Are we alone in the universe? Maybe not! This artist's conception provided by the Harvard-Smithsonian Center for Astrophysics depicts an Earth-like planet orbiting an evolved star that has formed a stunning "planetary nebula" (AP photos / NASA)
Are we alone in the universe? Maybe not!

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Earth has a few more near-twin planets outside our solar system, tantalizing possibilities in the search for extraterrestrial life.

Astronomers have announced that depending on definitions, they have confirmed three or four more planets that are about the same size as Earth and are in the not-too-hot, not-too-cold "Goldilocks Zone" for liquid water to form.

These planets are likely to be rocky like Earth, and not gas giants or ice worlds. They get about the same heat from their star as we get from the sun, according to the latest results from NASA's planet hunting Kepler telescope.

But don't book your flights yet.

They may be close to Earth in size and likely temperature in the gargantuan scale of the universe, but they aren't quite close enough for comfort.

Consider two of the new planets, the nearest to Earth discovered to date. If they have atmospheres similar to Earth's a big if one would be a toasty 140-some degrees and the other would hover around zero, said study lead author Guillermo Torres, an astronomer at the Harvard-Smithsonian Center for Astrophysics.

Life conceivably could evolve and adapt to those temperatures, he said.

Oh, and they aren't actually within commuting distance of Earth. Those two are 500 and 1,100 light years away. A light year is 5.9 trillion miles.

What's important, said SETI Institute astronomer Douglas Caldwell, a study co-author who presented the findings at the American Astronomical Society meeting in Seattle, is that astronomers are a bit closer to finding twins of Earth and answering the age-old question: Are we alone?

"These planets do exist. We didn't know that before," Torres said in a phone interview from Cambridge, Massachusetts. "What we're really looking for is signs of life eventually. We're not there yet. It will take many years but this is the first step."

Torres' team confirmed earlier discoveries and added new ones, bringing the total known number of planets that are no bigger than twice Earth's size and in the habitable temperature zone to eight or nine. But that's only from a short search of a small part of our galaxy, so Torres believes that Earth-like planets are common throughout the cosmos, though he cannot prove it yet.

Torres likes to include one planet that would bump the new findings from three to four, but Caldwell said that planet may or may not be habitable.

Torres and Caldwell highlighted the two new planets that are closest in size to Earth. The closest, called Kepler 438-b, is only 12 percent larger than Earth and gets about 40 percent more energy from its star than we do from the sun, so it would probably be warmer, Torres said. It tightly circles a small cooler red star with its year lasting only 35 Earth days and the sun in its sky would be red, not yellow.

It may be hot, but "there are bacteria on Earth that live very comfortably in those temperatures, no problem," Torres said.

The other, Kepler 442-b, is about 34 percent bigger than Earth but gets only two-thirds of the energy from its sun as we do, Torres said.

NASA also announced that its planet-hunter telescope confirmed its 1,000th planet outside the solar system, most quite unlike Earth and not in the habitable zone. Added to those discovered by other telescopes, astronomers have now discovered more than 1,800 planets that are outside the solar system.

Critical thinking challenge: Why are scientists so interested in planets that are not-too-hot or not-too-cold for liquid water to form? Which forms of life can live without water?

Assigned 22 times

  • avery1228
    1/15/2015 - 05:24 p.m.

    I really enjoyed reading this! I have always been interested in things having to do with space, and our solar system, and it's very cool to think there could be life on other planets. It could go either way, I'm not sure which i believe in, whether we are alone in our solar system (and beyond that) or that there may be other living things, being aliens or any other type of creature. For the critical thinking, scientist are so set on new planets that are not-too-hot or not-too-cold because that's where they would find life most likely, if the temperature was either of these things water would not be able to form on that planet making it a non-livable place. I'd really like to read about this more!

  • danniemoji
    1/15/2015 - 05:30 p.m.

    I found this story to be very interesting. I have always wanted to learn more about space and about what's going on with other planets that we might be able to live on. It's amazing to know all this information and that if one day, we possibly build an aircraft that is fast enough to travel 1,100 light years away in a good time, we could live on other planets. I would have loved to have read more, because this really caught my eye. I love learning about space and this helped a lot!

  • GrantW-2
    1/16/2015 - 10:58 a.m.

    This article is about the potential of there being life on different planets and about the search for earth like planets that humans would be able to live on. Most of the planets are too hot or too big but there is other planets that could hold human life but they are 5 light years away which would mean if we wanted to get there we would have to make huge ships and live on them until we got there but it would probably take three or four generations to do so.

  • TaylorSeifert-Ste
    1/19/2015 - 08:46 p.m.

    I used to find myself constantly worrying about what would happen if our sun blew up, as a little kid. It's kind of comforting to know that scientists are getting closer to finding another planet that humans may one day be able to live on, but at the same time it all seems so unreal.

  • ShaniaWentz-Ste
    1/19/2015 - 09:35 p.m.

    Life on other planets is something that scientists have been trying to discover for years, maybe even centuries! It is something that some people believe in, and some do not. Other than the fact that most planets don't have the stability to maintain human lives, most people just go with the religious aspect that God only made lives on Earth. Even though I hope that there is life on other planets, I also hope that they are taken well care of.

  • ratiaira
    1/20/2015 - 01:43 p.m.

    if we are not alone that would be kind of scary because all these years and there have been other people living in the galaxy well milky way that is so weird but cool

  • rustico
    1/20/2015 - 04:08 p.m.

    Wow, that's very surprising. I thought there was earth like planets but not within our galaxy! I hope someday we find a perfect earth like planet. We just might treat the new EARTH 2.0 better. No pollution!

  • CorsonZ-Tan
    1/21/2015 - 08:27 a.m.

    I find this very interesting. The fact that there are two plants outside our galaxy that are twins of the earth is amazing. Now all we got to do is figure a way to those plants. So we can figure out if those plants can be lived on.

  • BenB10
    1/21/2015 - 04:19 p.m.

    Their may be hundreds of planets that can be lived on by humans, that may even have intelligent lifeforms living on them. Even though they may be livable they are all to far away to reach with are current technology. One of the planets is 500 light years away, a light year equals 5.9 trillion miles away. Right now scientists are looking for signs of life on the planets but it will take many, many years to get the results. If humans find another livable planet it may solve the oncoming crisis of space.

  • jarredc-Koc
    1/21/2015 - 09:21 p.m.

    In order for life, bacteria in this case, to exist on a planet, there must first be two things. The first is a habitable atmosphere. If bacteria cannot even survive on a planetoid surface, then humans most certainly can't. The second thing that is necessary for life is water. without water, life cannot have a energy source to nurish itself.

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