Vega

37 ± 3 L ☉

Wega ( Vega rare ) in the Bayer designation α Lyrae, the main star of the constellation is lyre ( Lyra ); the name derives from the Arabic expression النسر الواقع to - nasr al - ʿ wāqi, which means in translation " down poking ( eagle) ".

It is part of the great summer triangle and the white light of the brightest star in the northern sky. With their magnitude of 0.0 it was once used as a reference star brightness measurements ( photometry ).

  • 3.1 Increased infrared radiation
  • 3.2 dust disk
  • 3.3 Possible planetary system

General

Wega, together with the main stars of the constellations Cygnus and Adler called Summer Triangle. It is the fünfthellste star in the night sky and the second brightest star Arcturus by in the northern hemisphere. It is about 25 light-years from the Sun and thus a relatively nearby star. Together with Arcturus and Sirius Vega is one of the brightest stars in the neighborhood of the sun.

Vega has been extensively studied by astronomers. This meant that they were " probably as the most important star to the Sun " applies. Due to the precession of the earth about 14,000 years ago Vega was the North Star, and the Earth's axis is pointing in about 12,000 years back in the direction of Vega. However, Wega is the celestial pole by far not come so close as our current North Star.

The high brightness, Friedrich Wilhelm Struve suspect in 1835 that he was relatively close to our solar system and a distance determination would be possible. In 1838 he succeeded in measuring the tiny angular displacement as a result of Earth's orbit ( 0.13 " ) and thus the proof of the heliocentric world view. However Bessel him was thus preempted by a few months at the star 61 Cygni.

Wega served, inter alia, the astronomers than zero for the calibration of the photometric brightness scale (see also Polsequenz ). She was also one of the A0V star, which served as the zero point for the BV and UB color indices in the Johnson -Morgan UBV system due to their relatively constant intensity in the visible region of the spectrum.

Physical Properties

Wega is a bluish-white main sequence star, the fused like all main sequence stars in its core hydrogen into helium. With an age 386-572 million years ago, Vega is one of the even younger stars. It is relatively low in " metals " ( elements that have a higher atomic number than helium ). It is believed that Vega is a variable star that periodically changes very little in its brightness. Wega has twice the mass and the 37- times brighter than the sun.

Hydrogen is fused in the interior of the star by means of the Bethe- Weizsäcker cycle ( CNO cycle ) to form helium. This process requires a temperature of over 16 million K, which is higher than the core temperature of the sun. This fusion reaction is more efficient than the proton / proton reaction to the sun. The core is a convection section, which merges into a zone of radiation to the outside. When the sun is reversed. There is inside the radiation zone and towards the surface follow the convection zones.

The visible spectrum is affected by absorption lines of hydrogen, specifically the lines of the Balmer series, dominated. The lines of other elements are weak, most are still those of magnesium, iron and chromium recognizable. The X-ray radiation Wegas is very low. This suggests that the corona of the star is very weak or does not exist.

Since massive stars merge its hydrogen much faster than smaller stars, the lifetime of Vega 1 billion years ( equivalent to slightly less than one -tenth of the lifetime of the Sun) correspondingly short. So she soon has half of its main-sequence time behind. After that, they will swell into a red giant of spectral type M, only to end as a white dwarf.

Rotation

Previously it was assumed that Vega was a slowly rotating star with fairly constant surface temperature. According to measurements of DM Peterson Wega rotates very quickly to her by 4.5 degrees inclined to our line of observation axis, with 93 % of the speed that would tear the star.

Studies with the CHARA interferometer of the Mount Wilson Observatory in California have shown that the photosphere Wegas is at the equator to 2400 K cooler than at the poles. The cause that the temperatures at the poles 10 000 K and 7600 K at the equator amount is due to the rapid rotation about the polar axis within 12.5 hours. Due to this rapid rotation at 274 km / s at the equator to the pole diameter is compared to the equatorial diameter by 23% flattened, as the equatorial region is bulged by the centrifugal force.

The temperature difference can be explained by the position of the polar region, which is located much closer to the hot stellar interior. This effect is referred to as a gravity - darkening. From the Earth looks out over one of the poles Wegas.

Frequency of the elements

Astronomers refer to elements whose atomic number is higher than that of the helium as " metals ". The metallicity of Wegas photosphere is with [M / H] = -0.5 approximately 32% of the value of the sun's atmosphere. For comparison, Sirius has with [M / H] = 0.5 on the threefold occurrence of metals to the sun. The proportion of the elements are heavier than helium, is at about the sun: ZSonne = 0.0172 ± 0.002. This Wega contains only about 0.54 % heavier elements than helium.

The unusually low metallicity Wegas makes it a weak Lambda Bootis star ( a group of stars with low metallicity ). However, the reason for the existence of such chemically unusual A0 -F0 - Spektralklassensternen remains unclear. One possibility is in the diffusion or in the material loss of the star. Stellar models show that this would normally only occur at the end of the lifetime of the phase of the fusion of hydrogen. The star could also come from an interstellar cloud of gas and dust that was unusually metal-poor, have arisen.

The observed ratio of helium to hydrogen Wegas is 0.030 ± 0.005, which is about 40% lower than that of the sun. This could be caused by the disappearance of a helium - convection zone near the surface. The energy transport is instead done by a radiation zone, which could cause an abnormality of the frequencies by diffusion.

Magnetic field

2009 was detected by French astronomer, a magnetic field with the stellar spectropolarimeter of the Bernard- Lyot NARVAL telescope. In the spectrum of the star they found the so-called Zeeman effect. The spectral lines are broken by the influence of the magnetic field. The strength of the magnetic field of Vega is about 50 micro - Tesla between the earth and the sun.

System

From measurements in the infrared region, we know that there is matter accumulations at Vega. Vega was the first star (1983 ), in which they discovered a dust disk.

Increased infrared radiation

One of the first findings of the Infrared Astronomical Satellite ( IRAS ) was the discovery of an increased infrared radiation from Vega. This radiation coming from an area with a radius of 10 " to the star. With the known distance of the star to get to a radius of 80 AU. It is believed that this radiation is from an area floating in the particles of the order of 1 mm. Smaller particles of matter would be removed by the radiation pressure or fall in the star by the Poynting - Robertson effect.

Dust disk

The increased radiation in the infrared range, we know that Vega is surrounded by a disk of gas and dust. This dust is probably the result of collisions between objects in an orbiting debris disk. This is similar to the Kuiper Belt in our solar system.

2003 British astronomers calculated that the properties of this disk can probably best be explained by a planet similar to Neptune. Thus, the Vega system would be the one star system that resembles our solar system most possibly. The center of the habitable zone of Vega is 7.1 AU. A planet with this distance it would have an orbital period of 10.9 years.

Stars, showing an excessive radiation due to the dust in the infrared region of the spectrum, and " Vega " type called star. Irregularities in Wegas dust disk could also at least point to a planet that could have a size similar to that of Jupiter, orbits around Vega.

Possible planetary system

Despite an intensive search and many guesses, no planet could be detected up to now. However, a planetary system can not be ruled out.

Movement

The Vega is part of the Castor moving clusters. The star of this collection all have the same speed and come from a common origin. Besides Wega are still Castor, Fomalhaut, α Cephei ( Alderamin ) and α Librae ( Zuben -el- dschenubi ) member of this movement cluster. You have to have all of a similar age.

Although Vega is at present only the fünfthellste star in the sky, they will always be brighter by their own movement, which runs in the direction of the sun, with time. In about 210,000 years she will be the brightest star in the night sky and remain so for about 270,000 years. The maximum apparent brightness, which they reached, in 290,000 years at -0.81 may lie.

History

Vega was the first star (other than the sun ), from which a photographic image was created. 1850 William Cranch Bond and made ​​John Adams Whipple at the large telescope of the Harvard College Observatory a daguerreotype of Wega to. She was also among the first stars whose distances were determined using the Parallaxenverfahrens and its spectrum was also photographed.

Culture and Literature

In Chinese love story of Cowherd and Weaver, which is celebrated every year in China as Kwee and in Japan as Tanabata, Wega is the "Star of the weaver " (Chinese织 女星/织 女星, Pinyin Zhīnǚ Xing, Japanese Shokujo -sei or织 姫 星, Orihime - boshi ), by the " sky River " ( Milky Way ) of the cowherd ( Altair ) is disconnected.

The Invaders (AKA The Invaders ) is a famous American science fiction series of 1960er/70er-Jahre.

In 1997 filmed novel Contact by Carl Sagan is an encrypted radio signal, which contains the blueprint of a transportation machine, received from the direction of Vega. The played in the film by Jodie Foster protagonist Eleanor " Ellie " Arroway travels with the replica machine to the Vega system.

The male protagonist Adam Bates from the novel by Myron Levoy Adam and Lisa claims it originated from the planet Vega X. It is his attempt to forget his bad childhood, in which he was abused by his father with a chain.

In the first six episodes of the radio drama series Commander Perkins the eighth planet Vega plays the main world of the series. Template is the series Perry Rhodan, in the Vega has a system of 42 planets, and also saw the eighth planet of the Vega as a novel basis.

There is a band from the United States, founded Celestial rock in March 2011 with the name of the signal to Vega

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