Super-Earth planets are planets between the size of Earth and Neptune. Find out about the research team called Red Dots and their planetary discoveries.
I can still remember the excitement in the farmhouse as my parents, my brothers and I gathered around the TV set for the highly anticipated series premiere of Lost in Space. Its creators based it loosely on the comic book series called The Space Family Robinson.
In turn, the comics came from the classic novel The Swiss Family Robinson. Lost in Space was about a family of space travellers on their way to an Earth-like planet in the closest star system to Earth, Alpha Centauri. They lost their way because of a saboteur.
I was too young to realize how campy the show was at the time. The early shows contained some semblance of serious science fiction. Even so, as the seasons went by, the show relied more and more on comedy and outlandish plots to draw in their young, baby boomer audience.
That There Really Is an Earth-Mass Planet in Alpha Centauri
Science fiction has a habit of coming true in the long run. That turned out to be the case even with a knockabout farce like Lost in Space. We now know that there is a real-life planet with a mass similar to Earth in the Alpha Centauri system.
The system is about four light-years from Earth in the constellation Centauri. It consists of three stars, the closest of which is called Proxima Centauri. In 2016, a group of astronomers called Red Dots discovered Proxima Centauri b, a planet only 30% larger than Earth, orbiting in the star’s habitable zone where liquid water could exist. It’s closer to its star than the Earth is to the Sun.
Proxima Centauri is a red dwarf star, which is where the team gets its name. Borrowing from Carl Sagan’s Pale Blue Dot, the Red Dots team looks for Earth-like exoplanets orbiting nearby red dwarfs in our part of the galaxy. Planets like these would take on a reddish shade.
Red Dots Look for Earth-Like planets Orbiting Red Dwarfs
On top of Proxima Centauri b, they also located an Earth-mass planet around our second-closest neighbour, Barnard’s Star, in 2018. Then in 2019, they found three more terrestrial planets around a third red dwarf called GJ 1061.
This week, the journal Science published a paper from the Red Dots team announcing yet another discovery. This time, they’ve located two Super-Earth planets orbiting the brightest red dwarf star in the sky, Gliese 887 (aka GJ 887). It’s closer to us than GJ 1061.
The planets, Gliese 887b and Gliese 887c, both fall just inside the edge of GJ 887’s habitable zone, which is must closer than that of our Sun. That’s because red dwarfs are much dimmer than main-sequence stars. Liquid water might not be possible outside the habitable zone, but water vapor might be.
Gliese 887 is Remarkably Stable and Quiet
GJ 887 is remarkably stable and quiet as stars go. It has very few sunspots or solar flares compared to the Sun. That means it doesn’t have a turbulent solar wind, which might blow away the planets’ atmospheres if it was more intense. Mercury has virtually no atmosphere, for instance.
The team’s latest red dwarf also doesn’t vary much in brightness. the host star’s stability will make it easier for future studies to look for atmospheres and other signs of life on these new Super-Earth planets.
At this point, the researchers aren’t able to work out the inclinations of the planets’ orbits, so they can’t provide us with a precise estimate of their masses. Still, their minimum weights appear to be somewhere between those of Earth and Neptune, qualifying them as Super-Earth planets.
Two Broad Techniques for Monitoring Exoplanets
There are two broad techniques for locating exoplanets. One is to monitor a star’s brightness for periods of dimming. This darkening can be a planet passing in front of it and blocking its light.
The other approach is to watch for wobbles in the star’s motion. Wobbles like these are a sign that gravity from planets is pulling it back and forth as they go around it.
The Red Dot team used the wobble technique. They used the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at the European Southern Observatory in Chile.
A Year Lasts 9 Days on One Planet and 22 Days on the Other
From the signals received by HARPS, the research team determined that a year on Gliese 887b lasts just nine days and only twenty-two days on Gliese 887b. For some perspective, a year on our innermost planet, Mercury takes 88 days, and Mercury isn’t much bigger than the moon.
Gliese 887 isn’t far away in interstellar terms. It’s about eleven light-years away from our Sun. That puts it further out than Proxima Centauri at four light-years, but still in our vicinity.
The Red Dots detected a third signal, but they weren’t able to pin it down. It could be coming from a third Super-Earth planet with an orbit of about fifty days.
Third Super-Earth Planet with an Orbit of Fifty Days
If the third signal pans out, its planet would be well inside the habitable zone of Gliese 887. It would be an even more promising candidate in the search for life beyond the solar system.
These newly discovered planets are timely. The new James Webb Space Telescope launches at the end of March 2021. It will be the perfect instrument to take these discoveries further and answer the questions arising from these new Super-Earth planets.
The Red Dots say they’re “an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely, are there Earth-like planets around the nearest stars?” They’re right to believe that just about everyone is curious about that question.
“Are There Earth-Like Planets Around the Nearest Stars?”
Understanding whether life here on Earth is unique or whether it’s a commonplace throughout the galaxy would help us find our place in nature. All human cultures have stories about where the world came from, but these days it feels like science has snatched them all away.
We’re now on the brink of an exciting era where a new story is coming into view. Because it’s science-based, we can all accept it as literally true, and it belongs to all of us.
The Red Dots play an essential role in this process. Their focus on nearby red dwarfs has been a highly productive strategy.
Dr. Sandra Jeffers, from the University of Göttingen, is the lead author of the study. She explains it this way. “These planets will provide the best possibilities for more detailed studies, including the search for life outside our Solar System.”
We always have more to learn if we dare to know.
Learn more:
Super-Earths discovered orbiting nearby red dwarf
A multiplanet system of super-Earths orbiting the brightest red dwarf star GJ 887
Astrobiology: Three Questions We Need to Answer
Earthlike Planet Found by NASA’s TESS
Intelligent Life on Other Planets – Odds of Finding It
