Hubble detects giant 'cannonballs' shooting from unseen star

NASA's Hubble Space Telescope has detected mysterious stellar "cannon fire" - superhot blobs of gas, each twice as massive as the planet Mars, being ejected at very high speed near a dying star, say scientists including one of Indian origin.
The plasma balls are zooming so fast through space it would take only 30 minutes for them to travel from Earth to the Moon, researchers said.
This stellar "cannon fire" has continued once every 8.5 years for at least the past 400 years, they said.
The fireballs present a puzzle to astronomers, because the ejected material could not have been shot out by the host star, called V Hydrae.

The star 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 the nuclear fuel that makes them shine. They have expanded in size and are shedding their outer layers into space.

The current best explanation suggests the 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 the US.

"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 said.
Researchers used Hubble's 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, unveiling information on its velocity, temperature, location and motion.
The data showed a string of monstrous, superhot blobs, each with a temperature of more than 9,400 degrees Celsius - almost twice as hot as the surface of the sun.

The researchers compiled a detailed map of the blobs' locations, allowing them to trace the first behemoth clumps back to 1986.
The study was published in The Astrophysical Journal.