Small planets sometimes generate gargantuan buzz. For weeks, eager media outlets have been reporting rumors that a potentially habitable planet is circling the star closest to our sun, a red dwarf called Proxima Centauri.
Now, finally, astronomers are ready to unveil this alien world.
Observations made with a telescope in Chile have indeed revealed a planet about as massive as Earth that orbits Proxima Centauri, which is a cosmic walk to the corner store at just 4.24 light-years away. And if conditions are right, the planet is in an orbit that’s warm enough for liquid water to survive on its surface.
Illuminated by a pale reddish light, the world orbits the smallest star in a triple system known as Alpha Centauri, which shines in the southern constellation Centaurus.
The Alpha Centauri system, long a wonderland for science fiction authors, is often considered a destination for humanity’s first leap into interstellar space—as well as a potential haven for future civilizations fleeing the inevitable destruction of Earth as we know it.
“A habitable, rocky planet around Proxima would be the most natural location to where our civilization could aspire to move after the sun will die, five billion years from now,” says Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and an adviser to the Breakthrough Starshot project.
Even before today’s announcement, Breakthrough Starshot had announced its plan to send tiny spacecraft to the Alpha Centauri system later this century. But don’t expect any postcards from the new planet anytime soon: It will take more than 20 years for a spacecraft traveling at a monstrous 20 percent of the speed of light to reach Proxima Centauri, and another 4.24 years for any data to arrive back on Earth.
Proxima Centauri is part of the triple star system Alpha Centauri, seen here in a composite picture from the Digitized Sky Survey 2 [Image: ESO, Davide De Martin & Mahdi Zamani]
Exoplanet fans may recall that this isn’t the first time a world has been reported in the Alpha Centauri system. In 2012, astronomers announced that a potential Earth-mass planet orbited the sunlike star Alpha Centauri B—another discovery that was prematurely revealed by impatient publications. But that planet vanished when follow-up observations failed to confirm its existence and instead suggested that noisy data and the star’s own activity were masquerading as a planet.
With this new observation, the next star system over again joins the thousands of faraway stars known to host planetary residents—and it looks like it’ll take a rather skilled cosmic magician to make this world disappear.
Based on data collected over 54 nights, the signature of the planet is strong, popping out even when the data are inspected by eye and not a computer algorithm.
“It’s pretty unambiguous,” says Yale University’s Greg Laughlin. “This isn’t a case where you kind of have to resort to black arts to pull the signal out.”
Known as Proxima b, the planet was discovered by a team of scientists working on the Pale Red Dot project—a twist on Carl Sagan’s description of Earth, which looks like a pale blue dot from afar.
Scientifically, the discovery is not exactly a surprise. The last decade of exoplanet discoveries has revealed that red dwarf stars like Proxima are very likely to host planets, and a large fraction of those worlds should be somewhat like this new one: small, rocky, and warm enough for water to flow on its surface.
While earlier searches for planets around Proxima had officially turned up empty, there were tantalizing signs that at least one planet could be there, waiting to be detected with a more comprehensive search.
As a planet goes about its orbital business, its gravity tugs ever so slightly on its star, causing the star to wobble. Larger planets naturally produce bigger wobbles. Smaller, Earth-mass planets tug almost imperceptibly on their stars, requiring long observing campaigns with extremely sensitive instruments to detect.
Observations taken sporadically between 2000 and 2014 had hinted at the presence of a planet in an 11-day orbit around Proxima, but its shaky signature wasn’t clear enough to be anything more than a tease. Determined to see if a planetary hand really was the source of Proxima’s wobbles, the Pale Red Dot team aimed Earth’s sharpest wobbly-star watcher, the High Accuracy Radial velocity Planet Searcher (HARPS), at the red dwarf earlier this year.
From its location at the European Southern Observatory's site in La Silla, Chile, HARPS measured the motion of the star night after night, and scientists eagerly waited as one data point after another came in. The team almost immediately noticed the same 11-day signal in the data. About 20 nights in, Guillem Anglada-Escudé began to admit that maybe they had a detection—and after another 10 evenings, he started drafting a paper describing the finding, which is published August 24 in Nature.
“We tried to remain as skeptical as possible, because we were collecting one data point per night,” says Anglada-Escudé, of Queen Mary University of London. “We didn’t want to claim something like this and then have to pull it a couple of months later.”
The data suggest Proxima b is 1.3 times Earth's mass and takes 11.2 days to orbit its star, putting it in the region where the star’s feeble light is warm enough to keep any surface water flowing.
"If this really is a planet, the 11-day signal shouldn’t depend too much on when we observe the star. The planet should always be there," Weiss says. "If anyone tries this experiment again a few years from now and doesn't see the same signal, that's a bad sign."
Update: Mars set for for giant dust storm 'within months' that will envelop the entire planet
Mars frequently experiences powerful dust storms as part of its seasonal changes based on the orbital rotations around the sun. In as little as a few months, this phenomena is set to continue in dramatic fashion as NASA’s global Jet propulsion labs are predicting Mars to experience a mega dust storm which could blanket the plant in its entirety.
NASA suggest that such storms possess the capacity to temporarily block all solar energy from entering the surface of Mars, disrupting and even damaging a number of Mars exploration vehicles and jeopardising a host of current missions. Because the majority of NASA’s mechanical explorer vehicles, Satellites and Telescopes have electronic that run off solar power during these periods they are severely interrupted and can even be permanently damaged.
NASA suggests that there have been 9 recorded events of similar description since 1924, with the latest of these events occurring in 2007. However they suggest that this ‘No. of events is no doubt higher’ as more recent observations would currently suggest.
As Mars approaches the middle of its dust storm season on the 29th of October, it is assumed that this powerful dust storm will begin to form and develop over the coming months, lasting weeks at a time. These storms begin as local systems which develop into regional systems and potentially global systems- with these vast systems previously cutting off power to the NASA robots ‘Spirit’ and ‘Opportunity’ for a significant duration of time during 2007. Due to these power failures, significant measures were taken to ensure that power could be restored to these vehicles.
Scientists have speculated that these dust storm patterns have occurred due to changes in the planets orbital motion which are influenced in relation to the sun and other planets in which the average Mars rotation is 1.9 years. Research had shown that the greater the momentum that Mars garners on orbit, the stronger the dust storms become.