Hi all,
I'm new here and this is my first post. The reason I'm posting is that ever since HD 28185 has been discovered, I've thought that it is our best chance for finding a compatible planet (so called 'Next Earth') to colonize. However, the 'experts' haven't focused on it, which I think is a huge mistake. Please read my article on this, and let me know your thoughts. If you'd like, you can e-mail me at
astro_kct@hotmail.com
~ Thanks
The Case for HD 28185b:
An argument for why HD 28185b may be the most viable
Next-Earth of all known exoplanets
by kct
In the search for extraterrestrial life, there is an interesting subcategory investigating potential habitable planets. Astrophysicists agree that a planet must pass certain criteria in order to be considered a likely candidate for extraterrestrial intelligence. But if one was simply looking for a habitable planet (i.e. one that life could be sustained), as opposed to an inhabited planet (i.e. one that life, perhaps intelligent life, already exists), the criteria become a bit less stringent.
Habitable Zone
A key prerequisite for a planet to be deemed habitable is it must reside in the star system’s ‘habitable zone’ (HZ). In other words, it must orbit in the region of a solar system where temperature and pressure are such that liquid water can firmly exist on the planet surface, and where carbon-based life forms can live or evolve. This zone changes as the star ages, but for a star similar to our own sun, the HZ would roughly be between 0.95 astronomical units (AU) to 1.37 AU. HD 28185b not only meets this criteria, it hits the bulls-eye! ‘Big Blue,’ as I dubbed it for reasons that will become clear, orbits its star at a distance of 1.03 AU—almost precisely the same distance that Earth orbits around the sun.
The orbital distance alone is not the only criteria for a ‘habitable zone’: the orbit itself must be fairly circular, otherwise life-forms would alternately be burned or frozen as the planet moved towards and away from, its sun. Again, ‘Big Blue’ passes the test with flying colors: with an eccentricity of just 0.07 AU (± 0.04), HD 28185b’s orbit is nearly circular, once again much like the Earth’s. Finally, for the convenience of future human colonists, the planet’s period should be fairly similar to our Earth year—again, HD 28185b’s delivers, with a Big Blue-year consisting of 385 days, just 20 days longer than our own.
Main-sequence Star
Still, all this stuff about a habitable zone would be worthless if the star it orbited around was not of the right spectral class. In Search for Extra-Terrestrial Intelligence (SETI) terms, a planet’s corresponding star would have to be a G-class ‘main-sequence’ (V) yellow star (the temperature of the star is classified as O, B, A, F, G, K and M), which burns long and steady enough to support the evolution of life. Our sun is a G2V yellow star, and any star that would anchor a solar system capable of supporting life in its habitable zone would have to be a G-class ‘main-sequence’ (V) star (some theorize that some F-type or K-type stars could also provide enough stability for life, but for simplicity we’ll stick with G-class stars here). The star HD 28185 is a G5V yellow star, again superbly meeting this key criterion.
The Box
So wow, we’ve discovered a planet that is almost exactly as far away from its star as Earth is from its sun, smack in the middle of the ‘habitable zone,’ and its star is that rare, precious G-type main-sequence star?! This is major news—when is NASA sending a probe? Unfortunately, this is where every scientific article grinds to a halt. As a reader, examining article after article making an unnecessary (and I propose wrong) assumption, it’s as though each author has the inability to think outside the boundaries created by the commonalities of our own solar system.
A Massive Dilemma
HD 28185b is 5.6 times the mass of Jupiter, or about 1800 times the mass of the Earth. Such a massive, jovian planet would almost certainly be a gaseous planet, right? After all, every example of a massive planet in our own solar system is in fact gaseous: Jupiter, Saturn, Neptune, and Uranus are giant balls of gas, with intense atmospheric pressures and likely no solid rocky ‘ground’ for life-forms to live and/or develop.
Differentiation between Earth-sized and Earth-like planets
So for years we have been able to detect Jupiter-sized planets around extrasolar stars, only to dispose them as likely candidates for habitability due to their mass. Sustaining life, each scientist states, requires a small, rocky planet, not a large, gaseous planet. Perhaps the use of the term ‘jovian’ to describe both planets of similar mass as Jupiter as well as its gaseous nature is where this problem originated. But ask yourselves for just a minute, what if a planet’s large mass did not inevitably necessitate a gaseous planet? Well, make that leap outside the box, and it opens a vast new range of possibilities.
Doing so reveals that Santos, Mayor, Naef, Pepe, Queloz , Udry, and Burnet may have made a much bigger discovery than any of us have realized, perhaps finding the ‘Big Blue’ companion to Earth (that little blue marble in space) three years ago, and every scientist in the globe thoroughly dismissed this precious information as just another ‘jovian’ planet discovery.
Sample-size
Any pollster or mathematician will tell you that sample-size is essential to deriving an accurate determination for any calculation. A sample-size of nine (as in the planets of our solar system), when the overall field is one of billions (if not trillions) would be laughed at by any mathematician. It’s like asking nine people how they’ll vote in the upcoming election, and using that to predict the overall voting pattern for the entire country. Actually, it is significantly worse than that, since there are exponentially more planets in the galaxy than people in the United States. Yet that is exactly what we are doing when we eliminate any planet from consideration as a habitable planet simply due to its mass.
The Problem with Pressure
Now wait a second, some will still say. You forgot about gravity and atmospheric pressure. Well, in fact, gravity is actually not much of a problem: while Jupiter is 318 times the mass of the earth, its gravity is only 2.5 times the Earth’s—this is because gravity is also a function of the planet’s density and radius, so a massive planet could easily have gravity very similar to that of the Earth if it was less dense. I assert that any planet with gravity anywhere from 0.20 to 2.5 that of the Earth’s would be something that the human race could adapt to. There is no reason to believe HD 28185b would not have a favorable mass-gravity ratio.
Atmospheric pressure is a bit trickier. After all, Venus could have potentially been an interesting candidate if not for its bone-crushing atmospheric pressure. A planet more than five times the mass of Jupiter would almost certainly create crushing atmospheric pressure, would it not? Well, once again, not necessarily: Venus’ crushing pressure is a function of its heavy atmosphere, which is partly due to its gas composition (mainly CO2 and sulfuric acid). But imagine, if you will, an atmosphere primarily composed of nitrogen, with small parts of oxygen and H2O. In this scenario of, let’s say over 90% nitrogen, this gas, commonly acknowledged as vital to life, has the added benefit of reducing the partial pressure of oxygen and other gases.
That, of course, would be an almost ideal scenario. Even in a less hospitable atmosphere, a planet large enough to have the mass of 5.6 times that of Jupiter (and be rocky vice gaseous, as discussed previously) would almost certainly contain huge mountain ranges that dwarf those of Earth. As we hike up those mountains, the atmospheric pressure would eventually get to a level comfortable for life to exist. In a world the size of HD 28185, even the mountain ranges alone would cover a habitable area many times that of the entire Earth. Jupiter itself has a hospitable atmospheric pressure if you go up high enough in its methane clouds—the problem with Jupiter is primarily its gaseous state and gas composition, not it’s pressure. After all, if one goes deep enough in Earth’s oceans, the pressure is just as crushing and inhospitable as that of any exoplanet. But again, this jovian-by-association stigma has kept scientific thinking inside a box and has hampered scientific innovation and discovery.
A Great Risk-Reward Ratio
Critics may point out that there have been a couple of key assumptions made in this paper in order for HD 28185b to prove hospitable to life. Still, I maintain that those assertions are just as likely in our infinite universe as the common assumption that a jovian-size planet must also be a Jupiter-like planet and that the only Earth-like planets out there must also be Earth-sized. I challenge those assertions—and fortunately we have the means within our grasp to determine the viability of HD 28185b in the very near future.
The Terrestrial Planet Finder (TPF), a NASA mission scheduled for 2015, will have the means through the science of spectroscopy to determine whether exoplanets have atmospheres and establish whether they are habitable. Such a mission would expose the atmospheric composition of HD 28185b, and tell us whether Next-Earth lies within our grasp. However, with plans to focus on terrestrial planets, defined in the narrow sense I described above, the fear is that HD 28185b and other jovian-size planets in the habitable zone will be overlooked in favor of smaller planets. And that would be a shame, as a great opportunity for discovery may be missed.
So what will we do? Faced with such potentially great reward as the discovery of the Next Earth (‘Big Blue’), will we let our imagination guide us to greatness, or will we continue to remain confined within our narrow understanding of the cosmos? I submit that there is no choice at all: we must determine its atmosphere, and if the results yield favorable conditions, it would launch a new era in aeronautics similar to that of the great automobile and computer technology eras, one that could see us developing the right spacecraft to reach the HD 28185 star system within 50 years.
Dare to Dream
Let your imagination release your imprisoned possibilities.
-- Robert H. Schuller
Man's mind, once stretched by a new idea, never regains its original dimensions.
-- Oliver Wendell Holmes
The true sign of intelligence is not knowledge but imagination.
-- Albert Einstein
Our imagination is the only limit to what we can hope to have in the future.
-- Charles F. Kettering