Zombie Star - Blog Posts
When a star more massive than our sun reaches the end of its life cycle, it goes in a spectacular blaze of glory known as a supernova. This explosion indicates that the star is dunzo, dead, or whatever we call it in the parlance of our times. But a new study found that one unusual star zombie-Jon-Snowed itself and as an astronomer tells Inverse, no one knows quite how.
In November, a couple lovely people brought my attention to articles about a recent discovery that headlines consistently referred to as the ‘zombie star.’ What the heck is a zombie star? What makes it a zombie? I found a zombie star from 2014 in addition to the one in 2017 and I dug into the life cycle of the average star to get a sense of what undeath looks like in stars.
Below the cut are my sources, music credits, a vocab list, and the transcript of this episode. Suggest what you think I should research next by messaging me here, tweeting at me at @HDandtheVoid, or asking me to my face if you know me. Please subscribe on iTunes, rate it and maybe review it, and tell friends if you think they’d like to hear it! Also, welcome if you found me through PodCon!
(My thoughts on the next episode are the International Space Station, the transit of Venus, or astronaut training practices. The next episode will allegedly be up on New Year’s Day, January 1st. We’ll see about that.)
Glossary
Chandrasekhar limit - the upper limit for the mass of an astronomical body that can support extreme density without imploding: about 1.4 times the mass of our Sun. Any white dwarf star that has less than that mass will stay a white dwarf forever; any star that exceeds the Chandrasekhar limit will end in a supernova.
dwarf nova - a close binary system of a red dwarf, a white dwarf, and an accretion disk around the white dwarf. They brighten by 2 to 6 magnitudes depending on the stability of the disk, which loses material to the white dwarf. Categorized as a cataclysmic variable.
neutron star - a type of star that has gone supernova, when the surviving core is 1.5 to 3 solar masses and contracts into a small, very dense, very fast-spinning star.
nova - a close binary system of a white dwarf and a secondary star that’s a little cooler than the Sun. The system brightens 7 to 16 magnitudes in 1 to 100 days, and then the star fades slowly to the initial brightness over a period of several years or decades. At maximum brightness, it’s similar to an A or F giant star. Recurrent novae are similar to this category of variable but have several outbursts during their recorded history. Categorized as a cataclysmic variable.
pulsar - a type of neutron star that spins very, very fast. Also a kind of variable star that emits light pulses usually between 0.0014 seconds and 8.5 seconds.
reflection telescope - reflects light rays off the concave surface of a parabolic mirror to get an image of a distant object. Higher contrast image, worse color quality.
spectroscopy - the study of light from an incandescent source (or, more recently, electromagnetic radiation and other radiative energy) that has its wavelength dispersed by a prism or other spectroscopic device that can disperse an object’s wavelength. The spectra of distant astronomical objects like the Sun, stars, or nebulae are patterns of absorption lines that correspond to elements that these objects are made up of.
supernova - a massive star that explodes with a magnitude increase of 20 or more. Supernovae have led us to realize that the expansion of the Universe is accelerating.
supernova progenitors - the kinds of stars and conditions that will result in certain types of supernovae.
white dwarf star - a star that has exhausted all of its nuclear fuel (i.e. no longer has hydrogen to convert into helium through nuclear fusion). It is the hot, dense core of a star. Unless it is acquiring/accreting matter from a nearby star, it will cool over time and become a dead star.
Script/Transcript
Sources
Chandrasekhar limit via PBS, Jan 2012
“The Chandrasekhar Limit is therefore not just as upper limit to the maximum mass of an ideal white dwarf, but also a threshold. A star surpassing this threshold no longer hoards its precious cargo of heavy elements. Instead, it delivers them to the universe at large in a supernova that marks its own death but makes it possible for living beings to exist.”
Type I and Type II supernovae via Space.com
Type Ia supernovae via Swinburne University of Technology
Type Ia Supernova Progenitors via Swinburne University of Technology
Zombie star via NASA, Aug 2014
Curtis McCully “I was very surprised to see anything at the location of the supernova. We expected the progenitor system would be too faint to see, like in previous searches for normal Type Ia supernova progenitors. It is exciting when nature surprises us.”
The abstract of the article McCully and his team wrote on Type 1ax supernovae via Nature Magazine, Aug 2014
Zombie star via CNN, Nov 2017
Arcavi: "My first thought was that this must be some nearby star in our galaxy, just varying its brightness. But when we got the first spectrum of it, we saw that it was in fact a supernova 500 million light-years away. My mind was blown. The fact that it got bright and dim five times was very unusual. We'd never seen a supernova do that before."
Arcavi: "This means that we still have a lot to learn about how massive stars evolve and how they explode."
Robert Evans via Sky and Telescope, Sept 2005
2017 zombie star articles I didn’t use because there were too many of them:
Air and Space Magazine, Nov 2017
The Atlantic, Nov 2017
BBC News, Nov 2017
BGR, Nov 2017
Carnegie Science, Nov 2017
Earth Sky, Nov 2017
Express UK, Nov 2017
The Guardian, Nov 2017
Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity
Filler Music: 'Toll Free’ by the Shook Twins off their album What We Do
Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught