 |
Our Galaxy's Habitable Zone
Where are the habitable planets in our galaxy and how numerous are they during the course of the galaxy's life? A new paper by researchers Michael G. Gowanlock, David R. Patton and Sabine M. McConnell seeks to provide answers to these questions.
We present a model of the Galactic Habitable Zone (GHZ), described in terms of
the spatial and temporal dimensions of the Galaxy that may favour the development
of complex life. The Milky Way galaxy is modelled using a computational approach
by populating stars and their planetary systems on an individual basis using MonteCarlo methods. We begin with well-established properties of the disk of the Milky
Way, such as the stellar number density distribution, the initial mass function, the
star formation history, and the metallicity gradient as a function of radial position and
time. We vary some of these properties, creating four models to test the sensitivity
of our assumptions. To assess habitability on the Galactic scale, we model supernova
rates, planet formation, and the time required for complex life to evolve. Our study
improves on other literature on the GHZ by populating stars on an individual basis and
by modelling SNII and SNIa sterilizations by selecting their progenitors from within
this preexisting stellar population. Furthermore, we consider habitability on tidally
locked and non-tidally locked planets separately, and study habitability as a function
of height above and below the Galactic midplane. In the model that most accurately
reproduces the properties of the Galaxy, the results indicate that an individual SNIa
is ∼5.6× more lethal than an individual SNII on average. In addition, we predict that
∼1.2% of all stars host a planet that may have been capable of supporting complex
life at some point in the history of the Galaxy. Of those stars with a habitable planet,
∼75% of planets are predicted to be in a tidally locked configuration with their host
star. The majority of these planets that may support complex life are found towards
the inner Galaxy, distributed within, and significantly above and below, the Galactic
midplane.
(Habitable planets [pdf])
In this Figure, Model 1 is plotted. Top Left panel: The number of planets that are habitable (tidally-locked and non-locked) as a function of radial distance and time. We trace the history of each habitable planet to determine in which periods they remain habitable. It is clear, given the assumptions made in our model, that the number of habitable planets is greatest in the inner Galaxy, at all epochs. Top right panel: The fraction of stars with a habitable planet as a function of time and radial distance. We trace the history of each habitable planet to determine in which periods they remain habitable. Given the assumptions made in the model, the inner region of the Galaxy exhibits the highest probability of having habitable planets at the present day. At R∼5-11 kpc, at the present day, the entire range has roughly the same probability of having habitable planets. Lower Left panel: The number of habitable planets integrated over all epochs as a function of radial distance and height above the midplane. We predict that the position in the Galaxy with the greatest number of habitable planets is located in and around the midplane in the inner Galaxy. Lower Right panel: The fraction of habitable planets integrated over all epochs as a function of radial distance and height above the midplane. The region with the greatest fraction of habitable planets exists above the midplane in the inner Galaxy. The high metallicity that produces a high planet formation rate and the lower stellar density that exists well above the midplane at this radial position permits a greater fraction of habitable planets to form.
When I read about this kind of research, I think about the science fiction authors who expanded our ideas about life in the galaxy, like E.E. 'Doc' Smith and Isaac Asimov. Your favorites?
From A Model of Habitability Within the Milky Way Galaxy by Michael G. Gowanlock, David R. Patton and Sabine M. McConnell.
Scroll down for more stories in the same category. (Story submitted 7/15/2011)
Follow this kind of news @Technovelgy.| Email | RSS | Blog It | Stumble | del.icio.us | Digg | Reddit |
Would
you like to contribute a story tip?
It's easy:
Get the URL of the story, and the related sf author, and add
it here.
Comment/Join discussion ( 1 )
Related News Stories - (" Space Tech ")
Mercury Capsule Ablative Shielding
'...a synthetic which air-friction would erode away.' - Doc Smith, 1934.
Heinlein And Russian Quail In Orbit
'No earth-hatched bird can learn to fly in that fashion...' - Robert Heinlein, 1942.
Space Construction Tools For Large Structures By OAC
'Mass-produced in the orbiting factories...'
Comercial Airlock 'Bishop' Now On ISS
'They put the bones and the glass can that had contained the soup into the double-doored partition or vestibule...' - John Jacob Astor IV, 1894.
Technovelgy (that's tech-novel-gee!) is devoted to the creative science inventions and ideas of sf authors. Look for the Invention Category that interests you, the Glossary, the Invention Timeline, or see what's New.
Current News
Nuclear Batteries May Pack Inner Punch
'... the most super-valuable substance in the solar system.'
Elon Musk STILL Wants To Make Heinlein's 1940's Speedster
'As she neared the barrier the car surged and lifted...'
Mercury Capsule Ablative Shielding
'...a synthetic which air-friction would erode away.'
Heinlein And Russian Quail In Orbit
'No earth-hatched bird can learn to fly in that fashion...'
Listen Up, Coppertop - Wearable Device Turns You Into A Battery
'It's our way or the highway.'
Solar Powered Robot Cleans Up Solar Panels For Free
'... with large padded feet, who were apparently polishing their way the whole length of Rama's six artificial suns.'
Spot Arm From Boston Dynamics Picks Up Like Heinlein's Hired Girl Robot
'Anything larger than a BB shot it picked up and placed in a tray on its upper surface...'
Electric Vehicle Prices Will Drop To $2,890
'the human seats took up two-thirds of the room in each'
TIGER Ultimate Mobility Vehicle From Hyundai
'He admired the fast-plodding, articulated legs...'
Drones Communicate With Each Other Using Quantum Encryption
'the curious absent look of a robot talking on the TBR circuits...'
Space Construction Tools For Large Structures By OAC
'Mass-produced in the orbiting factories...'
SpinCare Electrospins And Shoots Wound Dressing
'Over her lacerated right shoulder he sprayed art-derm...'
Tesla Model S And X Moves Toward KITT Knight Rider Styling
Now, that was a Pontiac Trans Am with some real style.
Sophia Robots By The Thousands
'There is a built-in microphone that hears everything you say, and an electric brain that selects a suitable answer.'
Scaly-Foot Snail Works With Iron
'Micro-Scale suit tiles fabricated by genetically engineered metal affinity bacteria...'
Updated Piaggio Gita Personal Robot Porter
'Carry his bag... and follow him faithfully...'
