Stellar winds, the source material for the universe, are clumpy

by HeritageDailyJanuary 25, 2019



Illustration of a high-mass X-ray binary system made up of a compact, incredibly dense neutron star paired with a massive 'normal' supergiant star. New data from NASA's Chandra X-ray Observatory shows that the neutron star in the high-mass X-ray binary, OAO 1657-415, passed through a dense patch of stellar wind from its companion star, demonstrating the clumpy nature of stellar winds. Credit : NASA/CXC/M.Weiss


Data recorded by NASA’s Chandra X-ray Observatory of a neutron star as it passed through a dense patch of stellar wind emanating from its massive companion star provide valuable insight about the structure and composition of stellar winds and about the environment of the neutron star itself.

A paper describing the research, led by Penn State astronomers, appears January 15, 2019, in the journal, Monthly Notices of the Royal Astronomical Society.

“Stellar winds are the fast-flowing material–composed of protons, electrons, and metal atoms–ejected from stars,” said Pragati Pradhan, a postdoctoral researcher in astronomy and astrophysics at Penn State and the lead author of the paper. “This material enriches the star’s surroundings with metals, kinetic energy, and ionizing radiation. It is the source material for star formation. Until the last decade, it was thought that stellar winds were homogenous, but these Chandra data provide direct evidence that stellar winds are populated with dense clumps.”

The neutron star observed is part of a high-mass X-ray binary system–the compact, incredibly dense neutron star paired with a massive ‘normal’ supergiant star. Neutron stars in binary systems produce X-rays when material from the companion star falls toward the neutron star and is accelerated to high velocities. As a result of this acceleration, X-rays are produced that can inturn interact with the materials of the stellar wind to produce secondary X-rays of signature energies at various distances from the neutron star. Neutral–uncharged–iron atoms, for example, produce fluorescence X-rays with energies of 6.4 kilo-electron volts (keV), roughly 3000 times the energy of visible light. Astronomers use spectrometers, like the instrument on Chandra, to capture these X-rays and separate them based on their energy to learn about the compositions of stars.

More:
https://www.heritagedaily.com/2019/01/stellar-winds-the-source-material-for-the-universe-are-clumpy/122586