Wolf-Rayet Star “Nasty 1” Transitional Stage in Evolution of Massive Stars

A very rapidly evolving, supermassive star with a newly formed nebula only a few thousand years old

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Space news (supermassive stars: Wolf-Rayet stars; star NaSt1) – 3,000 light-years away on the edge of a pancake-shaped disk of gas moving at 22,000 mph – 

Astronomers using the Hubble Space Telescope have discovered new clues concerning a nearby supermassive, rapidly aging star they have nicknamed “Nasty 1”. Designated NaSt1 in astronomy catalogs, “Nasty 1” when first discovered decades ago was identified as a non-typical Wolf-Rayet star with an orbiting disk-like structure. A vast disk estimated to be almost 2 trillion miles wide astronomers now think formed due to a companion star snacking on its outer envelope. Putting NaSt1 in a class of Wolf-Rayet stars astronomers haven’t observed often during the human journey to the beginning of space and time. A star type possibly representing a transition stage in the evolution of supermassive stars. 

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“We were excited to see this disk-like structure because it may be evidence for a Wolf-Rayet star-forming from a binary interaction,” said study leader Jon Mauerhan of the University of California, Berkeley. “There are very few examples in the galaxy of this process in action because this phase is short-lived, perhaps lasting only a hundred thousand years, while the timescale over which a resulting disk is visible could be only ten thousand years or less.” 

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Study leader Jon Mauerhan of the University of California, Berkley. Credit: University of California, Berkley.

In the case of NaSt1, computer simulations show a supermassive star evolving really fast and swelling as it begins to run out of hydrogen. Its outer hydrogen envelope is loosely bound and is gravitationally stripped from the star- astronomers call this process stellar cannibalism – by a more compact, nearby companion star. In the process the more compact star gains mass, while the more massive star loses its hydrogen envelope, exposing its helium core and eventually becoming a Wolf-Rayet star. 

The mass-transfer model is the favored process for how Wolf-Rayet stars evolve at the moment and considering at least 70 percent of supermassive stars detected, so far, are members of binary star system, this seems logical. Astronomers used to think this type of star could also form when a massive sun ejects its hydrogen envelope. But the direct mass loss model by itself can’t account for the number of Wolf-Rayet stars observed relative to less-evolved supermassive suns in the Milky Way.  

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“We’re finding that it is hard to form all the Wolf-Rayet stars we observe by the traditional wind mechanism because the mass loss isn’t as strong as we used to think,” said Nathan Smith of the University of Arizona in Tucson, who is a co-author on the new NaSt1 paper. “Mass exchange in binary systems seems to be vital to account for Wolf-Rayet stars and the supernovae they make, and catching binary stars in this short-lived phase will help us understand this process.” 

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Co-author of study Nathan Smith of the University of Arizona in Tucson. Credit: The University of Arizona.

Astronomers computer models show that the mass-transfer process isn’t always perfectly efficient. Matter can only transfer from NaSt1 at a certain rate, left over material begins orbiting, creating a disk-like structure. 

“That’s what we think is happening in Nasty 1,” Mauerhan said. “We think there is a Wolf-Rayet star buried inside the nebula, and we think the nebula is being created by this mass-transfer process. So this type of sloppy stellar cannibalism actually makes Nasty 1 a rather fitting nickname.” 

Observing Nasty 1 (star NaSt1) through the clock of gas and dust surrounding this star system hasn’t been easy. The intervening disk-like structure even blocks the view of the Hubble Space Telescope. Scientists haven’t been able to measure the distance between the stars, their mass, or the volume of material transferring to the smaller companion star.  

Astronomers have been able to discover a few items concerning the disk-like structure surrounding Nasty 1. Measurements indicate it’s traveling at around 22,000 mph in the outer nebula, a slower speed than recorded in other stars of this type. Scientists think this indicates a much less energetic supernova than was recorded for other events, like Era Carinae. In this case and other similar stars, the gas in the outer nebula has been recorded in the hundreds of thousands of miles per hour. Nasty 1 could be different supernova animal altogether.  

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High atop the Cerro Manqui peak at the Las Campanas Observatory in Chile the twin the Walter Baade Telescope is the first of the twin 6.5-meter Magellan telescopes to be completed. Credit: Ico.cl

Nasty 1 could also lose its outer envelope of hydrogen intermittently. Previous studies in the infrared light provided clues indicating the existence of a dense pocket of hot gas and dust close to the central stars in the region. More recent observations using the Magellan Telescope located at the Las Campanas Observatory in Chile has also detected a bigger pocket of cooler gas and dust possibly indirectly blocking light from these stars. Astronomers think the existence of warm dust in the region implies it formed just recently, perhaps intermittently, as elementally enriched matter from the stellar winds of massive stars collides, mixes, flows away, and cools. Irregular stellar wind strength, the rate at which star NaSt1 loses its outer envelope, could also help explain the observed clumpy structure and gaps noted in the outer regions of the disk.  

Astrophysicists used NASA’s Chandra X-ray Observatory to measure the hypersonic winds screaming from each star. Readings showed a scorching hot plasma, indicating colliding stellar winds producing high-energy shockwaves that glow in X-rays. This is consistent with previous data collected on other evolving Wolf-Rayet star systems. We’ll get a better view once the outer hydrogen of Nasty 1’s (star NaSt1) depleted, and the mass-transfer process completes. Eventually, the gas and dust in the lumpy, disk-like structure will dissipate, giving us a clearer view of this mysterious binary star system.   

 

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NASA’s Chandra X-ray Observatory has shown the cosmos is full of objects and events far beyond anything we imagined when we first started the human journey to the beginning of space and time. Credit: NASA/Chandra

Nasty 1’s still evolving!

“What evolutionary path the star will take is uncertain, but it will definitely not be boring,” said Mauerhan. “Nasty 1 could evolve into another Eta Carinae-type system. To make that transformation, the mass-gaining companion star could experience a giant eruption because of some instability related to the acquiring of matter from the newly formed Wolf-Rayet. Or, the Wolf-Rayet could explode as a supernova. A stellar merger is another potential outcome, depending on the orbital evolution of the system. The future could be full of all kinds of exotic possibilities depending on whether it blows up or how long the mass transfer occurs, and how long it lives after the mass transfer ceases.” 

Astronomers continue to study Nasty 1 and its peculiar, unusual disk-like structure looking for clues to explain the mysteries surrounding its origin. 

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The Giant Magellan Telescope

A side view of the Giant Magellan Telescope. Credit: GMTO Corporation
A side view of the Giant Magellan Telescope.
Credit: GMTO Corporation

Space news (March 31, 2016) – high up on an Andes Mountain peak in Las Campanas, Chile – 

High up on the dry, barren Cerro Las Campanas in the Atacama Desert in Chile construction of the Giant Magellan Telescope (GMT) began on November 11, 2015. The latest of many state-of-the-art telescopes housed in the Las Campanas Observatory, the GMT implements primary mirrors that are a marvel of modern engineering and glassmaking. Part of a new breed of super-giant-sized ground-based telescopes, it’s designed to open windows peering into unknown regions of the cosmos.  

Sunset over the GMT, work begins. Credit: GMTO Corporation
Sunset over the GMT, work begins.
Credit: GMTO Corporation

Six 27-foot (8.4 meters) mirror segments surround a central mirror, forming an optical surface 80-feet in diameter with a total light-collecting area of 3961 sq ft (386 square meters). Light from the edge of the cosmos will reflect off of the primary mirrors, strike seven smaller, flexible secondary mirrors, and then hit the center mirror before heading to advanced CCD imaging devices. The concentrated light is then measured to determine distance and composition of the material at the edge of the universe. 

The first GMT primary mirror segment on the polishing machine at the Steward Observatory Mirror Lab. Credit: GMTO Corporation
The first GMT primary mirror segment on the polishing machine at the Steward Observatory Mirror Lab.
Credit: GMTO Corporation

Utilizing a flexible secondary mirror with a surface capable of adjusting to counteract atmospheric turbulence, the GMT will have a resolving power ten times greater than the Hubble Space Telescope. Gathering more light than any telescope ever designed or engineered, controlled by advanced, state-of-the-art computers, it will transform twinkling lights into clear, steady points of light. Known as “adaptive optics” the actuators under the surface of the secondary mirrors constantly adjust, allowing the GMT to see through the Earth’s atmosphere. 

The light gathering ability and resolution of the GMT can image light reflected off of exoplanets orbiting stars light-years away, despite the glare of the host star. One day, light reflected off a rocky planet, much like Earth, will fall upon the mirror assembly of the Giant Magellan Telescope (GMT). Analysis of the light will show a blue planet, with oxygen in the atmosphere and soil, much like Earth. A planet capable of acting as a cradle for a new human Genesis, if we can travel to it? 

Perched on a dry Andes mountain at 8,500 ft (2,550 meters), the air above the telescope’s clear and clean, and the night sky dark. From here, the GMT will give us insight into the makeup of stellar matter that formed the first galaxies to appear after the Big Bang. The mystery of dark matter and dark energy and the ultimate fate of our universe. The destinations and secrets of the cosmos it reveals will alter our view of reality and understanding of the bigger universe. The Giant Magellan Telescope’s our next great spaceship-to-the-stars.

Boarding passes available sometime in 2021! 

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