stars

The Stars

green flare

When observing the sky at night we will discover thousands of stars. Although they are seen very small are in realidada much more great that our Sun. Each star is a great gas ball that burns in the deep thing with the space.

 

birth

Young stars

The stars, like the people, are born, grow and die. Are born from great dust and gas clouds that are in the space. After thousands of years this dust and gas are joined to form a great ball that turns. The ball warms up so much that begins to shine. A star has been born.

A typical star is divided in nucleus, mantle and atmosphere. In the nucleus it is where the nuclear reactions take place that generate their energy. The mantle transports this energy towards the surface and according to the transport, by convection or radiation, it will be divided in two zones: convective radian and. Finally, the atmosphere is the most superficial part of the stars and the only one that is visible. It is divided in chromosphere, photosphere and solar corona. The stellar atmosphere is the coldest zone of stars and in them the matter ejection phenomena take place. But in the crown, it supposes an exception to what has been shelp since the temperature returns to increase until reaching the million degrees at least. But it is a deceptive temperature. In fact this layer is very little dense and is formed by ionized particles highly accelerated by the magnetic field of the star. Their great speeds confer to those particles high temperatures to them. Throughout their cycle the stars even undergo changes in the size of the E layers in the order in which they get ready. In some the radiating zone will the other way around be placed before the convective one and in others, depending as much on the mass as of the phase of fusion in which it is. Also, the nucleus can also modify its characteristics and their size throughout the evolution of the star. The age of the majority of stars oscillates between 1000 and 10 000 million years; although some stars even can be older. The observed star older, THERE AM 1523-0901, has a considered age of 13 200 million years, very near the age considered for Universo, of about 13 700 million years.

The stars shine by million years, soon they spend his fuel and they get to die. The greatest stars (much more great that the Sun) are those that shine more, but also those that less last. When they die collapse in second and Supernova happens a gigantic called explosion. Some less great stars stop shining and they are contracted little by little until they have a so great gravity that the star forms a point very dense call Black hole or Black Hole. The black holes work as if they were space eddies, swallow everything what it is close. Its force is like not even the light can escape. Black holes Are bodies with an extraordinarily great gravitational field. Any electromagnetic radiation nor luminous cannot escape, for that reason they are black. They are surrounded by a “spherical border” that allows that the light between but does not leave. There are two types of black holes: HD bodies and little mass concentrated in a very small space, and bodies of density low but very great mass, as it happens in the centers of the galaxies. If the mass of a star is more of twice the one of the Sun, it arrives a little while in his cycle in which nor only the neutrons can support the gravity. The star collapses and it becomes black hole. Luminous cones the British scientist Stephen W. Hawking has dedicated good part from his work to the study of the black holes. In its book “History of the Time” explains how, in a star that is collapsing, the luminous cones that it emits begin to curve themselves in the surface of the star. When small becoming, the gravitational field grows and the light cones incline more and more, until no longer they can escape. The light goes out and he becomes black.

Supernova

 

Constellations

From the antiquity the man when looking the stars at night imagined that uniting them with lieas imaginary they could form certain figures; these are called Constellations. They have being, animal names of mitogía and object. Aymara mythology is much more interesting to study because it had the calls “dark constellations”; Coats took into account the calls “from Coal” that they are dark regions in Vía Láctea.

blue spaceyYou knew that?

Shurnarkabtishashutu is the star with the longest name. It is a word in Arab who means “under the horn to the south of the bull”!

The light of the Sun takes in arriving at the Earth 8 minutes. The light of the star nearest the Solar System Alpha Centauri, takes four years in arriving until us!

 

 

In order to define the color of a star, the Johnsons and Morgan (1950), created system UBV (of English Ultraviolet, Blue, the Visible one). The measurements were realised by means of a photoelectric photometer to measure the intensity of the radiation the specific wavelengths:

 

 

With these data a series of scales could be created: (B-V), (U-B) and (B-V). Whichever major the number, redder is the star.

 

The table next shows the electromagnetic spectrum, with its wavelengths.

Denomination and Wavelength
  • Gamma rays
  • 0.00000007 to 0,001 Å
  • X-rays
  • 0.001 to 100 Å
  • Luz Ultravioleta
  • 100 to 3900 Å
  • Luz Visible
  • 3900 to 7500 Å
  • Luz Infrarroja (photographic)
  • 7500 to 15000 Å
  • Near infrared
  • 15000 to 200000 Å
  • Distant infrared
  • 0.002 to 0,1 cm.
  • Microwaves (radar waves) 0.1 to 250 cm.
  • High frequencies (television)
  • 2.5 to 15 M.s
  • Short wave of radio
  • 15 to 180 M.s
  • Aeronautical control range
  • 750 to 1500 M.s
  • Long wave of radio
  • 1500 ms in future
  •  

    The scales are the following:

     

    1 Å (Ångstron) = 1x10-8 cm (centimeters) = 1x10-10 m (meters)

     

    The human eye is only able to perceive the small portion that corresponds to the visible light, located between 3900 Å and 7500 Å, where the minor is near the violet and the major of the red one. The Sun emits in all the wavelengths, but they only arrive at the surface a small portion from these, the others are restrained by the atmosphere: ozone absorbs but the high wavelengths until the ultraviolet one, and the aqueous vapour absorbs great part of the infrared ones.

     

    Espectrales types

    The phantom is the band of colors that obtains when dispersing the light coming from a star, the characteristics of each phantom depend on the temperature of the superficial layers of the star.

    When dispersing the light that crosses one narrow groove can be observed on the phantom a series of dark lines that crosses it, the calls spectral lines, each hidden certain specific part of the phantom. These sets of lines correspond to certain chemical elements, each pertaining one to one especially, and since they are unique depending the temperature is possible to determine the composition of the stellar atmosphere.

    These lines are dark because they absorb part of the energy of the star, therefore are called absorption lines and they take place when the radiation coming from the nucleus of the star crosses a zone but it fries (but superficial).

    Sometimes in certain phantoms they are visible lines that unlike the absorption lines shine but that the rest of the continuous spectrum, is the calls lines of emission, produced by a gas warmed up to certain temperature. This usually is observed in stars that are surrounded by a gaseous envelope to high temperature.

     

    The spectral types are classified by letters, from the major to the smaller temperature of the following way:

    blue spacey

    OR B TO F G K M L T and C S

    Blue stars. Few spectral lines and weak. They show multiple ionized atoms, especially There am III, C III, N III, OR III, If V. B 15000 Bluish stars white. The line of There am II is not visible. They are observable lines of OR II, If II and mg II. It appears the line of There am I. Continues being few lines A 9000 White stars. The line of H I (lines of Balmer) dominates the phantom. There am it I am not visible. They begin to appear the lines of neutral metals. F 7000 Yellowish stars white. Remarkable increase of the amount of lines of H I, but falls in intensity. The lines of ionized metals increase. G 5500 Yellow stars. The intensity of the lines of neutral metals increases, whereas those of H I fall. K 4000 Orange stars yellow. The phantom is dominated by the lines of metals. Molecular bands OTi. M 3000 Red stars. The bands of OTi are very prominent. Several lines of neutral metals are visible. For phantoms beyond the M4 the absorption lines of the OTi are very severe, and it becomes difficult to observe the continuous spectrum.

    She contains colder the red dwarves and the hotter brown dwarves, than stay due to the fusion of the deuterium and gravitational contraction. They present VO (vanadium oxide) in absorption as the cold Ms but, reaching a maximum in L0. The Uncle decreases in abundance until almost disappearing in L7. The brown dwarves present absorption line of lithium. The lines of alkaline metals, especially Potassium, become very strong as low the temperature. Absolute magnitudes between 18 and 24.

    Only visible in the infrared. The phantom is rich in methane (as giant planets) and molecules of water and iron hydride (FeH) Carbon stars (very red since the compounds of this element absorb the blue wavelengths). They are giant where the Uncle is replaced by compound as C2, CH and Cnn. They are subdivided in addition to by the temperature (that goes in parallel to the normal sequence from G4 to M8), by the force of the carbon bands. Ex: C7,4. Ex: R Leporis (variable) Red giant stars (they go parallel to class M) that also present more carbon than the normal giants and where the Uncle is replaced by the ZrO (zirconium oxide) and also pesentan yttrium and barium. Ex: chi Cygni (variable) Exists intermediate classes as MS and SC according to the abundance of the descriptos elements.

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