A Supernova in Waiting

One of the best candidate stars to go supernova in our neighborhood is Eta Carinae in the constellation of Argo Navis in the southern hemisphere.  From my apartment in New York City, I logged into my friend’s computer in Chile.    Thus, I had the opportunity to remotely image this star and its famous “Homunculus” nebula with a friend’s very large telescope in Chile.  Although today Eta carinae is a 6th magnitude star, it was 0 magnitude in the mid 1800s during an eruption, consistent with its stellar classification as a rare Luminous Blue Variable.  NGC3372 is the nebula associated with it and it is a well-known target for astrophotography.


Eta Carinae is soon to go supernova because not only is it one of the most massive stars ever observed (over to 150 solar masses) but also because back in 1840 the star ‘erupted’ and brightened considerably becoming one of the brightest stars in the sky.  It has since faded back to about magnitude 6, making it mostly invisible except to the keenest naked eye. 


The Homunculus Nebula, surrounding Eta Carinae, is a bipolar nebula formed from the material ejected during the Great Eruption. This nebula, resembling a tiny human figure (hence its name ‘Homunculus’), is a focus of study due to its unique shape, rapid expansion, and complex chemical composition. It provides a real-time laboratory for understanding the dynamics of massive star outbursts.  You can see one of the lobes in my picture, the yellow/orange shell to the right of the star itself.  There are some more detailed pictures of the Homunculus on the web taken by space telescopes if you want to google it.  Right next to this is the dark “Keyhole Nebula” or NGC 3372 which is likely the molecular gas cloud that gave rise to this massive star in the first place.  The proximity and interaction of Eta Carinae with the Homunculus and Keyhole Nebulae present a unique opportunity for astrophotography. The varying brightness of Eta Carinae, the evolving structure of the Homunculus Nebula, and the silhouette of the Keyhole Nebula against the backdrop of the Carina Nebula make this region particularly interesting for imaging and observation.

If Eta Carinae were to go supernova, it would be an extraordinary event observable from Earth, even potentially visible in broad daylight. This stellar explosion would dramatically brighten the night sky, likely outshining most other stars and possibly reaching a brightness comparable to the full moon. The immense energy and light emitted would make it a beacon across the celestial sphere, creating a spectacle for astronomers and enthusiasts worldwide.

The aftermath of such a supernova in its stellar neighborhood would be significant. The explosion would eject vast amounts of material into space, enriching the surrounding interstellar medium with heavy elements. This ejected matter could eventually contribute to the formation of new stars and planets. The shockwave from the supernova would interact with nearby nebulae, such as the Homunculus and Keyhole Nebulae, altering their shapes and compositions.

As for the remnant of Eta Carinae post-supernova, it could form either a neutron star or a black hole, depending on the final mass of the stellar core. If the core’s mass is below a certain threshold (typically around 2-3 solar masses), it would likely form a neutron star.  However, if the core is more massive, it would collapse into a black hole. Given the massive nature of Eta Carinae, many astronomers speculate that a black hole is the more likely outcome.  Just for fun I asked ChatGPT to create an artistic representation of what such an explosion would look like to us here on Earth… WOW!  I can’t wait!

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