Central star in a planetary nebula reveals details of its life

Stars like our sun finish their lives as white dwarfs. A few of them are surrounded by a planetary nebula consisting of gasoline ejected by the dying star shortly earlier than its loss of life. A global analysis workforce led by Professor Klaus Werner of the Institute of Astronomy and Astrophysics on the College of Tübingen has for the primary time studied a central star of a planetary nebula positioned in an open star cluster.

The researchers had been capable of exactly decide the mass that the central star misplaced throughout its lifetime. The outcomes are printed within the journal Astronomy & Astrophysics.

There are greater than a thousand open star clusters within the Milky Way. Every of them contains a group of as much as a number of thousand stars which have fashioned concurrently from a dense cloud of gasoline and dust. “The celebs in a cluster are all the identical age; that has a particular significance for astrophysics,” Klaus Werner studies. They differ solely in mass. “The extra huge a star is, the quicker it consumes its nuclear fuel by fusing hydrogen into helium. So its life is shorter and it evolves right into a white dwarf quicker,” he explains.

Snapshot of celestial growth

The commentary of a star cluster exhibits, like a snapshot, the event of stars of various lots on the identical age, Werner says. “In astronomy, star clusters can be utilized as a sort of laboratory the place we will measure how dependable our theories of stellar evolution are,” he says. One of many largest uncertainties within the idea of stellar evolution is how a lot matter a star loses throughout its lifetime, he says, including that such mass loss is substantial.

“Stars like our sun lose just below half their mass by the point they’ve advanced into white dwarfs. Stars with eight occasions the mass of the sun lose about 80% of their mass,” says the astrophysicist. The connection between the celebs’ beginning mass and the mass on the time of loss of life as a white dwarf is understood in astronomy because the initial-final mass relation.

The mass of white dwarfs in star clusters could be straight associated to the mass that they had at beginning, Werner says. “The info from very younger white dwarfs are significantly beneficial, as these are the central stars of planetary nebulae,” he explains. Thus far, solely three star clusters are identified to include a planetary nebula. “None of their central stars had been studied earlier than as a result of they’re all very distant and faint,” Werner says.

Particular chemical composition

The analysis workforce pointed one of many world’s largest telescopes, the ten-meter GRANTECAN tele-scope on the Canary Island of La Palma, on the central star within the Messier 37 star cluster and analyzed its spectrum. The mass was decided to be 0.85 solar masses, placing the unique mass at 2.8 solar lots.

“So the star has misplaced 70% of its matter throughout its lifetime,” Werner explains. One other peculiarity, he says, is its particular chemical composition. The star not had hydrogen on its floor; Werner says this means an uncommon occasion in its latest previous—a short flare-up of nuclear fusion.

With the ability to make a exact dedication of the initial-final mass relation is of basic significance in astrophysics, says Werner. It determines whether or not a star evolves right into a white dwarf, turns into a neutron star in a supernova explosion, and even whether or not a black hole stays as the ultimate stage. And but, Werner factors out, “new generations of stars are fashioned from the ejected matter, enriched in heavy components as merchandise of nuclear reactions. That is what the chemical evolution of galaxies—and finally the complete universe—relies upon upon.”