The light of a parent star is a bit of a double-edged sword for exoplanet hunters. Dips in this light as the orbiting bodies pass in front of their stars have revealed the presence of thousands of exoplanets, but at the same time the blinding light makes it impossible to directly photograph the comparably fainter body ... well, without some highly advanced technology, that is. An initiative launched this week called Project Blue has outlined plans for a telescope designed specifically to overcome this problem. By the end of this decade, the group plans to launch it into orbit and point it at the Alpha Centauri star system, with the goal of directly imaging habitable planets nearby to our very own Earth for the first time.
The Alpha Centauri system generated a bit of buzz recently when astronomers discovered a potentially habitable planet circling its smallest star, the red dwarf Proxima Centauri, just four short light-years away. But the two larger stars in the system are also relevant to our search for extraterrestrial life due to their similarities to our own star, and it is here that the Project Blue team will be directing its gaze.
By scanning the habitable zones around Alpha Centauri A and B, the team is gunning for its own "Pale Blue Dot" moment, the iconic photograph taken by the Voyager spacecraft in 1990 that shows our planet Earth as a tiny speck amidst the vastness of space. If an exoplanet in the habitable zone happens to feature an atmosphere and liquid water on the surface, then it may just pop its pale blue body into frame for an equally dramatic and significant photo.
But detecting an Earth-like exoplanet next to its parent star has been compared to spotting a firefly next to a lighthouse from 10 miles away (16 km). It would take some seriously sophisticated technology to suppress the light of the parent star in just the right way that the planet could be directly observed in reflected starlight, but the Project Blue team believes that this technology's moment is about to arrive.
Because of Alpha Centauri's proximity, Project Blue's compact space telescope will use a 45-50 cm aperture (Hubble's is 2.4 m, for comparison). It will also depend on multi-star wavefront control and advanced post-processing techniques to spot these planets, but key to its success is a little something called a coronagraph. These are instruments designed to block out light emanating from the sun's surface, and have been under development for use in space missions since the 1990's.
Studies, field tests and test flights have shown that the technology will soon be mature enough to be launched into orbit, according to Jon Morse, CEO of non-profit BoldlyGo which is one of the organizations behind Project Blue. He tells us that coronagraphs are now capable of achieving the necessary contrast and can operate with enough stability to directly image exoplanets around nearby stars, and that a key component called a deformable mirror, which helps to sharpen the images, is now capable of functioning in space.
This means that the coronagraph launched on Project Blue's telescope could potentially fill holes in our vision left by Kepler and Hubble, which lack the contrasting ability to directly image orbiting planets, even those in the relatively nearby Alpha Centauri system.
The James Webb space telescope to be launched in 2018 will have some coronagraphic capabilities at infrared wavelengths that should enable it to image gas giants like Jupiter, but it won't have the same deformable mirror technology as Project Blue's telescope. NASA is planning a mission to follow the James Webb Telescope called the Wide Field InfraRed Survey Telescope (WFIRST), which is expected to carry a coronagraph for direct imaging but it is not scheduled to launch until the mid-2020s.
Project Blue aims to launch by the end of this decade and rather than study a variety of interstellar phenomenon, it will focus solely on the Alpha Centauri system and the prospect of habitable planets.
"An important fact is that the Alpha Centauri system contains two stars that are relatively close to each other," Morse tells New Atlas. "The Project Blue coronagraphic camera will be optimized specifically for this special case of needing to suppress the light from both stars in order to see the much fainter planets around either of them."
The two-year intensive study of the neighboring system will see the telescope snap lots of photos, which the team will sift through and use post-processing techniques to shine a light on these very faint bodies. The cost is expected to be less than US$50 million, though Morse tells us that are aiming to pull it off for half of that. The team will spend the remainder of this year finding partners and kicking off fundraising, then move onto design and prototyping next year, ahead of a final build and launch into low-Earth orbit in 2019.
The short animation below shows a render of Project Blue's telescope.
Source: Project Blue