Planet Orbits Quiet Star 11 Light-years Away

Astronomers have discovered a potentially rocky planet around a red dwarf star just 11 light-years away.

Temperate exoplanet 11 light-years away

This artist’s impression shows the temperate planet Ross 128 b, with its red dwarf parent star in the background.
ESO / M. Kornmesser

I spent countless nights as a child gazing up at the night sky and wondering what was out there. Did those stars harbor planets, and if so, were those planets anything like our Earth? Could there be other stargazers, looking up at an alien sky?

The exoplanet field, which has exploded in the last 20 years, is beginning to answer these questions. With thousands of planets identified around other stars, the field has moved beyond discovery to statistical understanding. We now know that small rocky planets like our Earth are common and that the most common type of star (M dwarfs) is one of the most likely hosts for planets. These statistics are evident in the recent discovery of Proxima b, a planet orbiting our closest stellar neighbor, but that’s not the only planet around a nearby star.

At a distance of 11 light-years, Ross 128 is the 15th closest star to the Sun. Like Proxima Centauri, it’s an M-class star with about 16% the Sun’s mass. Xavier Bonfils (University of Grenoble-Alpes, France) and colleagues measured the star’s movements using the HighAccuracy Radial velocity Planet Searcher spectrograph at the European Southern Observatory’s La Silla Observatory in Chile, showing that Ross 128 is home to a planet. The results have been published online and will appear in an upcoming issue of Astronomy & Astrophysics.

The potentially rocky world circles its star every 9.9 days, with a mass at least 1.3 times that of Earth, making it the second closest Earth-size planet within the habitable zone of its star. This zone, defined as the region in which water could exist in liquid form on a rocky planet’s surface, hugs its star more tightly than it would in the solar system because of the star’s low luminosity. Ross 128b is 20 times closer to its host star than the Earth is to the Sun, but receives just 40% more light than we do on Earth. Because Ross 128 is small and cool compared to the Sun, that light would be much redder than sunlight.

Ross 128b is an exciting exoplanet because, unlike many low-mass stars, its host is relatively well-behaved. Our own star burps and coughs up charged particles, resulting in solar flares and storms that, at their worst, can severely disrupt electrical equipment such as GPS satellites and power grids. Most low-mass stars, on the other hand, are cauldrons of activity. They unleash flares more often and more energetically — the flares are typically an order of magnitude stronger than the Sun’s. This behavior is thought to severely limit the development of life on these stars’ planets. However, the activity decreases with the star’s age, and fortunately for any potential inhabitants of Ross 128b, the star is old. It doesn’t flare as often as its younger counterparts, such as Proxima Centauri and TRAPPIST-1.

So while our new planetary neighbor may have a dim, old, red sun, it is a welcome addition to the exoplanet census. In coming years, it will be the target of atmospheric studies, which are most efficient around nearby systems. Atmospheric composition, specifically signs of oxygen, methane and water, may just be the smoking gun that answers that Big question: “Are we alone?”

3 thoughts on “Planet Orbits Quiet Star 11 Light-years Away

  1. Rick

    Mr. Bochanski would profit from a proofreader.

    In his interesting November 15, 2017 article in Sky & Telescope, he’s offered what is basically a first draft. The article is entitled: “Planet Orbits Quiet Star 11 Light-years Away.”

    The first passage worth noting is:

    “At a distance of 11 light-years, Ross 128 is the 12th closest star to the Sun. Like Proxima Centauri, it’s an M-class star with about 16% the Sun’s mass.

    As a matter of rhetoric (not grammar), it would have been smoother if he had named the subject of his article, Ross 128, before going into detail about the class and size.

    He then goes on with:

    “Like Proxima Centauri, it’s an M-class star with about 16% the Sun’s mass.”

    Since Mr. Bochanski refers to the Sun for comparison, it seems an omission to NOT mention that the Sun is a G Class star.

    “We now know that small rocky planets like our Earth are common and that the most common type of star (M dwarfs) is the most likely hosts for planets.”

    It would have improved clarity to state the average mass of M Class stars (0.3 of our Sun) for completeness, again, since he was comparing 128 Ross to the Sun.

    A more serious problem related to accuracy, and it occurred with the following statement:

    “(128 Ross) hugs its star more tightly than in the solar system because of the star’s low luminosity. ”

    1. It is not IN our Solar System. That should have been re-written.

    2. The use of the word “because” is flat out wrong. This creates a false cause-and-effect relationship. The close orbit is not BECAUSE OF the low luminosity. Nor is the low luminosity related to the close orbit.

    Then he writes: “…Because Ross 128 is small and cool compared to the Sun, that light would be much redder than sunlight.

    This should read: be “much redder than (capital S) Sunlight,” because the light referenced is from our Sun, not just any sun.

    Lastly, Mr. Bochanski writes:

    “So while our new planetary neighbor may have a dim ….”

    The reference to “our new planetary neighbor” is general in a mushy sort of way. That phrasing fits the as-yet-unseen 9th planet in our Solar System, but it is less suitable referring to something which is a planet on the 12th star out away from us.

    S&T is extremely valuable. It deserves quality writing.

    1. Monica YoungMonica Young

      Dear Rick,
      I’m afraid you changed one of the quotes you’re referencing. The correct quote is “This zone, defined as the region in which water could exist in liquid form on a rocky planet’s surface, hugs its star more tightly than it would in the solar system because of the star’s low luminosity.” (emphasis added is mine) You abbreviated the quote and added “(Ross 128)”, but that’s not how it was written in the text — the sentence is referencing the habitable zone, not the planet, and the habitable zone is indeed dependent on the star’s luminosity.

      Also, according to S&T’s style (which we adopt for consistency across the website and magazine), we do capitalize Sun, but we do not capitalize sunlight. Likewise, we capitalize Earth but not earthbound.

  2. DHAndrews

    We are not alone. Oh, there may not be another planet in all the Universe that has trees and grass and “Beings” on it, but that fact does not necessarily mean that we are alone. Jesus of Nazareth told his friend Peter that he had 20 legions of angelic beings (>1,000,000) that could be brought to his defense if He chose. Considering that we are also told that fully one third of the angelic beings fell from the Heavens, we can assume there is at least another 10 legions of fallen angels or demons. The total of both the Angelic and the fallen being is probably much higher as these numbers here are based on the number being immediately available for a single purpose – I would think the numbers would be measured in Billions or Trillions rather than millions.

    The number is not important – the fact that they are there is important because we also know that if we are individually allied with the God of the Universe, then God, and you become the majority stakeholder in the universe and time.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.

COMMENT