In an rather strange sighting, NASA’s Hubble Space Telescope has managed to detect what can be dubbed as giant ‘cannonballs’ said to be twice the size of planet Mars shooting out of a star.
These ‘cannonballs’ are not solid, but instead are superhot blobs of gas that are being ejected at very high speed near a dying star called V Hydrae. The speed of these hot blobs of gas is so fast that they will take only 30 minutes for them to travel from Earth to the Moon. This stellar “cannon fire” has continued once every 8.5 years for at least the past 400 years, researchers add.
The star from which these blobs are being shot out is a bloated red giant, residing 1,200 light-years away, which has probably shed at least half of its mass into space during its death throes. Red giants are dying stars in the late stages of life that are exhausting their nuclear fuel that makes them shine. They have expanded in size and are shedding their outer layers into space.
Researchers are puzzled by this phenomena as they believe that it wouldn’t have been shot by the star and instead these plasma balls were launched by an unseen companion star. According to this theory, the companion would have to be in an elliptical orbit that carries it close to the red giant’s puffed-up atmosphere every 8.5 years. As the companion enters the bloated star’s outer atmosphere, it gobbles up material.
This material then settles into a disk around the companion, and serves as the launching pad for blobs of plasma, which travel at roughly a half-million miles per hour. This star system could be the archetype to explain a dazzling variety of glowing shapes uncovered by Hubble that are seen around dying stars, called planetary nebulae, researchers said. A planetary nebula is an expanding shell of glowing gas expelled by a star late in its life.
“We knew this object had a high-speed outflow from previous data, but this is the first time we are seeing this process in action,” said Raghvendra Sahai of NASA’s Jet Propulsion Laboratory in Pasadena, California, lead author of the study. “We suggest that these gaseous blobs produced during this late phase of a star’s life help make the structures seen in planetary nebulae.”
Sahai and his team used the Hubble and specifically its Space Telescope Imaging Spectrograph (STIS) to conduct observations of V Hydrae and its surrounding region over an 11-year period, first from 2002 to 2004, and then from 2011 to 2013. Spectroscopy decodes light from an object, revealing information on its velocity, temperature, location, and motion.
They were able to identify a string of monstrous, superhot blobs, each with a temperature of more than 17,000 degrees Fahrenheit — almost twice as hot as the surface of the sun. The researchers compiled a detailed map of the blobs’ location, allowing them to trace the first behemoth clumps back to 1986.
Over the years the blobs have moved as far as 37 billion miles away from V Hydrae, more than eight times farther away than the Kuiper Belt of icy debris at the edge of our solar system is from the sun. The blobs expand and cool as they move farther away, and are then not detectable in visible light. But observations taken at longer sub-millimeter wavelengths in 2004, by the Submillimeter Array in Hawaii, revealed fuzzy, knotty structures that may be blobs launched 400 years ago, the researchers said.
To explain the ejection process of these blobs, researchers developed a model of a companion star with an accretion disk to explain the ejection process based on their observations. Their model provides a plausible explanation about these ejecting blobs. The model helps explain the presence of bipolar planetary nebulae, the presence of knotty jet-like structures in many of these objects, and even multipolar planetary nebulae.
A surprise from the STIS observation was that the disk does not fire the monster clumps in exactly the same direction every 8.5 years. The direction flip-flops slightly from side-to-side to back-and-forth due to a possible wobble in the accretion disk.
Astronomers have noted that V Hydrae is obscured every 17 years, as if something is blocking its light. Sahai and his colleagues suggest that due to the back-and-forth wobble of the jet direction, the blobs alternate between passing behind and in front of V Hydrae. When a blob passes in front of V Hydrae, it shields the red giant from view.
The team’s results appeared in the August 20, 2016, issue of The Astrophysical Journal.