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Stars Variables: An Introduction (I) (Note that it fried)

had promised to publish a simple introduction to the topic of variable stars. As I already had written for many years, but was available on a page that no longer exists, I'll get it back through the blog VariaStar. I take it for good this remake if it is useful to pers onas that p irst time approaching the world of variable stars.

Variable Star: An Introduction (I)

A variable star is any star in the sky whose brightness is not constant but change with time. Although it is suspected that the Arabs already know the variability of Algol, Beta Persei, the first reference is to secure a star in the constellation of the Whale, which Fabricius observed in 1596 in the third magnitude when it was omitted from the maps, which called Mira (wonderful), and Bayer independently cataloged under the name omicron Ceti in 1603.

What appeared to be a few anomalies in the unchanging sky for astronomers of the seventeenth century were already more than three hundred by the end of last century and today are about 40000, which is why variable stars are a branch Astronomy independent today. However, and paradoxically, the importance of ee. vv. reside outside their own area, extending the full knowledge of the universe. Stellar variability responds to particular moments in the life of a star, or the interactions between the stars that make up double or multiple systems, or effects between a star and a surrounding material, or phenomena on the surface, etc, etc. Thus, in this way, variable stars are real testbeds to study the structure and evolution of stars, the fluids in the interstellar medium, exotic objects in the galaxy, or as many problems of astrophysics.

Classification of Variable Star

The variability in the brightness of a star can be caused either by:

1-fault of the star itself. In this case we Extrinsic Variables that are not ee. vv. strictly speaking, but rather specific instances of binary stars in which a hidden component of other observers. So this is also called eclipsing variables. Can be of three types: Type beta PerseiTipo beta Lyrae type W Ursae Majoris

2 - The physical structure and all kinds of processes that occur in the star. These are the stars Variables Intrinsic or Physics. This is the kind of ee.vv. to which we will pay more attention. There are two main types of ee.vv. Physical:

Pulsed . Have a brightness variation usually soft and maintains a clear schedule. May be of the following subtypes:

Cepheid (classical) (short-period Cepheids)


RV Tauri type


beta Canis Majoris type


RR Lyrae Type


Delta Scuti type


Look
Type

semiregular


alpha-2 type Venaticorum canum




Eruptive . Are sharp variations in brightness, not follow, in many cases, an appreciable frequency. They present 2 subtypes:


Eruptive Irregular


Eruptive Cataclysmic
Supernovae:
Type I
Type II

News:
Ballroom

; Glasses
; Very Slow

U Geminorum type

Z Camelopardalis Type

Type Z Andromedae (symbiotic stars)

R Coronae Borealis type

Nomenclature of Variable Star

Like ordinary stars, the variables are named according to the constellation to which it belongs, identified by a Latin letter beginning with R (with so as not to be confused with Bode star catalog, which uses the alphabet from A to Q) followed by the genitive of the Latin name for the constellation within which it is.
When it comes to Z name starts with two letters, beginning a series that runs from the RR to RZ. If more variables are found in pairs series will begin with S, T, etc, to Z, combined with the R, S, T, etc to Z. Also it is possible to do sets of 2 letters from A to Q combined with the letters A through Z.

With this system 334 can be classified variable stars in a constellation when recognizing new such objects shall be named with the prefix V and the serial number (which must be from 335), accompanied by the Latin genitive of the constellation name. There are also variables that receive the traditional name or the name of Bayer to be known long before the discovery of its variability: Beta Persei (Algol), Chi Cygni, for instance.

A variable star also receives a numerical designation, the number of Harvard, which corresponds to their coordinates in the epoch 1900.0. On the other hand, different kinds of variable stars are designated by the name of a star which is usually the first such discovery and is the prototype of behavior that is classified.

Peter Doig Exhibition Poster

A nova out of the ordinary

On March 10 some Japanese observers detected an explosion in the variable star V407 Cygni. The strange thing was the intensity of the blast, which reached a maximum brightness of 7.4, when often remain in the 13 sleep.

V407 Cygni is a symbiotic variable. Symbiotic star is called a binary star in which coexist with a very sharp contrast in their spectral types (ie, their surface temperatures). This difference is evident in their spectra, which were impossible to read until it was determined that responded to the combination of those for each component of a dual system. Similarly, in a symbiotic variable shows a very long period of revolution, which means that the hotter component (and small and compact) revolves around a star enough massive so you have to do it at a distance take years to complete one revolution. It should be a big star and cold, a condition that meets a red giant.

symbiotic variables are strange in their behavior, show regular variations similar to those of a Mira variable (which are variations of the red giant component, acting as such type of variable), can present occasional eclipses when the plane of rotation of the system is a suitable inclination, or, without a clear periodicity, flare or outburst "very similar to lso given in the so-called cataclysmic variables, by mechanisms quite similar.

The symbiotic are kind of all-in-one variable stars: pulsating, tiling, eclipsing and eruptive, and herein lies part of its interest in astronomical objects.

And it does not end here, the symbiotic also can erupt in a violent way, with much wider than a regular pop. It is an explosion similar to those of a classical nova, and is considered as a category of nova, we will refer to this as a symbiotic nova.

And this is what has happened to V407 Cygni. Around its compact hot component has been an accumulation of hydrogen gas to achieve higher levels of density and pressure conditions found to begin nuclear fusion that leads to Helio. This fusion takes place in an abrupt and explosive, which is manifested in the explosion of nova.

In the case of not knowing the progenitor of the nova can be identified as symbiotic by the length of the burst and its own spectral characteristics. But in this case we know the system has occurred, which is a symbiotic variable more or less well known.

From now until later this year is expected to V407 Cyg remains on a scale accessible to visual observation with telescopes modest. Can be an object of interest in the summer observations to be located in this constellation as typical summer as Swan.