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Sunlike Stars With Only Low Mass Planets And Debris Disks

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A list of sun-like stars with super Earth planets and thick debris disks detected. The lack of a large Jovian may allow the debris disk to get so thick.

  • 61 Virginis System - A system containing a 5.1 ME Hot Super-Earth b (which is hot enough to have emissions on its night side) and one and possibly two other further out Neptunians (c and d [unconfirmed] and possibly a fourth), and a massive Kuiper Belt around a very Sun-like star only 28 light years away. All planets would fit inside Venus' orbit and have high eccentricities, especially the outermost one. This is the closest planetary system around a G-type star, which is one of the only very sun-like stars visible to the naked eye. It is the first non-borderline G-class main sequence star found to have a super-Earth. A lack of a Jovian planet and an unseen further out Neptunian may explain the large amount of cometary debris detected. Systems like this may avoid a heavy bombardment period, but instead undergo a steady rain of occasional cometary impacts for billions of year. Of the six sunlike stars within 10 parsecs, this star would be the one most likely to have an older version of Earth orbiting it. This postulated planet would have only microbes left as its star became hotter.
  • 82 Eridani System - 82 G. Eridani is also known as 82 Eri, HR 1008, Gl 139, and HD 20794. One of the nearest star systems with planets. It is one of the dimmer yellow dwarf stars. Has three radial velocity detected super Earth planets orbiting closer than the habitable zone. The outermost one d is the largest (5 times Earth's mass, twice its radius, rocky-water composition) is about the same distance as Mercury is from the Sun. The middle one c is 0.1 au closer and is the smallest (2.5 Earth's mass, 1.5 its radius) and is likely a rocky-iron in composition. The innermost one is at 0.1 AU and just slightly larger than c, but more massive and of a more rocky-water composition. A dust disk was also found about 20AU from the star. The 2007 book "Habitable Planets for Man", released prior to the discovery of the planetary system, placed this as the most habitable star system within reach of mankind.
  • HD 69830 System - First planetary system found that does not have a Jupiter-sized planet around a normal star (K0 spectrum). Contains 3 Neptunians and the first discovered asteroid belt that is like the size and age as the Sun's. The debris from this belt that was detected was from the breakup of an asteroid, is 20 times as massive as our own, and would cause zodiacal lights 1000 times brighter than we see from Earth. The smallest and outermost planet may be a 10 ME super Earth, is within the habitable zone, and is an inner shepherd for the asteroid belt. Halo 3 features a fictitious moon around this planet.
  • HD 38858 System - A G-type star with low mass planets and a debris disk.
  • Tau Ceti System - Tau Ceti is also known as HD 10700, HR 509, and Gl 71. The nearest single G-class yellow dwarf to the sun, somewhat smaller than the Sun. A popular science fiction subject and one of two targets of SETI-forerunner Project Ozma in the 1960s. Despite being somewhat older than the sun, it has an extensive asteroid and/or comet field 10-50 AU, with the bulk between 35 and 50 AU. It has about ten times as much material as the Sun. This would make life difficult. It is a metal deficient star, so it is thought less likely to host rocky planets. Traditional dopplar spectrometry has ruled out any large Jupiter sized planets at Jupiter like distances or closer in, which was thought to be good for any potentially habitable planets. Five candidate rocky super Earth planets were detected though using a new method of planetary detection. This method made predictions of the stellar "noise" activity that might obscure detection of a planet based on the long history of dopplar measurements done on this system. Deviations from this prediction pointed towards the existence of planets. Confirmation using more established methods is needed. These planets are labeled b through f as you go outward, span 0.1 AU to 1.35 AU, and get larger the further you go out (at least 2 ME to 6.6 ME). The outermost two are near the habitable zone and were originally hailed as possibly being the nearest and smallest known habitable planets. More recent modeling indicates they are not actually habitable though. Planet e is probably too close to the star and only in the HZ if generous assumptions are made. Planet f has probably only been in the habitable zone for about a billion years as a result of its star becoming hotter, which might make biosigns difficult to detect from Earth, considering it took 2 BY for biosigns to become detectable around the Earth. Since the star has a higher magnesium to silicon ratio than the Sun, these planets compositions could be quite different that the Solar System's. The lower mantles could be dominated with ferropericlase, which is not very viscious, which may make the rocks of the mantle flow easier than on Earth, affecting volcanism and tectonics. One of 5 PICTURE-C targets selected for sub-orbital coronograph observation.

Similar Red Dwarf Systems

  • BD-11°3759 System - BD-11°3759 is better known as Gliese 581. Small nearby Red Dwarf with six planets in tight circular orbits. Several planets were announced in the habitable zone, but have since been retracted due to being due to sunspots rotating in view during it's 130 day rotation. E is the smallest known dopplar-detected exoplanet and a Super Mercury, b is a hot Neptunian, c is a super-Venus and the first detected in the HZ (initially heralded as habitable, but later thought too hot due to the greenhouse effect). G (1/4 stellar rotation) was the most controversial heralded as the first habitable Super-Earth and "Eyeball Earth", but was disproven. D (1/2 stellar rotation) was later thought to be an even more promising planet for life as it was big enough for a decent greenhouse effect even though it was at the outer edge of the habitable zone, was later thought to also not exist, but then its existence was re-affirmed. F was thought to be a cold super-Earth, but also disproven. The star is not very active. A massive Kuiper Belt was found, which may have been allowed to exist because the system lacks a Jovian class planet. A further out Neptunian may be responsible for the cometary collisions that produced the debris.

Related Article:

My ThoughtsEdit

This seems to be a common type of planetary system, including most of the very nearest single sunlike stars with planets and half of those a little further out. In general, systems that have planets in them but don't have massive Jovians tend to have thick debris disks. The Jovians tend to disperse the debris belt, thinning them out. I found it interesting that the Sun's Kuiper Belt could not be detected from the nearest star with even the most sophisticated technology, so detecting a disc at this time means it must be a very large one. These systems should have a name. How about LMP-HMD? Low Mass Planets - High Mass Disk Systems? Shorten it further to be LPMD (Light Planets, Massive Disks)?

The article says this pattern may also hold true for Red Dwarfs. Do they have as massive discs to start out with so that we can detect them? Is the one they detected an anomaly, or only the first of many found. There's so few Jovians around red dwarfs that most red dwarfs could be put into this category.

Can the detection of a large debris disk be used to imply the lack of Jovian? Can a Jovian detected imply the lack of a large debris disk?

I want to ask "how do they know there aren't any Jovians they haven't discovered yet", but then I have to remember that they've often ruled out planets of a certain size out to a certain orbit period. There was this one Jupiter/Saturn analog planet that they discovered though with microlensing that they said suggested solar systems like our own was common though (see ).

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