A new study has projected that a future NASA telescope could be capable of discovering up to 1,400 new worlds, some of which may boast a mass comparable to that of the Earth. The orbital telescope, which has been nicknamed WFIRST, will build on the legacy of earlier missions to answer fundamental questions surrounding the nature of the universe, and potentially aide in the search for extraterrestrial life.
The Wide Field Infrared Survey Telescope (WFIRST) is a future flagship mission that is expected to follow in the wake of the much-delayed James Webb Space Telescope (JWST).
NASA committed to go ahead with the project back in February 2016. In May 2018, WFIRST passed an important evaluation from the Agency Program Management Council, ushering the endeavor into the preliminary design phase.
The paper telescope has a budget of US$3.2 billion, and has a planned launch date hovering somewhere in the mid-2020s. However, if the development woes of the JWST has taught us anything, its that the budgets of ambitious flagship projects are likely to dramatically overrun, and early launch estimates can in hindsight be wildly aspirational.
WFIRST is being designed with two key objectives in mind. The telescope will make detailed observations of the cosmos in an attempt to glean the nature of dark energy, the enigmatic pressure that some astronomers believe to be the driving force behind the expansion of the universe.
The observatory will also be tasked with finding previously unknown planets, many of which, it is expected, will orbit significantly further from their parent stars than most alien worlds discovered to date.
In this sense, the project will build on the exoplanet hunting foundations laid down by the Kepler Space Telescope, which, after nine and a half years of exploring the universe, was finally decommissioned in October 2018, having effectively run out of fuel.
"Kepler began the search by looking for planets that orbit their stars closer than the Earth is to our Sun," said Matthew Penny, a postdoctoral researcher in The Ohio State University's Department of Astronomy and lead author of the new study. "WFIRST will complete it by finding planets with larger orbits."
The telescope is designed to locate these distant worlds using a technique called gravitational microlensing. This essentially involves watching for a bending or magnification of the light emitted from a distant star resulting from the gravitational influence of an orbiting exoplanet as it passes between the stellar body and the watching telescope.
Microlensing was first predicted by Albert Einstein's General Theory of Relativity.
By analyzing the light from the background source, astronomers can determine the mass of the orbiting world, and also the distance at which it orbits its star. However, microlensing events are very rare, sometimes occurring for only a few hours every few million years per exoplanet.
To catch as many microlensing events as possible, WFIRST will stare unblinkingly at 100 million stars at the heart of the Milky Way for long periods of time.
Should WFIRST be given the money and time needed to transition from the drawing board to space, the telescope would be capable of scanning a 2 square degree section of the sky, with a resolution surpassing that of any similar mission. This would allow it to scan a galaxy 100 times faster than the Hubble Space Telescope.
"Although it's a small fraction of the sky, it's huge compared to what other space telescopes can do," comments Penny. "It's WFIRST's unique combination – both a wide field of view and a high resolution – that make it so powerful for microlensing planet searches. Previous space telescopes, including Hubble and James Webb, have had to choose one or the other."
According to the authors of the newly-published research, their work represents the most detailed estimate to date of the yield of exoplanet discoveries that we could expect from WFIRST. The team used a suite of simulations that took into account a plethora of factors, including the full range of proposed WFIRST designs submitted to date, to draw their conclusions.
Since astronomers began their search 3,917 confirmed exoplanets have been discovered, according to the NASA Exoplanet Archive. The new study estimates that WFIRST could identify a further 1,400 worlds orbiting stars beyond our Sun, including roughly 100 with a mass similar to or lower than that of the Earth.
An analysis of the worlds discovered through microlensing could reveal, for example, how often different types of exoplanets are formed. Using this information astronomers could shed light on just how rare our solar system is. This has implications for the ongoing search for extraterrestrial life, as our home system is the only one known to be capable of hosting life.
The research has been published in the Astrophysical Journal Supplement Series.
Source: The Ohio State University
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