Rubin Planetarium Video - Binary Stars

A binary star system consists of two stars that orbit around a common center of mass. Usually the two stars are too close to each other to be seen separately; that is, they will appear in a telescopic image to be a single point of light.

If a binary system is viewed from the right perspective (i.e., “edge-on” along the orbital plane) it is possible for one star to pass in front of the other. This is called an eclipsing binary. When an eclipse occurs, the measured brightness of the binary star system will temporarily decline as one star blocks some or all of the light of the other.

Binary star systems are interesting to scientists for a wide range of reasons. One of the most valuable applications for binary systems is that their orbital parameters can be used to measure the masses of the stars.

It is estimated that LSST will discover 24 million eclipsing binary star systems. They will be used for a variety of scientific investigations, e.g., measuring the properties of stars that span a wide range of masses and evolutionary stages (protostars to white dwarfs).

Storyboard

This sequence shows a close binary system consisting of two stars of different masses. The system is shown top-down (to reveal orbital geometry around the center of mass) and then edge-on (to show them as an eclipsing binary). At the end, a planet is shown in the system to illustrate that exoplanets have been found orbiting around binary stars.

The animation illustrates stars of the following parameters:

A G3V star with a mass of 1.15 solar masses, a radius of 1 solar radii, and a temperature of 5670 K.

A K2V star with a mass of 0.4 solar masses, a radius of 0.7 solar radii, and a temperature of 4620 K.

From the mass ratio, the smaller star is 2.9x farther from the center of gravity than the larger star.

Data from: http://www.isthe.com/chongo/tech/astro/HR-temp-mass-table-byhrclass.html

00:00

We begin with an empty starfield with our viewing perspective shifting to bring the orbiting binary stars into view.

00:10

We linger on the top-down view to show the two stars. The relative brightness and surface temperatures of the stars (which are indicated by their colors) reflect their different masses and stellar types. The center of mass falls inside of the larger star, which is close enough to have an appreciable heating effect on the near side of the smaller star. The stars are distorted through tidal interactions into oblong, egg-like shapes (expanding into, but not filling their Roche lobes).

00:20

The viewpoint begins rotating towards an edge-on view, showing a perspective where the two stars dramatically eclipse one another.

00:40

We pull away from the stars to see their orbit from a distance, more approximating a telescopic view with a less exaggerated perspective.

01:00

A planet moves into view. The illumination on the planet changes as the stars eclipse one another, becoming subtly dimmer when the fainter red star passes behind the larger one, and dimming dramatically (and becoming redder) as the fainter star blocks some of the light of the larger one as it passes in front.

Contact and Usage Survey

If you use this video for any purpose, please fill out this survey so the LSST team can understand usage and make any improvements necessary: https://forms.gle/yJS2mMrSja2PvGHCA

Contact: Amanda Bauer, Head of LSST Education and Public Outreach abauer@lsst.org

Additional References

https://www.lsst.org/sites/default/files/docs/sciencebook/SB_6.pdf

https://arxiv.org/abs/1105.6011

https://arxiv.org/abs/1201.5140