Ask almost anyone you know what supernovae are, and you’ll probably hear how they’re the result of a star coming to the end of its life and exploding. On the other hand, most people get confused by the standalone term “novae,” as it’s quite the unexplored territory in modern astronomy.
Indeed, in addition to the powerful stellar explosions that we call supernovae and attribute to the death of a star, smaller (non-super) nuclear bursts dubbed novae are known to occur near the surface of white dwarf stars throughout the Milky Way at least 50 times annually.
Image Credit: Michigan State University
Although there've been several spectacular theories over the years about why novae occur, it’s been tough to prove the correctness of one from the next. Fortunately, researchers from Michigan State University appear to have successfully validated at least one of our modern theories.
Using data collected by both the All Sky Automated Survey for SuperNovae (ASAS-SN) and the Fermi Gamma-ray Space Telescope, the researchers observed a nova dubbed ASASSN-16ma that was discovered in October of 2016 and took several gamma ray measurements over the time that it lapsed.
From the results, the researchers think they can finally explain how novae occur once and for all. They’ve published their findings in the journal Nature Astronomy.
According to the findings, powerful shockwaves of vastly different temperatures colliding with one another are likely the catalyst behind these previously-unexplained explosions.
“Astronomers have long thought the energy from novae was dominated by the white dwarf, controlling how much light and energy are emitted,” said Laura Chomiuk, a co-author of the study and an astronomer at Michigan State University. “What we discovered, however, was a completely different source of energy – shockwaves that can dominate the entire explosion.”
Citing a statement from Michigan State University, the start of the nova explosion emits a slow-moving cool wave of gaseous material. Shortly after, a fast-moving warm wave quickly follows in its footsteps. The latter eventually catches up with the colder wave and causes a powerful shockwave resulting in the powerful nuclear explosion we call a nova.
Moreover, it seems that the second, hotter wave has a significant influence over how bright and hot the explosion will be. Previously, astronomers thought that the white dwarf played a role in determining these factors, so the findings were eye-opening, to say the least.
“The bigger the shock, the brighter the nova,” Chomiuk said. “We believe it’s the speed of the second wave that influences the explosion.”
The data received from these observations was so detailed that the researchers have virtually no doubts about the accuracy of the current findings. Additionally, it's thought that these results could help us better understand larger supernovae and the mechanisms behind them.
“The nova’s brightness and how strong our data were really surprised me,” explained study lead author Kwan-Lok Li, another astronomer with Michigan State University. “Other novae may take days or weeks for us to collect sufficient data. This one, though, was visible after just one day, and we knew it was a good one.”
As it would seem, astronomers peered at ASASSN-16ma at just right time to capture potent information about novae. Without the data they collected, we might still wonder in mystery about the forces behind these bursts of extreme heat and light.
It should be interesting to see what further research has to say about these incredible forces of nature.
Source: Michigan State University