Although there are about 10 of them in the Milky Way every year, astronomers have never observed a single one from start to finish.
All new - new stars - arise in a close binary system of stars, when one of the stars has passed the phase of a red giant. It leaves behind a white dwarf residue. Then, when he and his partner star get close enough, the white dwarf's massive gravitational pull pulls matter - mostly hydrogen - out of the other star.
Hydrogen accumulates on the surface of the white dwarf, forming a thin atmosphere. The star heats up the hydrogen, and eventually flares up when the gas pressure becomes extremely high. It’s not just a merger: it’s fast and unrestrained.
When a fast merger occurs, we see light and a new atmosphere of hydrogen is thrown out of the white dwarf into space. In the past, astronomers believed that these bright lights were just the birth of ordinary stars, and the concept of "nova" hung in the air.
Astronomers now refer to these types as "classical" novae; there are also repetitive nova when the process is repeated.
This process releases a ton of energy: not only visible light, but also gamma rays and X-rays. The end result is that some of the stars that could only be seen through a telescope can be seen with the naked eye at the time of the explosion.
All this is widespread in astronomy and astrophysics, but much is just theory.
Recently, astronomers using the BRITE (BRIght Target Explorer) constellation of nanosatellites were fortunate enough to observe the entire process from start to finish, confirming the theory.
BRITE is a constellation of nanosatellites created to "study the stellar structure and evolution of the brightest stars in the sky and their interactions with the local environment." They operate in low Earth orbit and have few restrictions on the portion of the sky that they can observe. BRITE is a coordinated project between Austrian, Polish and Canadian researchers.
This first-ever observation of a new one was pure coincidence. BRITE spent several weeks observing 18 stars in the constellation Karina. Once a new one appeared: BRITE COO Rainer Kuschnigg discovered it during a daily examination.
“Suddenly, a star appeared on our recordings, which was not there the day before. I've never seen anything like it in all my years of mission! " - Rainer Kuschnig.
Nova V906 in the constellation Karina. In images B and C, the stars before and after the outburst are new.
“But what makes a previously inconspicuous star explode? The answer to this question is still not known for certain,”he said.
The explosion of nova V906 in the constellation Karina gives researchers some answers and confirms some theoretical concepts.
V906 Carinae was first discovered by the Polish All-Sky Automated Survey supernova tracking project. Fortunately, it appeared in the region of the sky that BRITE has been observing for several weeks, so BRITE has data on the nova.
“It is amazing that for the first time our satellites were able to observe a new star even before its actual eruption, and many weeks later,” - Otto Koudelka, project manager for the BRITE Austria satellite.
Before V906 Carinae is about 13,000 light years old, so this event is already history. “After all, this new star is so far away from us that it takes about 13,000 years for its light to reach Earth,” explains Weiss.
“This fortunate circumstance played a decisive role in making it possible to register the event” nova “with unprecedented precision,” explains Konstanze Zvinz, BRITE Science Team Leader, at the Institute of Astronomy and Particle Physics at the University of Innsbruck.
According to the press release, Zvinz immediately realized that "we have access to observational materials that are unique throughout the world."
Novelties such as V906 Carinae are thermonuclear explosions on the surface of white dwarf stars. For a long time, astrophysicists believed that the luminosity of a new star was driven by constant nuclear combustion after an initial explosion of unbridled fusion. But the data from BRITE suggests something different.
In a new article, the authors show that impulses play a greater role than thought. The authors say that "impulses caused by the ejection of a nova may prevail over the ejection of [energy] nova."
These impulses can also be associated with other events such as supernovae, stellar mergers and tidal destruction, according to the authors. But so far, researchers have not seen evidence of this.