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Línea del Tiempo - Descubrimiento de Partículas


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Hadrones Exóticos


Los hadrones exóticos son partículas subatómicas hechas de quarks y algunas de gluones, pero que no entran dentro del esquema normal de hadrones. Los hadrones exóticos no tienen el mismo contenido de quarks que los hadrones ordinarios: los bariones exóticos tienen más que los tres quarks de los bariones comunes, y los mesones exóticos no tienen un quark y un antiquark como los mesones ordinarios.



Bariones Exóticos y su estructura interna

-Pentaquark
Está compuesto de cuatro quarks y un anti-quark.


-Dibarión
Está compuesto de dos quarks Up, dos quarks Down, y dos quarks Strange.



Mesones Exóticos y su estructura interna

-GlueBall
Está compuesto únicamente de gluones, no contiene quarks. Los GlueBalls son difíciles de detectar en aceleradores de partículas ya que suelen combinarse con mesones ordinarios.



-Tetraquark
Está compuesto de cuatro quarks.



-Mesón Híbrido
Está compuesto de uno o más pares de quark-antiquark, y uno o más gluones.


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Hadrones



Los hadrones son partículas subatómicas compuestas o agrupadas que interactúan mediante la fuerza nuclear fuerte (gluones). 

 Existen 2 tipos de hadrones:
  • Bariones: Fermiones (partículas de materia) compuestos. 
  • Mesones: Bosones (partículas de fuerza) compuestos.  


Bariones y su estructura interna

-Protón
El protón está compuesto de 2 quarks Up y un quark Down.
  

-Neutrón
El neutrón está compuesto de 2 quarks Down y un quark Up.


-Lambda
Lambda (Λ0) está compuesto de uds (Up, Down, y Strange). Existen varios tipos de Lambdas (Λ+
c
, Λ0
b
).


-Sigma
Sigma (Σ+) está compuesto de uus (2 quarks Up, y un quark Strange). Existen varios tipos de Sigmas (Σ0, Σ, Σ++
c
,...).


-Xi
Xi (Ξ0) está compuesto de uss (2 quarks Strange, y un quark Up). Existen varios tipos de Xi (Ξ, Ξ+
c
, Ξ0
c
,...).


-Omega
 Omega (Ω0
c
) está compuesto de ssc (2 quarks Strange, y un quark Charm). Existen varios tipos de Omegas (Ω
b
, Ω+
cc
, Ω0
cb
,...).

-Delta 
Delta (Δ++) está compuesto de uuu (3 quarks Up). Existen varios tipos de Delta (Δ+, Δ0, Δ).




HIPERÓN - Se refiere a bariones que contienen uno o más Strange quarks. Están compuestos de tres quarks livianos y al menos un Strange quark, también se llama Strange Baryons (Bariones Extraños).


Existen 4 tipos de hiperones: Sigma (Σ+, Σ0 y Σ), Lambda (Λ0), Xi (Ξ0 y Ξ), y Omega (Ω).

Mesones y su estructura interna

Los Mesones son partículas subatómicas inestables compuestas de un quark y un antiquark.

-Pion
El Pion (π+) está compuesto de ud (1 quark Up, y un Anti-Down). Existen varios tipos de Pion (π0 y π).



-Eta Meson
Eta Meson (η) está compuesto de 3 quarks (Up, Down, y Strange), y sus respectivas anti-partículas (Anti-Up, Anti-Down, y Anti-Strange).


-Kaon
El Kaon (K+) está compuesto de us (1 quark Up, y un Anti-Strange). Existen varios tipos de Kaon (K0, K0
S
, K0
L
,...).


-D meson
El D meson (D+) está compuesto de cd (1 quark Charm, y un Anti-Down). Existen varios tipos de D meson (D0, D+
s
).



-B meson
El B meson (B+) está compuesto de ub (1 quark Up, y un Anti-Bottom). Existen varios tipos de B meson (B0, B0
s
, B+
c
).



Mesones Vectoriales

-Rho
El Rho (ρ+) está compuesto de ud (1 quark Up, y un Anti-Down). 



-Mesón Omega
El Mesón Omega (ω) está compuesto de ud (quarks Up y Down) y sus respectivas antipartículas (Anti-Up, y Anti-Down).



-Phi
El Mesón Phi (φ) está compuesto de ss (1 quark Strange y un Anti-Strange).



-J/Psi
El J/Psi (J/ψ) está compuesto de cc (1 quark Charm, y un Anti-Charm).



-Upsilon
El Upsilon (ϒ) está compuesto de bb (1 quark Bottom, y un Anti-Bottom). 


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Spaceship Earth


How is Earth moving in our Solar system?

Earth rotates on its axis once each day and orbits the Sun once each year. Earth orbits at an average distance from the Sun of 1 AU and with an axis tilt of 23 to a line perpendicular to the ecliptic plane



As Earth rotates, your speed around Earth’s axis depends on your location: The closer you are to the equator, the faster you travel with rotation.


Notice that Earth rotates from west to east, which is why the Sun appears to rise in the east and set in the west.

Earth takes a year to complete an orbit of the Sun, but its orbital speed is still surprisingly fast. Notice that Earth both rotates and orbits counterclockwise as viewed from above the North Pole.

 How is our solar system moving in the Milky Way Galaxy?

We move randomly relative to other stars in our local solar neighborhood. The speeds are substantial by earthly standards, but stars are so far away that their motion is undetectable to the naked eye. Our Sun and other stars in our neighborhood orbit the center of the galaxy every 230 million years, because the entire galaxy is rotating. 

Our Local Solar Neighborhood


The small box shows that stars within the local solar neighborhood (like the stars of any other small region of the galaxy) move essentially at random relative to one another. They also generally move quite fast. 

Galactic Rotation

Our solar system, located about 27,000 light-years from the galactic center, completes one orbit of the galaxy in about 230 million years. Even if you could watch from outside our galaxy, this motion would be unnoticeable to your naked eye. However, if you calculate the speed of our solar system as we orbit the center of the galaxy, you will find that it is close to 800,000 kilometers per hour (500,000 miles per hour). 

Stars at different distances from the galactic center orbit at different speeds, and we can learn how mass is distributed in the galaxy by measuring these speeds. Such studies indicate that the stars in the disk of the galaxy represent only the “tip of the iceberg” compared to the mass of the entire galaxy. 

Most of the mass of the galaxy seems to be located outside the visible disk, in what we call the halo. We don’t know the nature of this mass, but we call it dark matter because we have not detected any light coming from it. 

Studies of other galaxies suggest that they also are made mostly of dark matter, which means this mysterious matter must significantly outweigh the ordinary matter that makes up planets and stars. An even more mysterious dark energy seems to make up much of the total energy content of the universe. 

This painting shows an edge-on view of the Milky Way Galaxy. Study of galactic rotation shows that although most visible stars lie in the disk and central bulge, most of the mass lies in the halo that surrounds and encompasses the disk. Because this mass emits no light that we have detected, we call it dark matter.




How do galaxies move within the universe?


Galaxies move essentially at random within the Local Group, but all galaxies beyond the Local Group are moving away from us. More distant galaxies are moving faster, which tells us that we live in an expanding universe. 

Two small galaxies (known as the Large and Small Magellanic Clouds) apparently orbit our Milky Way Galaxy. 

For example, the Milky Way is moving toward the Andromeda Galaxy at about 300,000 kilometers per hour (180,000 miles per hour). Despite this high speed, we needn’t worry about a collision anytime soon. Even if the Milky Way and Andromeda Galaxies are approaching each other head-on, it will be billions of years before any collision begins. 

When we look outside the Local Group, however, we find two astonishing facts recognized in the 1920s by Edwin Hubble, for whom the Hubble Space Telescope was named: 

1)      Virtually every galaxy outside the Local Group is moving away from us.
2)      The more distant the galaxy, the faster it appears to be racing away. 

  Natural explanation: The entire universe is expanding. 

Are we ever sitting still?

We are never truly sitting still. We spin around Earth’s axis and orbit the Sun. Our solar system moves among the stars of the local solar neighborhood while orbiting the center of the Milky Way Galaxy. Our galaxy moves among the other galaxies of the Local Group, while all other galaxies move away from us in our expanding universe. 



 BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 



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The Scale of the Universe


How big is the Earth compared to our Solar system?

On a scale of 1 to 10 billion, the Sun is about the size of a grapefruit. Planets are much smaller, with Earth the size of a ball point and Jupiter the size of a marble on this scale. The distances between planets are huge compared to their sizes, with Earth orbiting 15 meters from the Sun on this scale. 



Seeing our solar system to scale also helps put space exploration into perspective. The Moon, the only other world on which humans have ever stepped, lies only about 4 centimeters (1 inches) from Earth in the Voyage model. 

The trip to Mars is some 200 times as far as the trip to the Moon, even when Mars is on the same side of its orbit as Earth. 



How far away are the stars?

On the 1-to-10-billion scale, it is possible to walk from the Sun to Pluto in just a few minutes. On the same scale, the nearest stars besides the Sun are thousands of kilometers away.

The nearest star system to our own, a three-star system called Alpha Centauri, is about 4.4 light-years away.




How big is the Milky Way?

Using a scale on which the Milky Way galaxy is the size of a football field, the distance to the nearest star would be only about 4 millimeters. There are so many stars in our galaxy that it would take thousands of years just to count them. 

The observable universe contains roughly 100 billion galaxies, and the total number of stars is comparable to the number of grains of dry sand on all the beaches on Earth. 






How do our lifetimes compare to the age of the universe?

On a cosmic calendar that compresses the history of the universe into 1 year, human civilization is just a few seconds old, and a human lifetime lasts only a fraction of a second. 

The cosmic calendar compresses the 14 billion-year history of the universe into 1 year, so that each month represents a little more than 1 billion years. This cosmic calendar is adapted from a version created by Carl Sagan.



BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 



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How Far is a Light-Year?



One light-year (ly) is defined as the distance that light can travel in 1 year. This distance is fixed because light always travels at the same speed—the speed of light, which is 300,000 km/s (186,000 mi/s).
We can calculate the distance represented by a lightyear by recalling that 

Distance = speed x time

For example, if you travel at a speed of 50 km/hr for 2 hours, you will travel 100 km. To find the distance represented by 1 light-year, we simply multiply the speed of light by 1 year:

1 light-year = (speed of light) x (1 yr)

That is, 1 light-year is equivalent to 9.46 trillion km, which is easier to remember as almost 10 trillion km.

BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 



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Our Modern view of the universe


Star Manufacture the Elements of Earth and Life 

By studying stars of different ages, we have learned that the early universe contained only the simplest chemical elements: hydrogen and helium (and a trace of lithium). We and Earth are made primarily of other elements, such as carbon, nitrogen, oxygen, and iron. Where did these other elements come from? Evidence shows that these elements were manufactured by stars—some through the nuclear fusion that makes stars shine, and others through nuclear reactions accompanying the explosions that end stellar lives.
 
By the time our solar system formed, about 4 billion years ago, earlier generations of stars had converted about 2% of our galaxy’s original hydrogen and helium into heavier elements. Therefore, the cloud that gave birth to our solar system was made of about 98% hydrogen and helium and 2% other elements. That 2% may seem a small amount, but it was more than enough to make the small rocky planets of our solar system, including Earth. On Earth, some of these elements became the raw ingredients of simple life forms, which ultimately blossomed into the great diversity of life on Earth today. 

How can we know that the universe was like in the past?

Light takes time to travel through space, so the farther away we look in distance, the further back we look in time. When we look billions of light-years away, we see pieces of the universe as they were billions of years ago. 



Because light takes time to travel through space, we are led to a remarkable fact: The farther away we look in distance, the further back we look in time. For example, the brightest star in the night sky, Sirius, is about 8 light-years away, which means its light takes about 8 years to reach us. When we look at Sirius, we are seeing it not as it is today but as it was about 8 years ago.

The Andromeda Galaxy (also known as M31) lies about 2.5 million light-years from Earth. Figure 1.3 is therefore a picture of how this galaxy looked about 2.5 million years ago, when early humans were first walking on Earth. 


Can we see the entire universe?

No. The age of the universe limits the extent of our observable universe. Because the universe is about 14 billion years old, our observable universe extends to a distance of about 14 billion light-years. If we tried to look beyond that distance, we’d be trying to look to a time before the universe existed. 



BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 





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Basic Astronomical Terms

Basic Astronomical Objects
  • Star - A large, glowing ball of gas that generates heat and light through nuclear fusion in its core. Our Sun is a star.
  • Planet - A moderately large object that orbits a star and shines primarily by reflecting light from its star. According to a definition approved in 2006, an object can be considered a planet only if it (1) orbits a star; (2) is large enough for its own gravity to make it round; and (3) has cleared most other objects from its orbital path. An object that meets the first two criteria but has not cleared its orbital path, like Pluto, is designated a dwarf planet.
  • Moon (or satellite) - An object that orbits a planet. The term satellite can refer to any object orbiting another object.
  • Asteroid - A relatively small and rocky object that orbits a star.
  • Comet - A relatively small and ice-rich object that orbits a star. 


Collections of Astronomical Objects
  • Solar system - The Sun and all the material that orbits it, including the planets, dwarf planets, and small solar system bodies. Although the term solar system technically refers only to our own star system (solar means “of the Sun”), it is often applied to other star systems as well.
  • Star system - A star (sometimes more than one star) and any planets and other materials that orbit it.
  • Galaxy - A great island of stars in space, containing from a few hundred million to a trillion or more stars, all held together by gravity and orbiting a common center.
  • Cluster (or group) of galaxies - A collection of galaxies bound together by gravity. Small collections (up to a few dozen galaxies) are generally called groups, while larger collections are called clusters.
  • Supercluster - A gigantic region of space where many individual galaxies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe.
  • Universe (or cosmos) - The sum total of all matter and energy—that is, all galaxies and everything between them.
  • Observable universe - The portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the entire universe.   

Astronomical Distance Units

  • Astronomical unit (AU) - The average distance between Earth and the Sun, which is about 150 million kilometers. More technically, 1 AU is the length of the semimajor axis of Earth’s orbit.
  • Light-year - The distance that light can travel in 1 year, which is about 9.46 trillion kilometers. 

Terms Relating to Motion
  • Rotation - The spinning of an object around its axis. For example, Earth rotates once each day around its axis, which is an imaginary line connecting the North Pole to the South Pole.
  • Orbit (revolution) - The orbital motion of one object around another. For example, Earth orbits around the Sun once each year.
  • Expansion (of the universe) - The increase in the average distance between galaxies as time progresses. Note that while the universe as a whole is expanding, individual galaxies and galaxy clusters do not expand. 
  
BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 

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Our Modern view of the universe

 What is our place in the universe?

Earth is a planet orbiting the Sun. Our Sun is one of more than 100 billion stars in the Milky Way Galaxy. Our galaxy is one of about 40 galaxies in the Local Group. The Local Group is one small part of the Local Supercluster, which is one small part of the universe



Billions of other galaxies are scattered throughout space. Some galaxies are fairly isolated, but many others are found in groups. 

Our Milky Way, for example, is one of the two largest among about 40 galaxies in the Local Group. Groups of galaxies with more than a few dozen members are often called galaxy clusters. 

On a very large scale, observations show that galaxies and galaxy clusters appear to be arranged in giant chains and sheets with huge voids between them. 

The regions in which galaxies and galaxy clusters are most tightly packed are called superclusters, which are essentially clusters of galaxy clusters. 

Our Local Group is located in the outskirts of the Local Supercluster.

Together, all these structures make up our universe. In other words, the universe is the sum total of all matter and energy, encompassing the superclusters and voids and everything within them. 

How did we come to be?

The universe began in the Big Bang and has been expanding ever since, except in localized regions where gravity has caused matter to collapse into galaxies and stars. The Big Bang essentially produced only two chemical elements: hydrogen and helium. The rest have been produced by stars, which is why we are “star stuff.” 



The Big Bang and the Expanding Universe

Telescopic observations of distant galaxies show that the entire universe is expanding, meaning that the average distances between galaxies are increasing with time. This fact implies that galaxies must have been closer together in the past, and if we go back far enough, we must reach the point at which the expansion began. We call this beginning the Big Bang, and from the observed rate of expansion we estimate that it occurred about 14 billion years ago. 

The universe as a whole has continued to expand ever since the Big Bang, but on smaller scales the force of gravity has drawn matter together. Structures such as galaxies and galaxy clusters occupy regions where gravity has won out against the overall expansion. That is, while the universe as a whole continues to expand, individual galaxies and galaxy clusters do not expand. 

Stellar Lives and Galactic Recycling

Within galaxies like the Milky Way, gravity drives the collapse of clouds of gas and dust to form stars and planets. Stars are not living organisms, but they nonetheless go through “life cycles.” A star is born when gravity compresses the material in a cloud to the point where the center becomes dense and hot enough to generate energy by nuclear fusion, the process in which lightweight atomic nuclei smash together and stick (or fuse) to make heavier nuclei.

The star “lives” as long as it can generate energy from fusion and “dies” when it exhausts its usable fuel. 

In its final death throes, a star blows much of its content back out into space. In particular, massive stars die in titanic explosions called supernovae. The returned matter mixes with other matter floating between the stars in the galaxy, eventually becoming part of new clouds of gas and dust from which future generations of stars can be born. Galaxies therefore function as cosmic recycling plants, recycling material expelled from dying stars into new generations of stars and planets. Our own solar system is a product of many generations of such recycling. 


BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition) 



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