Researchers used interferometry at the CHARA Array in California and published their results in Nature Astronomy. Interferometry joins light from several telescopes to reach much higher resolution, and the CHARA team adapted observing schedules to catch these transient eruptions.
Novae occur when a white dwarf gains material from a companion star and triggers a runaway nuclear reaction. Until now, the earliest stages were usually inferred indirectly because the expanding gas appeared as a single unresolved point. The new direct images show how ejecta are thrown out and how different flows interact, which is key to understanding how shock waves form in novae.
NASA’s Fermi-LAT had already shown that novae emit high-energy gamma rays. The team imaged two novae that erupted in 2021. V1674 Herculis was among the fastest: it brightened and faded in days and showed two perpendicular outflows while Fermi detected gamma rays. V1405 Cassiopeiae held its outer layers for more than 50 days before releasing them; when the material was finally ejected, new shocks produced gamma rays. Spectra from observatories such as Gemini matched the image structures and confirmed the collisions of flows.
Difficult words
- interferometry — method that combines light from several telescopes
- resolution — ability to see small details in an image
- transient — lasting only for a short time
- nova — star that suddenly becomes much brighternovae
- white dwarf — small, dense type of star
- ejecta — material thrown out from an explosion or star
- shock wave — powerful wave from sudden pressure changeshock waves
- gamma ray — very high-energy form of electromagnetic radiationgamma rays
- spectrum — range of light showing energy at different colorsSpectra
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Discussion questions
- How can direct images of the earliest nova stages help scientists understand how shock waves form? Give one reason.
- Which difference between V1674 Herculis and V1405 Cassiopeiae do you find most interesting, and why?
- The team adapted observing schedules to catch transient eruptions. What is one practical change observatories could make to observe these events more often?
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