Alien solar system boasts tightly spaced planets, unusual orbits

July 21, 2016 by Adam Lowenstein
This GIF shows the synchronized orbit of the Kepler-80 system. Credit: Florida Institute of Technology

Tightly spaced planets inside an alien solar system known as Kepler-80 boast a rare orbital configuration.

The study was led by Mariah MacDonald as an undergraduate with Darin Ragozzine, an assistant professor of physics and space sciences, both at Florida Institute of Technology.

The unusual planetary array highlighted in the study deepens the ongoing examination of similar systems known as STIPs – Systems with Tightly-spaced Inner Planets – and contributes to the understanding of how Earth formed.

The findings will be published soon in the Astronomical Journal and are currently available at mmacdonald.altervista.org/kepler-80.html . MacDonald and Ragozzine gratefully acknowledge the support of 11 coauthors.

Located about 1,100 light years away, Kepler-80, named for the NASA telescope that discovered it, features five small orbiting in extreme proximity to their star. MacDonald and Ragozzine determined the nature of the exoplanetary system through measurements taken with the telescope.

As early as 2012, Kepler scientists found that all five planets orbit in an area about 150 times smaller than the Earth's orbit around the Sun, with "years" of about one, three, four, seven and nine days. The planets' close proximity to each other and their star allowed the Kepler Space Telescope to detect tiny variations (about 0.001 percent) in the length of their "years" due to their mutual gravitational interactions.

Analysis by MacDonald and her collaborators revealed that the outer four planets had masses about four- to six-times that of Earth, though they shared Earth's rocky composition. All four planets have masses similar to one another, though the two outermost planets are almost twice as big. This was attributed to a very puffy hydrogen/helium atmosphere.

These properties are not uncommon for exoplanets, but having precise compositional estimates for multiple planets in the same planetary system is rare.

Another rare attribute of the Kepler-80 system is that its planets have "synchronized" orbits. "The outer four planets return to almost exactly the same configuration every 27 days," said Ragozzine. This effect is known as a "resonance" and helps the system remain gravitationally stable.

The study also explained the origin of the synchronized orbits in general – and possibly the tightly-spaced configuration. In a process called migration, the orbits of these planets shrank over time while they were forming. Simulations clearly showed that this migration effect caused the planets to lock into synchronized orbits just like those seen with Kepler-80.

Kepler has discovered hundreds of other STIPs, which consist of three to seven relatively small and closely packed planets that complete orbits in 1 to 100 days. This new form of planetary system, quite different from our own solar system, is changing the way scientists think about how planets form, including the Earth. With all the knowledge gained by the analysis of Kepler-80, this system is granting important insight into how STIPs formed.

Explore further: Exoplanets' complex orbital structure points to planetary migration in solar systems

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14 comments

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tblakely1357
2.7 / 5 (3) Jul 21, 2016
It seems the more planets we discover the more unusual our solar system is. It doesn't bode well for intelligent life out there.
richardwenzel987
5 / 5 (4) Jul 21, 2016
Insufficient data, really. For all we know, more exotic systems are ideal for intelligent life. For all we know, the solar system was not the most favorable environment for life. We need much more data. I hope we will have that data soon.
MandoZink
3.8 / 5 (5) Jul 21, 2016
It seems the more planets we discover the more unusual our solar system is. It doesn't bode well for intelligent life out there.


Think again. We may lack the imagination to understand the exotic life, unusual habitats, and orbital possibilities that will inevitably start showing up. The variety of systems out there we'll eventually come across is likely more massive than most of us can comprehend.

We really should look forward to an astronomical era of consistent and delightful surprises.
tblakely1357
3.8 / 5 (4) Jul 22, 2016
While life may be ubiquitous, higher lifeforms and especially intelligent life are going to need millions of years of orbital stability and stable planet rotation (something our huge moon provides). If either is not present, the climate changes would be so extreme and so frequent that higher lifeforms would never have a chance to develop.
wduckss
1 / 5 (3) Jul 22, 2016
Should be repeated measurements.
These results argue that gravity operates contrary to the laws of physics and that its impact does not decrease square of the distance.
When Saturn months we share the same orbit. https://en.wikipe...urn#List
antialias_physorg
3.8 / 5 (5) Jul 22, 2016
It seems the more planets we discover the more unusual our solar system is.

Note that detecting these planets close to the star doesn't say anything about the presence of more planets further out. So there's no real "pro" or "con"-life argument to be derived from this. We're not inclusively 'scanning' solar systems. Only the planets that are easily detected are seen.

millions of years of orbital stability and stable planet rotation

Only if such life develops on the surface (and I see no reason why that should be a limit for life).
It could develop in subsurface oceans - like the ones suspected on some moons in our own solar system.

Subsurface life would not require orbital stability nor rotational stability since the power source for such life isn't the sun but internal processes to the planet (radioactive decay)...and that is inherently a very "stable" process. Energy production via decay doesn't suddenly peak or drop off sharply.
torbjorn_b_g_larsson
3.7 / 5 (3) Jul 22, 2016
The annoying thing with these migrant systems is that they mess up easy estimates of which planets have Earth type atmospheres and which has not. Atmospheres would have a dependence on the distance to the young, initially unruly, star.

@tbalekly:
It seems the more planets we discover the more unusual our solar system is..


Reference needed.

While life may be ubiquitous, higher lifeforms and especially intelligent life are going to need millions of years of orbital stability and stable planet rotation (something our huge moon provides). If either is not present, the climate changes would be so extreme and so frequent that higher lifeforms would never have a chance to develop.


And here I can say straight up that there isn't any such references. Modern simulations has revealed a mistake in the old, and moonless planets has sufficiently long periods for complex life. E.g. Mars have 0.5 Gyrs between tilts, and max tilt is just twice ours.

[tbct)
torbjorn_b_g_larsson
3.7 / 5 (3) Jul 22, 2016
[ctd] Curiosity has confirmed such a long habitable period. (Though the extent of the climate variation isn't known yet.)

If anything, our own Moon is dangerously large. After 6 Gyrs, it will tidal lock Earth, which will tilt Earth axis freely over very short periods and extinguish all complex life Luckily we are already toast by then, thanks to our dangerously large Sun.

Let us face it, we got one of the worst place to live in, if we compare to what we could have had. (Smaller star, smaller moons, larger planet, ....).
Macksb
5 / 5 (2) Jul 22, 2016
"Another rare attribute" is that four of its planets are synchronized, with the outer four planets returning to almost exactly the same position every 27 days. See the third paragraph from the bottom of the article.

The details of that synchrony are interesting. As shown in the picture at the top, the outer "pair" appear to synchronize their orbits. The inner pair also appear to synchronize their orbits, but in a different way--180 degrees opposed.

This calls to mind Arthur Winfree's theory of coupled periodic oscillators, which he posited circa 1968. Systems of two periodic oscillators, when coupled, will display either exact synchrony (as the outer pair does here) or exact anti-synchrony (as the inner pair does here). One may also say that the synchrony of the outer pair (as a unit) is exactly opposed by the contrary synchrony of the inner pair (as a unit).
Macksb
5 / 5 (1) Jul 24, 2016
Kepler 223 has a similar 4 planet synchrony. See "Exoplanets complex orbital structure..." Physorg May 11, 2016.

The 4 planets in Kepler 223 are in 2 pairs, both of which are in 4:3 relationships. Considered as a 4 way system their orbits go 8-6-4-3 from the innermost planet to the outermost. Two cycles for the inner pair for every one cycle of the outer pair. One pair syncs 2:1 with the other.

The Kepler 80 pattern is almost the same, with orbital periods of 3, 4, 7 and 9 days, and a 27 day cycle. (See paragraphs 6 and 9 in above article.) Thus, in a 27 day cycle, the orbits starting with the innermost planet will be approximately 9, 7, 4, 3. That is close to the 8-6-4-3 pattern of Kepler-223.

Why the difference? Probably because Kepler 80 has a fifth planet in its system, the yellow planet that jumps around in the color illustration above. The yellow planet has an orbital period of one day--which is the amount by which 9 and 7 vary from 8 and 6.

Macksb
5 / 5 (1) Jul 24, 2016
My point is this: STIPs (systems with tightly spaced inner planets) might also be called, more generally, systems of coupled periodic oscillators. Orbits are periodic oscillations.

Art Winfree's law of coupled periodic oscillators provides insight into the likely patterns that systems of coupled periodic oscillators will exhibit. Orbital resonance patterns are related to Winfree's patterns.

Winfree was a bio mathematician, not a physicist. But IMO his law applies usefully to physics, including STIPs and much more. For more about Winfree's law, see "Coupled Oscillators and Biological Synchronization," by Steven H. Strogatz and Ian Stewart, Scientific American, Dec. 1993. A copy is available free online--Google the title.
Whydening Gyre
1 / 5 (1) Jul 26, 2016
Let us face it, we got one of the worst place to live in, if we compare to what we could have had. (Smaller star, smaller moons, larger planet, ....).

Sorry for the seemingly philosophic meandering, but...
I seem to notice a curious relationship tween adversity and diversity when reading articles (and subsequent comments) like this - It's almost as if diversity of environment variables (within a certain limit of parameters, of course) almost guarantees the likelihood of life...
Macksb
5 / 5 (1) Jul 27, 2016
Regarding 4:3 ratios of orbital periods, see also the newly discovered 4:3 ratios involving objects whose solar orbits are integer multiples of Neptune's solar orbit. Physorg article dated July 21, 2016 (one week ago) entitled "Newly discovered solar system objects resonate with Neptune."

Quote from the article:

"What was surprising is that...one of the new objects goes around the Sun once every time Neptune goes around (the sun) 4 times, while the other objects go around once every time Neptune goes around (the sun) 3 times."

This Is a 4:3 ratio that might be called indirect--a twist on the direct 4:3 ratio in the subject article above (4 exoplanets extremely close to their star in 9-7-4-3 orbits, and 4 other exoplanets extremely close to their star in direct 8-6-4-3 orbits.

The 4:3 synchrony appears in three interesting Physorg articles from May 11 to July 21.

Macksb
not rated yet Aug 11, 2016
See also "How a little mathematics can create some beautiful music" Physorg article dated July 21, 2016 and my comments thereto.

Though the article relates to music, the math (regular polygons, rhythms, center of gravity) match perfectly with the physics of orbital resonance and 4:3 synchrony.

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