The coming blindness of astronomy


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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.

The Very Large Telescope (VLT) is actually four 8-meter telescopes which can either be used separately or together, in which case the combined resolution mimics the equivalent of a 16-meter telescope. Because of this the telescope can see more deeply and in more detail than any other previously-built ground-based telescope. In fact, Hubble itself could not resolve the concentric shells that surround this supergiant star, the space telescope configured in such a way to make it unable to see them.

Yet, the VLT image is still fuzzy. It is also an infrared image, a wavelength that the human eye cannot see. To produce it the astronomers created a false-color image in visible light. This is not how the star would actually appear to our eyes.

Sadly, this is the future for astronomy. Back in the late-1990s, the astronomical community made the political decision to forgo replacing the Hubble Space Telescope with a bigger optical space telescope and instead decided to build the infrared James Webb Space Telescope. When (or should I say if?) the Webb telescope is completed and launched, it will have a single (though segmented) mirror 16-meters across, allowing it to see even more clearly than VLT. Moreover, it will be in space, and will therefore not have to peer through the cloudy, wavering atmosphere.

Nonetheless, it will look at space through infrared eyes. Hubble, the only large optical general observatory in space, is already more than twenty years old, and will almost certainly fail sometime in the next decade or so. There are no plans to replace it, and even if a plan was approved today (an unlikely possibility considering the state of the federal budget), it would still take about ten to twenty years to design, build, and launch that replacement. And though astronomers are building several ground-based telescopes far larger than VLT, all of them will still be on the ground, looking up through the hazy atmosphere. Even using adaptive optics, the images will not be as clear or as accurate as those produced by Hubble. And they will be infrared images, as the shorter wavelengths of optical light require so much computer power that adaptive optics is not yet capable of correcting its fuzziness.

Thus, when Hubble goes, we will no longer have an optical telescope in space, capable of producing sharp visual images of the universe. We will return to the days of yore (my youth), when astronomical images showed us fuzzy blobs that hinted at grand beauty, but refused to show it.

I find this situation appalling tragic. I also expect it will take the next generation to solve it, by the very people denied the view we have been blessed to have from Hubble for the past two decades.

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