Tag Archives: Eta Carinae

Eta Carinae’s next big show

Astronomers are gearing up to observe the next binary fly-by of Eta Carinae’s companion star over the next few weeks.

A binary system, η Carinae has two stars that swing past one another every 5.5 years. The bigger star — some 90 times the mass of the Sun — is incredibly unstable, always seemingly on the verge of blowing up. When the smaller companion star makes its closest approach to the primary star, as is happening now, the interaction between the two triggers violent changes in the high-energy radiation pouring out of the system.

Astronomers are watching the show in the hope of learning what drives this enigmatic system. In the 1840s, η Carinae had a mysterious eruption; in recent decades, it has again brightened unexpectedly. “The star is in an awfully deranged state, and no one knows why,” says Kris Davidson, an astronomer at the University of Minnesota in Minneapolis.

Eta Carinae is also famous because it was one of the first objects imaged by Hubble after its repair in 1993, and was thus the first stellar explosion ever caught on camera in a visually sharp and clear manner. (See my book The Universe in a Mirror for that fascinating story.)

The coming blindness of astronomy

Fried Egg Nebula

The European Southern Observatory today released this infrared image today of what astronomers have named the Fried Egg Nebula. Taken by the Very Large Telescope in Chile, the picture shows the concentric dust shells surrounding a post-red supergiant star, thought to be transitioning to the next stage of stellar evolution called a yellow hypergiant. As the press release explains,

The monster star, known to astronomers as IRAS 17163-3907, has a diameter about a thousand times bigger than our Sun. At a distance of about 13 000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500 000 times more brightly than the Sun. . . . If the Fried Egg Nebula were placed in the centre of the Solar System the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface. The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune. The outer shell has a radius of 10 000 times the distance from the Earth to the Sun.

Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events — this star has ejected four times the mass of the Sun in just a few hundred years. The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.

According to the science paper [pdf] describing this research, the stage of yellow hypergiants is a preliminary to the star evolving into a luminous blue variable, of which Eta Carinae is the most famous. In this next stage a star is thought to have a good chance of going supernova.

Though this image is truely spectacular, taken by a ground-based telescope of a star 13,000 light years away, what I find most significant about this image is its fuzziness. It reminds me of the kind of images astronomers and the public routinely accepted as the best possible, before the launch of the Hubble Space Telescope.
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