A frosty, chilly star about the same temperature as the North Pole, minus 54 and 9 degrees Fahrenheit (minus 48 to minus 13 degrees Celsius)
Space news (astrophysics: faint, cool stars; brown dwarfs) – the fourth closest detected star system to Earth, just 7.2 light-years toward the constellation Hydra –
A young, ambitious astronomer working at Pennsylvania State University’s Center for Exoplanets and Habitable Worlds discovered the dimmest, coolest brown dwarf detected during the human journey to the beginning of space and time. Kevin Lehman first noticed a fast moving object, quickly dubbed WISE J085510.83-071442.5, in March of 2013. Excited at a new discovery, he spent the next few days analyzing more images of the same part of the sky taken by NASA’s Spitzer Space Telescope and Gemini South Telescope on Cerro Pachon in Chile.
“It’s very exciting to discover a new neighbor of our solar system that is so close,” said Kevin Luhman, an astronomer at Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, University Park. “And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures.”
Kevin Luhman originally spotted the fast motion of WISE J085510.83-071442.5 in infrared images taken by NASA’s Wide-field Infrared Survey Explorer (WISE). Later analysis of infrared images taken by NASA’s Spitzer Space Telescope were needed to determine its chilly temperature of between minus (54-9) Fahrenheit [minus (13 – 48) degrees Celsius]. Astronomers would use measurements taken by Spitzer and WISE at different positions around the sun to determine its distance of 7.2 light-years from Earth using the parallax effect. To scientists, it added up to a brown dwarf or maybe a large Jupiter-size planet lost in space.
“This object appeared to move really fast in the WISE data,” said Luhman. “That told us it was something special.”
Additional calculations estimated the mass of WISE J085510.83-071442.5 at between 3 and 10 times the mass of Jupiter. It could be a gas giant like Jupiter that was flung out of its host star system by gravitational interactions with more massive bodies. Astronomers determined it was more likely a very cool brown dwarf than a large gas giant planet since they have been detected more often. If this is the case, it’s the coldest brown dwarf star discovered during the human journey to the beginning of space and time. A nice shiny feather in the hat of a young, aspiring astronomer on the rise.
“It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun’s nearest neighbors,” said Michael Werner, the project scientist for Spitzer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. JPL manages and operates Spitzer. “This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer.”
Work’s never done
Never one to rest on his laurels, in March of 2013, Kevin Luhman discovered a pair of warmer brown dwarf stars just 6.5 light-years from Earth during his analysis of WISE images. Since this time, his search for rapidly moving bodies close to Earth has also shown that the outer solar system probably doesn’t contain a large, undiscovered planet X or Nemesis, as people often refer to it. I did mention he was ambitious.
A very rapidly evolving, supermassive star with a newly formed nebula only a few thousand years old
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.
“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.”
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.
“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.”
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.
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.
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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An interstellar cloud of dust, hydrogen, helium and other gasses expanding at a rate of around 220,000 kilometers (136,700 miles) per hour
Space news (March 11, 2016) – 30,000 light-years away in the constellation Carina (The Keel) –
The Wolf-Rayet star WR 31a, near the centre of this Hubble image, is a bright celestial beacon ejecting hydrogen in layers that are interacting with extremely fast-moving stellar winds to produce the ring-shaped bubble of an interstellar cloud of dust, hydrogen, helium, and other gases viewed.
Wolf-Rayet stars are the most massive stars detected during the human journey to the stars. WR 31a started life with over 20 times the mass of Sol. Our Sun is a main sequence star which is actually a little bigger than average. The more mass a star has, the shorter its expected life, which accounts for the short life span of this bright celestial beacon. In the words of NASA, massive stars “Live fast and die hard”.
The mass of WR 31a puts it at the lower end of the mass scale for Wolf-Rayet stars, with the most massive estimates coming in at over 200 times the mass of our sun. The estimates of the mass of this type of star are still being worked on, so don’t take them to heart.
Astronomers estimate WR 31a is only 20,000 years old, give or take a few thousand, which is around 10 percent of its life expectancy according to current theory. The life cycle of Wolf-Rayet stars is only a couple hundreds thousand years long, a mere blink of the eye in cosmic terms, which means this massive star will end its days as a spectacular supernova.
The event we refer to as supernova is an essential part of the life cycle of the cosmos. Deep within these massive stars, the building blocks of the cosmos are created. It’s here the carbon, magnesium, calcium, and other elements that make up 4-5 percent of the universe are made using the extreme conditions that exist.
We’re all stardust traveling on a pale-blue dot in the distance, across the vastness of space-time to an unknown but dreamed of ending.