De spectrale energieverdeling van WD 2226-210 bovenop een afbeelding van de Helixnevel van de Hubble-ruimtetelescoop. De plot combineert optische, infrarood- en millimeterfotometrie, het Spitzer midden-infraroodspectrum en bovengrenzen van WISE, Spitzer, SOFIA, Herschel en ALMA. Modellen van de fotosfeer van de witte dwerg (vast) en infraroodexces die goed passen bij de gegevensdetecties (cirkels) en bovengrenzen (driehoeken). Helix-nevel. Krediet: NOIRLab; SED-tegoed: JP Marshall.
Zodra een ster voorbij de hoofdreeks is geëvolueerd – de langste fase van de evolutie van de ster, waarin de straling die wordt geproduceerd door kernfusie in de kern van een ster wordt gecompenseerd door de zwaartekracht – is het lot van eventuele planetaire systemen een raadsel. Astronomen weten over het algemeen niet wat er gebeurt met planeten voorbij dit punt en of ze zelfs kunnen overleven.
In een artikel dat onlangs verscheen in Het astronomisch tijdschriftDe onderzoekers gebruikten nieuwe gegevens van het Stratospheric Observatory for Infrared Astronomy ([{” attribute=””>SOFIA) and the Atacama Large Millimeter/submillimeter Array (
A Process of Elimination, and a Disruptive Origin
The Helix Nebula is an old planetary nebula – expanding, glowing gas ejected from its host star after its main-sequence life ended. The nebula has a very young
“In piecing together the size and shape of the excess emission, and what those properties infer regarding the dust grains in the white dwarf environment, we conclude that a disrupted planetary system is the best solution to the question of how the Helix Nebula’s infrared excess was created and maintained,” said Jonathan Marshall, the lead author on the paper and a researcher at Academia Sinica in Taiwan.
Once they realized the remnants of a former planetary system are at the origin of the infrared emission, they calculated how many grains need to be returning to the Helix Nebula’s center to account for the emission: about 500 million over the 100,000-year lifetime of the planetary nebula, conservatively.
SOFIA’s Role
SOFIA’s capabilities fell right into a gap between the previous Spitzer and Herschel observations, allowing the group to understand the shape and brightness of the dust, and improving the resolution of how far it spreads out.
“This gap lay around where we expected the dust emission to peak,” Marshall said. “Pinning down the shape of the dust emission is vital to constraining the properties of the dust grains that produce that emission, so the SOFIA observation helped refine our understanding.”
Though the researchers are not planning any follow-up observations of the Helix Nebula in particular, this study is a piece in a larger effort to use observations to understand what happens to planetary systems once their star evolves past the main sequence. The group hopes to study other late-stage stars using similar techniques.
Reference: “Evidence for the Disruption of a Planetary System During the Formation of the Helix Nebula” by Jonathan P. Marshall, Steve Ertel, Eric Birtcil, Eva Villaver, Francisca Kemper, Henri Boffin, Peter Scicluna and Devika Kamath, 19 December 2022, The Astronomical Journal.
DOI: 10.3847/1538-3881/ac9d90
SOFIA was a joint project of
