Folks , just like our Sun's energy output varies as it goes through Solar cycles (causing periodical ice ages on Earth) , so is the case with other stars in the Universe . However , mainstream astronomers and climatologists stubbornly adhere to the idea that Solar/Stellar output is constant and this couldn't be further from the truth .
The best possible evidence of this "variability" in energy output of stars is provided by the star called Betelgeuse . This strongly affirms the Electric Universe view of stars :-
Betelgeuse before (left) and after its unprecedented dimming in 2019. Credit: ESO/M. Montargès et al .
After a mysterious four-month fading streak, the star known as Betelgeuse could be on its way to regaining its shine.
Easily recognizable as the right ‘shoulder’ in the constellation Orion, Betelgeuse is normally one of the ten brightest stars in the night sky. But it began getting dimmer in October last year, and by mid-February it had lost more than two-thirds of its brilliance — a difference noticeable to the naked eye. But the star has now brightened by around 10% from its dimmest point, says Edward Guinan, an astrophysicist at Villanova University outside Philadelphia, Pennsylvania, whose team has been tracking it for 25 years.
“For now, it looks like it’s bottoming out,” says Andrea Dupree, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. “But who knows, maybe it will cough and go back down again.” A group of amateur and professional astronomers called the American Association of Variable Star Observers, also based in Cambridge, has also documented the upswing.
The reasons for the dimming remain a puzzle, Dupree says. Astronomers have proposed several explanations, but none is sufficient to explain all the observations, she adds.
Friendly giant
Betelgeuse is a favourite of stargazers worldwide. At a relatively close 220 parsecs (700 light years) from the Sun, the red supergiant — a large but relatively cool-burning type of star — has also been a boon for astronomers. Although its mass is just a dozen times that of the Sun, its dimensions are gigantic: if Betelgeuse were in the centre of the Solar System, it might engulf all the planets up to Jupiter.
As a consequence, it is one of the few stars that can be imaged in detail from Earth, as opposed to appearing as a single, unresolved dot of light. Since the 1990s, Dupree and others have been able to reveal features on its surface called convection cells — blobs of hot plasma that seethe up to the surface before cooling and falling back down. These are enormous: whereas convection cells on the Sun are roughly the size of France, those on Betelgeuse “are the size of from here to Mars”, Dupree says.
Because it is so bright, the star can overwhelm many state-of-the-art astronomical instruments, and observing it requires special measures. In ground-based infrared observations made this year, for example, Dupree and her collaborators had to use the telescope in ‘slew mode’ — quickly panning across the sky so that no spot on the camera sensor would be exposed to Betelgeuse’s light for too long.
But the star’s brightness is not a problem for Guinan. For decades, his team has been measuring it with a 25-centimetre amateur telescope set up in his colleague Richard Wasatonic’s garden in Allentown, Pennsylvania. The easy access has its perks for Wasatonic, Guinan says. “We take data every clear night, usually two nights a week. Whenever the sky clears, he just runs outside in his pyjamas.”
Broken routine
Guinan’s team has documented a roughly 425-day cycle of dimming in the star, but normally the brightness would vary by no more than 25%. Last year, Guinan says, he considered shutting down the programme because the team was “getting tired” of the star, but ultimately decided against it. “I told Richard, if we stop, it will do something,” he says.
Then, in October, Betelgeuse began to dim, and by December the fading had become so dramatic that Guinan decided to send out an online alert called an astronomer’s telegram. Many others rushed to observe the star.
One leading explanation for the dimming is the emergence of a large, unusually cool convection cell. Another is that the star could be moving behind a dust cloud. But Dupree says that the observations made so far seem mutually inconsistent. “The ultraviolet behaviour is different from the optical, which behaves differently from the infrared.”
Some have speculated that the star’s erratic swings in brightness mean it might be approaching the end of its life. Betelegeuse is estimated to be less than 10 million years old, but astrophysicists predict that it will end in a supernova explosion sometime in the next 100,000 years. When it does, it will be a spectacular sight — for weeks, it will be brighter than the full Moon and visible during the day. But what happens right before a star explodes in this way is unknown, and astronomers say the exact timing of the fiery end is impossible to predict. Still, says Guinan, “I’m cheering for it to blow up.”
List members , I think it is important here to highlight the VARIABLE nature of stars - our Sun being of that type as well , though fortunately for life on Earth , only mildly so !
**The other key point is that variable stars are also observed to be "pulsating" and actually contracting/expanding continuously . This also resonates well with the ancient cosmic philosophies such as "inside out" , "outside in" and "as above , so below" .
This reminds me of Nassim Haramein's "dynamic double torus" model , that provides for such ongoing contraction/expansion of stars . In any case , only a hollow star can expand/contract in this manner , a solid sphere would never show such behaviour :))
Here are a couple of wire frame simulations to understand how such expansion/contraction is taking place in a toroidal framework . The great thing is - hollow structure is an intrinsic part of the toroidal framework :-
A variable star is, quite simply, a star that changes brightness. A star is considered variable if its apparent magnitude (brightness) is altered in any way from our perspective on Earth. These changes can occur over years or just fractions of a second, and can range from one-thousandth of a magnitude to 20 magnitudes. More than 100,000 variable stars are known and have been catalogued, and thousands more are suspected variables. Our own sun is a variable star; its energy output varies by approximately 0.1 percent, or one-thousandth of its magnitude, over an 11-year solar cycle.
History of variable stars
The first modern identified variable star was Omicron Ceti, later renamed Mira. It had been described as a nova in 1596 by David Fabricius. In 1638, Johannes Holwards observed Omicron Cetipulsating in a regular 11-month cycle. This was an important discovery, as it helped verify that the stars were not eternal and invariable as ancient philosophers such as Aristotle had believed. The discovery of variable stars, along with reports of supernovae, paved the way for development of the science of astronomy.
In the abstract of a talk given to celebrate the 400th anniversary of Mira’s discovery, Dorrit Hoffleit, of Yale University, said, “Within the first century following Fabricius, four Mira-type variables were discovered, and in all cases it has been found that the stars were suspected of being novae long before their "official" discovery in the Western World. Three of the four had been recorded as novae in early Chinese or Korean records.”
In 1669, a second variable star was identified by Geminiano Monanari. It was an eclipsing variable called Algol, although its variability was not explained until more than a hundred years later by John Goodricke in 1784. The third variable star, Chi Cygni, was observed in 1686 and in 1704. Over the next 80 years seven more variable stars were identified.
Since 1850 numerous variable stars have been observed, a process aided by the development of photography. As of 2008, more than 46,000 variable stars in the Milky Way Galaxy were listed in the General Catalogue of Variable Stars.
Characteristics and composition of variable stars
There are a number of reasons for variability. These include changes in star luminosity or in star mass, and obstructions in the amount of light that reaches Earth. Pulsating variables swell and shrink. Eclipsing binaries get dimmer when a companion star moves in front, then brighten as the occulting star moves away. Some of the identified variable stars are actually two very close stars that exchange mass when one takes atmosphere from the other.
There are two different categories of variable stars. Intrinsic variables are stars whose luminosity physically changes due to pulsations, eruptions or through swelling and shrinking. Extrinsic variables are stars that change in brightness because of being eclipsed by stellar rotation or by another star or planet.
Three Cepheid variable stars, pulsating stars used to measure distance and age of objects, are visible in this view of the heart of the Milky Way. This image was taken using the South African Astronomical Observatory and released Aug. 24, 2011. (Image credit: N. Matsunaga)
Intrinsic variables
Cepheid Variables are very luminous stars, 500 to 300,000 times greater than the sun, with short periods of change that range from 1 to 100 days. They are pulsating variables that expand and shrink dramatically within a short period of time, following a specific pattern. Astronomers can make distance measurements to a Cepheid by measuring the variability of its luminosity, which makes them very valuable to the science.
Other pulsating variables include RR Lyrae stars, which are short period, older stars that are not as large as Cepheids; and RV Tauri stars, supergiants with greater light variations. Long-period pulsating variables include the Mira class, which are cool red supergiants with large pulsations; and Semiregular, which are red giants or supergiants with longer periods that can range from 30 to 1000 days. One of the best-known Semiregular Variables is Betelgeuse. Irregular pulsating variables have also been identified. These are usually red supergiants, but very little study has been done on them.
When it comes to changing astronomers’ perception of the universe, the Cepheid variable V1 played one of the pivotal roles. The important variable star allowed American astronomer Edwin Hubble to determine that the filmy nebula in which it lay was, in fact, another galaxy entirely, demonstrating that the Milky Way did not contain the entire universe.
"V1 is the most important star in the history of cosmology," astronomer Dave Soderblom of the Space Telescope Science Institute (STScI) in Maryland said in a statement. "It's a landmark discovery that proved the universe is bigger and chock full of galaxies.”
Cataclysmic Variables(also called Explosive Variables) brighten because of sharp or violent outbursts caused by thermonuclear processes either on the surface or deep inside. These include binary type stars, with two close stars having a mutual effect on mass. Supernovae, Novae, Recurrent Novae and Dwarf Novae are a group of stars that have dramatic or sudden magnitude increases, usually because of a stellar explosion.
Supernovae are the most dramatic, at times emitting as much energy as a whole galaxy. They can increase more than 20 magnitudes, becoming approximately one hundred million times brighter. Supernovae usually represent the death of a massive star, although the core can remain as a neutron star or remnants can form nebulae.
Novae and Recurrent Novae are close binary systems that are variable due to explosions on the surface, but the star is not destroyed. Nova Scorpii, which obtained peak brightness in 2007, is the brightest seen in recent years; Nova Cygni is the brightest seen in the last 70 years. The brightest measured nova since 1901 was Nova Aquilae, which in 1918 shone almost as brightly as Sirius, the brightest star in the sky.
Dwarf Novae are double white stars that transfer mass and cause outbursts of regular variations. Another form of explosive variable are Symbiotic stars, close binary systems with a red giant and a hot blue star enmeshed in a cloud of dust or gas.
Eruptic Variables are stars with eruptions or flaring on the surface or interaction with other interstellar matter. There are quite a number of sub-types in this category, including luminous blue variables, flare stars, supergiants, protostars, and Orion variables. Some eruptic variables are close binary systems.
Extrinsic variables
Eclipsing Binary Stars are stars that pass in front of each other, causing fluctuation and obscuring of the light seen on Earth. Eclipsing binary stars may have their own planets, which eclipse their light similar to a lunar eclipse on Earth. One of the best-known eclipsing binary stars is Algol.
Rotating Stars are variable stars that show small light changes caused by patches of light spots on their surfaces. They may have bright spots at the magnetic poles. Rotating stars are often binary systems and can be non-spherical or ellipsoidal in shape, which causes brightness changes as they move.
Pulsars are rotating neutron stars — the core of long-exploded supernovae — that emit electromagnetic radiation that is only seen when the beam is pointing at Earth. Pulsars produce precise, measurable intervals of light, and are often compared to lighthouses as they periodically sweep beams of energy while they orbit.
Some fast-spinning pulsars rotate their city-size mass multiple times per second; these are known as millisecond pulsars. The fastest known millisecond pulsar rotates 43,000 times in a minute. According to NASA, “Millisecond pulsars are thought to achieve such speeds because they are gravitationally bound in binary systems with normal stars. During part of their stellar lives, gas flows from the normal star to the pulsar. Over time, the impact of this falling gas gradually spins up the pulsar's rotation.”
This photo taken by astronomers using the South African Astronomical Observatory shows the center of our Milky Way galaxy and two beacon-like pulsating stars, known as Cepheids, that serve as distance signposts for astronomers. This image was released Aug. 24, 2011. (Image credit: N. Matsunaga)
Variable stars: future research
Research on variable stars is extremely important as it gives scientists information on star properties of mass, radius, temperature and luminosity, as well as information on the structure and composition of the star and how it has evolved. Understanding the nature of variable stars requires systematic observation of behavior over many decades. Variable stars are analyzed visually and with photographic, photoelectric and calibrated charge-coupled device (CCD) techniques. Amateur astronomers play an important role in collecting data and submitting observations to the AAVSO International Database.
Within the different categories of variables, some are particularly valuable to astronomy, since their variability can be measured. Research into the Cepheid variables helps determine the age of the universe and has provided information on the distant galaxies. Studies of Mira variables are important to our understanding of our Sun. Supernovae give us insight into how the universe is expanding, while
Cataclysmic variables help in understanding active galaxies and supermassive black holes. Variable stars are a specific field of study in astronomy, providing important information on how and why things change over time. They play a significant role in our understanding of the universe .
List members , researchers from the Max Planck Institute have done this interesting study about the variable sunshine from our Sun , enclosed here for your reference . Then further below is a good close up view of what the giant star Betelgeuse might actually look like , with it's oversized spots - it unmistakably appears to be Hollow :-
Variable sunshine
Max Planck researchers explain why our Sun's brightness fluctuates
The Sun shines from the heavens, seemingly calm and unvarying. In fact, it doesn't always shine with uniform brightness, but shows dimmings and brightenings. Two phenomena alone are responsible for these fluctuations: the magnetic fields on the visible surface and gigantic plasma currents, bubbling up from the star's interior. A team headed by the Max Planck Institute for Solar System Research in Göttingen reports this result in today's issue of Nature Astronomy. For the first time, the scientists have managed to reconstruct fluctuations in brightness on all time scales observed to date – from minutes up to decades. These new insights are not only important for climate research, but can also be applied to distant stars. And they may simplify the future search for exoplanets.
The flows of hot plasma within the Sun create a characteristic pattern on its surface: the granulation. Bright and darker regions within this pattern change quickly. The granulation is mainly responsible for the Sun’s brightness variations that occur within less than five hours. This image of the granulation was taken in 2009 by the instrument IMaX on board the balloon-borne solar observatory Sunrise .
When an exoplanet transits in front of its parent star, the star darkens briefly. Even from a distance of many light-years, space telescopes register these changes – and thus detect the exoplanets. In theory. In practice, it's more complicated, as the brightness of many stars fluctuates, similar to that of the Sun.
These fluctuations can overlay the signals of passing exoplanets. “However, if we are aware of the details of the star's intrinsic brightness fluctuations, exoplanets can be detected with great precision”, says Alexander Shapiro of the Max Planck Institute for Solar System Research.
Shapiro and his colleagues have taken a first step in this direction with their current paper – with a detailed look at a special star: our Sun. Since the beginning of the space age, numerous spacecraft have delivered detailed data collected unaffected by the disturbances caused by the Earth’s atmosphere.
These data seriously challenge any model describing fluctuations in stellar brightness: can the measured fluctuations be reconstructed using a model? And is it possible to link the fluctuations to the physical properties of the star?
One particular difficulty: the brightness of our Sun varies on very different time scales. Some fluctuations have cycles of only a few minutes; others, which have an impact on Earth's long-term climate, can only be recorded by researchers over decades. A unified theory encompassing all of these time scales has so far been lacking.
The new study's tour de force lies exactly in this point. It proves that only two phenomena determine how bright our star shines. On the one hand are the hot plasma currents rising from the interior of the Sun, cooling and sinking again into its depths. The hot, ascending material is brighter than the plasma that has already cooled on the surface.
In this way, the currents generate a characteristic, rapidly changing pattern of light and dark areas, known as granulation. Typical structures within this granulation are several hundred kilometres in size. “Granulation primarily causes rapid brightness fluctuations, with time-scales of less than five hours”, says Max Planck researcher and co-author Natalie Krivova.
The Sun’s magnetic fields are responsible for our star’s long-term brightness variations. At its surface, they become… [more]
On the other hand, the Sun's variable magnetic fields play a decisive role. During periods of high activity, they can be recognized on the visible surface of our star by way of dark regions (sunspots) and especially bright areas (faculae). Compared to granulation, both structures are very large; some sunspots can even be discerned with the naked eye from Earth. In addition, variations in their number and form are considerably slower. Changes in the Sun's magnetic field therefore lead to brightness fluctuations across time scales of more than five hours.
For their analyses, the researchers employed data obtained from instruments on the SOHO (Solar and Heliospheric Observatory) and SDO (Solar Dynamics Observatory) space probes, which have been recording the brightness patterns and the magnetic fields on the surface of the Sun for years. Using these records, some of which cover a 19-year period of solar development, they were able to analyze brightness fluctuations and in turn compare them with measured data obtained from PICARD and SOHO (obtained by another instrument than recorded the magnetic field).
All previously measured brightness fluctuations – both rapid and very long term – can be reproduced in this way. “The results of our study show us that we have identified the governing parameters in our model”, concludes Sami K. Solanki, Director at the Max Planck Institute for Solar System Research and second author of the study. “This will now allow us, finally, to model the brightness fluctuations of other stars”.
Betelgeuse – a giant with blemishes
Gigantic star spots are probably the reason for the recent drop in brightness of the red giant star
Betelgeuse, the bright star in the constellation of Orion, has been fascinating astronomers in the recent months because of its unusually strong decline in brightness. Scientists have been discussing a number of scenarios trying to explain its behaviour. Now a team led by Thavisha Dharmawardena of the Max Planck Institute for Astronomy have shown that most likely unusually large star spots on the surface of Betelgeuse have caused the dimming. Their results rule out the previous conjecture that it was dust, recently ejected by Betelgeuse, which obscured the star.
Red Supergiant: An artist's impression of Betelgeuse. Its surface is covered by large star spots, which reduce its brightness. During their pulsations, such stars regularly release gas into their surroundings, which condenses into dust.
Red giant stars like Betelgeuse undergo frequent brightness variations. However, the striking drop in Betelgeuse's luminosity to about 40% of its normal value between October 2019 and April 2020 came as a surprise to astronomers. Scientists have developed various scenarios to explain this change in the brightness of the star, which is visible to the naked eye and almost 500 light years away. Some astronomers even speculated about an imminent supernova. An international team of astronomers led by Thavisha Dharmawardena from the Max Planck Institute for Astronomy in Heidelberg have now demonstrated that temperature variations in the photosphere, i.e. the luminous surface of the star, caused the brightness to drop. The most plausible source for such temperature changes are gigantic cool star spots, similar to sunspots, which, however, cover 50 to 70% of the star’s surface.
“Towards the end of their lives, stars become red giants,” Dharmawardena explains. “As their fuel supply runs out, the processes change by which the stars release energy." As a result, they bloat, become unstable and pulsate with periods of hundreds or even thousands of days, which we see as a fluctuation in brightness. Betelgeuse is a so-called Red Supergiant, a star which, compared to our Sun, is about 20 more massive and roughly 1000 times larger. If placed in the centre of the solar system, it would almost reach the orbit of Jupiter.
Because of its size, the gravitational pull on the surface of the star is less than on a star of the same mass but with a smaller radius. Therefore, pulsations can eject the outer layers of such a star relatively easily. The released gas cools down and develops into compounds that astronomers call dust. This is why red giant stars are an important source of heavy elements in the Universe, from which planets and living organisms eventually evolve. Astronomers have previously considered the production of light absorbing dust as the most likely cause of the steep decline in brightness.
To test this hypothesis, Thavisha Dharmawardena and her collaborators evaluated new and archival data from the Atacama Pathfinder Experiment (APEX) and the James Clerk Maxwell telescope (JCMT). These telescopes measure radiation from the spectral range of submillimetre waves (terahertz radiation), whose wavelength is a thousand times greater than that of visible light. Invisible to the eye, astronomers have been using them for some time to study interstellar dust. Cool dust in particular glows at these wavelengths.
“What surprised us was that Betelgeuse turned 20% darker even in the submillimetre wave range,” reports Steve Mairs from the East Asian Observatory, who collaborated on the study. Experience shows that such behaviour is not compatible with the presence of dust. For a more precise evaluation, she and her collaborators calculated what influence dust would have on measurements in this spectral range. It turned out that indeed a reduction in brightness in the sub-millimetre range cannot be attributed to an increase in dust production. Instead, the star itself must have caused the brightness change the astronomers measured.
Physical laws tell us that the luminosity of a star depends on its diameter and especially on its surface temperature. If only the size of the star decreases, the luminosity diminishes equally in all wavelengths. However, temperature changes affect the radiation emitted along the electromagnetic spectrum differently. According to the scientists, the measured darkening in visible light and submillimeter waves is therefore evidence of a reduction in the mean surface temperature of Betelgeuse, which they quantify at 200 K (or 200 °C).
Light and dark: These high-resolution images of Betelgeuse show the distribution of brightness in visible light on its surface before and during its… [more]
“However, an asymmetric temperature distribution is more likely,” explains co-author Peter Scicluna from the European Southern Observatory (ESO). “Corresponding high-resolution images of Betelgeuse from December 2019 show areas of varying brightness. Together with our result, this is a clear indication of huge star spots covering between 50 and 70% of the visible surface and having a lower temperature than the brighter photosphere.” Star spots are common in giant stars, but not on this scale. Not much is known about their lifetimes. However, theoretical model calculations seem to be compatible with the duration of Betelgeuse's dip in brightness.
We know from the Sun that the amount of spots increases and decreases in an 11-year cycle. Whether giant stars have a similar mechanism is uncertain. An indication for this could be the previous brightness minimum, which was also much more pronounced than those in previous years. “Observations in the coming years will tell us whether the sharp decrease in Betelgeuse's brightness is related to a spot cycle. In any case, Betelgeuse will remain an exciting object for future studies,” Dharmawardena concludes.
Folks, the largest stellar spot on Betelgeuse is practically one third of it's surface area...it's a GAPING hole clearly showing this star's Hollow interior.
List members , we have earlier discussed how the "Double Dynamo Model" for stars (including our Sun) is the most convincing theory yet to explain the behaviour of stars .
So , on that note , I am now sharing two heavy-duty studies done on all MAGNETICALLY powered stars . This can be an excellent deep dive for those interested in understanding the inner dynamics of Hollow stars , more closely :-
