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2 potentially habitable 'Super-Earths' and a record-setting 'Cold Neptune' found in exoplanet haul

An artist’s illustration of the newfound exoplanet GJ180 d, which is the nearest temperate super-Earth to us that is not tidally locked to its star, making it more likely to be able to host life.
An artist’s illustration of the newfound exoplanet GJ180 d, which is the nearest temperate super-Earth to us that is not tidally locked to its star, making it more likely to be able to host life.
(Image: © Robin Dienel, courtesy of the Carnegie Institution for Science)

Astronomers have found two more potentially life-supporting alien planets in our neck of the cosmic woods, as well as a weird and record-setting "cold Neptune."

The two possibly habitable worlds orbit the red dwarf stars GJ229A and GJ180, which lie about 19 light-years and 39 light-years from Earth, respectively. That's not far in the grand scheme of things, considering that our Milky Way galaxy's famous disk is about 100,000 light-years wide. (The sun's nearest neighbor star, Proxima Centauri, is about 4.2 light-years away.)

Red dwarfs, which make up about 70% of the Milky Way's stellar population, are significantly smaller and dimmer than the sun. So, these stars' "habitable zones" — the range of orbital distances where liquid water could be stable on a world's surface — lie much closer in than they do in sunlike systems.

Related: 10 Exoplanets That Could Host Alien Life

Indeed, habitable-zone red dwarf planets tend to be tidally locked, always showing the same face to their star, just as Earth's moon always shows us its "near side." Tidal locking isn't a great thing for habitability, because it can leave a world with a scorching dayside and a frigid nightside (though a thick atmosphere can distribute heat globally and mitigate the extreme temperatures). 

But the newfound planets around GJ180 and GJ229A — known as GJ180 d and GJ229A c, respectively — orbit far enough away to avoid tidal locking, discovery team members said. And that makes GJ180 d a record-breaking world.

“GJ180 d is the nearest temperate super-Earth to us that is not tidally locked to its star, which probably boosts its likelihood of being able to host and sustain life," team leader Fabo Feng, of the Carnegie Institution for Science in Washington, D.C., said in a statement.

As Feng said, GJ180 d is a super-Earth, a world slightly bigger than our own; the newfound exoplanet's mass is at least 7.5 times that of Earth, the researchers determined. GJ229A c is a super-Earth, too, harboring at least 7.9 Earth masses. GJ180 d completes one orbit every 106 Earth days, and GJ229A c does the same every 122 Earth days, the scientists reported in a study announcing the finds, which was published last week in The Astrophysical Journal Supplement Series.

GJ229A c resides in a binary system consisting of a red dwarf and a brown dwarf (which is called GJ229B). Brown dwarfs are curious objects bigger than gas-giant planets but too small to undergo fusion reactions in their core. This explains another name for them: "failed stars."  

As GJ180 d's name indicates, it's not the only known world in its system. Astronomers had previously discovered two planets circling that red dwarf, GJ180 b and GJ180 c. 

Related: The Strangest Alien Planets (Gallery)

Artist’s concept of the surface of the newfound planet GJ229Ac, the nearest temperate super-Earth to us that is in a system in which the host star has a brown dwarf companion.

Artist’s concept of the surface of the newfound planet GJ229Ac, the nearest temperate super-Earth to us that is in a system in which the host star has a brown dwarf companion. (Image credit: Robin Dienel, courtesy of the Carnegie Institution for Science)

Astronomers don't know much about the two newfound super-Earths, but they could learn more soon. The planets' relative proximity to our own solar system makes them good targets for study by powerful future instruments such as NASA's James Webb Space Telescope, which is scheduled to launch next year, the researchers said.

"Our discovery adds to the list of planets that can potentially be directly imaged by the next generation of telescopes," Feng said. "Ultimately, we are working toward the goal of being able to determine if planets orbiting nearby stars host life."

"We eventually want to build a map of all of the planets orbiting the nearest stars to our own solar system, especially those that are potentially habitable," study co-author Jeff Crane, also of the Carnegie Institution, said in the same statement.

The newly discovered "cold Neptune," GJ 433 d, doesn't seem like a good candidate for life, but it's interesting for other reasons. The planet, which is at least 4.9 times more massive than Earth, orbits a dim red dwarf just 29.5 light-years from Earth.

"GJ 433 d is the nearest, widest and coldest Neptune-like planet ever detected," Feng said.

The alien world is also a good candidate for follow-up study, including direct imaging, Feng and colleagues said.

The researchers made the new discoveries after reanalyzing data gathered by the European Southern Observatory's (ESO) Ultraviolet and Visual Echelle Spectrograph (UVES) instrument during a survey of 33 nearby red dwarfs from 2000 to 2007. These were radial-velocity measurements — observations that can reveal stellar motion caused by the gravitational tugs of orbiting planets.

The team supplemented the UVES data with measurements made by three other instruments: the Carnegie Planet Finder Spectrograph (PFS) at Las Campanas Observatory in Chile, ESO's High Accuracy Radial velocity Planet Searcher (HARPS) at La Silla Observatory in Chile and the High Resolution Echelle Spectrometer (HIRES) at the Keck Observatory in Hawaii.

This work resulted in a total of five newfound alien planets, as well as eight unconfirmed exoplanet candidates.

The new study is part of a flood of exoplanet data that began pouring in a decade ago with the launch of NASA's recently deceased Kepler space telescope (which hunted alien worlds using the "transit method," a strategy that's different from the radial-velocity technique employed by UVES, HARPS, HIRES and PFS). Astronomers have confirmed more than 4,100 exoplanets to date, and about 70% are Kepler finds. 

Mike Wall's book about the search for alien life, "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook

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  • Sam
    Great. This method does find Earth planets farther out from the star than does the transit method..
    Reply
  • rod
    Admin said:
    Astronomers have found two more potentially life-supporting alien planets in our neck of the cosmic woods, as well as a weird and record-setting 'cold Neptune.'

    2 potentially habitable 'Super-Earths' and a record-setting 'Cold Neptune' found in exoplanet haul : Read more

    "As Feng said, GJ180 d is a super-Earth, a world slightly bigger than our own; the newfound exoplanet's mass is at least 7.5 times that of Earth, the researchers determined. GJ229A c is a super-Earth, too, harboring at least 7.9 Earth masses."
    "The newly discovered "cold Neptune," GJ 433 d, doesn't seem like a good candidate for life, but it's interesting for other reasons. The planet, which is at least 4.9 times more massive than Earth, orbits a dim red dwarf just 29.5 light-years from Earth. "GJ 433 d is the nearest, widest and coldest Neptune-like planet ever detected," Feng said."

    Okay, these exoplanets orbit red dwarf stars and the inclination of their orbits, important in the radial velocity method is not well determined so these are minimum masses, they could be much larger. The cold Neptune cannot be 4.9 earth masses - that would be a smaller super-earth than the other two, GJ180 and GJ 229A. Some more research will be underway concerning these exoplanets. The super-earths near 7.5 and 7.9 earth masses could also be 2 earth radii in size or larger. In our solar system, planets like this do not exist. GJ 433 d orbital period is 36 days, the others 106 and 122 days and closer to their parent stars than Mercury is to our Sun. https://phys.org/news/2020-01-cold-neptune-temperate-super-earths-orbiting.html
    The Extrasolar Planets Encyclopaedia
    Reply
  • Edward Coulter
    Sam said:
    Great. This method does find Earth planets farther out from the star than does the transit method.
    True, as long as the star is small and the planet is big. This method won't work well for stars of both about 1 solar mass (our own) and planets of 1 earth mass unless sensitivity of wobble detection can be improved enormously. I am not sure where we are at now though.

    The degree of a star's wobble depends on the relative masses of the two objects and the separation distance. So what would calculations show about our earth? By which I mean with present techniques, could the wobble of our sun be detected due to the gravitational attraction of the orbital rotation of 1 earth mass at 1 AU distance and viewed from, say, a distance of 10 light years? If not, we will never find a habitable planet by our standards let alone interesting alien life.

    And even if such a planet were found, it proves nothing about life. Our science cannot get us or our instruments to even the nearest planet in a human life span. Discouraging.
    Reply
  • Mario G
    Admin said:
    Astronomers have found two more potentially life-supporting alien planets in our neck of the cosmic woods, as well as a weird and record-setting 'cold Neptune.'

    2 potentially habitable 'Super-Earths' and a record-setting 'Cold Neptune' found in exoplanet haul : Read more
    4 light yrs are around 9,500 billion kms and today our spaceships manage like 100,000 kms/day. Only 1 billion kms could be reached in around 10,000 days (27 yrs). What we the humans could gain knowing the closest exoplanet is at 4 light years away?
    Reply
  • rod
    FYI, New Horizons traveled about 16 km/s. Moving at this velocity at a constant rate, it will take nearly 75,000 years to travel 4 light-years distance. Traveling similar to some meteor shower velocities observed on Earth - 35 km/s, 34285 years.
    Reply
  • pindiespace
    I'm puzzled why the LARGER planets are called "super-earths" and the SMALLER planet is called a "cold Neptune". If the smaller planet is only 5-6 times the size of Earth it is not like Neptune, which is 17 times larger than Earth. Also, the "super-Earth" sizes at 7x are quite a bit larger than anything likely to be actually Earthlike.
    Reply
  • rod
    I commented earlier, the report said about the cold Neptune, "The newly discovered "cold Neptune," GJ 433 d, doesn't seem like a good candidate for life, but it's interesting for other reasons. The planet, which is at least 4.9 times more massive than Earth"

    Here is a report on GJ 433 d using the exoplanet list, http://exoplanet.eu/catalog/gj_433_d/ The mass is "Mass*sin(I)" and is 4.94 Jupiter masses, not earth masses. The mass upper limit is provided because the lower limit is not well measured. I ran a MS SQL query against the database for exoplanet masses in the range 1.5 to 10 earth masses. There are 169 listed in a database of 4168, confirmed exoplanets now. Our solar system has no such planets like this, same for hot jupiters and other exoplanet varieties reported now.
    Reply
  • pindiespace
    rod said:
    I commented earlier, the report said about the cold Neptune, "The newly discovered "cold Neptune," GJ 433 d, doesn't seem like a good candidate for life, but it's interesting for other reasons. The planet, which is at least 4.9 times more massive than Earth"

    Here is a report on GJ 433 d using the exoplanet list, http://exoplanet.eu/catalog/gj_433_d/ The mass is "Mass*sin(I)" and is 4.94 Jupiter masses, not earth masses. The mass upper limit is provided because the lower limit is not well measured. I ran a MS SQL query against the database for exoplanet masses in the range 1.5 to 10 earth masses. There are 169 listed in a database of 4168, confirmed exoplanets now. Our solar system has no such planets like this, same for hot jupiters and other exoplanet varieties reported now.

    Great, that explains things! However, if it is 5x the size of Jupiter, why call it a "Neptune"? Distance? In terms of composition, it must have an interior more like Jupiter than Neptune.
    Reply
  • rod
    pindiespace said:
    Great, that explains things! However, if it is 5x the size of Jupiter, why call it a "Neptune"? Distance? In terms of composition, it must have an interior more like Jupiter than Neptune.

    FYI, you have a good eye here. I think there is confusion between GJ 433 d vs. GJ 433 c, this is the cold Neptune in the research papers, Search for Nearby Earth Analogs. II. Detection of Five New Planets, Eight Planet Candidates, and Confirmation of Three Planets around Nine Nearby M Dwarfs
    This report in the abstract says about GJ 433 c, "In addition, we find GJ 433 c, a cold super-Neptune belonging to an unexplored population of Neptune-like planets."

    This makes more sense because Mass*sin(i) is 0.09055 MJup. Exoplanet research and studies can be fun but confusing at times too, like the different names and letters used :)---Rod
    Reply