the stars originally formed elsewhere as a cluster and later spiraled inward. But no trace has been found of the trail of stars this process would have left behind.
Cosmic Rosetta Stone: How The First Stars In The Universe Came Into Existence Science Daily - August 1, 2008
Researchers believe that our universe began with the Big Bang about 13 billion years ago, and that soon after that event, matter began to form as small dust grains and gases. How the first stars formed from this dust and gas has been a burning question for years, but a state-of-the-art computer simulation now offers the most detailed picture yet of how these first stars in the universe came into existence, researchers say. The composition of the early universe was quite different from that of today, and the physics that governed the early universe were also somewhat simpler. Dr. Naoki Yoshida and colleagues in Japan and the U.S. incorporated these conditions of the early universe, sometimes referred to as the "cosmic dark ages," to simulate the formation of an astronomical object that would eventually shine its light into this darkness.
Big Bang Ripples Formed Universe's First Stars National Geographic - July 31, 2008
Ripples in the early universe following the big bang 13.7 billion years ago caused gases to coalesce into the luminous seeds of the first stars, a new computer simulation reveals. Such stellar embryos, or protostars, were the universe's first astronomical objects and its first sources of light. Previous telescope observations have shown that very distant - and thus very old - cosmic objects contain heavy elements such as carbon and iron, which are formed only by the nuclear reactions inside full-grown stars. This suggests that massive stars must have existed even earlier in the universe's history than telescopes can see. Until now, the earliest stages of primordial star formation had not been modeled in detail.
Red dwarf emits brightest burst of light ever, according to astronomers MSNBC - May 19, 2008
A tiny star recently unleashed what is considered the brightest burst of light ever seen in the universe from a normal star, astronomers announced today. Shining with only 1 percent of the sun's light and boasting just a third of the sun's mass, this run-of-the-mill star previously was nothing to write home about. On April 25, the red dwarf star, known as EV Lacertae, unleashed a mega-flare, packing the power of thousands of solar flares. Since the star is located 16 light-years away, in reality, the flare actually occurred 16 years ago. The flare was first seen by the Russian-built Konus instrument on NASA's Wind satellite in the early morning hours of April 25. Two minutes later, Swift's X-ray Telescope caught the flare. The star remained bright in X-rays for eight hours before settling back to normal. It would have been visible to the naked eye if the star had been easily observable in the night sky at the time. EV Lacertae's constellation, Lacerta, is visible in the spring for only a few hours each night in the Northern Hemisphere.
Stars that Bend Time Thunderbolts - March 11, 2008
A University of Michigan press release announces "warped space-time" around a so-called "neutron star." Could electricity provide a better explanation? The smeared lines of an iron spectrum have given NASA and University of Michigan astronomers another mystery to solve when it comes to explaining the universe. Using the XMM-Newton and the JAXA/NASA x-ray observatories, high-velocity particles in orbit around Serpens X-1 seem to indicate relativistic effects. According to Sudip Bhattacharyya of NASA's Goddard Space Flight Center:
Sun-like Star Flips Its Magnetic Field Like Our Sun Science Daily - February 27, 2008
It has been known for many years that the Sun's magnetic field changes its direction every 11 years, but this is the first time that such a change has been observed in another star. The team of astronomers, who made use of Canada-France-Hawaii Telescope atop Mauna Kea, are now closely monitoring tau Bootis to see how long it will be before the magnetic field reverses again.
Planets form twice for two old stars BBC - January 10, 2008
Two old stars may be undergoing a second episode of planet formation, long after their initial window of opportunity. Astronomers believe the stars once had orbiting companions, but that these were engulfed when the stars expanded. This caused matter to be ejected from the stars, forming a disc of dust and gas from which planets could form anew.
"Blue Blobs" in Space Are Odd Stars National Geographic - January 9, 2008
Mysterious "blue blobs" about 12 million light-years away are actually clusters of orphan stars that formed in an unlikely part of the universe, new images released today reveal. The blobs were spotted near a galaxy called M82 using the Very Large Array of radio telescopes and the GALEX space telescope, which showed the objects' ultraviolet glow. An analysis of archived high-resolution images from the Hubble Space Telescope then revealed that the blobs were clusters of mostly young stars. Scientists were surprised by the find, because the clusters of bright, massive stars sit along a wispy bridge of gases connecting M82 to two other galaxies it collided with 200 million years ago. This means that the stars are in the middle of nowhere.
Star "Jewel Box" Spotted by Hubble National Geographic - October 3, 2007
Extreme Star Cluster Bursts Into Life Science Daily - October 3, 2007
Starburst Cluster in NGC 3603 NASA - October 5, 2007
A Star with a Comet's Tail NASA - August 16, 2007
Colossal tail trails dying star BBC - August 15, 2007
White Dwarf Pulses Like A Pulsar Science Daily - January 3, 2008
White dwarfs are commonly believed to be stellar corpses, the dense, slowly cooling remnants of low to medium mass stars. So scientists were surprised to find a high-energy x-ray pulse coming from the white dwarf known as AE Aquarii. Scientists say the emission looks like that of a pulsar - a rotating neutron star formed after a supernova, the life-ending explosion of a massive star.
A mere 20,000 light-years from the Sun lies NGC 3603, a resident of the nearby Carina spiral arm of our Milky Way Galaxy. NGC 3603 is well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies. Surrounding the cluster are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years.
Dark matter clues in oldest stars BBC - September 15, 2007
A computer model of the early Universe indicates the first stars could have formed in spectacular, long filaments.
Comets Tails and Stars
Odd Star Sheds Cometlike Tail, Astronomers Say National Geographic - August 16, 2007
The star Mira sheds a comet like tail of rich material as it streaks through space - something that has never been seen before - astronomers announced today. Acting sort of like a cosmic Johnny Appleseed, the star is leaving behind carbon, nitrogen, oxygen, and other important "seed" elements needed for new stars, planets, and potential life to form.
Astronomers using a NASA space telescope, the Galaxy Evolution Explorer, have spotted an amazingly long comet-like tail behind a star streaking through space. The star, named Mira after the Latin word for "wonderful," has been a favorite of astronomers for about 400 years, yet this is the first time the tail has been seen. Galaxy Evolution Explorer--"GALEX" for short--scanned the popular star during its ongoing survey of the entire sky in ultraviolet light. Astronomers then noticed what looked like a comet with a gargantuan tail. In fact, material blowing off Mira is forming a wake 13 light-years long, or about 20,000 times the average distance of Pluto from the sun. Nothing like this has ever been seen before around a star.
The appendage, which measures a colossal 13 light years in length, was spotted by Nasa's Galaxy Evolution Explorer (Galex) space telescope.The researchers said that nothing like it had ever been spotted around a star.
Ancient star nearly as old as the universe NBC - May 12, 2007
Long before our solar system formed and even before the Milky Way assumed its final spiral shape, a star slightly smaller than the sun blazed into life in our galaxy, formed from the newly scattered remains of the first stars in the universe. Employing techniques similar to those used to date archeological remains here on Earth, scientists have learned that a metal-poor star in our Milky Way called HE 1523 is 13.2 billion years old-just slightly younger than 13.7 billion year age of the universe. Our solar system is estimated to be only about 4.6 billion years old.
Hubble Spies Dazzling Death of a Sunlike Star National Geographic - February 14, 2007
Despite losing one of its most popular cameras last month, the Hubble Space Telescope is still proving its worth, capturing a new round of awe-inspiring images with its remaining camera
Massive Star Forms by Absorption, Not Collision Scientific American - September 28, 2006
Astronomers have captured the strongest evidence yet that the growth of high-mass stars occurs by the rapid absorption of hot gas and not by the collision of several smaller stars. Researchers observed a young high-mass star that seems to be pulling in a rotating disk of gas and spraying some of that gas outward in jets, as modeling predicts.
'Dead star' erupts for big show BBC - April 7, 2006
Scientists are studying the violent outburst of a dead star as it tries to fire back into life. The white dwarf star in the Ophiuchus constellation has exhausted its own nuclear fuel but is now stealing it from a neighboring giant. Every 20 years or so, it gathers sufficient material to explode with enough intensity to be seen from Earth with the naked eye. The so-called recurrent nova event has now flared up six times in 108 years.
Planets around Dead Stars NASA - April 5, 2006
The infrared telescope surveyed the scene around a pulsar, the remnant of an exploded star, and found a surrounding disk made up of debris shot out during the star's death throes. The dusty rubble in this disk might ultimately stick together to form planets. This is the first time scientists have detected planet-building materials around a star that died in a fiery blast.
New Kind of Cosmic Object Discovered National Geographic - February 15, 2006
A multinational team of astronomers has discovered an entirely new kind of cosmic object. The small, highly compressed neutron stars, named Rotating Radio Transients (RRATs), are likely related to pulsars. Neutron stars are the staggeringly dense cores of massive stars left behind after supernova explosions. The objects contain one and a half times the mass of our own sun packed into a space the size of a large city.
NASA's Spitzer Uncovers Hints Of Mega Solar Systems Science Daily - February 8, 2006
... two huge "hypergiant" stars circled by monstrous disks of what might be planet-forming dust.
Chandra X-ray Observatory Images Of N49B, The Remains Of An Exploded Star Science Daily - April 2004
The Chandra image of N49B, the remains of an exploded star, shows a cloud of multimillion-degree gas that has been expanding for about 10,000 years.
Diamond star thrills astronomers BBC - February 16, 2004
Twinkling in the sky is a diamond star of 10 billion trillion trillion carats.
Mystery of bizarre double star unraveled MSNBC - January 2004
Black hole consumes star but can't digest it all - This artist's conception shows a super-giant star in front of a black hole in the SS 433 double-star system. The black hole pulls material from the star, and that material whirls into a disk (shown in white) surrounding the black hole. All that activity causes the disk to throw off high-speed jets, shown in blue and red.
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Star "Jewel Box" Spotted by Hubble National Geographic - October 3, 2007
Extreme Star Cluster Bursts Into Life Science Daily - October 3, 2007
Starburst Cluster in NGC 3603 NASA - October 5, 2007
A Star with a Comet's Tail NASA - August 16, 2007
Colossal tail trails dying star BBC - August 15, 2007