If you happen to be in the vicinity of the star V Hydrae while reading this, you may want to move out of the way.
Something near the star — a bloated red giant 1,200 light-years from Earth — is shooting giant balls of superhot plasma, each of which is twice as massive as Mars and almost twice as hot as the surface of the sun. Astronomers estimate that this stellar “cannon fire,” detected by the Hubble Space Telescope, has been occurring once every 8.5 years for at least the past 400 years.
The mysterious part of the whole affair is this — we do not know where these gigantic balls of fire are coming from.
“The current best explanation suggests the plasma balls were launched by an unseen companion star,” NASA said in a statement released Thursday. “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.”
Scientists now believe that understanding the exact mechanism behind the creation of these balls of fire near the star may be key to comprehending the “dazzling” variety of structures previously observed in planetary nebulae — structures that, despite their name, have nothing to do with planets and are simply an expanding shells of glowing gas expelled by stars in their death throes.
“We suggest that these gaseous blobs produced during this late phase of a star's life help make the structures seen in planetary nebulae,” Raghvendra Sahai, an astronomer at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a study on the cosmic cannonball, said in the statement. "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."
Between 2002 and 2004, and then from 2011 to 2013, a team led by Sahai used Hubble’s imaging spectrograph to conduct observations of V Hydrae and its surrounding regions. This revealed a massive string of superhot blobs, each with a temperature of more than 17,000 degrees Fahrenheit.
“The observations show the blobs moving over time,” Sahai said. “The data show blobs that have just been ejected, blobs that have moved a little farther away, and blobs that are even farther away.”
Sahai and his colleagues used data gathered by Hubble to create a model that invokes the presence of a companion star with an accretion disk to explain the ejection process. The model revealed that the direction in which the balls of fire are ejected flip-flops slightly from side-to-side — possibly due to a wobble in the accretion disk. The red giant is also obscured every 17 years when one of the blobs passes in front of it from Earth's perspective.
"This model provides the most plausible explanation because we know that the engines that produce jets are accretion disks," Sahai said. "The model we propose can help explain the presence of bipolar planetary nebulae, the presence of knotty jet-like structures in many of these objects, and even multipolar planetary nebulae. We think this model has very wide applicability."