Wolf-Rayet Star WR 31a Blows Hubble a Bubble

An interstellar cloud of dust, hydrogen, helium and other gasses expanding at a rate of around 220,000 kilometers (136,700 miles) per hour 

Sparkling at the centre of this beautiful NASA/ESA Hubble Space Telescope image is a Wolf–Rayet star known as WR 31a, located about 30 000 light-years away in the constellation of Carina (The Keel). The distinctive blue bubble appearing to encircle WR 31a, and its uncatalogued stellar sidekick, is a Wolf–Rayet nebula — an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds interact with the outer layers of hydrogen ejected by Wolf–Rayet stars, these nebulae are frequently ring-shaped or spherical. The bubble — estimated to have formed around 20 000 years ago — is expanding at a rate of around 220 000 kilometres per hour! Unfortunately, the lifecycle of a Wolf–Rayet star is only a few hundred thousand years — the blink of an eye in cosmic terms. Despite beginning life with a mass at least 20 times that of the Sun, Wolf–Rayet stars typically lose half their mass in less than 100 000 years. And WR 31a is no exception to this case. It will, therefore, eventually end its life as a spectacular supernova, and the stellar material expelled from its explosion will later nourish a new generation of stars and planets.
Credit: NASA/ESA

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. 

Watch this YouTube video on Wolf-Rayet star WR 31a.

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Superstar Binaries Like Eta Carinae More Common Than First Thought

Astronomers using NASA’s Spitzer and Hubble space telescopes discovered similar superstar binaries in four nearby galaxies

Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble, and transformed the binary into a unique object in our galaxy. Astronomers cannot yet explain what caused this eruption. The discovery of likely Eta Carinae twins in other galaxies will help scientists better understand this brief phase in the life of a massive star. Credits: NASA, ESA, and the Hubble SM4 ERO Team
Eta Carinae’s great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble, and transformed the binary into a unique object in our galaxy. Astronomers cannot yet explain what caused this eruption. The discovery of likely Eta Carinae twins in other galaxies will help scientists better understand this brief phase in the life of a massive star.
Credits: NASA, ESA, and the Hubble SM4 ERO Team

Space news (February 15, 2016) – 7,500 light-years away in the southern constellation of Carina

Astronomers combing through data provided by the Hubble and Spitzer space telescopes looking for superstar binaries like Eta Carinae think they have finally found a few additional instances in nearby galaxies. 

The signature balloon-shaped clouds of gas blown from a pair of massive stars called Eta Carinae have tantalized astronomers for decades. Eta Carinae has a volatile temperament, prone to violent outbursts over the past 200 years. Observations by the newly repaired Space Telescope Imaging Spectrograph (STIS) aboard NASA’s Hubble Space Telescope reveal some of the chemical elements that were ejected in the eruption seen in the middle of the 19th century. Image credit: NASA/ESA
The signature balloon-shaped clouds of gas blown from a pair of massive stars called Eta Carinae have tantalized astronomers for decades. Eta Carinae has a volatile temperament, prone to violent outbursts over the past 200 years.
Observations by the newly repaired Space Telescope Imaging Spectrograph (STIS) aboard NASA’s Hubble Space Telescope reveal some of the chemical elements that were ejected in the eruption seen in the middle of the 19th century.
Image credit: NASA/ESA

We knew others were out there,” said co-investigator Krzysztof Stanek, a professor of astronomy at Ohio State University in Columbus. “It was really a matter of figuring out what to look for and of being persistent.

Astrophysicists had previously conducted a survey of data on seven galaxies provided by the pair of space telescopes between 2012-2014. During this extensive study of the data, scientists found no superstar binaries similar to Eta Carinae. They determined they needed to devise a more sensitive way to identify possible candidates. 

Astronomers devised an optical and infrared fingerprint to detect and identify these five superstar binaries similar to Eta Carinae. With Spitzer we see a steady increase in brightness starting at around 3 microns and peaking between 8 and 24 microns,” explained Khan. “By comparing this emission to the dimming we see in Hubble’s optical images, we could determine how much dust was present and compare it to the amount we see around Eta Carinae.

During the follow-up survey conducted in 2015, astronomers discovered data indicating the existence of five superstar binaries similar to Eta Carinae in four nearby galaxies. 

The nearby spiral galaxy M83 is currently the only one known to host two potential Eta Carinae twins. This composite of images from the Hubble Space Telescope's Wide Field Camera 3 instrument shows a galaxy ablaze with newly formed stars. A high rate of star formation increases the chances of finding massive stars that have recently undergone an Eta Carinae-like outburst. Bottom: Insets zoom into Hubble data to show the locations of M83's Eta twins. Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and R. Khan (GSFC and ORAU)
The nearby spiral galaxy M83 is currently the only one known to host two potential Eta Carinae twins. This composite of images from the Hubble Space Telescope’s Wide Field Camera 3 instrument shows a galaxy ablaze with newly formed stars. A high rate of star formation increases the chances of finding massive stars that have recently undergone an Eta Carinae-like outburst. Bottom: Insets zoom into Hubble data to show the locations of M83’s Eta twins.
Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and R. Khan (GSFC and ORAU)

In nearby galaxy M83, just 15 million light-years away, astronomers discovered two superstar binaries similar to Eta Carinae. They also found one superstar binary each in NGC 6946, M101 and M51, located between 18-26 million light-years away.

Researchers found likely Eta twins in four galaxies by comparing the infrared and optical brightness of each candidate source. Infrared images from NASA's Spitzer Space Telescope revealed the presence of warm dust surrounding the stars. Comparing this information with the brightness of each source at optical and near-infrared wavelengths as measured by instruments on Hubble, the team was able to identify candidate Eta Carinae-like objects. Top: 3.6-micron images of candidate Eta twins from Spitzer's IRAC instrument. Bottom: 800-nanometer images of the same sources from various Hubble instruments. Credits: NASA, ESA, and R. Khan (GSFC and ORAU)
Researchers found likely Eta twins in four galaxies by comparing the infrared and optical brightness of each candidate source. Infrared images from NASA’s Spitzer Space Telescope revealed the presence of warm dust surrounding the stars. Comparing this information with the brightness of each source at optical and near-infrared wavelengths as measured by instruments on Hubble, the team was able to identify candidate Eta Carinae-like objects. Top: 3.6-micron images of candidate Eta twins from Spitzer’s IRAC instrument. Bottom: 800-nanometer images of the same sources from various Hubble instruments.
Credits: NASA, ESA, and R. Khan (GSFC and ORAU)

An additional study indicates each of these five candidates has the same optical and infrared fingerprint as Eta Carinae. Astronomers think within each a high mass star is buried in five to ten solar masses of gas and dust, like Eta Carinae. 

More study’s needed

They plan additional study of these five candidate superstar binaries similar to Eta Carinae, to determine if they’re indeed what they were looking for. The launch of the James Webb Space Telescope, late in 2018, will enable additional and better study of these five possible superstar binaries. 

The James Webb Telescope’s Mid-infrared instrument (MIRI) has ten times the angular resolution of the Spitzer Space Telescope. It’s also most sensitive to the wavelengths needed to detect superstar binaries at their brightest. 

Combined with Webb’s larger primary mirror, MIRI will enable astronomers to better study these rare stellar laboratories and to find additional sources in this fascinating phase of stellar evolution,” said Sonneborn, NASA’s project scientist for Webb telescope operations. It will take Webb observations to confirm the Eta twins as true relatives of Eta Carinae.

Take the journey of the Spitzer Space Telescope here.

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Discover Eta Carinae here.

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