Stars: Things are happening on Vega

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Stars: Things are happening on Vega
Stars: Things are happening on Vega

On Vega it goes around

Stars are not always round. According to new findings, Vega in the Lyra constellation is apparently flattened and is rotating around its own axis at breakneck speed. Which wouldn't be so bad - if Vega of all things weren't one of the most important comparison standards in astronomy.


It's such a thing with colors: red isn't always red, blue ranges from sky and cob alt to turquoise, and yellow doesn't always shine in the same way. In general, what color is the sun? Red in the morning, white at midday and yellow when the sky is overcast? Such vague information may be sufficient for postcards from vacations, science wants to know more about it. And not only from the sun, but from all the stars. Because depending on the composition of the colorful splendor of light, sophisticated conclusions can be drawn about the properties of the points in the firmament.

The meticulous demands of the astronomers are therefore only satisfied by highly precise information, for which the starlight has to be broken down into its full width. On earth, this task is sometimes performed by raindrops, which break the sunlight, reflect it and present it to the astonished human children as a rainbow. For stellar objects, researchers have built extra spectrometers that can also spread the weak glow of the stars. The well-known rainbow colors appear, interrupted in certain places by fine dark lines. These form when atoms in the outer layers of a star swallow part of the light. This would provide a first important clue to the chemical composition of the glowing sphere.

Depending on the appearance of the spectra, astronomers classify all stars into spectral classes denoted by the letters O, B, A, F, G, K and M (easy to remember with the auxiliary clause: " Oh, Be A Fine Girl/G uy, Kiss Me!"). If you take a closer look, there are differences that are taken into account by a further classification with the numbers 0 to 9. The further east a star is classified, the hotter it gets, while it gets cooler as it approaches the M end. As a G2 star, our Sun is placed relatively in the middle.

Because color matters are so complicated, it is necessary to determine a comparison star for each spectral type, which serves as a kind of ideal model. Like any standard, this star should be constant and unfussy-reliably boring. Vega in the constellation Lyra, after all the second brightest star in the northern sky and the fifth brightest in the entire firmament, is one of these standards. It is the zero point of the spectral type A0 and also represents the luminosity class V. It is therefore a very important pivot in countless spectroscopic star measurements. And this Vega of all people has now turned out to be a wild shaky candidate.

A team of astronomers led by Deane Peterson from the University of Stony Brook in the US state of New York came to this conclusion. The scientists investigated inconsistencies in recent studies of the Vega spectrum: The star is simply too bright compared to similar stars and has oddly shaped lines in the spectrum. So the researchers took a closer look at it again with three coupled telescopes, which together can compensate for disruptive effects of the earth's atmosphere. They fed their data into a model - and found that Vega is by no means the quiet, boring star everyone thought he was.

On Vega, things literally go round instead. The star rotates so fast on its own axis that it almost tears it apart. The speed at the equator is around 272 kilometers per second - this is enough to hurl its matter far outwards at low latitudes - Vega has the shape of a somewhat flattened sphere. Because the more distant regions are farther from the heating center, they also have a lower temperature: while the poles are around 10,000 degrees Celsius hot, the equator is around 2,400 degrees cooler.

The star's rapid rotation went undetected for so long because its axis of rotation points almost exactly toward Earth. Now that it is known, however, even more supposedly certain knowledge about Vega is beginning to f alter. For example, the proportion of heavy elements such as iron was determined using incorrect assumptions and is probably incorrect. A different composition, in turn, leads to new values for the probable ages of the star and the disk of gas and dust that surrounds it. Instead of the approximately 350 million years estimated so far, both could already be 570 million years "Image". alt="

Unexpectedly, astronomy is confronted with a model boy who does not behave in an exemplary manner at all, but for a long time was considered the standard for a multitude of studies. Now it is a question of meticulously measuring Vega and then estimating how great the damage is that the rotating star has caused in the scientific field. It is quite possible that one or the other astronomer would wish Vega to rotate ten percent faster - the star would fly apart at that speed.

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