Rectangular space telescope much better suited for the search for a second Earth

With a space telescope whose primary mirror is not round but rectangular, we could find half of all probably existing Earth-like exoplanets up to 30 light years away in less than four years using technology that is already available. At least that is what a US research team claims in a recently published scientific article in which the concept is presented in detail. The group explains that an instrument with a 20-meter-long and only one meter wide primary mirror would not just fit into existing rockets. It should also find dozens of Earth-like exoplanets in our cosmic neighborhood and whether there is ozone in their atmosphere. Such evidence would then be a strong indication of photosynthesis and thus extraterrestrial life.

Feasible with available technology

As research leader Heidi Newberg from Rensselaer Polytechnic Institute in the US state of New York explains in an accompanying article, sun-like stars at comparatively close distances are currently of particular interest in the search for extraterrestrial life. On the one hand, only these offer conditions comparable to those in our solar system, and on the other, only these could be visited in a reasonable amount of time. At the same time, however, technology is nowhere near ready to search for exoplanets that resemble our Earth and could therefore enable the emergence of Earth-like life using methods that have been proposed or even tested to date. However, this is precisely not the case for her team's proposal.

The article shows that a device roughly the size of the James Webb Space Telescope could certainly find Earth-like exoplanets around nearby stars if the mirror is not round. The resolution achieved over the long edge is sufficient to resolve such a celestial body separately from its star if both are aligned in parallel. The rectangular mirror could also be rotated for this purpose. In principle, a space telescope set up in this way would be able to find half of all Earth-like exoplanets around nearby stars in just three and a half years, the research team claims. These could then be studied in more detail.

Newberg admits that the design needs to be further developed and optimized before the promised performance is actually confirmed. However, there are no obvious requirements for the proposed technology that would require intensive technical development work, as is the case with alternative proposals. She is referring in particular to the idea of increasing the mirror surface of a space telescope by using several synchronously flying satellites, for example. The positioning precision required for this cannot be achieved at present. This also applies to ideas of blocking the light of a star for an instrument using a precisely flying satellite so that a much fainter exoplanet can be detected.

Search for Earth 2.0

The rectangular space telescope could be launched into space using existing rockets and soon search for a second Earth, the team believes. Using methods that have also already been proposed, probes could even be sent to it, which could arrive there at least in the course of a human lifetime. The scientific article with the calculations for the concept has now been published in the journal Frontiers in Astronomy and Space Sciences, where the accompanying article can also be found. The team adds that the concept is also suitable for other observations in which two closely spaced point sources have to be distinguished. The only disadvantages are longer exposure times and more complicated data analysis.

(mho)