New planet changes view of universe
By Amanda Jermyn



With the exciting new discovery of the Earth-like planet, Proxima b, in our own backyard the stuff of science fiction dreams might just possibly come true. While many Earth-sized exoplanets have recently been discovered, particularly by NASAís Kepler mission, this latest discovery inspires our imagination because, in astronomical terms, it is so close. It orbits Proxima Centauri, the star nearest to our solar system, only 4.22 light years from Earth. Itís thought to be a rocky planet, just slightly larger than Earth. Whatís more, it lies in the Goldilocks zone, where it is not too hot and not too cold for liquid water to exist. And if liquid water can exist so, potentially could life.

Proxima b is only 4.6 million miles from the red dwarf star it orbits, about 5% the distance between the Earth and the sun, so you might think it would be too hot for life. However, as a red dwarf, this star is much smaller and much cooler than our sun, making the temperature just about right to support liquid water.

This red dwarf star, Proxima Centauri, is part of the Alpha Centauri star system, containing two much larger, brighter stars, as well. The planet has not been seen directly but was discovered by observing through telescopes the wobble of its star caused by the gravitational pull of the orbiting planet. The size of the wobbles tells us that Proxima b is at least 1.3 times the mass of Earth, though it could be larger in size than our planet, and the frequency of the wobbles tells us that it orbits its star every 11.3 days, compared to Earthís one year to orbit the sun.

Because Proxima b orbits so close to its star it is probably tidally locked, meaning that the starís gravitational pull makes one side always face the star while the other side is always in darkness, just like our moon. This makes for more extreme temperatures, which is not such good news for life, though it doesnít necessarily preclude it. The planetís proximity to its star also exposes it to way more radiation than we receive on Earth, which is also not good for life, though life forms might still thrive underground. Its close orbit of a red dwarf also means the sky is likely to be orange or red rather than blue.

So even though it appears that Proxima b has a lot in common with Earth, it is likely to be an alien world in many ways. And thereís a lot about it that remains a mystery. We donít know if it formed in its current position or started out farther out and migrated inward, closer to its star. Itís also unclear if it really does have water or an atmosphere, although both seem likely. We also donít know if it has a magnetic field like we have that could protect life from the starís harmful radiation. Even if conditions there might be conducive to life, that doesnít mean it exists, nor that it ever did. And if it does exist, would it be in a form that we might recognize? We know that even here on Earth life exists in so many forms, and under such varied conditions, so itís quite possible that in alien worlds it might be vastly different.

The challenge will be to find out. Even though Proxima b is our closest known planet outside the solar system it is still about 25 trillion miles away. Any spacecraft traveling at the speed of NASAís New Horizons probe, currently our fastest craft, would take about 78,000 years to get there. This nixes any prospects of Earthlings finding refuge there should anything bad befall our planet. However, there is hope, at least for finding out more about this newly discovered planet. While current telescopes canít directly view Proxima b, those still in development may be able to do so. There is hope too in the Breakthrough Starshot project, recently announced by Stephen Hawking and other top scientists, which plans to send hundreds of tiny light-powered space probes out into space, traveling at about one fifth the speed of light, to take and send photos back to Earth. Given its relative closeness, Proxima b provides a tantalizing new target for this project. Even so, such a robotic probe would likely take about 20 years to get there, with another four years for the photos to come back. Though this time line may seem far off in the future, some of us here today may still be alive to learn of its discoveries.

One of the main reasons Proxima b captures our imagination is its closeness to Earth, with the prospect of revealing its secrets some time in the near future. Finding life on another planet would be huge. If it turned out to be similar to life on Earth, this could enhance our understanding of the origins of life and the laws governing its evolution, and if it turned out to be very different, this might challenge our concept of life itself. Either way, it would change the way we view the universe forever.

Join the Springfield Stars Club on Tuesday, September 27th at 7:00pm at the Springfield Science Museum for a talk by Jim Zebrowski on ďThe Real Martian: Earth Explores the Red Planet!Ē Jim will provide a short history of our fascination with Mars and its exploration by orbiting spacecraft and rovers. He will also compare the scientific view of the planet to the Hollywood version portrayed in the movie ďThe Martian.Ē Jim is a Solar System Ambassador for NASAís Jet Propulsion Laboratory and President of the Aldrich Astronomical Society in Paxton, MA. He is active in astronomy outreach and education. Refreshments will be served, and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per non-member.