The detection of signs of life on distant exoplanets is hampered by errors that arise due to the thermal expansion of the telescopes used to study them. However, the use of a new alloy could improve the situation.
Telescopes and materials
A new development in materials science may help in the study of signs of life on exoplanets. At first glance, there seems to be no connection between these two industries. However, in reality, there is a connection. We are talking about the design of telescopes that collect light passing through the atmospheres of exoplanets.
By studying it, it is possible to find signs of certain substances called biomarkers, which either contribute to the processes involving living beings or are products of those processes themselves. However, the proportion of such light in the total radiation flux is negligible, so telescopes have to be fantastically accurate instruments.
And ultramodern electronics alone are not enough for this. The telescope mirror must remain stable. Scientists require that fluctuations in its shape and size not exceed 10 picometers over a period of 10 hours, which is only 1/10 of the diameter of an atom.
The main obstacle to achieving these indicators is temperature deformation of the mirror. No matter how perfect the material is, it still expands when heated, which introduces significant errors. And therefore, the development of new alloys may be a way out of the situation.
Negative expansion coefficient
And this is where alloys developed by ALLVAR, commissioned and financially and technically supported by NASA, can help. Their main feature is negative thermal expansion, meaning that they contract when the temperature rises and expand when it falls.
For example, the ALLVAR 30 alloy has properties under which a 1 m sample will contract by 0.003 mm when the temperature rises by 1°C. For comparison, under the same conditions, it expands by 0.0023 mm.
Scientists want to integrate ALLVAR 30 into the design of future telescopes so that it compensates for the expansion of conventional materials, and, in general, the thermal stability of even very large mirrors should increase 200 times.
To demonstrate that alloys with negative thermal expansion can provide ultra-stable structures, the ALLVAR team already conducted an experiment in which test structures made of Ti6Al4V alloy were fastened together using their design. It proved the effectiveness of this approach.
Other applications
In addition, a series of tests conducted by NASA Marshall showed that the ultra-stable stands were able to achieve almost zero thermal expansion, corresponding to the mirrors in the above-mentioned analysis. This result means that the mirror’s shape changes by less than 5 nm on average when the temperature changes by 28 K.
In addition to ultra-stable structures, negative thermal expansion alloy technology has improved the performance of passive thermal switches and has been used to eliminate the negative effects of temperature changes on bolted joints and infrared optics.
These applications may influence the technologies used in other NASA missions. For example, these new alloys were integrated into the cryogenic unit of Roman’s coronagraph technology demonstration. By adding washers with negative thermal expansion, it was possible to use pyrolytic graphite thermal tapes for more efficient heat transfer.
According to phys.org
