sábado, septiembre 24, 2022
InicioTechnologyA cosmic thriller: Astronomers seize dying star blowing smoke rings

A cosmic thriller: Astronomers seize dying star blowing smoke rings

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A rendering of the star V Hydrae, or V Hya for short. In its death throes, the star emitted a series of expanding rings that scientists calculated are being formed every few hundred years, per UCLA astronomer Mark Morris.
Enlarge / A rendering of the star V Hydrae, or V Hya for brief. In its loss of life throes, the star emitted a sequence of increasing rings that scientists calculated are being fashioned each few hundred years, per UCLA astronomer Mark Morris.

ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO/AUI/NSF)

Astronomers have caught a pink large star going via its last loss of life throes in unprecedented element, revealing an uncommon characteristic. The star, generally known as V Hydrae (or V Hya for brief), ejected six distinct rings of fabric, in accordance with a preprint accepted for publication within the Astrophysical Journal. The particular mechanism of those mysterious «smoke rings» fashioned just isn’t but understood. Nonetheless, the remark might probably shake up present fashions for this specific late stage of stellar evolution and shed additional mild on the destiny of our personal Solar.

“V Hydrae has been caught within the technique of shedding its environment—in the end most of its mass—which is one thing that the majority late-stage pink giants do,» stated co-author Mark Morris, an astronomer at UCLA. Nevertheless, «That is the primary and solely time {that a} sequence of increasing rings has been seen round a star that’s in its loss of life throes—a sequence of increasing ‘smoke rings’ that now we have calculated are being blown each few hundred years.»

Purple giants are one of many last levels of stellar evolution. As soon as a star’s core stops changing hydrogen into helium by way of nuclear fusion, gravity begins to compress the star, elevating its inner temperature. This course of ignites a shell of hydrogen burning round an inert core. Ultimately, the compression and heating within the core trigger the star to develop considerably, reaching diameters between 62 million and 620 million miles (100 million to 1 billion kilometers).  The floor temperatures are comparatively cool by stellar requirements: a mere 4,000 to five,800 levels F (2,200 to three,200 levels C). So these stars tackle an orange-red look, therefore the pink large moniker.

V Hydrae is a carbon-rich star located 1,300 light-years away in the constellation Hydra.
Enlarge / V Hydrae is a carbon-rich star positioned 1,300 light-years away within the constellation Hydra.

IAU and Sky & Telescope

Ultimately, the helium in a pink large’s core can be spent, and the core will shrink once more. The star then turns into an asymptotic large department (AGB) star (the ultimate pink large stage). The inside construction of an AGB star consists of a central core of carbon and oxygen, a shell the place fusion is popping helium into carbon, and one other shell the place hydrogen is popping into helium. These stars sometimes produce dramatic pulses of elevated brightness each 100 to 1,000 days. As well as, intense floor winds trigger a gaseous cloud generally known as a circumstellar envelope to kind across the star.

These intense stellar winds will finally expel the environment and stellar envelope, and the star will turn out to be a white dwarf star inside a planetary nebula. The quicker the speed at which an AGB star loses its mass, the nearer it’s to that last transition. Our Solar will finally turn out to be a pink large in about 5 billion years, finally progressing to an AGB earlier than lastly evolving right into a planetary nebula with a white dwarf star at its heart.

That is the method as astronomers have understood it for years. The bizarre traits of V Hya have them rethinking issues, nevertheless. Positioned 1,300 light-years away within the constellation Hydra, V Hya is a carbon-rich star, that means its environment incorporates extra carbon than oxygen. It has a excessive loss fee for its mass, so astronomers surmise that it is in all probability within the technique of shedding its environment to turn out to be a planetary nebula.

Rendering showing the carbon-rich star V Hya in its final act.
Enlarge / Rendering displaying the carbon-rich star V Hya in its last act.

ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO/AUI/NSF)

This AGB star can be intriguing as a result of each eight years or so, there are massive plasma eruptions, and sharp decreases in brightness happen roughly each 17 years. These occasions counsel the presence of a companion star that’s barely seen. (The dips in brightness may very well be attributable to a cloud linked to this second star passing in entrance of V Hya.)

This newest examine combines knowledge from the Hubble Area Telescope with observations utilizing the Atacama Massive Millimeter/submillimeter Array (ALMA), incorporating infrared, optical, and ultraviolet knowledge to seize V Hya’s loss of life throes throughout a number of wavelengths. The star is way away and surrounded by dense mud, however the increased decision capabilities of ALMA revealed its rings and outflows in nice element.

The timing was additionally serendipitous. “V Hya is within the transient however vital transition part that dying stars undergo on the finish of their lives,” stated co-author Raghvendra Sahai, an astronomer at NASA’s Jet Propulsion Laboratory. “It’s the part after they lose most of their mass. It’s probably that this part doesn’t final very lengthy, so it’s tough to catch them within the act. We obtained fortunate with V Hya, and have been capable of picture all the totally different actions occurring in and round this star to higher perceive how dying stars lose mass on the finish of their lives.”

Sahai and his co-authors discovered that the star is shedding its environment by blowing a sequence of smoke rings, which have expanded outward during the last 2,100 years or so to kind a dusty disk-like area round V Hya. The group dubbed that construction DUDE (disk present process dynamical growth).

Their observations additionally revealed high-speed blasts of gasoline expelled from the star in reverse instructions, perpendicular to the smoke rings, forming two hourglass-shaped constructions. These constructions are increasing quickly at greater than half-a-million miles per hour (240 km/s). «The invention that this course of can contain ejections of rings of gasoline, simultaneous with the manufacturing of high-speed intermittent jets of fabric, brings a brand new and engaging wrinkle to our understanding of how stars finish their lives,” Morris stated.

All of this means that the star is present process a notably fast evolution, which runs counter to the present mannequin. «Our examine dramatically reveals that the normal mannequin of how AGB stars die—via the mass ejection of gasoline by way of a gradual, comparatively regular spherical wind over 100,000 years or extra—is at greatest incomplete, or at worst, incorrect,» stated Sahai. “It is rather probably {that a} shut stellar or substellar companion performs a major function of their deaths. Within the case of V Hya, the mixture of a close-by and a hypothetical distant companion star is accountable, not less than to some extent, for the presence of its six rings, and the high-speed outflows which are inflicting the star’s miraculous loss of life.”

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