Sean Eberts Professor Danko ESC1000 3 Feb 2023 Binary Stars Binary stars are an incredible part of our universe. While you may think that every star that you observe in the night sky is its own entity, independent of interactions from other stars, this is often not the case. A binary star is actually two stars, who both orbit a common center of mass. While many stars seem to be individual, more than eighty percent of all stars that we can observe are actually binary stars. They are scattered throughout the night sky. This essay will cover some aspects of these stars, such as the different types of binary stars, the effects that these stars have on each other and other celestial bodies, and their significance in our universe. In 1617, Galileo Galilei was the first to discover that one star seemed to actually be two. In reality, it ended up being six stars. These are known today as visual binaries, despite not being called that at the time. After him, in 1802, Sir William Herschel was the first to use the word “binary” when referring to these celestial bodies after documenting around seven hundred pairs of stars. Using this information, it was found that there is usually a brighter star (called the primary star) and a dimmer star (known as the secondary star). As technology developed, there came to be a few different classifications of binary stars. These include wide, close, visual, spectroscopic, eclipsing, and astrometric binaries. There are also ‘double stars’, which appear to be close together when viewed by the naked eye, but are in fact nowhere near each other. Wide binary stars do orbit each other, but they are distant enough that they tend to not have much effect on each other when compared to other binary stars due to their distance. Close In the binary system J0806, two white dwarf stars orbit one another every 321 seconds. Image courtesy of www.space.com/22509-binarystars.html binaries, as the name implies, are much The red giant star Mira A (right) and its companion, a close binary pair. Image courtesy of www.space.com/22509- more proximal and they can transfer mass binary-stars.html from one body to another. Occasionally, the gravitational forces from these stars become so great that the primary star can exert a strong enough gravitational pull to engulf the secondary star. A visual binary is a set of stars that are separated enough so that they can be witnessed with telescopes and some binoculars (these account for roughly five to ten percent of visible stars). A spectroscopic binary star, on the other hand, appears closer than visual binaries. In order to determine the distance these stars have from each other, scientists measure the wavelengths of light emitted by these stars. Eclipsing binaries have orbits that are on such an angle to Earth that one will pass in front of the other. Astrometric binaries seem to have empty space around them, and while the primary star is visible, the secondary star can sometimes not be seen. This is due to the secondary star being hidden by the primary star, sometimes because of glare. While binary stars can have an effect on one another, it is important to remember that these stars still function relatively normally. That is, they emit heat and light, and they will eventually consume all products within themselves and burn out. Binary stars can have pretty normal lifespans, until one of these stars turns into a red giant. Once this happens, it can create a type of ‘envelope’ which will, in turn, take in the other star. Within this envelope, the stars get closer and closer to each other, which causes an immense heat but also a slowdown in orbit. Eventually, the envelope around these stars overheats and gets moved away from the two stars. At this point, the primary star is simply a leftover core which will eventually become a white dwarf. Then, the secondary (also called the companion) star starts to swell and leak gas into the white dwarf. The white dwarf then will have an increase in mass, until a critical mass is reached, and The engulfment and eventual ejection of a secondary star by its primary companion. Image courtesy of www.universetoday.com/156883/binary-starslive-complicated-lives-especially-near-the-end/ explodes. This causes the companion star to be ejected away, ready to affect other stars it may come across. Stars are instrumental to life as we know it. They provide us with warmth and light, such as with our Sun. The orbit that binary stars possess with each other can have a profound effect on potential life for planets near these stars. Life needs a relatively stable environment to thrive in. The issue that lies with binary stars is that the constant gravitational shifts and movements of these stars can cause large amounts of disparity for an environment. Despite this, it is possible that binary stars in either the ‘close’ or ‘wide’ classifications may be able to allow for potential life. Our Sun, being our primary source of heat and light, is very predictable; we have a set day and night cycles, relatively stable temperatures, and predictable amounts of light and radiation every day. Since binary stars can potentially change their orbit with each other, it could alter what day-to-day life would be like on a planet, which could result in negative impacts on that planet’s environment. In addition, while it seems like our Sun is not a binary star (any other observable star seems incredibly far away), scientists in the 1980’s believed in the possibility of our Sun being part of a binary star system. They suggested that there may be a second star - named Nemesis - which was in orbit with the Sun. It is stated that this star may be either a brown, An eclipsing binary star. Image courtesy of www.astronomical.org/astbook/binary.html dim red, or white dwarf. Since the Earth has had periodic mass extinctions in its history, it is thought that the occasional passing-by of this other star may be the culprit. With NASA launching its Wide-field Infrared Survey Explorer (WISE) in 2010, it is believed that this ‘Nemesis’ star may appear eventually, and then we may begin to know more about the Sun and its potential partner. However, until then, our Sun is believed to not be in a binary star system. Binary stars, and the research that goes into finding out more about them, can help us to find out more about our universe. Most of the knowledge that we have regarding the masses and radii regarding stars is a direct result of what we have found out from studying binary stars. Oftentimes, a star’s distance, movement speed, and brightness can be measured relatively easily, but its mass cannot. However, there is a way to determine the mass of some binary stars. This is accomplished by using Kepler’s third law. The equation correlating to this law allows us to take the distance of the two stars in a binary system, as well as the period of their orbit, to find out their mass. However, this is very difficult to accomplish on some binary star systems (such as spectroscopic, eclipsing, and astrometric) due to the nature of these systems. The way that they are positioned and oriented doesn't allow for precise measurements of these systems. That being said, there are still many binary star systems that can be studied with more clarity and ease. This research allows us to measure the masses of stars where it was deemed impossible before their discovery. In closing, binary stars are a vital part of our universe. While it may appear that every star we see is its own entity, independent of other stars, the opposite is true. They make up most of the stars that we can see, and are instrumental in furthering our knowledge of how they interact with each other and the objects around them. There are many different types of these stars, and the way that they interact with each other is dependent on factors such as their mass, orbit, and other nearby celestial bodies. The improvement of technology over the years has allowed for further investigation and research into the different types of these stars. Binary stars have been, and continue to be, one of the most intriguing parts of our universe. Works Cited Gough, Evan. “Binary Stars Live Complicated Lives, Especially near the End.” Universe Today, 7 Oct. 2022, https://www.universetoday.com/156883/binary-stars-live-complicated-livesespecially-near-the-end/. Palma, Christopher. “Binary Stars.” Binary Stars | Astronomy 801: Planets, Stars, Galaxies, and the Universe, https://www.e-education.psu.edu/astro801/content/l5_p7.html. Staff, Space.com. “Binary Star Systems: Classification and Evolution.” Space.com, Space, 17 Jan. 2018, https://www.space.com/22509-binary-stars.html. Ware, Don. “Binary Stars.” Peoria Astronomical Society, http://www.astronomical.org/astbook/binary.html.
