Why This Mission?
We believe a sister Earth could exist not too far from the place we call home, and that our generation has a unique opportunity to discover it. Ten years ago, we didn’t know if planets like Earth were common in the universe. Then NASA’s Kepler mission launched and discovered thousands of rocky planets orbiting stars, some of which are at a distance from their parent star where liquid water could exist on the surface. It’s estimated that there are more Earth-like planets in the universe than people alive today. Taking a picture of one of these rocky worlds orbiting another star is our next big challenge.
Why Alpha Centauri?
Quite simply, we believe Alpha Centauri is the best target for direct imaging an Earth-like planet in coming years.
Alpha Centauri is our closest neighboring solar system at only 4.37 light years away. The close proximity allows us to design a small telescope and keep the mission cost down, making our mission more affordable than a project that would use similar technology to conduct a survey of star systems further away.
Alpha Centauri has two stars (Alpha Cen A and B) similar to our Sun in size, brightness and temperature. This is an incredible opportunity for the Project Blue mission because it increases the likelihood of discovering a planet in a habitable zone.
Alpha Centauri is the focus of many research efforts because of its proximity to Earth. The quest to detect planets around the Alpha Centauri stars has been ongoing and spans the entire range of detection methods including ‘wobble’ (radial velocities, astrometry), photometric and direct imaging techniques. Project Blue is unique in pursuing a dedicated coronagraphic space telescope mission, but is one of numerous efforts seeking to improve on past attempts.
A small, rocky planet was recently discovered in the habitable zone around Proxima Centauri, called Proxima b. Proxima Centauri is the third star in the Alpha Centauri system, though it is much smaller than Alpha Cen A or B. The exoplanet Proxima b was detected indirectly; scientists measured a small ‘wobble’ in the motion of the star due to the gravity of the planet in its orbit. Although Proxima b orbits in the habitable zone of its parent star, the star is such a small, dim star (called a red dwarf) its habitable zone and Proxima b’s orbit are incredibly close — nine times closer than Mercury is to our Sun. This is why Project Blue is not trying to image Proxima b. It would take a much larger telescope to resolve the star from the planet, and not even the largest space telescopes being planned could do so in visible light. But the good news is that we now know that there’s a terrestrial-class planet orbiting one of the stars in the Alpha Centauri system. This makes us optimistic that there could be other rocky planets orbiting Alpha Cen A and B.
The Science & Technology
Science Objective
Directly detect and characterize Earth-like planets in the aCen A&B system.
Science Impact
We aim to provide the scientific community with an instrument capable of investigating the Alpha Centauri system within about 3 years. Any planets Project Blue finds will be excellent potential targets for future large space telescopes being developed by NASA and other space agencies. In particular, if any potentially habitable planets are found, there will be a substantial surge of interest to apply spectroscopic techniques to discern details about the nature of the planets and their atmospheres.
Project Blue will demonstrate and test coronagraph and wavefront technologies similar to ones that could be used on much larger future space telescopes currently being studied by NASA, and thus help to retire technical risks and hone the observing techniques and data processing algorithms for those missions.
The Technology
With advanced optics technology, we’ll use a technique called 'direct imaging' to dim the light from the stars in Alpha Centauri, enabling us to see any surrounding exoplanets. By working in visible light, we hope to gather key details about their composition. Capturing an image of a planet — actually seeing it in visible light — will help us begin to characterize its atmosphere and surface characteristics, especially its potential for oceans.
The ~50-cm (or slightly less than 20-inch) diameter aperture telescope is small enough to fit on a coffee table, but powerful enough to detect a small, rocky exoplanet in the Alpha Centauri system. The challenge is like trying to see a tiny firefly buzzing around two feet from a powerful lighthouse light from 100 miles away. And since Alpha Centauri has two bright stars close to each other, we have to suppress the light of both stars. Our specialized starlight suppression system consists of:
An instrument called a coronagraph to block starlight, using either the Phase Induced Amplitude Apodization (PIAA) or Vector Vortex technique;
A deformable mirror, low-order wavefront sensors, and software control algorithms to manipulate the incoming light and achieve multi-star wavefront control (MSWC); and
Post-processing methods, called Orbital Differential Imaging (ODI), to enhance image contrast.
Such a system, including the MSWC and ODI features, has been proposed and published for suppressing the light from Alpha Centauri A and B simultaneously to detect surrounding exoplanets. In order for the telescope to accomplish such an amazing technical challenge, we have to send it to space, where it can operate outside the distorting effects of Earth’s atmosphere. We’ll launch it on a small commercial rocket and place it into a low-Earth orbit designed to provide stable conditions needed for making such precise measurements.
See our SpaceBites videos with updates on exoplanet science & technology.
“The potential payoff for this mission would be incredibly profound. By directly imaging another planet in the closest star system to our own, Project Blue could gather vital data that would indicate if any planets there are habitable. [...] If [the mission] should prove to be successful, Project Blue would allow for some of the greatest scientific finds in history.”