Between 2002 and 2006, scientists were treated to a rare delight on their cosmic buffet table. The red giant star, V838 Monocerotis, is recorded over the four year period appearing to release stellar ejecta into its surrounding nebula. For the first time, we can watch a star explode.
V838 Monocerotis, no stranger to controversy, has a storied history before this phenomenon had been recorded. Originally thought to be a large red giant with a solar radii of 380 times the size of our sun, with a B-type companion, white dwarf companion. Later analysis and conjecture made it a variable star whose brightness and size were inconsistent and thought to be as large as 1500 solar radii, making it one of the stellar giants in our galaxy.
For you math nerds: Solar radius is a unit of distance used to express the size of stars in astronomy equal to the current radius of the Sun: 1 R ? = 6.955 × 10^8 m meaning, the solar radius is approximately 695,500 kilometers (432,450 miles).
Adding to the controversy is this recent glamour shot of a visible burst of visible phenomena streaming outward from the star. Not quite a supernova, not quite a normal nova, it defies easily analysis and for scientists is half the fun. Despite what it looks like this is NOT merely an explosion, per se, but a discharge of energy igniting or illuminating the gaseous nebula in which the star resides in. The event increased the visibility of the star making it one of the brightest events in the galaxy.
First thought to be a nova, this stellar explosion or emission of light is what happens when two stars share a close orbital relationship, causing materials transitioning between the two to grow in brightness as the smaller companion ignites the gaseous material before dimming again. These types of nova are called cataclysmic variable stars.
Given the distance of the explosion, an estimated 20,000 to 30,000 light years away and in a region of where intense star formation is considered to be less likely, there are likely to be a variety of reasons this event occurs.
It is challenging to try and determine from a visual-light only display because the main action of the video may be occurring in a different spectrum, or might be easier to detect if we could view the scene in high energy particle or electromagnetic emissions such as X-rays or gamma rays.
Since so much is in flux about the V838 Monocerotis itself, it’s size, its mass, the number of companion stars, if it has planets, the chance at getting an accurate diagnosis may require a significantly longer period of study of the information gathered by the space telescope.
If I were to hazard a guess, knowing what is able to be surmised about the star, would have to be a destabilization of the star’s inner makeup. If indeed, the star is a super-massive red giant, it may be capable of vast energy emissions as its gaseous body slowly condenses while it consumes its hydrogen fuel supplies converting them to helium.
This conversion may be unequally distributed given the mass of the star and could possibly cause “star-quakes” – rapid energy emissions or even stellar ejecta similar to this burst.
This would likely be the simplest line of thought, because large and hyper-massive stars are inherently unstable. To create an effect like this one, may have been more likely to have been caused by the rapid absorption of a significant amount of mass, such as super-large jovian-like planets being absorbed or falling into the sun.
Since planets don’t fall, perhaps the star is growing larger as stars are want to do as their fuel diminishes. Our own sun, when its hydrogen fuel supplies run low will expand, absorbing the orbits of Mercury, Venus and eventually, even the Earth, billions of years from now before becoming a white dwarf.
This is one of the suspected paths toward the image, since there are a number of spikes in luminosity during the period the film is shown.
My personal view is one where the smaller companion star which may be also a massive star, but far less than V838 Monocerotis, could have merged with the primary star, though what could have caused their respective barycenter’s to collapse is still in question.
Perhaps the fuel scenario mentioned earlier could explain why the two eventually crashed into each other and eventually destabilized their relationship. Such an infusion in mass could have caused the stars to shed a portion of the stellar shell of the giant creating this visual phenomena, called a common envelope. If that is the case, and the smaller companion has not be completely absorbed, this may happen again in the future similar to other less visually impressive variable stars.
In any case, V838 Monocerotis’ fireworks display is one of the few times scientists have managed to catch a clear sequence of images of such a phenomenon over an extended period. It is likely to provide a host of information on cataclysmic variable stars in the future.