Milky Way growth chart reveals how galaxy evolved

Scientists have made a cosmic growth chart of the Milky Way, an innovative blending of data collected by the ongoing Sloan Digital Sky Survey and a new technique to determine the ages of stars.

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> PHOTO: This image shows the latest results as coloured dots superimposed on an artist’s conception of the Milky Way. Red dots show stars that formed when the Milky Way was young and small 12 – 13 billion years ago, while blue shows stars that formed more recently 1- 2 billion years ago, when the Milky Way was big and mature.

That’s much as expected. The bulge is oldest, the thick disk came next and then the thin disk last. Not sure how they generated the chart, though, you need accurate distances to stars for that, and the Gaia first data release is due out mid 2016. Without that there’s no way to know the distances to those stars.

> “This is somewhat revolutionary because ages have previously been considered very hard to get, particularly from stellar spectra”

Not just difficult, impossible. For any star on the main sequence (90% of its life) there is absolutely no way to determine how old the star is. Certainly the concentration of heavy elements in the spectrum increases with time, but that can’t be distinguished from heavy elements that were in the gas cloud that got absorbed into the star when it formed. Outside the main sequence, the determination of the age of a star gets much easier.

mollwollfumble said:

> PHOTO: This image shows the latest results as coloured dots superimposed on an artist’s conception of the Milky Way. Red dots show stars that formed when the Milky Way was young and small 12 – 13 billion years ago, while blue shows stars that formed more recently 1- 2 billion years ago, when the Milky Way was big and mature.

That’s much as expected. The bulge is oldest, the thick disk came next and then the thin disk last. Not sure how they generated the chart, though, you need accurate distances to stars for that, and the Gaia first data release is due out mid 2016. Without that there’s no way to know the distances to those stars.

> “This is somewhat revolutionary because ages have previously been considered very hard to get, particularly from stellar spectra”

Not just difficult, impossible. For any star on the main sequence (90% of its life) there is absolutely no way to determine how old the star is. Certainly the concentration of heavy elements in the spectrum increases with time, but that can’t be distinguished from heavy elements that were in the gas cloud that got absorbed into the star when it formed. Outside the main sequence, the determination of the age of a star gets much easier.

Conclusion – wait for the first Gaia Space Telescope data release in mid 2016.