Since astronomers first observed the stellar explosion known as V445 Puppis in 2000, this object has remained one of the most enigmatic in the Milky Way galaxy. A thick layer of dust obscured the true source of the explosion for over two decades, preventing a clear understanding of the nature of the star system that produced it.
Today, an international team of astronomers, utilizing the capabilities of the Hubble Space Telescope and a number of ground-based and space-based observatories, succeeded in uncovering the secrets of this rare explosion, announcing an unprecedented discovery of "cosmic bullets" launched at enormous speeds, in addition to identifying the nature of the star system responsible for this unique event.
This discovery represents an important step towards understanding one of the rarest types of stellar explosions, and may help scientists explain how some of the supernova explosions that astronomers rely on to measure the dimensions of the universe originate.
Hubble breaks through the veil of dust after 25 years
Researchers relied on data from the Hubble Space Telescope, NASA's TESS satellite, the Very Large Telescope in Chile, and a range of other observatories to study the system after the dust cloud that had obscured it for more than 20 years dissipated.
During this observation, the team discovered dense clumps of gas, likely oxygen-rich, traveling at speeds of nearly 32 million kilometers per hour. Scientists dubbed them "cosmic bullets" because of their speed and the shape of their trajectory.
John Mills, a researcher at the University of Warwick in Britain, said: "The origin of these bullets remains a mystery, and we believe they formed after the explosion, but similar objects have never been observed around any other new supernova."
Scientists confirm that this phenomenon has never been seen before in any stellar explosion of this type, making the system unique among all known systems.
What is a helium nova?
The study showed that V445 Alcothel is not an ordinary new nova, but a helium nova, the rarest type of new nova known in our galaxy, and the only one confirmed so far.
This occurs when a white dwarf, the remnant of a sun-like star, absorbs helium gas from a companion star that has lost its outer hydrogen envelope, becoming what is known as a "helium star." As helium accumulates on the white dwarf's surface, the temperature and pressure gradually increase until a violent thermonuclear explosion occurs.
An illustration of a white dwarf star feeding on a stellar companion prior to the eruption of a type Ia supernova (Image credit: Robert Lea (created with Canva))
An artist's rendering of a white dwarf consuming material from a companion star before it explodes as a Type I supernova (Robert Lea-Canva).
When this system exploded at the end of 2000, enormous clouds of matter erupted from it, extending over 1.5 trillion kilometers and forming butterfly-winged dipole flows, while thick dust covered the entire system, preventing scientists from knowing the nature of the two stars that caused the explosion.
After this dust was removed, it became clear that one of the components of the system was a helium star, which is one of the rarest types of stars, as only a few thousand of these objects are known in a galaxy containing hundreds of billions of stars.
A new explosion may be imminent.
The discovery did not stop there; observations revealed that the white dwarf had resumed swallowing helium from its companion star, the same process that led to the explosion in 2000.
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