Posted on 12/28/2022 11:14:08 AM PST by Red Badger
Bold Colour Image depicting the Solar System (NASA)
Since the landmark discovery in 1992 of two planets orbiting a star outside of our Solar System, thousands of new worlds have been added to a rapidly growing list of 'exoplanets' in the Milky Way galaxy.
We've learnt many things from this vast catalogue of alien worlds orbiting alien stars. But one small detail stands out like a sore thumb. We've found nothing else out there like our own Solar System.
This has led some to conclude that our home star and its brood could be outliers in some way – perhaps the only planetary system of its kind.
By extension, this could mean life itself is an outlier; that the conditions that formed Earth and its veneer of self-replicating chemistry are difficult to replicate.
If you're just looking at the numbers, the outlook is grim. By a large margin, the most numerous exoplanets we've identified to date are of a type not known to be conducive to life: giants and subgiants, of the gas and maybe ice variety.
Most exoplanets we've seen so far orbit their stars very closely, practically hugging them; so close that their sizzling temperatures would be much higher than the known habitability range.
Artist's impression of an ultra-hot Jupiter transiting its star. (ESO/M. Kornmesser)
It's possible that as we continue searching, the statistics will balance out and we'll see more places that remind us of our own backyard. But the issue is much more complex than just looking at numbers. Exoplanet science is limited by the capabilities of our technology. More than that, our impression of the true variety of alien worlds risks being limited by our own imagination.
What's really out there in the Milky Way galaxy, and beyond, may be very different from what we actually see.
Expectations, and how to thwart them Exoplanet science has a history of subverting expectations, right from the very beginning.
"If you go back to that world I grew up in when I was a kid, we only knew of one planetary system," planetary scientist Jonti Horner of the University of Southern Queensland tells ScienceAlert.
"And so that was this kind of implicit assumption, and sometimes the explicit assumption, that all planetary systems would be like this. You know, you'd have rocky planets near the star that were quite small, you'd have gas giants a long way from the star that were quite big. And that's how planetary systems would be."
For this reason, it took scientists a while to identify an exoplanet orbiting a main sequence star, like our Sun. Assuming other solar systems were like ours, the tell-tale signs of heavyweight planets tugging on their stars would take years to observe, just as it takes our own gas giants years to complete an orbit.
Based on such lengthy periods of a single measurement, it didn't seem worth the trouble to sift through a relatively short history of observations for many stars to conclusively sift out a fellow main-sequence solar system.
When they finally did look, the exoplanet they found was nothing like what they were expecting: a gas giant half the mass (and twice the size) of Jupiter orbiting so close to its host star, its year equals 4.2 days, and its atmosphere scorches at temperatures of around 1,000 degrees Celsius (1800 degrees Fahrenheit).
Since then, we've learnt these 'Hot Jupiter' type planets aren't oddities at all. If anything, they seem relatively common.
We know now that there's a lot more variety out there in the galaxy than what we see in our home system. However, it's important not to assume that what we can currently detect is all that the Milky Way has to offer. If there's anything out there like our own Solar System, it's very possibly beyond our detection capabilities.
"Things like the Solar System are very hard for us to find, they're a bit beyond us technologically at the minute," Horner says.
"The terrestrial planets would be very unlikely to be picked up from any of the surveys we've done so far. You're very unlikely to be able to find a Mercury, Venus, Earth and Mars around a star like the Sun."
How to find a planet
Let's be perfectly clear: the methods we use to detect exoplanets are incredibly clever. There are currently two that are the workhorses of the exoplanet detection toolkit: the transit method, and the radial velocity method.
In both cases, you need a telescope sensitive to very minute changes in the light of a star. The signals each are looking for, however, couldn't be more different.
For the transit method you'll need a telescope that can keep a star fixed in its view for a sustained period of time. That's why instruments such as NASA's space-based Transiting Exoplanet Survey Satellite (TESS) is such a powerhouse, capable of locking onto a segment of the sky for over 27 days without being interrupted by Earth's rotation.
VIDEO AT LINK..................
The aim for these kinds of telescopes is to spot the signal of a transit – when an exoplanet passes between us and its host star, like a tiny cloud blotting out a few rays of sunshine. These dips in light are tiny, as you can imagine. And one blip is insufficient to confidently infer the presence of an exoplanet; there are many things that can dim a star's light, many of which are one-off events. Multiple transits, especially ones that exhibit regular periodicity, are the gold standard.
Therefore, larger exoplanets that are on short orbital periods, closer to their stars than Mercury is to the Sun (some much, much closer, on orbits of less than one Earth week), are favored in the data.
The radial velocity method detects the wobble of a star caused by the gravitational pull of the exoplanet as it swings around in its orbit. A planetary system, you see, doesn't really orbit a star, so much as dance in a coordinated shuffle. The star and the planets orbit a mutual center of gravity, known as the barycenter. For the Solar System, that's a point very, very close to the surface of the Sun, or just outside it, primarily due to the influence of Jupiter, which is more than twice the mass of all the rest of the planets combined.
Unlike a transit's blink-and-you-miss-it event, the shift in the star's position is an ongoing change that doesn't require constant monitoring to notice. We can detect the motion of distant stars orbiting their barycenters because that motion changes their light due to something called the Doppler effect.
As the star moves towards us, the waves of light coming in our direction are squished slightly, towards the bluer end of the spectrum; as it moves away, the waves stretch towards the redder end. A regular 'wobble' in the star's light suggests the presence of an orbital companion.
Again, the data tends to favor larger planets that exert a stronger gravitational influence, on shorter, closer orbits to their star.
Aside from these two prominent methods, it's possible on occasion to directly image an exoplanet as it orbits its star. Though an extremely difficult thing to do, it may become more common in the JWST era.
According to astronomer Daniel Bayliss of the University of Warwick in the UK, this approach would uncover an almost opposite class of exoplanet to the short-orbit variety. In order to see an exoplanet without it being swamped by the glare of its parent star, the two bodies need to have a very wide separation. This means the direct imaging approach favors planets on relatively long orbits.
However, larger exoplanets would still be spotted more easily through this method, for obvious reasons.
"Each of the discovery methods has its own biases," Bayliss explains.
Earth with its year-long loop around the Sun sits between the orbital extremes favored by different detection techniques, he adds, so "to find planets with a one year orbit is still very, very difficult."
What's out there?
By far, the most numerous group of exoplanets is a class that isn't even represented in the Solar System. That's the mini-Neptune – gas-enveloped exoplanets that are smaller than Neptune and larger than Earth in size.
Rocky planet surrounded by purple haze and a star in the distance on the left
Illustration of the mini-Neptune TOI 560.01, orbiting its solitary star. (W. M. Keck Observatory/Adam Makarenko)
Most of the confirmed exoplanets are on much shorter orbits than Earth; in fact, more than half have orbits of less than 20 days.
Most of the exoplanets we've found orbit solitary stars, much like our Sun. Fewer than 10 percent are in multi-star systems. Yet most of the stars in the Milky Way are members of a multi-star systems, with estimates as high as 80 percent seen in a partnership orbiting at least one other star.
Think about that for a moment, though. Does that mean that exoplanets are more common around single stars – or that exoplanets are harder to detect around multiple stars? The presence of more than one source of light can distort or obscure the very similar (but much smaller) signals we're trying to detect from exoplanets, but it might also be reasoned that multi-star systems complicate planet formation in some way.
And this brings us back home again, back to our Solar System. As odd as home seems in the context of everything we've found, it might not be uncommon at all.
"I think it is fair enough to say that there's actually some very common types of planets that are missing from our Solar System," says Bayliss.
"Super Earths that look a little bit like Earth but have double the radius, we don't have anything like that. We don't have these mini-Neptunes. So I think it is fair enough to say that there are some very common planets that we don't see in our own Solar System.
"Now, whether that makes our Solar System rare or not, I think I wouldn't go that far. Because there could be a lot of other stars that have a Solar System-type set of planets that we just don't see yet."
An artist's illustration of many planets and stars in the Milky Way. This artist's illustration gives an impression of how common planets are around the stars in the Milky Way. (ESO/M. Kornmesser) On the brink of discovery The first exoplanets were discovered just 30 years ago orbiting a pulsar, a star completely unlike our own. Since then, the technology has improved out of sight. Now that scientists know what to look for, they can devise better and better ways to find them around a greater diversity of stars.
And, as the technology advances, so too will our ability to find smaller and smaller worlds.
This means that exoplanet science could be on the brink of discovering thousands of worlds hidden from our current view. As Horner points out, in astronomy, there are way more small things than big things.
Red dwarf stars are a perfect example. They're the most common type of star in the Milky Way – and they're tiny, up to about half the mass of the Sun. They're so small and dim that we can't see them with the naked eye, yet they account for up to 75 percent of all stars in the galaxy.
Right now, when it comes to statistically understanding exoplanets, we're operating with incomplete information, because there are types of worlds we just can't see.
That is bound to change.
"I just have this nagging feeling that if you come back in 20 years time, you'll look at those statements that mini-Neptunes are the most common kind of planets with about as much skepticism as you'd look back at statements from the early 1990s that said you'd only get rocky planets next to the star," Horner tells ScienceAlert.
"Now, I could well be proved wrong. This is how science works. But my thinking is that when we get to the point that we can discover things that are Earth-sized and smaller, we'll find that there are more things that are Earth-sized and smaller than there are things that are Neptune-sized."
And maybe we'll find that our oddball little planetary system, in all its quirks and wonders, isn't so alone in the cosmos after all.
You failed to capitalize “bible” to Bible! You’re going to hell!
Actually, the standardization of spelling in English remains contentious. Ever see Scots orthography?
I have a right to criticize, even if it’s subjective. Your seeming desire to stifle that marks you as left-leaning.
“We’ve Never Found Anything Like The Solar System.”
That remark clearly indicates the author has neither any idea of historical remarks nor geo-whatever evidence. It is actually quite infuriating to me that the author thinks we have reached such intelligence that surely we would’ve found evidence of said systems by now. IDIOT!!
Opus what?
The salient statement in your reference on the Drake equation:
“The challenge (at least for now) is that astronomers don’t have firm numbers on any of those variables, so any calculation of the Drake Equation remains a rough estimate for now. ‘
Translated into normal English: any predictions resulting from the Drake equation are essentially based on numbers astronomers have pulled out of their posterior orifices.
Truth be told, unless we have some idea of the odds of life developing on an Earth-like planet (and we have no idea of those odds, since we have no idea of the step-by-step mechanisms of going from a promordial soup to a primitive bacterium) it doesn’t matter how many galaxies, stars, earth-like planets exist - we’ll stil have no idea whether life is plentiful or rare - well, not unless ET stops by and says Hi! some day.
I was stationed in England for a year and a half, I learnt several different usages and spellings in written and spoken English.
Dang! I knew I’d screw it up eventually!
“so any calculation of the Drake Equation remains a rough estimate for now. “
AKA wild a$$ guess.
Not anymore then having a kid disobey you... :-)
Bump
Personal theory: since humanity (i.e., regular humans) will continue to exist, less the resurrected and transformed Christians, all those planets and solar systems exist to house the ever-growing population of people. The saints will supervise angels in terra-forming those planets to make them fit for human existence, and so humanity will spread (light speed no longer being a limit) throughout the universes infinitely.
The Drake equation is a proposal dependent on conjecture, verified by speculation, and documented by assumptions.
Earth’s a superfreak?
Superfreak!
It’s superfreaky?
Bible prophecy is what proves the creator God of the Bible. Only God, being omniscient, knows the future. How accurate he is can be proven, hundreds of prophesies in the Old Testament about Jesus Christ, for instance, who came on the scene hundreds of years after those prophesies.
These considerations troubles me. Why, you might ask. Because FR is probably the most conservative site on the web. And what do we see on this thread, but post after post by unbelievers in God.
This is prophesied, by the way, that it would happen, in passages like 2 Peter 3:3-7, for instance, that scoffers will come in the last days. And what do we see, on probably the best representation of what’s left of believing Americans (America the nation having the most faith in God) with a Biblical worldview, post after post by scoffers, skeptics, and some outright atheists.
Many cosmological arguments on this thread whether there is a creator God or not. But this is one argument I haven’t seen yet, that only God knows the future. And right here on FR, where you would expect to find a great preponderance of conservative believers, I am not seeing it.
Which proves God true. These unbelieving times being prophesied, and we’re seeing it right here on FR of all places.
I’m not sure if C.S. Lewis thought if we were alone or if there were other beings in the Universe (perhaps the later). I know that he did posit the idea that if there were other beings he wondered if they had fallen into sin or if they were still in their Garden of Eden.
And then he wrote something that I find amazing. Something along the lines of how we were the fortunate ones to have fallen into sin so that we could experience the wonderful grace of God.
Interesting and profound way of looking at it. Although it might just be him making lemonaide out of lemons. I’d prefer to be in the Garden of Eden with God. (Well - until I screwed up and got cast out.)
I think that is an equally valid theory. The brain spins when one thinks about all the stuff NOT mentioned regarding eternity and the universe, and just unbelievably huge and incomprehensibly infinite it is. It’s hard to imagine that it is all there (including the part we can’t see) just to give us twinkly stars.
Yep. It’s very interesting to ponder.
I recently came up with two theories.
1. There was nothing special about the tree of the knowledge of good and evil. Rather, he told us not to eat of it and, when we did, we had knowledge of good and evil. We had disobeyed and we were ashamed. In the end, it was just another tree.
And I think of it like he’s dad, we’re a 12 year old, and the tree is the car. He tells us not to drive it, but we take the keys and take it for a spin. In the end, he was going to, when we were 16 and ready, give us the keys and give us the car, but we rushed it and smacked a tree joyriding.
Our ability to discover earth-sized planets is limited. It’s like being blind and claiming that nothing exists because you cannot see it.
An infinite God will create an infinite universe.
How long ago?
Wasn’t a valid spelling in Ireland in the 1970s that I recall. Any other word ending in “-rn” had the suffix “-ed” as the past tense.
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