Is anyone out there? HDST could tell us

A futuristic project for the heir to Hubble and the James Webb: a super-telescope with a mirror 12 meters in diameter to be placed in orbit in the thirties. For now little more than a dream, however, described in detail in a report just published by a group of USA astronomers.
Take a group of astronomers of the most quoted of the United States. Put them around a table. And ask him to design the telescope of their dreams. It’s more or less what he did the AURA, the Association of Universities for Research in Astronomy. The result, published last Monday, is a relationship, midway between vision and reality, describing the potential heir to Hubble and JWST. A relationship that has time for the future and the conditional way. A relationship that begins quoting the prediction of an astrophysicist of Italian descent, the Nobel Riccardo Coats.


Credit: STScI

In the next century – provided Coats in 1997 – humanity will have the tools to “study the evolution of the Universe as well as to relate causal physical conditions during the Big Bang with the development of RNA and DNA.” Well, the next century is now. “The time is ripe to raise the challenge,” write the authors of “From Cosmic Birth to Living Earth”. And the instrument that would entrust the ambitious task already has a name: High Definition Space Telescope (HDST).
Grandson designated anchor unsurpassed Hubble Space Telescope (HST) and son of the James Webb (JWST, whose launch is planned for 2018), the visionary project promises, of course, features to embarrass even the most optimistic among the space engineers. Let’s look at a quick identikit. First of all, the mirror, which in this case is practically all: an eye composite (honeycomb, as for JWST) formed by segments 54, to be deployed at the destination until reaching 12 meters in diameter – double that of the already huge James Webb and five times to Hubble. A collecting area that are the envy at the best ground-based telescopes today, then, but it placed in the second Lagrange point (L2) that – already half of WMAP, Planck, Herschel and GAIA – has long become a paradise space astronomy. With all the ensuing problems, chief among them the burden: how to ship a mirror monster like that in a million and a half km from the Earth is, in fact, among the many aspects that border the HDST in the realm of desire, that to today more insurmountable.


Credit: C. Godfrey/Space Telescope Science Institute

Significantly larger than JWST, then, but also different in terms of sensitivity to the “colors”. Size aside, in fact, from the point of view of the coverage of the electromagnetic spectrum HDST promises to be more like “grandfather Hubble” than “father James Webb” so sensitive to visible and ultraviolet light, while JWST focuses on the infrareds . A choice with at least two important consequences: life expectancy and scientific objectives. As to the first, it is obvious: nothing infrared means no need for cryogenic liquids, destined sooner or later to run out. Being able to operate at room temperature, HDST may work for several years.
And the scientific goals? Given that a monster like you can ask virtually everything an astronomer has never dared to ask, if the sensitivity of the infrared James Webb makes it particularly suited to the study of stars and galaxies in the young, the ground of election HDST celestial bodies are small and relatively close: exoplanets.


Credit: D. Ceverino, C. Moody, G. Snyder, Z. Levay / STScI

In particular, those that orbit at about 600 stars that are within a hundred light-years away. One can estimate that has left the NASA Kepler probe, about one in ten of these stars could host a planet – with a size comparable to our – in “habitable zone”: that is to say, where the temperature is compatible with life so as we know it. In other words, a few dozen potential “sisters” of the Earth. Well, analyzing the atmosphere HDST might be able to tell us if indeed host some form of life. Could, in the conditional. And not just at the cost of balance: at least $ 10 billion, roughly the amount of the package of reforms that Greece is negotiating at this time. Moreover, to understand whether we are alone in the universe is one of those missions that no amount of money, even more stratospheric, will ever convince us to abandon.

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