Astronomers studying the binary star system called Swift J0503.7-2819 have disentangled the nature of the star system, leading to a better understanding of the system an its variability. TheSwift J0503.7-2819 star system is a binary system made up of a white dwarf star orbiting a normal star companion around a region of common center of mass.

Understanding Variable Stars

A variable star is a type of star that exhibits changes in its brightness over time. These fluctuations in brightness can occur for various reasons, such as pulsations, eruptions, external factors, or eclipses. Variable stars are essential for astronomers because they can provide valuable information about the properties and evolution of stars, as well as the distances to galaxies. There are several types of variable stars, including Cepheid variables, RR Lyrae variables, and Mira variables, each with distinct characteristics and patterns of variability.

Understanding Types of Variable Stars

There are two broad types of variable stars:

  • Intrinsic variables – these are stars that are 500 to 3,000 times brighter than the Sun with short periods that range between 1 to 100 days. The subtypes are Cepheid, Eruptic, and Cataclysmic variables.
  • Extrinsic variables – these are stars that vary because two stars are passing in front of each other. causing fluctuation and obscuring the light we see from Earth. The subtypes here a re eclipsing binary variables, and rotating stars.

Understanding the Subtypes of Variable Stars

Intrinsic Variable Stars

Intrinsic variable stars are stars that exhibit changes in brightness due to internal processes. These variations can be caused by pulsations, eruptions, or other physical changes within the star itself. Some common types of intrinsic variable stars include:

  1. Cepheid Variables: Cepheid variables are massive, luminous stars that undergo regular pulsations, causing their brightness to change periodically. They have a well-defined relationship between their pulsation period and luminosity, making them useful as “standard candles” for measuring cosmic distances. Two main classes of Cepheid variables exist: Classical Cepheids and Type II Cepheids, with the former being more massive and luminous.
  2. Cataclysmic Variables: Cataclysmic variables are binary star systems in which a white dwarf and a companion star orbit each other closely. The white dwarf accretes material from its companion, leading to instabilities and occasional violent outbursts, causing drastic changes in brightness. Examples of cataclysmic variables include novae, dwarf novae, and some X-ray binaries.
  3. Eruptive Variables: Eruptive variables are stars that display changes in brightness due to violent events or eruptions on their surfaces or within their atmospheres. This group includes several subcategories, such as:
    • Protostars (e.g., T Tauri stars), which experience irregular brightness fluctuations due to the accretion process during their formation.
    • Luminous Blue Variables (LBVs), massive stars that undergo sporadic outbursts accompanied by significant mass loss.
    • Flare stars, low-mass stars that exhibit sudden, short-lived increases in brightness due to magnetic activity and flares.

Extrinsic Variable Stars

Extrinsic variable stars are stars whose brightness changes because of external factors rather than internal processes. These factors can include eclipses, transits, or the effects of rotation. Some common types of extrinsic variable stars include:

  1. Eclipsing Variables: Eclipsing variables are binary star systems in which the orbital plane is aligned with the observer’s line of sight. As a result, one star periodically passes in front of the other, causing an eclipse and a temporary decrease in the system’s overall brightness. The most well-known type of eclipsing variables is the Algol-type (or Beta Lyrae) systems.
  2. Rotating Variables: Rotating variables are stars that exhibit brightness changes due to their rotation. This variability can be caused by several factors, such as uneven surface brightness (due to sunspots or other surface features), or an ellipsoidal shape caused by gravitational interactions in a close binary system. Examples of rotating variables include BY Draconis stars and Alpha2 Canum Venaticorum stars.

From intrinsic variables, which reveal insights into internal processes, to extrinsic variables, which highlight the impact of external factors, variable stars serve as essential tools for astronomers. The next section explains what the study uncovered.

Insight into the Swift J0503.7-2819 Star System

Astronomers, used the AstorSat spacecraft along with data from the Southern African Large Telescope, ESA’s XMM-Newton, and NASA’s Swift spacecrafts to study the system.

The study found that the star system is a Cataclysmic Variable that has an orbital period of about 4,897 seconds and a spin period of about 3,932 seconds. This confirms that the system is not completely synchronized. The study also found that the system is not an Intermediate Polar (IP) system, where the companion star has a strong magnetic field.


In summary, variable stars are celestial objects that exhibit changes in brightness due to a range of internal and external factors. These stars can be categorized into intrinsic variables, such as Cepheid variables, cataclysmic variables, and eruptive variables, which undergo changes in brightness due to processes occurring within the star itself. On the other hand, extrinsic variables like eclipsing and rotating stars experience brightness fluctuations due to external influences like orbital alignments or rotation.

The study of variable stars provides astronomers with invaluable insights into stellar properties, evolution, and the underlying physical processes responsible for their variability. By examining these intriguing celestial objects, researchers can better understand the universe’s inner workings and uncover new mysteries waiting to be unraveled.

In conclusion, variable stars serve as essential tools in our quest to explore the cosmos. As we continue to observe and analyze these fascinating objects, we expand our knowledge of the universe and take one step closer to unlocking its secrets. Through ongoing research and discoveries, variable stars will undoubtedly continue to play a vital role in shaping our understanding of the vast and enigmatic expanse that surrounds us.

Where To Get More Information

The following is an APOD that provides an excellent visualization of what a variable binary system looks like:

The link below goes to a detailed poster that describes the type of variable discussed in this article in more detail: