Thu. Mar 23rd, 2023
The view of Alpha Centauri A & B from the night sky in Chile.  (Bright stars on the top left of the mountain)
Enlarge / The view of Alpha Centauri A & B from the night sky in Chile. (Bright stars on the top left of the mountain)


The galaxy closest to the sun, Alpha Centauri, has been all the rage after the discovery of an Earth-sized world in the habitable zone around the smallest of its three stars, Proxima Centauri. However, scientists are just as eager to learn more about the planetary systems around α Centauri’s two larger sun-like stars, α Centauri A and B. Those systems could provide an environment even more favorable for an Earth-like planet.

While NASA has plans to eventually develop optical telescopes that could potentially image planets around these stars, some scientists say we shouldn’t wait that long. In addition, these scientists say that with a modest-sized telescope, we could begin searching for Earth-like worlds around Centauri A and B by the end of the decade. To that end, several organizations are planning to announce a private non-profit initiative to do just that. The project, titled “Project Blue,” will be announced on Tuesday.

Project Blue takes its name from the famous Pale Blue Dot image taken by Voyager in 1990, when the probe was about 6 billion km from Earth. Our planet filled only a single blue pixel against the vast, black, seemingly endless sky. Project Blue aims to capture such an image of one or more Earth-sized planets in the habitable zone around α Centauri A or B.

“We feel the time is right [when] there is a confluence of scientific impact and technology that is rapidly maturing,” said John Morse, CEO of the BoldlyGo Institute, which is a co-sponsor of the initiative with Mission Centaur. “We won’t resolve planetary features, but we think we have a good chance of seeing something like a light blue dot.”

Find a firefly next to a lighthouse

In an interview with Ars, Morse said he believes Project Blue can be realized for comfortably under $50 million. His goal is to reduce total costs to less than half of that. This price includes both the construction of the telescope and its launch by the end of the decade. He plans to launch his telescope as a “ride-share” on a larger rocket or on one of the smaller, dedicated microsatellite launchers under development.

Morse said Project Blue will use an “all of the above” fundraising strategy, starting with crowdfunding to start meaningful engineering work on the telescope’s design. In addition, the organization will also seek larger donations, starting with the donor network that has supported the Boldly Go Institute. The organization also seeks in-kind contributions from partners to keep costs down.

Image of Voyager's light blue dot.

Image of Voyager’s light blue dot.


Based on a number of technical studies, such as this one, Project Blue believes it can obtain sufficient resolution to image a planet around one of the α Centauri stars with a 50 cm or smaller telescope (the primary mirror of the Hubble Space Telescope is 2.4 meters).

Unlike the Kepler Space Telescope, which monitored 100,000 stars and looked for dimming light to determine when planets passed in front of their parent stars, Project Blue uses high-contrast imaging. Engineering studies have shown that, with an advanced coronagraph to block light from the stars and data processing techniques, such a telescope could reject light from the two stars at a rate of 10 billion to one. This is enough to allow direct imaging of a planet with observations made over several years. Put another way, such an observation system is comparable to detecting a firefly next to a lighthouse 10 miles away.

A bit of a gamble

Unfortunately, the telescope won’t have the power to resolve the Earth-sized planet around the red dwarf star Proxima Centauri, which is much cooler than the other two stars in the system. The world, Proxima b, orbits its star every 11.2 days at a distance of about 7.5 million km, about 5 percent of the distance Earth is from the sun.

Because that world is so close to its star, it is impossible for a telescope with a coronagraph, on the scale considered, to separate the planet’s light from its star. However, Morse said he believes the discovery of Proxima b has increased public attention to the α Centauri system, which should help Project Blue gain attention.

This is, of course, a bit of a guess. The planetary scientists don’t actually know if there are Earth-sized worlds lurking around α Centauri A and B in the habitable zones of the two stars. Using a different technique, in which a planet causes a subtle “wobble” on its parent star, astronomers in 2012 identified an Earth-sized world around α Centauri B. But the planet is so close to its star that it is thought to be is a charred star. rocky world.

Nevertheless, Morse said the odds are favorable for the existence of an Earth-like world. The proposed telescope should be able to resolve a world 0.5 to 1.5 times the size of Earth and orbiting within the “habitable zone” of the host star, where theoretically water could be attached to it. the surface could exist. Based on Kepler’s data, with two sun-like stars to search around, Morse said, statistically, the chance of at least one terrestrial planet entering the habitable zone is about 80 percent. With enough water on the surface, the planet would appear blue in any visible light created. And what a sight that would be.

By akfire1

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