Today we will be discussing the siriometer. Are you unfamiliar with this term? Well, that’s not surprising. It is rarely used, only known among a select few 😁. What could it possibly refer to? Hm. The word itself sounds like it might be the name of a device used for measurement. But what exactly? Something related to Sirius, perhaps? Sirius is a fascinating star, after all. So why does it have its own unique meter for measurement while other stars do not?
The vast distances of the cosmos
Let’s delve into the topic of stellar distances. In ancient times, humanity had no inkling of the immense span that separates us from the stars. After all, perceiving the universe in its full three-dimensional grandeur from our vantage point on Earth is an arduous task. In truth, we observe the heavens as if they were flattened onto a two-dimensional plane. This illusion creates the impression of a celestial dome suspended above our planet, adorned with countless tiny luminaries. It is no wonder, then, that this perception persisted for centuries. Many believed in the existence of a celestial vault encircling the Earth or a colossal spherical shell with stars affixed to it.
However, a few centuries ago, people realized that this was not true at all. Nonetheless, it took some time for astronomers to determine the distance of the stars. It was not until 1838 that Friedrich Wilhelm Bessel successfully calculated the parallax of a star for the first time.
Assuming everyone is familiar with the concept of parallax, just in case you are not.
Therefore, it is known that the Earth orbits the Sun. This fact was already widely known in 1838. Consequently, our planet occupies different positions in the solar system throughout the year. As a result, we observe distant stars from varying angles. In this particular case, we should observe a slight “shift” in the stars that are closer to us against the backdrop of more distant stars.
It’s incredibly simple to illustrate this concept with an example from our everyday lives. Just imagine yourself sitting in a compartment of a high-speed Moscow-Vladivostok train, gazing out the window. As the train rushes by, you see Christmas trees, birches, and other trees that line the railroad tracks whizzing past at an astonishing speed. However, the trees that grow farther away from the tracks, towards the edge of the field, seem to slowly drift by.
The same phenomenon occurs with stars, except they are all incredibly far away from us. The visible movement of even the closest star is minuscule. This is why it has taken so long to accurately measure their positions.
Bessel was the first person to successfully measure stellar distances, and now astronomers routinely measure billions of stars…
Once these vast distances were recognized, there arose a need to quantify them in some way.
Distances in everyday life are typically measured in meters and kilometers, and occasionally in centimeters or millimeters. However, when it comes to measuring distances in space, it becomes much more challenging. For instance, the moon is approximately 400,000 kilometers away from Earth. While this is still comprehensible, it is undeniably a large number. On the other hand, the Sun is a staggering 150 million kilometers away from us. Attempting to comprehend this immense distance is nearly impossible. Moreover, the star Sirius is situated a mind-boggling 86 trillion kilometers away from our solar system! Can you even fathom that? I certainly cannot. This number is beyond our imagination, and it’s worth noting that Sirius is considered to be relatively close to us. It is evident, my friends, that in order to grasp the enormity of the cosmos, we must employ alternative units of measurement.
And this is where the syriometer comes in. It’s not just any device, but rather a unique unit of distance. Renowned astronomer Frederick William Herschel is credited with its invention. It was Herschel who made the groundbreaking discovery of the planet Uranus back in 1781. As a scientist, he was driven by a burning desire to uncover the secrets of measuring astronomical distances, even though the technology of the time made it seemingly impossible. Nevertheless, his thirst for knowledge remained unquenchable.
Herschel pondered to himself, let’s hypothesize that all stars emit approximately equal amounts of light. In that case, the stars that we perceive as luminous in the celestial sphere ought to be nearer in proximity compared to those that appear less radiant. Sirius, the most brilliant star in the nocturnal firmament, shall serve as a point of reference for gauging the distance to all other stars. Let us suppose that Sirius is situated at a distance of one “siriometer” from our location. Consequently, a star that emits light four times dimmer than Sirius must be positioned at a distance of two siriometers away. This is due to the fact that brightness declines proportionally to the square of the distance: twice the distance, four times less luminous.
Admittedly, it was not an altogether faulty idea. Unless, of course, the stars were indeed emitting equivalent amounts of light. Unfortunately, this is not the case. As a result, Herschel’s findings turned out to be erroneous.
The yearly displacement and Sirius.
However, the concept of the syriometer gained popularity. This was because there was a need for some form of measurement for stellar distances. Hugo von Seeliger, a German astronomer, introduced the idea of the “Sirius range” based on the siriometer. This refers to the distance to a star that is sufficiently far away so that its annual stellar displacement is 0.2 arc seconds. To determine this, one must observe the star’s position at intervals of 6 months. To simplify, we observe the star and record its position. Then, we wait for the Earth to be on the opposite side of its orbit, which takes six months and brings us approximately 300 million kilometers away from the original point. Afterward, we observe the star once again. At this point, the star will have a different position, and the difference will be measured in degrees.
0.2 arc seconds is slightly less than one ten-thousandth of the apparent size of the full Moon in the sky.
No, the 0.2 arc second parallax does not represent the distance to Sirius. It represents a distance of 1.03 million Earth orbital radii. Zeliger discovered this to be quite surprising. So did the Swedish astronomer Carl Charlier, who proposed rounding this value slightly and defining one syriometer as one million radii of the Earth’s orbit.
In this scenario, Sirius would be located half a syriometer away from us. The bright star Vega is 2.2 syriometers away. Betelgeuse is 6.9 syriometers away, and so forth.
Other astronomers found it more convenient to define the unit of distance in terms of parallax at 1 arc second. They named their unit of distance measurement “parsec”.
Exclusively a light-year!
Charlier’s syriometer, proposed by American astronomer Heber Curtis, was deemed absurd. This sentiment was shared by all those who suggested the utilization of the parsec. Curtis firmly asserted that there was only one unit of measurement that fulfilled all the necessary criteria: the light-year.
This particular measurement is established on a fundamental aspect, the velocity of light, which could already be easily quantified at that time. Furthermore, it is straightforward and uncomplicated – light necessitates time to travel from point A to point B. A light-year denotes the distance that light traverses within the span of a year. Evidently, distances to stars are conveniently expressed in light-years. Similarly, they can be quantified in siriometers. Nevertheless, a light-year offers a much more lucid and convenient measurement.
Take Sirius, for instance. It is situated 8.6 light-years away. Vega, on the other hand, is 25 light-years away, while Betelgeuse is located as far as 643 light-years away. This is why Curtis believes that using the light-year as the unit of measurement for distances in space is perfectly acceptable. In fact, if we ever need to measure even larger distances, we can simply refer to light centuries or light millennia.
It is difficult to argue with Curtis on this matter. The light-year is an incredibly practical and easy-to-understand unit of measurement. However, it is worth noting that the light-year has never been officially recognized as a unit of measurement. In fact, the meter is the only officially recognized unit of distance measurement.
In the end, it seems that Curtis’s ideas fell on deaf ears. Nowadays, the field of astronomy has adopted the parsec as its preferred unit of measurement. A parsec is equivalent to approximately 31 trillion kilometers or 3.26 light-years.
There are several compelling reasons why individuals utilize the parsec as a unit of measurement. The primary reason is that the distance value in parsecs can be determined through simple observation and the calculation of the parallax angle.
However, it can still be somewhat complex. This is why light years continue to be used, especially when non-astronomers are communicating with one another.
Perhaps that star has vanished.
Maybe it’s simply grown old,
# It has long since departed from its orbit #
Like a precious jewel
From the setting of a ring?
Yet its cold light,
Fresh and chilling and wondrous light
rests here on the grass.
And it shall live on for a long, long time,
Moving from bush to bush,
From forehead to forehead,
And it will be passed down to others,
Like a melody.
As previously stated, in the early 17th century, Galileo made improvements to the visual tube available at the time and pointed it towards the sky. A friend of Galileo named this new instrument the telescope, which signifies its ability to see far.
Figure 160. A page from Galileo’s manuscript where he recorded his observations of Jupiter’s satellites
In 1610, Galileo started regularly observing the celestial bodies using a telescope. He was able to increase the magnification of the telescope from 3 to 32 times in a short period of time. These observations provided new insights into the extraterrestrial world.
For instance, Galileo made the groundbreaking revelation that the Moon, much like the Earth, possesses a intricate topography and is adorned with mountains and craters. He also made the momentous discovery of four satellites orbiting Jupiter (Fig. 160), observed sunspots, demonstrated its rotational motion, and accurately calculated its revolution period. Galileo’s telescope was ingeniously simple in design. To explore the far reaches of the cosmos, novel instruments and investigative techniques had to be developed. Initially, telescopes only enabled the observation of celestial objects that emit or reflect electromagnetic radiation within the visible part of the spectrum, as the Earth’s atmosphere absorbs radiation from other wavelengths.
Radio telescope.
In 1931, Carl Jansky, an astronomer from the United States, made a groundbreaking discovery when he detected short radio waves emanating from the heart of our galaxy. This monumental finding laid the foundation for the development of a new field of scientific study known as radio astronomy. Building upon Jansky’s work, the first radio telescope was constructed in 1937, marking a pivotal moment in the history of astronomy. In the years following World War II, significant advancements were made in the design and capabilities of radio telescopes, as illustrated in Figure 161.
Figure 161. A contemporary radio telescope
A radio telescope comprises of an antenna that receives incoming waves from space, a signal amplifier, and a device that converts invisible radio waves into visible radiation. Due to the low power of radio waves reaching the Earth, the antenna needs to be large and the amplifier must be highly sensitive. In today’s radio telescopes, the capturing antennas cover areas of tens of thousands of meters.
Cosmic rays.
Not only do various objects in the cosmos emit light, infrared radiation, and radio waves (Fig. 164), but they also release electromagnetic radiation at higher frequencies and streams of elementary particles known as cosmic rays. These rays primarily consist of protons and helium nuclei (alpha particles). They were first detected in the early 20th century when radiation from radioactive sources was observed above the Earth’s surface.
Figure 162. The most accurate results are obtained by telescopes installed on satellites. These include the Hubble Space Telescope (A) and Edwin Hubble, an American astronomer (1889-1953) (B).
Initially, it was believed that this radiation originated from the Earth itself. However, it was soon discovered that its intensity does not decrease but rather increases as the distance from the Earth’s surface increases. Therefore, cosmic rays come to Earth from outer space. They can originate from objects within our solar system as well as from much farther away, such as the stars in our galaxy and even beyond. Prior to the development of modern instruments, cosmic rays were the primary source of study for elementary particles. Some of these particles were first detected as part of cosmic rays.
Figure 163. The Hubble telescope has captured stunning images of various nebulae. Among them are the Cat’s Eye nebula (A), the Omega nebula (B), the Hourglass nebula (C), and the Butterfly nebula (D).
Figure 164. The night sky can be observed using different types of telescopes, such as an optical telescope (A), an infrared telescope (B), and a radio telescope (C).
The importance of spectral analysis.
Spectral analysis plays a crucial role in the study of planets, stars, and other celestial objects (§ 42). By analyzing the emission and absorption spectra of these objects, scientists can accurately determine their chemical composition and temperature. As we have learned in previous chapters, the temperature of an object affects its radiation, causing it to shift towards the shorter wavelengths of the spectrum. This is why the lowest temperature stars appear red and the hottest stars appear blue.
Measuring the Universe: Understanding its Units of Measurement
Years of dedicated research have provided humanity with a comprehensive understanding of the structure of the Universe and its various celestial objects, while also shedding light on the Earth’s position within it. The vast distances that separate stars and galaxies, as well as the astonishing speeds at which cosmic entities move, have brought about the realization that the Universe possesses unique qualities that are far removed from our everyday experiences. Consequently, this extraordinary realm has been aptly dubbed the megamir, signifying the grandiose nature of this cosmic expanse.
To gauge the magnitude of this world, it proves challenging to employ conventional units of measurement, such as kilometers. The resulting figures would reach such astronomical proportions that comprehending and comparing them would become exceedingly difficult. For relatively short distances, we utilize the astronomical unit, which is the average distance between the Earth and the Sun, equal to 149,600,000 km. Meanwhile, for considerably longer distances, we employ the light-year, which represents the distance that light travels in one year. Given that the speed of light is 300,000 km/s, and a year encompasses 31,536,000 s, we can easily calculate the quantity of kilometers contained within a light-year: a staggering 9.46 x 10^12 km, or 9,500,000,000,000,000 km! Occasionally, astronomical distances are measured in parsecs, a unit roughly three times the length of a light-year, equivalent to 3.1 x 10^13 km.
Based on the available data, it is clear that the Universe is incredibly vast and beyond our comprehension in terms of scale. The most advanced telescopes currently in existence have the capability to observe objects that are located a staggering 28 billion light years away, which is equivalent to 10^23 kilometers. This astonishing distance implies that the visible Universe possesses a diameter of approximately 60 billion light-years. However, recent calculations suggest that the Universe might be even larger, with a potential diameter of up to 80 billion light years. The immensity of such dimensions is truly mind-boggling. To put this into perspective, if we were to compare the diameter of the Universe to that of a globe, the size of the Solar System would be comparable to that of a bacterium.
Nevertheless, despite its relatively diminutive size, the Solar System, and more specifically, the Earth, hold immense significance for humanity. As Tsiolkovsky eloquently stated, they serve as our cradle.
Check your understanding
1. What did Galileo discover in the field of astronomy?
2. What is the reason behind choosing highlands as the ideal location for observatories?
3. What constitutes cosmic rays?
4. What scientific approach can be employed to ascertain the temperature and chemical composition of celestial objects?
Assignments
1. What is the distance between Earth and Sirius in kilometers if it is known to be 8.6 light-years away? Convert this distance to astronomical units and parsecs.
2. Create a report or presentation about the topic and progress of radio astronomy.
At a feast, two astronomers were gathered together and engaged in a heated argument. One of them confidently stated that it is the Earth that rotates and revolves around the Sun. On the other hand, the second astronomer firmly believed that it is the Sun that propels all the planets. These two astronomers were none other than Copernicus and Ptolemy. In an attempt to settle the dispute, the cook interjected with a grin. The master, intrigued by the debate, asked the cook for his insight on the matter. The cook responded, “I may not have personally visited the Sun, but I believe Copernicus is correct. After all, have you ever seen a cook as foolish as one who spins the hearth around the roast?”
Mankind originated and resides on the planet Earth. For a significant duration, humans were incapable of ascending even slightly above the Earth’s surface. According to the beliefs of numerous ancient civilizations, the Earth served as the Great Mother, bestowing bountiful harvests and thus acting as the progenitor and nurturer of all living beings. Above the Earth, there existed the Heavens – a mighty and formidable deity – the father figure who showered the Earth with rainfall, enabling the reproduction of life. In the mythology of certain cultures, the Earth symbolized the father figure, while the sky embodied the mother of the entire universe. The Earth possessed immense power, evident in its ability to attract all objects towards it. Russian folklore narrates the tragic tale of the bogatyr Svyatogor, who attempted to control the gravitational force exerted by the Earth.
Initially, little was known about the physical structure of the Earth and the sky. The prevailing belief was that the Earth was flat, possibly disk-shaped, with a solid celestial dome above it where the Sun, Moon, and stars moved. However, there had been a long-standing idea that the Earth was a sphere and may even revolve around the Sun. This concept was first proposed by Pythagoras, an ancient Greek scientist, in the 6th century BC. It is speculated that he may have learned this from the secretive Egyptian priests, who were reluctant to share their knowledge. The most compelling evidence for the ancient world’s understanding of the Earth’s spherical nature comes from Aristotle. He observed that all heavy objects fall to the Earth at equal angles. If the Earth were flat, these objects would not fall straight down but would instead be pulled towards the center of a flat planet. Since most objects are far from this center, they would fall at an inclined angle. Additionally, Aristotle noted that certain stars visible in Egypt or Cyprus were not visible in northern countries. This suggests that not only is the Earth shaped like a ball, but it is relatively small compared to the vast distances to the stars.
Approximately 300 years before the birth of Christ, the renowned ancient Greek geographer and mathematician, Eratosthenes (c. 276-194 B.C.), made an attempt to determine the size of the Earth through practical observation. He observed that on the day of the summer solstice, the Sun reached its highest point directly overhead in one of the cities in Egypt, causing it to illuminate the very bottom of a deep well. Eratosthenes then proceeded to measure the angle at which the Sun’s rays hit the ground in another city on the same day. By knowing the distance between the two cities, he was able to calculate the circumference of the Earth, and his calculations were remarkably accurate even by today’s standards.
The geocentric theory
is a heliocentric theory that states that the Earth is the center of the universe and that all other celestial bodies revolve around it. This theory was widely accepted for centuries before being replaced by the heliocentric model proposed by Nicolaus Copernicus in the 16th century. The geocentric theory was supported by various ancient civilizations, including the Greeks and the Romans, and was also a prominent belief in medieval Europe. However, with the advancement of scientific knowledge and the development of telescopes, observations and calculations made by astronomers such as Copernicus, Galileo Galilei, and Johannes Kepler disproved the geocentric theory and provided evidence for the heliocentric model. Today, the heliocentric model is widely accepted and forms the basis for our understanding of the solar system and the universe.
However, during ancient times, the theory of heliocentrism was not widely accepted. Instead, the geocentric model developed by Claudius Ptolemy (c. 90-160), a Greek astronomer, mathematician, physicist, geographer, and music theorist, gained universal recognition in the 1st century. Ptolemy, like many other scientists of his time, resided in Alexandria (Figs. 165, 166). In order to account for the complex movements of the planets, Ptolemy had to introduce new concepts and a sophisticated system of additional calculations. Despite these adjustments, his theory aligned so closely with observational data that it remained unchallenged for the next one and a half millennia.
Fig. 166. Ptolemy’s geocentric system
During the early Middle Ages, there was no consensus on the shape of the Earth, with most people accepting the concept of “the Earth’s firmament”. However, in the 11th and 12th centuries, Europe was introduced to the writings of ancient Greek philosophers. The ideas of Aristotle and Euclid gained popularity, even among influential Christian philosophers. By the beginning of the Renaissance, it became widely accepted that the Earth was a spherical object suspended in space, with the stars and planets orbiting around it on the firmament (which also included the Moon and the Sun).
The Heliocentric Theory by N. Copernicus
Nicolaus Copernicus (1473-1543), a Polish astronomer, mathematician, and economist, was the first to question the Ptolemaic system (Figure 167).
Illustration 168. The heliocentric model proposed by Copernicus
In his final work On the Circulation of the Heavenly Spheres, which was published posthumously, Copernicus expresses his astonishment at the excessive complexity of Ptolemy’s system. After examining the works of other ancient Greek scientists, Copernicus comes to the conclusion that the Sun must be the central point of rotation for the world (Fig. 168). According to his theory, the Earth and the planets orbit around the Sun, while the Moon is not a planet but rather a satellite of the Earth, orbiting around it. Therefore, the apparent daily motion of the Sun is actually an illusion caused by the Earth’s own rotation, which completes a full revolution on its axis in 24 hours. Similarly, the Sun’s apparent movement through the zodiac is not a result of its actual motion, but rather a consequence of the Earth’s orbit around the Sun. This new perspective greatly simplifies the calculations of planetary motion, although it does yield slightly less accurate results compared to the calculations made under the Ptolemaic system. This is because Copernicus assumes that the orbits of the Earth and the planets are circular rather than elliptical, which is their true shape. This discrepancy was the main reason why the heliocentric system faced prolonged objections.
Modern concepts regarding the movement of the Earth can be summarized in the following key statements:
1. The Earth, along with the other planets in our solar system, follows a slightly elongated elliptical orbit around the Sun, with the Sun situated at one of the focal points. The average velocity of Earth’s orbit is approximately 30 km/s.
2. During its orbital motion, the Earth completes a full revolution in about 365.25 solar days, which is equivalent to the number of rotations the Earth makes around its own axis. This time period is known as a sidereal year. Due to the additional 0.25 days, a full day is accumulated every four years, resulting in a leap year with 366 days.
3. The Earth’s position in relation to the Sun changes throughout the year due to the elliptical shape of its orbit. On average, the Earth is approximately 150 million kilometers away from the Sun. The point where the Earth is closest to the Sun is known as perihelion, whereas the point where the Earth is farthest away from the Sun is known as aphelion.
4. The Earth rotates on its axis, which is a straight line connecting the North and South Poles. However, this axis is not perpendicular to the plane of the Earth’s orbit; it is tilted at an angle. As a result, during half of the year, the North Pole faces the Sun, while during the other half, it is the South Pole that faces the Sun (Fig. 169).
Figure 169. Earth’s revolution around the Sun
The Earth undergoes a change in its state during the vernal and autumnal equinoxes, when it crosses the celestial meridian. In the hemisphere facing the Sun on these days, spring and then summer begin. The duration of daylight exceeds that of the night, and in the polar regions and areas above the Arctic Circle, the Sun remains visible throughout the day (polar day). On the other hemisphere, the opposite occurs: autumn arrives, temperatures drop, the length of daylight decreases, and in the polar regions, the Sun never rises above the horizon (polar night).
Test your knowledge
1. Who was the first person to determine the circumference of the globe and when did they do it?
2. Who first proposed the heliocentric theory and when? Why do you think this theory faced resistance at the time?
3. What is the shape of the Earth’s orbit?
4. Can you explain what aphelion and perihelion are?
5. What is the reason behind the occurrence of polar nights and polar days near the poles?
Tasks
These days, numerous structures with lofty ceilings are equipped with Foucault pendulums (Fig. 170) to demonstrate the Earth’s rotation on its axis. Elucidate the operational principle behind such a pendulum. If needed, consult literature or online resources for relevant information.
§ 62 Earth and its structure
An earthquake was unleashed upon the city of Constantine by a divine force.
The tremors reverberated throughout the city,
shaking the Hellespont,
the coastline with its majestic mountains and rocky formations,
as well as the regal chambers of the kings.
Even the temple, the circus, and the hippodrome were not spared,
as the walls of the city crumbled and shattered,
resulting in widespread devastation throughout Pomorie.
The Earth globe is not a perfect sphere, but rather a spheroid, with a flatter shape at the poles. This particular shape is called a geoid (derived from the Greek word for Earth, Gaia) 16.
Newton was the one who proved that the Earth has this exact shape. He used the following reasoning: two shafts need to be dug, one from the pole to the center of the Earth and another from the equator to the center of the Earth. These shafts could be filled with water. If the Earth were a perfectly spherical ball, the depth of these shafts would be the same. However, in the equatorial mine, unlike the polar mine, the water is affected by centrifugal force. Hence, for the water to reach equilibrium in both mines, the equatorial mine must be longer.
[Close]. This phenomenon is a consequence of the Earth’s rotation and the resulting centrifugal force. As a result, the equator has a diameter that is 43 km larger than the distance between the poles. The Earth’s average diameter is approximately 12,740 km, and its mass is 5 -10,24 kg.
Lithosphere.
The planet Earth is composed of three main layers: the solid crust, the mantle, and the metallic core (Figure 171). The crust, which is the uppermost part of the Earth’s solid shell, varies in thickness from 6 km beneath the ocean to 50-60 km on the continents. It primarily consists of oxides of silicon, with lesser amounts of aluminum, calcium, magnesium, iron, sodium, and potassium. As a result, the most abundant chemical element in the crust is oxygen. Underneath the crust lies the upper portion of the mantle, which is denser. Together, these layers make up the Earth’s solid outer shell, known as the lithosphere.
Illustration 171. Diagram illustrating the structure of our planet
The Earth’s lithosphere is composed of multiple tectonic plates that move slowly on the molten lower mantle, at a rate of a few centimeters per year. This movement leads to changes in the number and configuration of continents over time. It is theorized that 750 million years ago, there existed a single supercontinent, which eventually fragmented to give rise to the current Earth’s map.
The mantle, ranging from 35 to 3,000 kilometers in depth beneath the Earth’s surface, constitutes nearly 70% of the planet’s total mass. The primary chemical components of the mantle are oxygen, silicon, and magnesium.
The core, which lies deeper than the mantle, is composed of both liquid and solid parts. While the exact composition of the core is not fully understood, it is primarily made up of metals, with iron being the most prevalent. It is believed that the core undergoes radioactive decay, generating the internal heat of our planet. The temperature at the center of the Earth is estimated to reach 3000-5000 degrees Celsius, with pressures reaching several million atmospheres. Some of this heat manages to rise to the Earth’s crust.
Under high temperatures, the rocks that make up the crust or upper mantle can melt, giving rise to a molten substance known as magma. This magma is largely composed of silicon compounds and is commonly referred to as magma. When magma reaches the Earth’s surface, it is then referred to as lava.
Figure 172. Volcano: A – structure diagram; B – eruption;
1 – magma, 2 – continental crust, 3 – volcano cone, 4 – ocean, 5 – oceanic crust
Occasionally, large areas are engulfed by streams of molten rock and numerous cities are destroyed. One of the most well-known incidents with devastating consequences was the eruption of Vesuvius volcano in Southern Italy in 79 AD, which lasted for approximately one day and resulted in the destruction of three cities: Pompeii, Herculaneum, and Stabia, along with many villages and villas. The eruption was so powerful that its ash traveled as far as Egypt and Syria. In 2010, the Icelandic volcano Eyjafjallajokull unexpectedly awakened and emitted such a massive amount of ash that it dispersed throughout Europe and caused over 60,000 flights to be canceled.
The source of the heat that leads to the melting of solid rocks and the creation of magma remains a mystery. While some scientists argue that it is due to radioactive processes, the majority believe that this heat is generated through friction during the movement of lithospheric plates.
Seismic activity.
The occurrence of earthquakes can be attributed to the movement of tectonic plates. When a particular section of the Earth’s rock undergoes rapid displacement, it results in vibrational movements known as seismic waves. The epicenter of an earthquake refers to the area on the Earth’s surface directly above the origin, which is the shear point. Seismic waves propagate in all directions from the earthquake source, reaching speeds of up to 8 km/s. Special instruments called seismographs are utilized to detect and record these seismic waves. These devices are designed in a way that one part remains stationary while the other part shifts during a shock. Seismographs provide continuous recordings of seismic vibrations, even capturing minor shifts in the Earth’s surface. The strength of an earthquake is typically measured using twelve-point scales, with earthquakes ranging from 1-2 points only being detectable by instruments or very sensitive individuals, while those estimated at 11-12 points result in catastrophic events such as landslides, destruction of cities, and other significant damages. Approximately 10 thousand earthquakes that are felt by people occur on Earth each year, with around one hundred causing substantial destruction.
The hydrosphere and atmosphere.
Aside from the solid lithosphere, Earth possesses two additional layers – the hydrosphere and the gaseous atmosphere. The hydrosphere is comprised of the oceans, which encompass 70.8% of the planet’s surface, as well as freshwater bodies and water vapor in the atmosphere. Over 96% of Earth’s water is located in the oceans, approximately 2% is found in groundwater, glaciers, and permanent snow, and just about 0.02% of the total water can be found in surface water bodies on land. The global ocean is made up of five oceans (the Pacific, Atlantic, Indian, Arctic, and Southern) as well as the seas that connect them. The average depth of the World Ocean is 3800 meters, with the Mariana Trench in the Pacific Ocean being the deepest point, reaching approximately 11 km. Some seas are not separated from the ocean by land masses. An example of this is the Sargasso Sea near Central America, which is defined by sea currents rather than land boundaries.
In order for human life to be sustained, there must be an adequate supply of oxygen in the air. However, as one moves further away from the Earth’s surface, the atmospheric pressure decreases and the air becomes increasingly thin. At an altitude of 5 km above sea level, an unacclimatized individual experiences oxygen deprivation, which manifests as a decrease in physical performance. At 15 km above sea level, the atmosphere contains such a minimal amount of oxygen that breathing becomes impossible for humans.
Test your knowledge
1. What are the average dimensions and weight of the Earth?
2. What are the internal layers of the Earth? Which one of these layers includes the Earth’s crust?
3. What is the name of the magma that emerges on the Earth’s surface? Where does it erupt?
4. Define the epicenter of an earthquake.
5. Describe the troposphere. What gases are found in it and in what proportions?
Sirius is a binary system that is made up of a main-sequence star and a white dwarf (shown in the bottom left corner of the Hubble Space Telescope image). It is almost 10,000 times less luminous.
| 2.12 / 1.03 M ☉ |
| 1,711 / 0,008 R ☉ |
| 26,1 / 0,000 24 л ☉ |
| 9900 / 24 800 K |
| 16 km / s |
| 2.5 × 10 8 years |
Sirius, α CMa, 9 CMa (Flemsteed), GJ 244 A / B, BD-16 1591, HR 2491, HD 48915, HIP 32349, SAO 151881, GCTP 1577.00 A / B, LHS 219, LTT 2638, FK5 257
Sirius, also known as Alpha Canis Majoris (α Canis Majoris / α CMA) according to Bayer’s designation, is the dominant star in the Canis Major constellation. When observed from Earth, Sirius shines as the brightest star in the sky, second only to the Sun and surpassing Canopus and Arcturus in luminosity. It falls into the category of white stars, as classified by astronomer Pietro Angelo Secchi. Due to its declination, Sirius is never situated very high above the horizon when viewed from the temperate latitudes of the northern hemisphere. Its brilliance is slightly dimmed by atmospheric extinction compared to Arcturus (Canopus, meanwhile, remains invisible from these latitudes). Given its proximity and luminosity, Sirius has garnered significant attention from astronomers and has been at the forefront of several groundbreaking discoveries, including the detection of its proper motion and radial velocity.
Summary
- 1 Physical characteristics
- 2 Displacement relative to the Sun
- 3 Sirius A and Sirius B
- 4 Hypothetical old red color
- 5 History of distance calculation
- 6 Calendar
- 7 legends about Sirius
- 7.1 Mesopotamia
- 7.2 Ancient Egypt
- 7.3 Ancient Greece and Rome
- 7.4 Ancient China
- 7.5 Arabia
- 7.6 Polynesia
- 7.7 In Dogon culture
- 7.8 Heatwave
- 9.1 Bibliography
- 9.2 Related articles
- 9.3 External links
- 10.1 Notes
- 10.2 References
Physical characteristics
Sirius has an apparent magnitude of -1.46. It is unique among stars, along with Canopus, for having a negative apparent magnitude. Interestingly, Sirius was not included in the consideration when the apparent magnitude scale was established. The brightness of Sirius that we observe from Earth is not solely due to its intrinsic luminosity, which is indeed brighter than the Sun, but also because of its close proximity to our solar system. Situated only 8.6 light-years away from the Sun, Sirius is the fifth nearest star system to us. The four star systems that are closer to the Sun are the triple system of Alpha Centauri (4.37 light-years away), the Barnard star (5.96 light-years away), Wolf 359 (7.78 light-years away), and Laland 21185 (8.29 light-years away) (see List of nearby stars and brown dwarfs).
Position in relation to the Sun
Due to its relatively close proximity to the Sun, Sirius exhibits a significant proper motion, which means that its position in the sky changes more rapidly over time compared to many other stars. This motion was first discovered by Edmond Halley in 1717, who observed the difference between Sirius’ position and the recorded positions of ancient Greek astronomers, particularly Hipparchus. A hundred and fifty years later, using the newly introduced discipline of spectroscopy, William Huggins was able to demonstrate the radial velocity of Sirius, indicating its approach towards the Sun. This breakthrough came after an initial unsuccessful attempt with W.A. Miller in 1862-1863, where the limitations were due to the resolution of spectrographs. During the early 1860s, only radial velocities exceeding 300 kilometers per second could be detected, but within a few years, this limit was reduced to just a few kilometers per second. Huggins’ measurements at the time were uncertain, as he published a radial velocity of -40 km/s, whereas the current measured value is -7.6 km/s.
Sirius A and Sirius B
Sirius A and Sirius B are a binary star system located in the constellation Canis Major. They are the two brightest stars in the night sky and are easily visible to the naked eye. Sirius A is the larger and more massive star, while Sirius B is a white dwarf. The two stars orbit each other with a period of about 50.1 years.
One interesting fact about Sirius B is that it was the first white dwarf to be discovered. In 1844, astronomer Friedrich Wilhelm Bessel noticed irregularities in the motion of Sirius and hypothesized the presence of an unseen companion. This theory was later confirmed when the white dwarf was directly observed in 1862.
Another fascinating aspect of the Sirius system is its cultural significance throughout history. In ancient Egypt, Sirius was associated with the goddess Isis and was considered a symbol of rebirth and fertility. The star’s annual rising in the pre-dawn sky, known as the heliacal rising, was an important event in the Egyptian calendar.
Overall, Sirius A and Sirius B are a fascinating binary star system with a rich history and scientific significance. They continue to intrigue astronomers and stargazers alike with their beauty and unique properties.
Sirius, an easily visible star, is a bright star in the main sequence, belonging to the A0 or A1 spectral class. It has a mass of approximately 2.12 times that of the Sun and is estimated to be around 250 million years old. The surface temperature of Sirius is about 9,900 K, and its diameter is roughly 1.711 times that of the Sun. The diameter is determined through interferometry and stellar models. In terms of chemical composition, Sirius differs significantly from the Sun, with its iron content being three times higher. Additionally, a weak magnetic field has been observed on its surface.
The white dwarf Sirius B, which is situated to the left of Sirius A in the top image, has a companion with a half-life of 49.9 years. It was first discovered in 1862 by Alvan Graham Clarke and is one of the most well-known white dwarfs. Along with Procyon B and 40 Eridani B, it is among the three most massive white dwarfs. The Sirius A / Sirius B system has an elliptical orbit, with the distance between the two stars ranging from 8.1 to 31.5 astronomical units, with an average distance of 19.5 a.u. The previous pericenter of the system occurred in 1944 and 1994, and the next one is scheduled for 2044.
The angular separation between these two stars needs to be sufficiently large in order to distinguish between the two, but the task becomes exceedingly complex due to the significant difference in brightness. Sirius B, which is three times hotter than its counterpart, is primarily much smaller in size because it is a white dwarf, with a diameter comparable to that of Earth. As a result, its brightness is much lower than that of Sirius A, with an apparent magnitude of only 8.44. However, the presence of Sirius B and its orbital characteristics can be determined by studying the proper motion of Sirius A. The motion is not a straight line, as would be expected for an isolated star, but rather a curved path around an average straight trajectory.
Theoretical ancient crimson hue
Starting from 1760 with Thomas Barker, numerous scholars have made the claim that ancient writers depicted Sirius as having a red color. However, it is important to note that most of these writers, particularly poets, actually described Sirius as being bright, emphasizing its brilliance rather than its specific color. This is because the ancients understood that fire produced light. The astronomer Claudius Ptolemy described 6 stars with different colors, ranging from Antares to Sirius, and referred to them as hypokirros, which means slightly yellowish. However, this classification is obviously incorrect for Antares, as it is distinctly reddish. Several authors, including Seneca, mentioned the star known as Vacation blushing. This star is indeed Sirius, but it appears red due to atmospheric effects at its heliacal rising, which marks the beginning of the heat wave period. At this time, Sirius is at the same level as the horizon and is reddened by Rayleigh scattering. This atmospheric reddening was only discovered by Schiaparelli in 1896. Prior to that, it was believed that the star’s brightness changed (which is absurd because stars become red giants at the end of their lives) or that a cosmic cloud was causing a darkening effect (which was not reported). Chinese writers described Sirius as white but made predictions based on its color changes, which were caused by scintillation and were also observed in other planets due to atmospheric conditions. The controversy surrounding the color of Sirius reemerged in the 1960s, disregarding previous findings. The most comprehensive analysis of this issue was written by RC Ceragioli in 1995. Today, it is widely accepted that Sirius has always been white, appears reddish at the horizon, and exhibits multiple colors that shimmer under strong atmospheric turbulence. However, many journalists and websites choose to ignore these facts and continue to perpetuate the myth of Sirius being red in ancient times.
History of calculating distances
In his 1698 book, Cosmopheoro, Christiaan Huygens made an estimation of the distance from Sirius to be 27,664 times the distance between the Earth and the Sun (approximately 0.437 light years, which corresponds to a parallax of about 7.5 arc seconds). There were multiple unsuccessful attempts to measure the parallax of Sirius. Jacques Cassini attempted to measure it and found it to be 6 seconds. Other astronomers, including Neville Maskelyne, used observations made by Lacaille at the Cape of Good Hope and found a parallax of 4 seconds. Piazzi also attempted the measurement using Lacaille’s observations, but found the same result. Bessel, too, found no reasonable parallax in his measurements.
In 1832 to 1833, the Scottish astronomer Thomas Henderson first obtained significant magnitudes through his observations. He was later joined by the South African astronomer Thomas Maclear, who made observations from 1836 to 1837. Their findings, published in 1839, revealed a parallax value of 0.23 arc seconds. Henderson estimated that the error of the parallax did not exceed a quarter of a second, stating, “We may conclude that in general the parallax of Sirius does not exceed half a second.” This value of 0.25 arc seconds was widely accepted by astronomers throughout the nineteenth century. However, it is now known that Sirius actually has a parallax of 0.3792 ± 0.0016 arc seconds, resulting in a distance of approximately 2.637 parsecs. This confirms the accuracy of Henderson’s measurement.
Calendar
In ancient times, particularly in Greece, Sirius may have been utilized as a point of reference for establishing the calendar.
In Sparta, the ephors would convene every eight years to verify the alignment with the luni-solar calendar and the overall movement of the universe, an external reference indicated by the heliacal rising of Sirius.
In ancient Egypt, the calendar was based on the heliacal rising of Sirius, which served as a herald for the Nile flood, a critical event for the survival of the Egyptian people.
What are the drawbacks of Sirius in Sochi and who would benefit from it?
Elena Zhabinskaya 05.02.2022 No rubrics
That feeling when you’ve been a resident of Sochi for such a long time that you witness a part of its territory being abruptly separated and given a new name. But does anything truly change in the old familiar place with its new identity and status? Discover the details in the article “Sirius in Sochi: the downsides and the perfect fit.” And for those who read until the very end, there awaits a revelation of the hidden nuances of this trendy village, secrets that are rarely spoken out loud and are known only to the locals.
What is it?
What is the location of
Weather Forecast
The climate in Sirius is warmer than in Sochi due to its more southern location. In fact, it is the southernmost point of the country. Although the difference in weather between Sirius and central Sochi is not significant, based on my personal experience living near the border with Abkhazia, precipitation is slightly less frequent here. The same applies to snowfall: during particularly cold winters (such as 2021 and 2022), Sirius may experience dry or rainy weather, while central Sochi receives snowfall.
It may seem like a negligible distance, only half an hour by car, but there is still some variation in climate.
Who is an appropriate candidate for
