Welcome to Three Alpha! Since last time: In the Solar System, NASA has claimed evidence of a potential biosignature on Mars (but I wouldn’t get excited, there are other explanations); in the Galaxy, a white dwarf has been caught consuming a Pluto-like object; and in the Universe, astronomers have observed an unprecedented repeating gamma ray burst.

Meanwhile, in this edition of the newsletter we’re focusing on what we are actually looking at in two recent images of “butterflies”. Read on for more…

Similar names, not at all similar stars

Two new images have just been released, one of the “Butterfly Star” and the other of the “Butterfly Nebula”. Each contains a star in a nebula that looks a bit like a butterfly, but they actually show very different objects. Allow me to explain.

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The first, the Butterfly Nebula, or NGC 6302, is a planetary nebula surrounding a white dwarf. A white dwarf is the stellar remnant which is left after a relatively small star ends its life. A white dwarf is what the Sun will become after it dies. When such a star starts to run out of fuel, the balance between fusion and gravity is knocked out of whack and the star expands. It expands so much that its outer layers are thrown off into space, leaving behind the small, hot, white core. This is the white dwarf. The expelled outer layers expand to form the planetary nebula. (This has nothing to do with planets; the name is historical and comes from the fact that planetary nebulae looked a bit like planets in early telescopes).

The second, the Butterfly Star, or IRAS 04302+2247, is a star at the other end of its life. This is a star which is just being born, surrounded by a protoplanetary disk. That does have something to do with planets: the disk will spawn a new planetary system, in orbit around the new star. You can see the disk as the dark band in the centre. Outside the disk are two reflection nebulae. Those are nebulae illuminated by the light of the young protostar. The nebulae are created by jets from the young star; the disk surrounds the star’s equator and the jets come from the poles.

These two objects are both in the news because of new images showing more detail than we could previously see, thanks in part to new data from JWST. In the case of NGC 6302, infrared images from JWST have been combined with radio observations from ALMA to show this incredibly detailed view of the centre of the nebula. For the first time, this allows us to see the white dwarf and the material immediately surrounding it:

The new image of IRAS 04302+2247 allows us to not only see new details in the nebula, but we can actually see the protoplanetary disk. So here, in the same week, we got two new images from JWST, one showing a young star beginning its life, and the other showing the remains of a dead star which has finished its life.

Finally

There are now 6,000 confirmed exoplanets!

What is Three Alpha? Other than being the name of the newsletter you’re reading now, the name “three alpha” comes from the triple-alpha process, a nuclear chain reaction in stars which turns helium into carbon. Read more here.

Who writes this? My name is Dr. Adam McMaster. I’m an astronomer in the UK, where I mainly work on finding black holes. You can find me on BlueSky, @adammc.space.

Let me know what you think! You can send comments and feedback by hitting reply or by emailing [email protected].