The spectral vitality distribution of WD 2226-210 superposed on a picture of the Helix Nebula from Hubble Space Telescope. The plot combines optical, infrared, and millimeter photometry, the Spitzer mid-infrared spectrum, and higher limits from WISE, Spitzer, SOFIA, Herschel, and ALMA. Models of the white dwarf photosphere (strong) and IR extra exhibiting good suits to the information detections (circles) and higher limits (triangles). Helix Nebula. Credit: NOIRLab; SED credit score: J. P. Marshall.
Once a star evolves past the primary sequence – the longest stage of stellar evolution, throughout which the radiation generated by nuclear fusion in a star’s core is balanced by gravitation – the destiny of any planetary system it might have had is an enigma. Astronomers usually don’t know what occurs to planets past this level, or whether or not they may even survive.
In a paper printed just lately in The Astronomical Journal, researchers used new knowledge from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and the Atacama Large Millimeter/submillimeter Array (ALMA), in addition to archival knowledge from the Spitzer Space Telescope and the Herschel Space Observatory, to review the Helix Nebula. These observations present one potential rationalization for the destiny of those planetary stays.
A Process of Elimination, and a Disruptive Origin
The Helix Nebula is an previous planetary nebula – increasing, glowing gasoline ejected from its host star after its main-sequence life ended. The nebula has a very younger white dwarf at its heart, however this central white dwarf is peculiar. It emits extra infrared radiation than anticipated. To reply the query of the place this extra emission comes from, the astronomers first decided the place it couldn’t have come from.
Collisions between planetesimals – small, strong objects fashioned out of cosmic mud left over from the creation of a planetary system round a star – can produce this kind of extra emission, however SOFIA and ALMA did not see the big mud grains required for such objects to exist, ruling out one choice. The astronomers additionally didn’t discover any of the carbon monoxide or silicon monoxide molecules attribute of the gasoline disks that may encompass evolving post-main-sequence stellar techniques that precede objects just like the Helix Nebula, excluding one other potential rationalization.
Different strands of proof place strict constraints on the scale, construction, and orbit of the supply of the emission, and finally come collectively to determine the identical wrongdoer: mud – from full-fledged planets destroyed through the nebula’s formation – returning towards its interior areas.
“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,” mentioned Jonathan Marshall, the lead writer on the paper and a researcher at Academia Sinica in Taiwan.
Once they realized the remnants of a former planetary system are on the origin of the infrared emission, they calculated what number of grains have to be returning to the Helix Nebula’s heart 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 proper into a hole between the earlier Spitzer and Herschel observations, permitting the group to grasp the form and brightness of the mud, and bettering the decision of how far it spreads out.
“This gap lay around where we expected the dust emission to peak,” Marshall mentioned. “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 usually are not planning any follow-up observations of the Helix Nebula specifically, this research is a piece in a bigger effort to make use of observations to grasp what occurs to planetary techniques as soon as their star evolves previous the primary sequence. The group hopes to review different late-stage stars utilizing comparable strategies.
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 undertaking of NASA and the German Space Agency at DLR. DLR supplied the telescope, scheduled plane upkeep, and different help for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute on the University of Stuttgart. The plane was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational functionality in 2014 and concluded its ultimate science flight on September 29, 2022.
