It is one of the biggest battles ever seen.
In the Carina Nebula, a dynamic, evolving cloud of thinly spread interstellar gas and dust about 7500 light-years away, in the constellation of Carina, there is a battle between stars and dust.
A stunning new image reveals the area in unprecedented detail.
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This spectacular image of the Carina nebula reveals the dynamic cloud of interstellar matter and thinly spread gas and dust as never before. The massive stars in the interior of this cosmic bubble emit intense radiation that causes the surrounding gas to glow. By contrast, other regions of the nebula contain dark pillars of dust cloaking newborn stars. Eta Carinae can be seen in this image as part of the bright patch of light just above the point of the ‘V’ shape made by the dust clouds.
ETA CARINAES: THE STELLAR SYSTEM THAT LIT UP THE NIGHT SKY
Eta Carinae, located about 7,500 light-years away in the southern constellation of Carina, is famous for a 19th century outburst that briefly made it the second-brightest star in the sky.
This event also ejected a massive hourglass-shaped nebula, but the cause of the eruption remains poorly understood.
The system contains a pair of massive stars whose eccentric orbits bring them unusually close every 5.5 years.
The stars contain 90 and 30 times the mass of our Sun and pass 140 million miles (225 million kilometers) apart at their closest approach — about the average distance separating Mars and the Sun.
Eta Carinae can be seen in the image above as part of the bright patch of light just above the point of the ‘V’ shape made by the dust clouds.
‘The massive stars in the interior of this cosmic bubble emit intense radiation that causes the surrounding gas to glow, while other regions of the nebula contain dark pillars of dust cloaking newborn stars,’ European Southern Observatory experts say.
‘There’s a battle raging between stars and dust in the Carina Nebula, and the newly formed stars are winning – they produce high-energy radiation and stellar winds which evaporate and disperse the dusty stellar nurseries in which they formed.’
Spanning over 300 light-years, the Carina Nebula is one of the Milky Way’s largest star-forming regions and is easily visible to the unaided eye under dark skies.
It lies 60 degrees below the celestial equator, so is visible only from the Southern Hemisphere.
Within this intriguing nebula, Eta Carinae takes pride of place as the most peculiar star system.
This stellar behemoth – a curious form of stellar binary – is the most energetic star system in this region and was one of the brightest objects in the sky in the 1830s.
It has since faded dramatically and is reaching the end of its life, but remains one of the most massive and luminous star systems in the Milky Way.
Eta Carinae can be seen in this image as part of the bright patch of light just above the point of the ‘V’ shape made by the dust clouds. Directly to the right of Eta Carinae is the relatively small Keyhole Nebula – a small, dense cloud of cold molecules and gas within the Carina Nebula – which hosts several massive stars, and whose appearance has also changed drastically over recent centuries.
The Carina Nebula was discovered from the Cape of Good Hope by Nicolas Louis de Lacaille in the 1750s and a huge number of images have been taken of it since then.
But VISTA — the Visible and Infrared Survey Telescope for Astronomy – adds an unprecedentedly detailed view over a large area; its infrared vision is perfect for revealing the agglomerations of young stars hidden within the dusty material snaking through the Carina Nebula.
In 2014, VISTA was used to pinpoint nearly five million individual sources of infrared light within this nebula, revealing the vast extent of this stellar breeding ground.
VISTA is the world’s largest infrared telescope dedicated to surveys and its large mirror, wide field of view and exquisitely sensitive detectors enable astronomers to unveil a completely new view of the southern sky.
Last year a NASA study found Eta Carinaes, which is 7,500 light-years away, accelerates particles to such high energies some of them reach Earth as cosmic rays.
The star system consists of two huge stars orbiting each other that are so bright and massive that the radiation they produce rips off their surfaces and spews them into space at speeds comparable to the speed of light.
‘We know the blast waves of exploded stars can accelerate cosmic ray particles to speeds comparable to that of light, an incredible energy boost,’ said Kenji Hamaguchi, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the lead author of the study., which used data from NASA’s NuSTAR space telescope.
‘Similar processes must occur in other extreme environments.
‘Our analysis indicates Eta Carinae is one of them.’
Astronomers know that cosmic rays with energies greater than 1 billion electron volts (eV) come to us from beyond our solar system.
But because these particles — electrons, protons and atomic nuclei — all carry an electrical charge, they veer off course whenever they encounter magnetic fields.
This scrambles their paths and masks their origins.
Eta Carinae shines in X-rays in this image from NASA’s Chandra X-ray Observatory. The colors indicate different energies. Red spans 300 to 1,000 electron volts (eV), green ranges from 1,000 to 3,000 eV and blue covers 3,000 to 10,000 eV. For comparison, the energy of visible light is about 2 to 3 eV. The NuSTAR detection shows that shock waves in the wind collision zone accelerate charged particles like electrons and protons to near the speed of light. Some of these may reach Earth, where they will be detected as cosmic ray particles.
‘Both of Eta Carinae’s stars drive powerful outflows called stellar winds,’ said team member Michael Corcoran, also at Goddard.
‘Where these winds clash changes during the orbital cycle, which produces a periodic signal in low-energy X-rays we’ve been tracking for more than two decades.’
NASA’s Fermi Gamma-ray Space Telescope also observes a change in gamma rays — light packing far more energy than X-rays — from a source in the direction of Eta Carinae.
But Fermi’s vision isn’t as sharp as X-ray telescopes, so astronomers couldn’t confirm the connection.
To bridge the gap between low-energy X-ray monitoring and Fermi observations, Hamaguchi and his colleagues turned to NuSTAR.
Launched in 2012, NuSTAR can focus X-rays of much greater energy than any previous telescope.
Using both newly taken and archival data, the team examined NuSTAR observations acquired between March 2014 and June 2016, along with lower-energy X-ray observations from the European Space Agency’s XMM-Newton satellite over the same period.
Eta Carinae’s low-energy, or soft, X-rays come from gas at the interface of the colliding stellar winds, where temperatures exceed 70 million degrees Fahrenheit (40 million degrees Celsius).
Previous studies have found an area between the two stars where high velocity stellar winds, travelling up to ten million kilometres (6.2 million miles) an hour, are colliding.
Eta Carinae’s low-energy, or soft, X-rays come from gas at the interface of the colliding stellar winds, where temperatures exceed 70 million degrees Fahrenheit (40 million degrees Celsius)
But NuSTAR detects a source emitting X-rays above 30,000 eV, some three times higher than can be explained by shock waves in the colliding winds.
For comparison, the energy of visible light ranges from about 2 to 3 eV.
The team’s analysis, presented in a paper published on Monday, July 2, in Nature Astronomy, shows that these ‘hard’ X-rays vary with the binary orbital period and show a similar pattern of energy output as the gamma rays observed by Fermi.
The researchers say that the best explanation for both the hard X-ray and the gamma-ray emission is electrons accelerated in violent shock waves along the boundary of the colliding stellar winds.
Some of the superfast electrons, as well as other accelerated particles, must escape the system and perhaps some eventually wander to Earth, where they may be detected as cosmic rays
The X-rays detected by NuSTAR and the gamma rays detected by Fermi arise from starlight given a huge energy boost by interactions with these electrons.
Some of the superfast electrons, as well as other accelerated particles, must escape the system and perhaps some eventually wander to Earth, where they may be detected as cosmic rays.
‘We’ve known for some time that the region around Eta Carinae is the source of energetic emission in high-energy X-rays and gamma rays’, said Fiona Harrison, the principal investigator of NuSTAR and a professor of astronomy at Caltech in Pasadena, California.
‘But until NuSTAR was able to pinpoint the radiation, show it comes from the binary and study its properties in detail, the origin was mysterious.’