Rare Quadruple Star System in Milky Way

Rare Quadruple Star System in Milky Way

Why in News? 

Recently, scientists reported the discovery of a rare quadruple star system in the Milky Way. The system contains two red dwarfs and two cold brown dwarfs held together by gravity, making it unlike anything observed earlier in the Milky Way.

Key Highlights of the Recent Discovery 

• Recently, scientists reported a unique quadruple star system, it has been named UPM J1040−3551 AabBab. It is located in the Milky Way Galaxy. 
• Its rarity comes from the fact that it unites two red dwarfs with two brown dwarfs within a single stable system.
• The finding was reported in the Monthly Notices of the Royal Astronomical Society.
• The research was led by Professor Zenghua Zhang from Nanjing University, China with several global institutes including the University of Hertfordshire (UK), the Brazilian National Astrophysics Laboratory, the Southern Astrophysical Research (SOAR) Telescope in Chile, and the Center for Astrobiology in Spain. 
• The quadruple system offers a new angle to study stellar evolution.  
• Astronomers believe this could help refine models of star formation and explain why some systems hold multiple objects while others do not.
• It may also guide future missions that aim to map the structure of the Milky Way in greater detail.

What are Red Dwarfs?

• About: Red dwarfs are the smallest main-sequence stars that continue to shine through nuclear fusion. They are smaller, cooler, and dimmer than the Sun, with masses ranging from 0.08 to 0.6 solar masses. Their low temperature gives them a reddish appearance, which is why astronomers call them red dwarfs. These stars are extremely common in the Milky Way, with studies estimating that nearly 70–75% of stars in our galaxy belong to this category.

• Formation: Their origin follows the same star-forming process as larger stars. A giant molecular cloud of gas and dust collapses under gravity, leading to the birth of a protostar. When the core temperature reaches around 4 million Kelvin, hydrogen fusion begins. Since the star has less mass, the fusion process is slow and stable. This is why red dwarfs live much longer than heavier stars. Many red dwarfs are expected to exist for trillions of years, far exceeding the Sun’s estimated 10-billion-year lifespan.

• Features: Red dwarfs are known for their cool temperature, usually less than 3,500 Kelvin. They emit little visible light but shine strongly in the infrared spectrum. Despite their small size, they are extremely stable because of their slow fusion rates. They conserve fuel and shine steadily. Their small size also means they have intense stellar activity, including solar flares that can affect nearby planets.

• Significance: Red dwarfs dominate our galaxy in numbers. Their long lifespans mean that they will remain shining even when massive stars disappear. 

• Many exoplanets discovered in recent years orbit red dwarfs, making them central to the search for life beyond Earth. 

• Missions like Kepler and TESS have studied red dwarf systems to evaluate the possibility of stable planets in their habitable zones.

• • Scientists can better comprehend star evolution and the habitability of nearby exoplanets by researching young red dwarfs. 

What are Brown Dwarfs?

• About: Brown dwarfs occupy the space between the heaviest planets and the lightest stars. Astronomers often describe them as “failed stars” because they do not have enough mass to sustain hydrogen fusion at their cores. A brown dwarf generally has a mass between 13 and 80 times Jupiter’s mass. They are not bright like stars but not exactly planetary either. Their existence was first confirmed in the 1990s after years of theoretical prediction.

• Formation: Their birth process differs because they do not reach the conditions necessary for sustained hydrogen fusion. A cloud of gas may begin to collapse like in the case of stars, but if the mass is too low, the temperature in the core never reaches the level required for sustained hydrogen fusion. Instead, brown dwarfs may undergo brief periods of deuterium fusion or lithium fusion during their early stages. After that, they slowly cool down and fade over time.

• Features: They are special since they display traits of both planets and stars. They do not undergo continuous fusion, but they still emit heat and faint infrared radiation. They are generally cooler than red dwarfs, with surface temperatures ranging from 300 Kelvin to 2,800 Kelvin. Their faintness makes them nearly invisible in optical surveys. Astronomers often detect them using infrared instruments such as the Wide-field Infrared Survey Explorer (WISE) launched by NASA in 2009.

• Significance: Brown dwarfs are equally important because they fill the gap between stars and planets. Studying them helps astronomers understand the lower limits of star formation. 

• Astronomers also use them as reference points to test and refine stellar evolution models.

• Brown dwarfs often orbit stars, while in other cases, they move freely in space. This flexibility makes them valuable objects for exploring the diversity of celestial systems. 

• • The mass of the universe is largely invisible, manifesting as dark matter, and the examination of brown dwarfs presents significant hints regarding this cosmic enigma.

Star System and Its Types

• About: A star system is a group of two or more stars held together by gravitational force. Each star moves in an orbit that balances the pull of gravity with its own motion. These systems can be stable for billions of years. Astronomers believe that almost half of all visible stars are part of some kind of stellar system.

• • • Star systems form during the process of stellar birth. Stars and sub-stellar bodies originate when a giant cloud of gas and dust collapses under gravity and breaks into fragments. Each clump can give rise to one star. When these young stars are close, their mutual gravity binds them into a system.

• Types: 

• • A single star system contains only one star and its orbiting planets or smaller bodies. Example: Solar System. 
  • A binary star system features two stars revolving around a shared center of gravity, and such systems are the most frequently observed stellar pairs. Example: Sirius.
  • A triple star system usually has two stars orbiting each other closely, while the third star circles farther away. This arrangement creates a stable balance of gravitational forces. Example: Alpha Centauri, consisting of Alpha Centauri A, Alpha Centauri B, and a smaller red dwarf.
  • In higher-order systems multiple pairs of stars orbit each other in hierarchical patterns. For example, two binary pairs may orbit one another, forming a stable four-star system.