Have you ever seen arcs and rings in pictures taken by telescopes? When light from a distant object is distorted by a larger object along the same line of sight, these unusual features are caused. The distortion creates a giant lens which magnifies the background light source, allowing astronomy to observe objects embedded within those arcs and rings that are otherwise be too far and dim to see.
A group of researchers are trying to figure out a way to use our Sun as a lens for astronomy. They want to see distant exoplanets and to image an Earth-like exoplanet at a better resolution than the Apollo 8 Earthrise photo.
Slava Turyshev is a physicist at NASA's Jet Propulsion laboratory. The idea is to use the focal region of our own Sun to bend the light from an exoplanet and make it look bigger.
Turyshev said that using a conventional lens with a diameter equal to that of the Sun is similar. It's just figuring out the engineering now that the physics is there.
Turyshev says they could potentially image an Earth-sized exoplanet up to 100 light-years away.
Turyshev said that the SGL concept could rely on a fleet of smaller satellites that would use solar sails to propel it. It would take 25 years to travel 60 billion miles from the center of the universe to the center of the universe, if SGL were to use a gravity assist from the sun.
Turyshev said, "You don't need to fly systems like the size of Voyager, or Galileo, but can use smaller spaceships." You can assemble in space if you need to build a larger one. If we have smaller, multiple spaceships, we can use different means of taking them to space, such as using solar sails to propel them to deep space, or using rideshare opportunities to get to low Earth orbit.
The NASA Innovative Advanced Concepts (NIAC) Program, which funds research on visionary ideas that could transform future missions, believes the SGL concept is sound. One of the few ideas to be funded for all three phases of NIAC backing was the Solar Gravity lens project.
In a paper published in April 2022, Turyshev and Toth show that using technologies that are already available or in active development is feasible and challenging.
Turyshev said that the paper represented realistic sensitivity that could be obtained with the SGL. Under realistic conditions, it is possible to image Earth-like exoplanets in our neighborhood in weeks or months.
In June 2022, the team published a paper discussing the possibility of using the solar sails as starshades.
The Einstein ring on top of the bright solar corona is one of the challenges that Turyshev and Toth wrote about. The solar corona is brighter than the Einstein ring for a target like an Earth-like exoplanet.
The internal coronagraph wouldn't be able to block out this light. It would make it possible for a telescope with a smaller opening to be used. According to the paper, even a 40-centimeter (15.7 inch) telescope is enough to recover a good quality, resolved image of an exo- Earth.
In conjunction with the external starshade, one can extend the observational bandwidth to mid-IR. There is less noise from the solar corona when planets are self-luminous at the mid-infrared wavelength. There are many features of interest for exobiology in this part of the spectrum.
Turyshev said the development was significant and offered strong motivation to study the use of starshades in future SGL missions.
There has always been a lot of discussion about the first steps outside of the solar system. Multiple technology efforts could come together to make it possible, if the SGL concept is any indication.
"I think we are at the beginning of an exciting period where multiple efforts are coming together in the space industry, such as more economical access to space, small resilient spacecraft, and distributed capabilities where costs are now practical to bring exciting science." Within the lifetime of the present generation, we have the chance to ask ourselves if we are alone. The challenge is how to make use of the technology, accelerate their development, justify the steps to test it and then really use it.
The artist concept of many exoplanets. The credit is given to NASA.
There is a NASA/NIAC article on the project.
The Planetary Society wrote an article.
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