We Just Found 2 of The Most Earth-Like Exoplanets Yet, Only 12.5 Light Years Away

Astronomers are convinced they've found two new Earth-like planets in our galaxy, and both appear so similar to our own, they're now among the top 19 known exoplanets with potentially habitable environments.

Orbiting a neighbouring star in the constellation of Aries just 12.5 light years away, one of these two planets might in fact hold the greatest similarity to Earth we've discovered so far.

"The two planets resemble the inner planets of our Solar System," explainslead author Mathias Zechmeister, an astrophysicist at the University of Göttingen.

"They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form."

Despite its proximity, this nearby Teegarden's star was only discovered back in 2003. About ten times lighter than our own Sun and one of the smallest stars we know of, the old red dwarf, which is roughly 8 billion years old, has proved a challenge to research.

According to the team, other planetary systems around similar stars have always been detected using the transit method, when an orbiting planet passes in front of a star, blocking Earth's view and causing the bright celestial object to darken for a brief moment.

The alignment and dimness of Teegarden wouldn't lend itself to this method however, so astronomers instead used the CARMENES next-generation telescope designed specifically for such situations. Located at Spain's Calar Alto Observatory, the instrument allowed the researchers to look for any changes in the mini-star's radial velocity.

After three years of close observation, watching for any 'wobbles' produced by orbiting objects, more than 200 measurements indicate the existence of two new planets, now denominated as Teegarden b and Teegarden c.

To make sure the radial velocity data indicating these planets wasn't spoofed by variations in the star's brightness, the researchers complemented their observations with photometric (light measurement) data gathered about Teegarden's Star.

"These studies demonstrate that the signals of the two planets cannot be due to the activity of the star, even though we could not detect the transits of the two new planets," says astronomer Victor Sánchez Béjar from the Instituto de Astrofísica de Canarias (AIS).

Teegarden b is the innermost planet; according to the international team, it has a 60 percent chance of having a temperate surface environment, somewhere between 0° to 50°C and probably closer to 28°C. Teegarden c, on the other hand, sits farther out, and has a surface temperature more like Mars, sitting at roughly -47°C.

Given their minimum mass and their exposure to solar radiation, both planets have made the Habitable Exoplanets Catalog. In fact, Teegarden b has actually scored the highest Earth Similarity Index (ESI) ever.

While this doesn't necessarily mean that either planet is indeed habitable, it's certainly a promising sign. Zechmeister told The Guardian that if these planets are equipped with atmospheres, they could very well be hospitable to life.

"The planets Teegarden's Star b and c are the first planets detected with the radial velocity method around such an ultra-cool dwarf," the team writes in a paper describing the discovery.

"Both planets have a minimum mass close to one Earth mass, and given a rocky, partially iron, or water composition, they are expected to have Earth-like radii."

Lauren Weiss, an astrophysicist at the University of Hawaii who was not involved in this research, told National Geographic there were still some technical details that need to be teased out, but she was impressed by the overall quality of data.

While the team predicts that Teegarden b completes its orbit in 4.9 Earth days, and c does so in 11.4 days, Weiss argues that their journey might go even faster than that, which would inevitably reduce their habitability.

What's more, she adds, we don't yet know precisely how long it takes Teegarden to rotate on its axis; given that astronomers used radial velocity measurements to obtain their discovery, one of these planet detections might still be an artefact of the star's rotation - but probably not both.

As the 24th nearest star system to our own and the nearest fourth with potentially habitable planets, Teegardeen is an excellent candidate for future research, and its potential to harbour life has left us quite excited.

There could be up to 10 billion warm and cozy Earth-like planets in our home galaxy, new research reveals

An artist's concept of the planet Kepler-452b (right), the first near-Earth-size world to be found in the habitable zone of a star that is similar to our sun. The planet is 60% larger than Earth (shown left for comparison)

Our galaxy could be littered with warm, watery planets like Earth.

That's the conclusion of researchers at Penn State University, who used data from NASA's Kepler telescope to estimate the number of Earth-like planets in the Milky Way. Their results, published in The Astronomical Journalthis week, suggest that an Earth-like planet orbits one in every four sun-like stars. Totaled up, that means there could be up to 10 billion Earth-like worlds in our home galaxy.

The estimate is an important step in the search for alien life, since any potential life on other planets would most likely be found on an Earth-like world warm enough to hold liquid water.

So a better understanding of the potential number of Earth-like planets in the galaxy can inform projects like the Wide-Field Infrared Survey Telescope, which will launch into space in the mid 2020s and hunt signs of for oxygen and water vapor on distant planets.

"We get a lot more return on our investment if we know when and where to look," Eric Ford, a professor of astrophysics and co-author of the new study, told Business Insider.

Ford's team defined an Earth-like planet as being anywhere from three-quarters to one-and-a-half times the size of Earth, and orbiting its star every 237 to 500 days. That's presumably within the star's habitable zone - the "range of orbital distances at which the planets could support liquid water on their surfaces," as Ford described it in a press release.

"For astronomers who are trying to figure out what is a good design for the next major space observatory, this piece of information is an integral part of that planning process," he said.

5 to 10 billion planets like Earth

The researchers' estimate is based on data from NASA's Kepler space telescope. Launched in 2009, the telescope used what's known as the transit method to find worlds outside our solar system. It watched over 530,000 stars for tiny dips in a star's brightness that could be caused by a planet passing in front of it - transits, in other words.

This work transformed our understanding of the galaxy. Kepler found more than 2,600 exoplanets, revealed that there are more planets than stars in the Milky Way, and gave researchers new insight into the diversity of planet types. The telescope also allowed scientists to confirm for the first time that many exoplanets are similar to Earth.

The telescope retired last year after it ran out of fuel, but passed the planet-hunting torch to the Transiting Exoplanet Survey Satellite (TESS), which launched in April 2018.

Overall, Kepler's results suggested that 20% to 50% of the stars visible in the night sky had Earth-like planets in their habitable zones.

But Ford's team didn't want to estimate the number of Earth-like planets in the galaxy based solely on the exoplanets Kepler found, because the transit method is only good at detecting large planets close to their stars (since they block out more light). It's not great, however, at finding small planets farther from their stars. Plus, Kepler's method was biased toward small, dim stars about one third the mass of our sun.

So to estimate how many planets Kepler might have missed, the researchers created computer simulations of hypothetical universes of stars and planets, based on a combination of Kepler's planet catalogue and a survey of our galaxy's stars from the European Space Agency's Gaia spacecraft. Then the researchers' program "observed" those stars as Kepler would have.

The simulation gave the scientists a sense of how many exoplanets in each hypothetical universe Kepler would have detected, and which kinds. They could then compare that data to what the real Kepler telescope detected in our universe to estimate the abundance of Earth-sized planets in the habitable zones of sun-like stars.

"There are significant uncertainties in what range of stars you label 'sun-like,' what range of orbital distances you consider to be 'in the habitable zone,' what range of planet sizes you consider to be 'Earth-like,'" Ford said. "Given those uncertainties, both 5 and 10 billion are reasonable estimates."

Improving the search for aliens

An illustration of a potentially habitable exoplanet 31 light-years from Earth.

The next step in the search for alien life is to study potentially habitable planets to figure out what they're made of.

"Scientists are particularly interested in searching for biomarkers - molecules indicative of life - in the atmospheres of roughly Earth-size planets," Ford said.

Even if a planet is in a star's habitable zone, it still needs a substantial atmosphere to trap enough heat to sustain liquid water on its surface. Scientists can calculate the composition of an exoplanet's atmosphere by measuring how its star's light behaves as it passes through.

This is where Ford's research comes into play: If Earth-like worlds are abundant, there could be enough of them close by for NASA scientists to study with a smaller, cheaper telescope. If all the Earth-y worlds are far away, though, NASA would need to rely on more far-reaching telescopes.

The researchers recommended that future space missions plan for a range of possible incidences of Earth-like planets - between one for every 33 sun-like stars and one for every two sun-like stars.

"One of the important things here is not just giving a single number but understanding the range of possibilities," Ford said. "So that people who have to make decisions could hope for the best and plan for the worst and still be able to come up with a solid scientific strategy."

The Water Vapor Find on 'Habitable' Exoplanet K2-18 b Is Exciting — But It's No Earth Twin

Astronomers are finding more and more alien worlds that may be capable of supporting Earth-like life, but none of these exoplanets so far are carbon copies of our home world. 

The newest exciting find involves K2-18 b, a planet about 110 light-years from Earth that NASA's Kepler space telescopediscovered in 2015. 

K2-18 b lies in its parent star's "habitable zone," the range of distances that could support the existence of liquid water on a world's surface. Two teams of scientists announced this week that they've found water vapor in this world's air — a big milestone in the search for alien life.

"This is the only planet right now with the correct temperature [for Earth-like life] and water outside the solar system," Angelos Tsiaras of University College London's Centre for Space Exochemistry Data (CSED), the leader of one of the research teams, told reporters during a teleconference Tuesday (Sept. 10).

Tsiaras and his colleagues published their results today (Sept. 11) in the journal Nature Astronomy. The other research team, led by Björn Benneke of the Université de Montréal, posted its paperon the online preprint site arXiv.org Tuesday. The study by Benneke et al. has not yet been peer-reviewed.

Tsiaras and his colleagues stressed that K2-18 b is far from an Earth twin. The exoplanet is eight times more massive than our world, making it a "super-Earth," a type of world that's common throughout the Milky Way galaxy but is not represented in our own solar system.

Then, there's the matter of K2-18 b's star, a red dwarf much smaller and cooler than the sun. Because red dwarfs are so dim, their habitable zones reside much closer in; K2-18 b completes one orbit every 33 Earth days.

The alien planet may therefore be "tidally locked" to its star, always showing the red dwarf the same face, just as Earth's moon only ever shows its near side to us. But this would not be a dealbreaker for the existence of life.

"A tidally locked planet can also be habitable," said Ingo Waldmann of CSED, a member of Tsiaras' team. Modeling studies suggest that "the energy from the dayside can be quite equally distributed to the nightside," Waldmann added.

Tidally locked or not, such a world would be decidedly unlike Earth. Indeed, K2-18 b doesn't even boast Earth-like conditions, Tsiaras said. (The red-dwarf host star bathes K2-18 b in much higher levels of ultraviolet radiation than Earth receives from its sun, for example.) 

"It is definitely not a second Earth," he said.

But that shouldn't turn astrobiologists, or anyone else interested in the prospect of life beyond Earth, off to K2-18 b. After all, it's entirely possible — perhaps even likely, given the incredible diversity of alien worlds — that life has taken root on many different types of planets (and, perhaps, moons) throughout the galaxy. 

"The only question that we're trying to ask here, and we're pushing forward, is the question of habitability," Tsiaras said. "This is the planet that satisfies more [habitability] requirements than any other that we know right now."

Two Potentially Earth-Like Alien Planets Found Around Nearby Star

There are even more potentially habitable planets near Earth than we ever imagined. A research team discovered two Earth-like planets in our cosmic backyard, and they're located in the perfect zone for water to form on their presumably rocky surfaces.

The planets orbit a sun known as "Teegarden's star," which is only 12.5 light-years from Earth. (A light-year is the distance that light travels in a year, or roughly 6 trillion miles or 10 trillion kilometers.) The two planets look an awful lot like Earth and our neighboring worlds, the researchers said.

"The two planets resemble the inner planets of our solar system," lead author Mathias Zechmeister, a research scientist at the Institute for Astrophysics at the University of Göttingen in Germany, said in a statement. "They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form."

The results were obtained as part of the CARMENES search for exoplanets; CARMENES stands for "Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs."

According to that project's observations, the newly found worlds orbit their parent star with periods of roughly five days and 11 days, respectively. That's very quick compared to planets orbiting our own sun (even Mercury takes 88 days for a single circuit), but Teegarden's star is an M dwarf— a type of star that produces less light and energy than our own sun. Any potentially habitable worlds would be found huddled closer to this star than Earth is to the sun, or their water would freeze. Thus, their orbits would be quicker

More planets could be lurking in Teegarden's star's solar system, the research team added, as many stars have more than a couple of planets orbiting them. The research team tried to find more evidence of planets using the "transit" method, which looks for subtle dips of brightness as a world passes in front of its star.

The scientists didn't detect any transits, but they did point out a coincidence of cosmic geometry: Any potential inhabitants on the newfound planets could use the transit method to see Earth. That's because from the vantage point of Teegarden's star, Earth orbits its sun at just the right angle to transit across the face of our star, allowing any astronomers "out there" to spot us as we pass by.