The first planet that orbits a star other than the Sun, 51 Pegasi b, was discovered in October 1995. Nobody could have imagined it then, but since that first discovery and in just a couple of decades, astronomers have detected more than 5,200 worlds outside the borders of the Solar System -known as exoplanets-. An incredible figure that will undoubtedly continue to grow at a good pace. What is most exciting is that among all of them some are considered potentially habitable, at the right distance from their star to harbor liquid water. And within that promising group could be the jackpot, the true twin of the Earth. Small, rocky and tempered by a sun like ours. A place where, one way or another, life is able to make its way. But finding him, if he exists, is not easy.
Perhaps it will be achieved by a space telescope called, due to size and ambition, to succeed James Webb, the 6.5-meter ‘time machine’ launched into space more than a year ago. It is called the Habitable Worlds Observatory (HWO) and its objective is to search for traces of life on planets similar to ours. It was presented by NASA at a recent meeting of the American Astronomical Society and, at the moment, it is barely a sketch on paper. Its requirements will be studied this year by an interdisciplinary team and it could be ready by the early 2040s.
“The HWO is scheduled to observe in the optical, ultraviolet, and near-infrared spectra. It will be segmented and about 6 meters in diameter,” Roser Juanola-Parramon, a scientist at the Laboratory of Exoplanets and Stellar Astrophysics at NASA’s Goddard Space Flight Center, describes to this newspaper. Like Webb, it will sit at L2, a gravitational balance point 1.5 million kilometers from Earth.
“But unlike the Webb, it will be designed for maintenance and robotic updates for future missions in orbit, which will extend the life of the telescope and its instruments,” says the researcher. It is the same as, at the time, was done with the veteran Hubble Space Telescope.
THE HWO might look like this NASA project, Luvoir B
Little else is known about the HWO, not even its appearance. Nor does it have an assigned budget, but NASA intends to avoid a repeat of what happened with the James Webb, with which cost overruns (it shot up to 10,000 million dollars) and delays accumulated. For this reason, he has proposed a more conservative approach. The telescope will take advantage of and adapt technologies already developed, such as Webb’s segmented mirror; or in development, such as the Nancy Grace Roman coronagraph, a 2.4-meter space telescope that will search for dark energy and exoplanets and whose launch is expected by the end of this decade. This instrument consists of an optical system that blocks starlight so that light from exoplanets can be observed.
Photos from 25 worlds
Since it will work with optical light, which has shorter wavelengths than Webb’s infrared light, the HWO will need much tighter control over the shape of its mirror. And the coronagraph will have to be even better than Roman’s, which can block light from a star 100 million times brighter than its planet. It will have to do the same for stars 10 billion times brighter.
Once operational, the telescope’s main objectives will be to detect and characterize approximately 25 planets located in the habitable zones of a hundred nearby stars and to search for biological signatures (evidence of life). It is the minimum necessary to confirm statistically if life is common in our galaxy, the Milky Way. In addition, you will study our cosmic origins, the physics of the universe, and the diversity of worlds inside and outside the Solar System.
For Juanola-Parramon, the construction of this new observatory is necessary because it is “the only one that will allow us to answer questions such as: Are we alone in the universe? Are there planets similar to Earth? To do this, we must “characterize them (the discovered worlds), study their atmospheres and detect biological signatures.”
So far, astronomers have been able to understand the atmospheres of some planets, but they are gaseous worlds that revolve around very small stars, M dwarfs that are very different from the Sun. With these characteristics, it is unlikely that they could support life. At least not as we know it.
The great desire of astronomers “is to be able to have the image of a terrestrial-type planet orbiting a star similar to the Sun. Because until now, the only life we know of has developed on Earth. It is the only thing we can compare with”, says Pedro J. Amado, from the Institute of Astrophysics of Andalusia (IAA-CSIC). “But to this day there is no instrument built or under construction that can do it. Hence the importance of the HWO », he adds.
The researcher explains the difficulties in finding a habitable planet: «The smaller the planet, the smaller its atmosphere and the brighter its star, the more difficult it is to observe it. It’s like putting a two-watt LED bulb next to a million stadium lights. You have to nullify all that light to detect it, something the HWO will be capable of.