NASA’s Hubble Space Telescope has once again delivered a breathtaking view of the cosmos, this time capturing the violent drama of one of the galaxy’s most tempestuous star systems.
Symbiotic stars
At the heart of this celestial spectacle lies a symbiotic star system called R Aquarii, located about 700 light-years from Earth. A symbiotic star is a binary system where a red giant and a white dwarf interact. This often leads to dramatic outbursts as the white dwarf siphons material from the red giant.
In this case, the red giant is around 400 times larger than our Sun and fluctuates dramatically in brightness over a period of roughly 390 Earth days. At its peak, this giant star shines nearly 5,000 times brighter than the Sun.
But it’s not the red giant that steals the show in R Aquarii. Instead, its much smaller companion, a white dwarf, drives the system’s wild behavior.
White dwarfs are the remnants of once-normal stars that have exhausted their fuel and don’t undergo fusion anymore. After shedding their outer layers, these stars leave behind dense cores that pack a sun’s worth of mass into a volume the size of Earth. Despite their small size, white dwarfs have intense gravitational fields and powerful magnetic forces. In R Aquarii, the white dwarf plays a pivotal role in unleashing massive outbursts of energy.
An explosive dance
The system has a 44-year orbital period, meaning that every 44 years, the stars pass close to one another. During these close approaches, the white dwarf’s intense gravity pulls material from its bloated companion. It siphons off hydrogen from the red giant’s outer atmosphere.
This stolen gas accumulates on the surface of the white dwarf, eventually reaching the point where nuclear fusion ignites, triggering a massive explosion akin to a hydrogen bomb. This process is called a nova, and it can happen repeatedly, each time the dwarf star gathers enough material to reignite fusion.
These explosions send out jets of superheated plasma, traveling through space at speeds of over one million miles per hour. According to NASA, if you could ride on one of these jets, you’d travel from Earth to the Moon in just 15 minutes. As the plasma shoots outward, it twists and curls due to the powerful magnetic fields generated by the two stars. The stunning spiral pattern this creates makes the region appear as a cosmic volcanic eruption. And this is what Hubble snapped photos of.
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A vivid sight across the ages
The nebula surrounding R Aquarii may be the remnant of a nova-like explosion. Interestingly, this nova may have been witnessed by Japanese astronomers in 930 AD. However, the system was described for the first time in 1810 by German astronomer Karl Ludwig Harding.
Hubble first imaged this system in 1990 and has snapped several photos of it since. Over the span of just a few years, the nebula surrounding the stars changed shape dramatically, reflecting the pulsations of the red giant and the recurring explosions on the white dwarf’s surface.
Though white dwarfs are common, it is rare to observe one in such a dramatic interaction with a red giant. Most white dwarfs quietly cool down over billions of years, slowly fading as they radiate away the remaining heat from their earlier life stages. However, in systems like R Aquarii, the presence of a nearby red giant star disrupts this quiet end, leading to the spectacular displays of energy that Hubble has captured.
