The Goldilocks area takes its name from the fairy tale “Goldilocks and the Three Bears”. Goldilocks is a picky little girl whose porridge needs to be just right – neither too hot nor too cold. The same is true of life itself — or at least the kind of water-based life we’re familiar with on Earth.
Because a planet has to be “just right” or be able to support life, it can’t be so cold that water only exists as frozen ice, and it can’t be so hot that the water boils away. It is believed that only planets within a certain range of orbits called the “Goldilocks Zone” – or officially known as the “habitable zone” – are capable of supporting life.
Definition of the habitable zone
When a planet’s orbit puts it too close to its parent star, it’s too hot for liquid water to exist, and when it’s too far away, it’s too cold. However, the actual distances that define the habitable zone vary between stars.
Our own Sun is a G-type yellow dwarf and there is no doubt where its habitable zone lies because Earth occupies that zone and orbits about 150 million kilometers from the star.
But for M-type red dwarfs, which are smaller and cooler than the Sun, the habitable zone is much closer to the star. For a larger, hotter A-type star like Sirius, the Goldilocks zone is further out NASA.
For astrobiologists looking for life on other planets, staying in the habitable zone is just one of the factors to consider. Take our own moon, for example. It’s obviously in the Goldilocks zone because it’s so close Earthbut there is no liquid water on its surface.
According to Space.com, atmospheric pressure and composition must also be taken into account. That makes them moonwhich has no atmosphere to speak of, unable to bear life on its own.
It’s also important not to interpret too much into the word habitable. Even if the conditions on a planet are just right for liquid water to exist, that doesn’t necessarily mean it’s inhabited. That’s exactly what scientists haven’t figured out yet Origins of Life on Earthso we don’t know what other fine ingredients are necessary besides water and an atmosphere.
Our own solar system is the most studied of all planetary systems. Theorists have figured out where its Goldilocks zone should be by estimating a planet’s surface temperature based on the amount of solar heat it receives.
So far, the results are consistent with what we know from observations. Earth—a very watery planet teeming with life—lies comfortably within the habitable zone. Mars, which used to have plenty of water but is now a barren desert, lies just off its outer edge. On the inner edge is Venus – a scaldingly hot planet, thanks to its proximity to the Sun and its super-thick atmosphere NASA.
Exoplanets in the Goldilocks Zone
The discovery of something new exoplanets Orbiting distant stars has become almost commonplace. But it’s always exciting to be found in your parent star’s Goldilocks zone.
That’s what happened in 2016 in the case of Proxima B, which orbits the Sun’s nearest neighbor in space – the red dwarf Proxima Centauri, just over 4 light-years away. It’s so small and dark that its habitable zone is a very short distance away, but Proxima B — which whizzes around the star once every 11 days — is safely within it, they say European Southern Observatory (ESO).
Another much-studied red dwarf is Trappist-1. At around 40 light-years, it’s farther away than Proxima, but still a close cosmically neighbor. Trappist-1 is notable for having seven known rocky planets, three of which are in the star’s Goldilocks zone, according to NASA.
It is possible for water to exist on all seven planets, but only on the three within the habitable zone in a liquid state. It would take the form of atmospheric water vapor on planets closer to the star, or ice on those farthest from them. Astronomers are understandably interested in learning more about the Trappist 1 system, and it is one of the planned targets for the James Webb Space Telescope.
The ultimate engineered solar system
When a solar system forms there is no reason why planets should preferentially appear in the habitable zone, and the TRAPPIST-1 system is unusual in having up to three planets there.
But is there a theoretical limit to how many planets can be squeezed into the Goldilocks zone? That’s a question that astrophysicist Sean Raymond answered on his blog planetplanet.net .
It turns out that there is actually a theoretical limit at which the system becomes unstable because the planets are too close together. Raymond invented what he calls “the ultimate engineered solar system,” with a total of 412 planets in the habitable zone, arranged around eight concentric orbits rotating alternately in prograde and retrograde directions.
Build theoretical solar systems
Here Sean Raymond, inventor of the Ultimate Engineered Solar System, talks about his work.
How did you come to create such a strange arrangement of planets?
“My daily task is to understand how planetary systems form, what makes the solar system different from exoplanet systems that we have discovered, and what types of orbital configurations are stable and which are not. I wanted to find out what kind of orbital architecture would maximize the number of planets in the habitable zone – remain stable, but without having to worry about how the system would have formed. Luckily, I was able to use several recent papers by scientists for inspiration. I’ve also tested the craziest systems with computer simulations to make sure it all holds together.”
Why do you call it the ultimate “engineered” solar system?
“Originally I built two systems, each with about 30 planets in the habitable zone. These systems could plausibly form in nature if just the right sequence of events took place (like rolling a six on two dice ten times in a row). But I can’t imagine how the Ultimate Engineered Solar System could form naturally. A system with equally spaced planets distributed along rings orbiting in opposite directions is just impossible to my knowledge. So if such a system exists, I would argue that it must have been built on purpose, presumably by the engineers of a super-advanced civilization.”
If such a system really existed, how could we detect it from Earth?
“It would be quite difficult to detect because the signals we measure to infer the presence of exoplanets – typically the radial velocity or transit signals – could end up being so confusing that, in the case of the ultimate technique, they are mistaken for noise.” could system.”
For more information about the Goldilocks zone, see “The Goldilocks Zone: Necessary Conditions for Extraterrestrial Life (Searching for Other Earths)” by Laura La Bella and that Video on the habitable zone established by ESA.
- Michele Johnson, “Habitable zones of different stars“, NASA, December 2009.
- Paul Sutter”We don’t really understand the habitable zones of alien planets“ space.com, February 2021.
- Sean Raymond, “The ultimate engineered solar system‘, planetplanet.net, accessed April 2022.
- NASA, “What is the habitable zone?“, 2021
- Sara Rigby, “What does it mean when an exoplanet is “habitable”?“, Science Focus, 2020
- ESO, “Planet found in habitable zone around nearest star“, August 2016
- NASA, “Largest group of Earth-sized planets in the habitable zone found in TRAPPIST-1’s orbit‘, accessed April 2022.
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