Elena's Legacy. Texts written by Elena, excerpts from texts she liked, her artworks.

Thursday, December 14, 2017

Gravity and Black Holes

When the gravity is sufficiently high, nothing, not even light, can get out. Such a place is called a black hole. Enigmatically indifferent to its surroundings, it is a kind of cosmic Cheshire cat. When the density and gravity become sufficiently high, the black hole winks out and disappears from our universe. That is why it is called black: no light can escape from it. On the inside, because the light is trapped down there, things may be attractively well-lit.

Even if a black hole is invisible from the outside, its gravitational presence can be palpable. If, on an interstellar voyage, you are not paying attention, you can find yourself drawn into a irrevocably, your body stretched unpleasantly into a long, thin thread. But the matter accreting into a disk surrounding the black hole would be sight worth remembering, in the unlikely case that you survived the trip.

Cyg X-1, a mysterious brilliant, blinking source of X-rays, visible over interstellar distances. Image: © Elena

Thermonuclear reactions in the solar interior support the outer layers of the Sun and postpone for billions of years a catastrophic gravitational collapse. For white dwarfs, the pressure of the electrons, stripped from their nuclei, holds the star up. For neutron stars, the pressure of the neutrons staves off gravity. But for an elderly star left after supernova explosions and other impetuosities with more than several times the Sun’s mass, there are no forces known that can prevent collapse. The star shrinks incredibly, spins, reddens and disappears. A star twenty times the mass of the Sun will shrink until it is the size of greater Los Angeles: the crushing gravity becomes 10(10) g’s, and the star slips through a self-generated crack in the space-time continuum and vanishes from our universe.

Black holes were first thought of by the English astronomer John Mitchell in 1783. But the idea seemed so bizarre that it was generally ignored until quite recently. Then, to the astonishment of many, including many astronomers, evidence was actually found for the existence of black holes in space. The Earth’s atmosphere is opaque to X-rays. To determine whether astronomical objects emit such short wavelengths of light, an X-ray telescope must be carried aloft. The first X-ray observatory was an admirably international effort, orbited by the United States from an Italian launch platform in the Indian Ocean off the coast of Kenya and named Uhuru, the Swajili word for “freedom”.

In 1971, Uhuru discovered a remarkably bright X-ray source in the constellation of Cygnus, the Swan, flickering on and off a thousand times a second. The source, called Cygnus X-1, must therefore be very small. Whatever the reason for the flicker, information on when to turn on and off can cross Cyg X-1, no faster than the speed of light, 300, 000 km/sec. Thus Cyg X-1 can be no larger than 300,000 km/sec X 1/10000 sec = 300 kilometers across. Something the size of an asteroid is a brilliant, blinking source of X-rays, visible over interstellar distances.

Black Holes

Fascination with space is omnipresent. Whether it takes the form of amateur stargazing, science fiction books and films, horoscope readings or scientific endeavors, interest in the stars and the sky is abundant. The fact comes as no surprise, since after all, space is by far the largest part of the world, at least as humanity knows it. To illustrate, all the planets, stars, intergalactic gas, comets and debris in the Universe comprise only an approximate 5% of its totality ( the rest being 3 quarters dark energy, and 1 quarter dark matter, as depicted graphically in another entry). So, how small is Earth compared to the rest of the Cosmos? Insignificantly tiny, indeed! Well, at least in size. But aside from the celestial bodies mentioned, there are also black holes. Now these, exemplify the definition of mysterious…

Dancing With the Stars is a television show portraying celebrities as dance competition contestants. Nonetheless, the phrase can convey other meanings such as in this dancing couple constellation (fictional). Notwithstanding, most constellations requires quite a bit of imagination to be reconstructed. Image: Copyright © Elena

Along these lines, Horowitz (2011) explains that the mystery surrounding black holes, which constitute thermodynamic entities, started to be elucidated in the 1970s. The author also outlines the fundamentals of string theory, crucial to understanding the puzzle. Also, the gauge set of principles may provide an alternative explanation to the formation and evaporation of such objects. Interestingly, the supersymmetry characteristic of the postulate is hoped to be shown for the first time in history by the famous Large Hadron Collider (particle accelerator) being built at CERN.

Amazingly, the area of a black hole cannot decrease (Hawking, 1971). But it can, however, evaporate, although the memory of what was drawn into it disappears with the event. Still, theoretically the information could be recovered from the remnants.

A giant planet. Light and Dark or Space Exploration. In a black hole, the ‘event horizon’ is the point of no return, beyond which light cannot escape due to velocity properties. Image: Copyright © Elena

Depending on one’s opinion, black holes may be the most interesting elements in the Cosmos. The mystery continues to fail to be completely understood, despite significant progress with telescopes such as Hubble, Voyager and theoretical advances in knowledge.

References:

Hawking, S. W. (1971). Gravitational radiation from colliding black holes. Physical Review Letters, 26, 1344 -6.
Horowitz, G. T. (2007). Black holes, entropy, and information. ArXiv, 1: 1-8.

Wonders of Grandiosity

The Wonders of Grandiosity

Galaxy (immense conglomeration of stars, planets and other cosmic bodies orbiting a center of a denser cluster).

As Star Trek: The Next Generation Captain Jean-Luc Picard used to say, space is the last frontier. Science fiction fascination with the Cosmos is well signified in the popular media by such popular franchises as Star Wars, Star Trek and Stargate. Notorious sci-fi writers include Isaac Azimov (Three Laws of Robotics), Clarke (2001: Space Odyssey), Orwell (1984) and Huxley (Brave New World), among others.

Aside from captivating authors’ minds, the Universe has likewise attracted the interest of scientists. Astrophysics, astronomy, planetary science, astrochemistry and astrobiology all deal with the stars and the sky. Coversely, astrology is an art, largely nonscientific predictions of one’s future (such as the horoscope) based, however, on factual positioning of stellar objects at the moment of one’s birth or during particular events.

Solar System planet Saturn, easily recognizable by its characteristic rings. Photo in public domain

Astrophysics lectures are available online, thanks to the open learning project. Many prestigious universities participate, including Harvard, Yale and Columbia Universities.The lecture was posted online with several others as part of an open learning project. Several other outstanding universities offer free courses online.

The ether is approximately 74% black energy, 22 black matter, and 4 stars, planets, comets, intergalactic gas and debris combined. No one is yet certain as to what black energy is, paradoxically, since it is by far the largest component.

Television sitcom the Big Bang Theory, starring Jim Parsons, takes its name from the notion that everything came to be due to a blast. According to the Hubble telescope and contrary to Albert Einstein’s static universe concept, the whole is still expanding.

The largest star in the world as we know it is VY Canis Majoris. By scalar comparison, our Sun, an average star, is but a tiny dot next to it. The again, there are many giants and hypergiants in between (Arcturus, Aldebaran, Cephei, etc.). The proportions from moon to the superstar are beautifully portrayed by the German science magazine Wissens in an amazing video from German Science Magazine Wissen ‘Our Small World’ (Unsere Kleine Welt). As a brief aside, despite proposed grammatical reforms, all nouns continue to be capitalized in German).

Jupiter, the largest planet of our Solar System, consisting entirely of gas. Interestingly, the spot seen in the picture above represents a storm. Photo source: public-domain-image.com

Before Pluto lost its planetary status, there were 9 planets in the Solar System. In order, they orbit the center: Mercury, Venus, Mars, Earth, Jupiter, Neptune, Saturn, Uranus, and Pluto.

Space Definitions

About Space, Univers and Cosmos

The following definitions aim to outline the most commonly used terms related to space (synonymous with the Cosmos and the Universe). Some of the basics (overview), black holes and astrophysics are discussed at greater length elsewhere. Evidently, list non-exhaustive.

Asteroid – Small rocky stellar body. An impressive number ofasteroids orbit the sun, between Mars and Jupiter, and are called the asteroid belt.

Astral – Anything that has to do with stars.

Astrobiology – The study life and living organisms in deepspace, if any.

Astrochemistry – Chemistry (the study of elements and their interactions) as related to interstellarlocations.

Astrology – Predictions and postulates stemming from thebelief that the positions of stars influence lives of individuals and outcomesof events.

Astronomy – The pure and applied science studying celestial objects.

Astrophysics – Branch of astronomy that concentrates on physics.

Black Hole – A mysterious area from which nothing, including light, can escape.

Comet – Small celestial bodies containing ice, rock and dust, often seen with a trail resembling a tail.

Constellation – A collection of stars representing an imaginary drawing, widely used in astrology to predict (non-scientifically) the future.

Illustration: Old Drawing

Dark Energy – Hypothetical form of energy present in the Universe in very large quantities (most of the Cosmos, cosmology).

Dark Matter – Matter that cannot be directly seen due to failure to reflect light and electrophysiological properties (astronomical and cosmological theories)

Dust – Cosmic or space dust is differentiated by its molecular composition and its type (interplanetary, interstellar, intergalactic, etc.).

Dwarf – Dwarf stars are smaller than the norm; there are white and brown dwarf stars. If Jupiter was larger and more massive, it would become a brown dwarf. By the same toke, at the end of its life cycle stars such as the sun become white dwarfs.

Galaxy – A massive collection of stars, solar systems and planets. Stars are counted in the billions and orbit around the center of the galaxy. Galaxies sometimes merge, for example, according to astrophysical theories, the Milky Way (our galaxy) and the nearest galaxy, Andromeda, will collide in infinitely many years.

Light year – A unit of measure of distance (and not of time!), used to describe the immense distances in the Universe and referring to the colossal amount of kilometers or miles traveled by light in an Earth year.

Nebula – A cloud of dust, gas and other particles deep in space.

Quasar – A highly active galactic nucleus.

Solar System – The planetary system we live in. The system has as it center our sun, while the planets in orbit are (in order from the star) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Pluto used to be considered a planet, but lost its planetary status since many similar dwarf planets (such as Erin and Sirius) have been discovered. Likewise, satellites, such as the Moon, or Saturn’s Titan, orbit the planets themselves.

Solar storm – Storms on our sun are cyclical, taking place roughly every eleven Earth years.

Star Attitude. The word star can also refer to celebrities or otherwise renown individuals, as well as projects or other objects that stand out (e.g. a star product). Image: Copyright © M. Jorgensen (Elena)

Star – A large sphere of plasma, contained together by the forces of gravity. Very large stars are called giants, there are red, and orange giant and hypergiants. The largest star in the world is VY Canis Majoris.

Telescope – A tool used to look at stars, ranging in complexity and capacity from amateur stargazing to professional, international observatories and probes sent into space.

From Our Sun to Canis Majoris

Astronomy, Astrophysics and Cosmology: From Our Sun to VY Canis Majoris

Anthropocentricrefers to the human being focused view, as if everything revolved around humans,just as anthropomorphic means humanizing inanimate objects or ascribing human qualities to other sentient beings. Although we tend to think of our planet, our continent, our country, our state or province, our city, town or village, or even our house or room, as the center of the world, on a stellar bodies and celestial objects scale, the Earth is quite tiny. For example, with Pluto gone, the Earth is 4th in size among the planets of the Solar System.

However,the relative sizes of rock and gas planets differ. Conversely to Earth’s structure of a core, mantle and crust, massive planets such as Jupiter are made entirely of gas and contain no solid core whatsoever. Nonetheless, these planetary masses still generate combustion and are likewise hotter at the center.

Jupiter and its satellites. Approximate, estimated relative sizes of gas planet Jupiter, the Sun, and Sirius, a star outside the Solar System, one of the brightest stars in the night sky, and part of the Canis Majoris constellation. Image: © Elena (Megan Jorgensen)

Moreover, satellites such as the Moon are numerous, with Jupiter counting up to 64 moons in orbit. Curiously, Saturn’s moon Titan, hosts a lake composed of liquid methane.

Starsakin to our Sun, vary in size, mass and power. Alike many mammals, the lifecycle of a star, from birth to supernova or implosion, goes through different stages. Stellar conglomerations cover redhypergiants and orange giants, as well as, degenerate white dwarfs – the termused to refer to a dying star. Furthermore, large gaseous planets such as Jupiter couldpotentially be brown dwarfs, if their internal combustion and mass were higher.

The largeststar known to man in the Cosmos is VY Canis Majoris, in the Canis Majoris Dwarf Galaxy. Still, Pollux, Aldebaran, Arcturus, Rigel, Sirius, Binary Cephei VV,Antares and Betelgeuse are all larger than the Sun. Despite this, other starsare naturally smaller, such as Wolf 359. Notwithstanding, some of the mostmysterious phenomena in cosmology and astronomy pertain to black holes.