The stunning Ant Nebula is shooting out mysterious laser emissions into space, revealed the European Space Agency (ESA). This strange phenomenon shouldn’t occur unless there’s more to this spectacular nebula than meets the eye.
Located some 3,000 to 6,000 light-years away from Earth, in the southern constellation Norma, the Ant Nebula is a planetary nebula shaped in the form of two fiery lobes that protrude from a dying white dwarf star.
Or, at least, that was the consensus until now.
This description, jotted by NASA two decades ago, after the Hubble Space Telescope imaged the Ant Nebula in 1997 and 1998, is now being challenged by an international team of astronomers, who discovered something odd about the famous nebula.
Eager to get to the bottom of the enigmatic laser emissions, which were picked up by the ESA’s Herschel Space Observatory, the astronomers are proposing a bold idea. Their theory is that the Ant Nebula — named after the two lobes that look like an ant’s body, notes ScienceDaily — could be hiding a second star in its center, meaning that it’s actually a binary star system.
Here’s their explanation as to why this could be possible.
According to the Herschel observations, the laser emissions seeping out of the Ant Nebula — also known as Menzel 3, after astronomer Donald Menzel, who first discovered it in 1922 — are extremely rare. Toshiya Ueta, principal investigator of the Herschel Planetary Nebula Survey project, points out that they’ve only been detected “in a handful of objects” because they require certain conditions in order to exist.
Identified as hydrogen recombination line laser emission, this rare phenomenon “needs very dense gas close to the star,” states the ESA. However, there’s no way the white dwarf in the center of the nebula would be able to keep this much gas around it unless it had a little help from a star companion.
This hypothesis, detailed in a study that appeared today in the Monthly Notices of the Royal Astronomical Society, gained even more ground after astronomers compared the Herschel observations with computer simulations of the Ant Nebula.
“When we observe Menzel 3, we see an amazingly intricate structure made up of ionized gas, but we cannot see the object in its center producing this pattern,” says lead author Isabel Aleman, an astronomer with the Leiden Observatory in the Netherlands.
However, the density of the laser-emitting gas contained around the nebula is around 10,000 times higher than in an ordinary planetary nebula, as well as that of the gas within Menzel 3’s lobes.
“The only way to keep gas close to the star is if it is orbiting around it in a disk,” says study co-author Albert Zijlstra, from the University of Manchester in the U.K.
As Zijlstra points out, the team actually spotted such a dense disk located right “in the very center” and even managed to get an edge-on view of it.
The team believes that the laser-emitting gas disk is produced by the white dwarf as it sucks in mass ejected by its dying companion star.
“The disc suggests the white dwarf has a binary companion, because it is hard to get the ejected gas to go into orbit unless a companion star deflects it in the right direction,” Zijlstra explains.
Goran Pilbratt, Herschel project scientist at the ESA, also chimed in on the new discovery.
“This study suggests that the distinctive Ant Nebula as we see it today was created by the complex nature of a binary star system, which influences the shape, chemical properties, and evolution in these final stages of a star’s life.”