Mysterious nebula formed from 'The Great Eruption' is 3D printed by NASA scientists

Monday, July 14, 2014, 5:35 PM - In the mid-19th century, a star in the southern sky named Eta Carinae suddenly flared brightly as it produced The Great Eruption - becoming the second brightest star in the night sky as it expelled what is now known as the Homunculus Nebula. Using ultra-accurate readings of this nebula, scientists with NASA's Goddard Space Flight Center have produced a 3D printed model that you can hold in the palm of your hand.

Due to the presence of the nebula, it was difficult to see what lay at its core, so Eta Carinae was once thought to be the single largest star we've ever discovered. However, closer observations and modelling of the nebula showed that there were actually two stars there, not one (now the title probably goes to yellow hypergiant star HR5171). Eta Carinae A is a hypergiant blue star (technically called a Luminous Blue Variable or LBV), which started out as about 150 times more massive than our Sun, and big enough that we could fit a billion stars like our Sun inside it and still have room to spare. The companion that orbits it - Eta Carinae B - is a smaller supergiant star that is roughly 30 times more massive than our Sun, is hotter than Eta Carinae A, and is thought to be the source of much of the light illuminating the nebula. The nebula itself, which contains about 10-40 solar masses worth of matter, was expelled by Eta Carinae A (meaning that it is now less than 150 solar masses), which is nearing the end of its lifespan. Astronomers apparently still aren't sure exactly why the star threw off this immense amount of material, however insights into the nature of the binary pair allowed them to model how the nebula was sculpted by their gravity as they orbit each other.

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Credit: NASA Goddard (inset: NASA, ESA, Hubble SM4 ERO Team)

Although there's some thought that Eta Carinae A may produce more 'Great Eruptions' with time, one day, possibly within the next decade or maybe millions of years from now, the star will finally 'give up the ghost' (so to speak) and explode into an incredible supernova or hypernova. It may have already done so, and the light and radiation from it is still traversing the 7,500 light years between it and our star system. Although supernovas and hypernovas can be devastating to nearby star systems, Eta Carinae is far too distant to cause us any harm here on Earth's surface. Anyone in orbit would have to worry about exposure to cosmic rays from the explosion, and they may also damage electronics in our satellites around Earth and on robotic missions around and on planets or satellites without a magnetic field (like Mercury, Venus, Mars and the Moon). These immense explosions are also known to emit an intense beam of radiation known as a Gamma Ray Burst (or GRB). If a GRB from Eta Carinae were to be aimed at our solar system, anyone on the side of the planet facing the star would have a very bad day when it arrived here, and everyone on the other side would go through some very bad times over the course of the weeks and months afterwards, as it would have a devastating effect on our atmosphere (read Phil Plait's excellent explanation here). However, the shape and orientation of the nebula shows us that the beam would be aimed away from us, as it would punch out of the 'hole' in each lobe (shown in the image above).

However, when this event does happen, the explosion will be so bright that it will outshine every other object in the night sky, including the Moon, and it may even be visible during the daytime. Given our safe distance and location, it should be an incredible sight to see.

To read more about Eta Carinae and the Homunculus Nebula, see NASA's website (click here), and if you have a 3D printer, you can even download the model to print your very own copy of the nebula (see the related links at the bottom of the NASA page).