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What's new with massive stars?

What’s new with massive stars?
Editors

Massive stars are fascinating objects, and I like to call them the “queens” of the stars because they truly rule all aspects of life in every galaxy. They eject huge quantities of material throughout their lives in flows called stellar winds. The exact properties of such winds still remain uncertain, with values for the rates of mass-loss differing by up to two orders of magnitude.


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Securing an accurate knowledge of wind characteristics is important, as stellar winds inject large amounts of mass and energy into their environments, thereby affecting the whole evolution of their home galaxies. For example, winds can start or halt star formation in their neighborhoods, they change the fates of massive stars, and they are sources of chemical and mechanical feedback into the interstellar and intergalactic medium. Winds are intrinsically unstable, and the generated shocks heat a fraction of the winds to millions of degrees, leading to X-ray emission. X-rays thus provide an important tool to uncovering the structure of stellar winds.

reddwarf_nielsen

In the past decade, Europe’s X-ray observatory XMM-Newton, has monitored one of the closest and brightest massive stars, Zeta Puppis. These unprecedented sensitive observations reveal surprising results. First, although strong X-ray variability on the timescale of hours was expected, XMM-Newton did not witness it, which implies that the wind must then be highly fragmented (more than 100,000 hot or cool pieces, a number that far exceeds theoretical predictions).
The X-ray flux changes on timescales of days, however, which is linked to the presence of large-scale structures in the wind, possibly spiral-like features co-rotating with the star. Further-more, we could pinpoint the emission zones: the X-ray emission arises from a superposition of several components, with the cooler plasma generated in large zones extending up to 100 stellar radii and the hotter plasma located in smaller zones at a few stellar radii from the star.
Zeta_Puppis

This is the first time constraints have been placed on the location of the X-ray emission and the number of fragments in a stellar wind of an adult massive star.

Fast facts

Evidence of martian water

Some 3.7 billion years ago, liquid water likely flowed into the 118-mile-long (190 kilometers) martian valley called Tinto Vallis, a section of which is seen in this image from the European Space Agency’s Mars Express, released February 14. A number of tributaries fed into a smaller valley (top right), and both valleys fed into Palos Crater (not pictured). Scientists believe the shorter valley formed after volcanic activity turned ice under the planet’s surface into water, which seeped and bubbled up to the surface.

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Source: Astronomy.
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