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Mass Transfer in Binary Stars
John M. Blondin, Marcedes T. Richards, Michael L. Malinowski (North Carolina State University)
The binary star Algol (Beta Persei) was the first eclipsing variable star ever discovered, and it's still the most famous one. Algol brightens and fades like clockwork every 2.87 days, and its changes are very plain to the unaided eye. The variation in its brightness is caused by one star in the system periodically blocking the other as they orbit. Astronomers have discovered that matter from one star actually flows onto the other star! This supercomputer calculation shows what that matter flow might look like.
Video: 935 kB, MPEG
Stellar distortion
The calculations shown in this visualization demonstrate that, when matter flows from one star in the Algol system to the other, the stars become distorted from their normal spherical shapes. The matter flows through a single critical point between the two stars, called the inner Lagrangian point,
and interacts with the heat and radiation from the stars to form twisted braids, loops and streamers.
Charles Liu
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Violent Stellar Winds in an X-ray Binary System
Jeff Benensohn, Don Q. Lamb (University of Chicago), Ronald E. Taam (Northwestern University)
The majority of stars in our Milky Way Galaxy exist in binary or multiple systems. These systems consist of two or more stars that are bound gravitationally to one another. Our Solar System is an example of a gravitationally-bound system, the Sun being massive enough to attract the nearby planets. However, if we consider a binary star system, a logical question to ask is what happens when these two stars evolve? In many cases, one star evolves faster than the other, causing material from the evolving star to expand outward. This material is pulled in by the companion. For massive stars, the stellar remnant left behind will be a black hole or a neutron star. Simultaneously, the companion star is evolving and matter is eventually thrown back onto the stellar remnant. This material is heated to extreme temperatures as it arrives at the super-dense black hole or neutron star, causing it to glow in X-ray wavelengths. Astronomers call these systems X-ray binaries.
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The simulation
This animation depicts an X-ray binary system consisting of a neutron star and a supergiant star. The neutron star is very dense, about 10 kilometers (6 miles) in diameter with the mass of 1.5 Suns. The supergiant companion star is about 7 times larger and 15 times more massive than our Sun. The neutron star has a massive gravitational pull, causing the winds from the companion star to be violently pulled into the neutron star. The result is a swirling mess of material in the stellar system, demonstrating the harsh environment produced by the strong gravitational force from the neutron star.
Eve Klein
