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--------------------------- 1872 - New solar systems.
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- Our Solar System appears to be unique by comparison to the 2,325 exoplanets that have been discovered to date. We have inner rocky worlds, outer gas giant planets and no planets closer to the Sun than the planet Mercury.
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- That number, over 2 thousand other planets, are orbiting their star. Our proto star started out as an opaque ring of gas and dust. From this disk 4 rocky planets evolved with 88 day to 687 day orbits.
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- What has been discovered to date are giant gas exoplanets with 12 year to 165 year orbits. These gas giants are 150 times the mass of our 4 terrestrial planets. How different can you get?
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- The first discoveries of exoplanets occurred in 1996. They were all gas giants planets orbiting very close to their star, completing an orbit in a few days. This extremely hot environment for planet formation is contradictory to classical theories for a solar system. To reconcile, the theorists concluded the planets formed farther out and then migrated inward to these tighter orbits.
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- After thousands of exoplanet solar system discoveries the further conclusion is that they are all different. There does not appear to be a standard model for solar system formations. The “average” system contains “ super Earths” orbiting shorter than 100 days. Only about 10% of the systems have gas giants like Jupiter and Saturn.
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- So, why is our inner solar system depleted in mass, ( i.e. only the 4 rocky planets), rather than the super-Earths inside the orbit of Mercury , which is 88 days. The best theories today is that planet orbits “drift“. Once a planet grows large enough its gravitational influence propagates through the rotating disk. This perturbation causes positive and negative feedback forces between the planets. Exchanges of momentum and energy occur.
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- Computer simulations are busy trying to simulate is happening for our Solar System. One working theory is that because Saturn has lower mass its inward migration rate is faster than Jupiter’s When their orbits reach a point of “mean motion resonance”, Jupiter completes 3 orbits as Saturn completes 2 orbits. A 3 to 2 resonance occurs.
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- The resonance orbits exchange momentum and energy to achieve an amplified common gravitational influence on each other. These two giant planets cleaned out a giant gap in the planetary disk.
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- Jupiter migrated outward from the Sun shepherding planetesimals in its path through the disk. This triggered a collisional cascade that eroded the inner orbit planetesimal population. The inner planets received swarms of debris bleeding off their orbital energy. The 4 terrestrial planets, Mercury, Venus Earth, Mars, coalesced hundreds of millions of years later is all the remains.
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- Jupiter - Saturn resonance locked in Uranus and Neptune into resonance orbits as well. Their nearly circular orbits and resonances settled down into enduring stability for our Solar System.
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- Beyond Neptune another mystery appeared. The Kuiper Belt objects have an unexpected structure. The orbits of the larger objects are highly clustered. They seem to be subject to a common , large perturbation To get the computer simulations to work we need an unobserved 9th Planet 10 times the mass of the Earth. Its eccentric orbit would take 20,000 years.
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- We have more to learn to write the complete biography of our Solar System over its 4.6 billion years lifetime. Here is the short story:
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- Halfway out from the center of the Milky Way Galaxy a giant molecular cloud collapsed into its core creating a proto sun and a disk of gas and dust. The spinning proto sun created magnetic field that accreted into a star. The orbiting disk was full of growing planetesimals , a few super Earths, and began accreting gas into proto-Jupiter and proto-Neptune. Jupiter and Saturn lock in resonance and drift to the outer Solar System.
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- The inner gap to the Sun was occupies by rocky debris. The outer giant planets were encircled by a ring of “icy” debris. The 4 rocky planets and the asteroid belt formed from the rocky debris. The outer planets shifted out of resonance creating chaotic shifts that may have ejected a 9th planet until the system restabilized their orbits. The Kuiper Belt sent a barrage of impactors hurtling through the inner solar system. Possibly bringing water and life to the planet Earth 3.8 billion years ago.
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- The Earth’s and life’s biography continues to be written. The miracle resides in the fact that we are here writing and reading this biography. It is like your hand drawing a sketch of itself drawing a hand. Whose hand is guiding the whole process?
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- This past year 1,284 more exoplanets have been discovered in “other solar systems“. Previously 1,041 planets had been discovered starting in 1996. The breakthrough in the rate of discovery was made by software. The NASA Kepler telescope collects the data on hundreds of candidates at once. The software parses out the true signal from the noise. Astronomers were working on one at a time. The new software analyzes 100’s all at once.
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- Kepler requires 3 planet transits to prove the candidate is an orbiting planet. 84 have orbital periods longer than 100 days. The longest period is 510 days. Obviously , we need to watch the same spot for a long time to capture 3 of these transits. It is 15 years of hard work ( See Review # 1070 The Kepler Space Telescope )
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- Today there are over 3,000 planet candidates to be validated. 1,284 that have been validated our mini-Neptunes in size, at the lower limits of being a giant gas planet. The biggest sample are super-Earth size, some Earth size and some Neptune size.
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- How do astronomers measure orbits to tell if a candidate is a transiting planet?
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- They measure the redshift of lightwaves. It is the Doppler Effect like with sound waves except with lightwaves. As the light source is coming towards us the wavelength is shortened, the frequency appears to increase, and the lightwave is shifted towards the blue end of the light spectrum.
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- If the edge of the star is rotating towards us the frequency is “ blue shifted” Lightwaves sourced on the opposite side of the star are traveling away form us. They are “redshifted”. The wavelengths appear wider, or stretched, towards the red end of the spectrum.
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- If there is a planet orbiting the star, And, if its orbit plane is in our line of sight, the planet will block the blue-light shift and an orbit time later will block the red-light shift. Repeat this several times to make certain the data is pure and not corrupted by sunspots of interstellar clouds, or systematic errors in measuring the light intensity.
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- Then the data can be used to calculate the rotation rate of the star, the rotation rate of the planet’s orbit, and the distance of the planet from the star.
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- This artificial color shift created by the planet blocking the light is called the “Rossiter-McLaughlin Effect”
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- If the orbit is “ retrograde” with the star blue-red sequence is reversed.
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- It is only a couple decades ago we had only 9 planets to study, including Pluto. Today we have “ Dwarf Planets” outside Pluto and possibly another 9th planet in our Solar System. And, we have another 2,325 exoplanets to study , with more discoveries to come. Stay tuned, an announcement will be made shortly.
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- Request these Reviews to learn more:
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- #1826 - How big is our Solar System? Does the math for calculating the mass in our Solar System. Evidence of Dark Matter and Planet X.
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- Lists 5 other Reviews about our Solar System.
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----- 707-536-3272 ---------------- Monday, May 16, 2016 -----
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