The Orion's Arm Universe Project Forums

Exoplanet Discoveries and Updates
I made this thread to list the systems in Orion's Arm I come across where real-world discoveries have found additional celestial bodies/structures in them. Mentioning other planets in the system might be useful for when somebody wants to write more about the system, and also for the characterization of the spotlighted planet itself...

Within 50 light-years of Sol
82 G. Eridani - Contains Terranova
EG article
Wikipedia article
The article lists three real planets of b, c (unconfirmed), d, and two apparently fictional planets of Terranova and another one. Real-world discover have since found planet e, f (unconfirmed), and g (unconfirmed). The planet f, at 10 Earth masses, nicely occupies the habitable zone, so, taking its name into account, Terranova has to be turned into a Mars-size Arean/Hermean trojan planet (as to not exceed the mass limit of stable trojan planets, said to be 1/25 in the Wikipedia and 2.74% by a paper found by radtech, posted on Discord).

HR 8832 / Gliese 892 - Contains Uoagranyu
EG article
Wikipedia article
Contains 5 confirmed planets and 2 unconfirmed planets, none in the star's habitable zone, so feel free to put Uoagranyu at 0.5 AU.

Nu2 Lupi - Contains NewRoot
EG article
Wikipedia article
In real life, three super-Earths orbit the star in close orbit. In Orion's Arm Universe, all of them has been dissembled. Kudos to whoever wrote this Big Grin
I'm thinking of turning this thread into exoplanet discoveries and updates announcement article. Is it possible to rename it to 'Exoplanet Discoveries and Updates Thread' or something like that and move it to Real Life But OA Relevant?

Anyways, let's start with the discovery from 13 August 2019: Gliese 1061. The discovery was announced by Red Dots project, which is a continuation of the Pale Red Dot project, which was initiated to confirm the existence of Proxima Centauri b.

The star, Gliese 1061, is an M5.5V star, with a surface temperature of 2953 K. Its luminosity is mere 0.0017 Sol. It rotates slowly, taking ~130 days to rotate once, and combined with its age of over 7 billion years mean that it has a MUCH lower activity than Proxima Centauri, which is good news.

This system was announced to contain three worlds:

Gliese 1061 b
- semi-major axis: 0.021 AU
- orbital period: 3.204 days
- minimum mass: 1.38 Earths
Gliese 1061 c
- semi-major axis: 0.035 AU
- orbital period: 6.689 days
- minimum mass: 1.75 Earths
Gliese 1061 d
- semi-major axis: 0.054 AU
- orbital period: 13.031 days
- minimum mass: 1.68 Earths

According to Drew Ex Machina's analysis, both three worlds are more likely to be terrestrial, but without knowing what the exact mass of these worlds, it's kinda hard to say.

Next, irradiance. Drew Ex Machina's article suggests that the first two worlds likely received too much sunlight, and are likely experienced runaway greenhouse effect, turning them into Venuslike worlds. The third world, Gliese 1061 d, is more promising and may be either an ocean planet, an ice planet, or an Earthlike world of a sort. However, there is a chance that the planet has been desiccated during the early era. If so, the planet could've turned into a Venusian world.

Other factors include radiation, which seems to not be as much of a problem as worlds around Proxima Centauri, and tidal heating caused by gravitational interaction with the host star and its neighbors, which could create spectacular geysers on Gliese 1061 d, or simply turn it into a volcanic world.

It is important to note that the star's low temperature could mean its planets have too much carbon monoxide in their atmospheres for human habitation.

I also made this a sticky thread so it will stay at the top of the forum.

By the way, here are the links to the older planet discovery threads in this Forums, going back to 2015.

Proxima Centauri b #1
Proxima Centauri b #2
TRAPPIST-1b, c, d, e, f, g, h
Ross 128 b
Barnard's Star b
Proxima Centauri c
Teegarden's Star b, c
Beta Pictoris c

Stay tuned for future finds!
HR 5183 b, a cold eccentric Jupiter
On 26 August 2019, there was an announcement of the discovery of not another boring temperate terrestrial planet around a red dwarf, but a gas giant in a wide, eccentric orbit around a sunlike star. Here is Caltech's article on the planet.
This planet, known as HR 5183 b has the following properties:

HR 5183 b
Semi-major axis: 18 AU, give 6 or take 4.
Orbital period: 74 years, give 43 to take 22.
Eccentricity: 0.84
Minimum mass: 3 Jupiters

This eccentricity implies a violent encounter with another gas giant in this system. Where that gas giant is currently at is unknown, but probably outside the HR 5183 system.
While this is not the first eccentric Jupiter discovered, this is the first one found in such a large orbit. Its orbit takes it as close to its G0V type star as 3 AU, and as far away as 33 AU. I believe there is still a possibility of an Earthlike world in this system, but it would probably be quite disturbed by the gravitation effects from this large world.

Evidence of an exo-Io in orbit around WASP-49b
WASP-49b is known to have extensive sodium envelope, far from the planet's surface enough to rule out the 'sodium's coming out of the planet' option. There are several other options, but one of them is the possibility of a satellite with extensive volcanic activities, similar to Io. At this point, more data is required to determine whether if this is really a moon or not. This potential moon, WASP-49b I, would compete with Kepler-1625b's Neptune-sized planet-satellite for the first confirmation of an exomoon.

Semi-major axis: 0.0378 AU
Orbital period: 2.7817387
Mass: 0.378 Jupiters (120.2 Earths)
Radius: 1.115 Jupiters
In case if anybody missed the news that's been flying around, here's a Jovian-type planet circling a tiny red dwarf star. It even comes with a sibling.

GJ 3512 b
Semi-major axis: 0.3380 AU
Orbital period: 203.59 days
Eccentricity: 0.4356
Minimum mass: 0.463 Jupiters
Discovery announcement: 26 Sep 2019

Also, a second planet candidate has been detected in this system as well, receiving the designation GJ 3512 c.

GJ 3512 c
Semi-major axis: 1.2 AU
Orbital period: >1,390 days
Minimum mass: >0.17 Jupiters
Discovery announcement: 26 Sep 2019

The discovery of GJ 3512 b was a complete surprise due to how massive it is compared to its parent star, which is only 250 times more massive than the planet itself. This meant this planet couldn't have formed by the usual planetary formation method, core accretion. The alternate method, disk instability, is instead put forward as an alternative. Notably, previous research suggested that disk instability planets tend to be more massive than 4 Jupiter masses.
This is a failed star, rather than a giant planet. But the end result is the same, a non-luminous object.
There were additional discoveries in a young solar analog known as V1298 Tauri, making the total planet count for this system four.

V1298 Tauri c
Semi-major axis: 0.0825 AU
Orbital period: 8.24958 days
Eccentricity: <0.43
Radius: 5.59 Earths
Discovery announcement: 10 Oct 2019

V1298 Tauri d
Semi-major axis: 0.1083 AU
Orbital period: 12.4032 days
Eccentricity: <0.21
Radius: 6.41 Earths
Discovery announcement: 10 Oct 2019

V1298 Tauri b
Semi-major axis: 0.1688 AU
Orbital period: 24.1396 days
Eccentricity: <0.29
Radius: 10.27 Earths
Discovery announcement: 26 Feb 2019

V1298 Tauri e
Semi-major axis: 0.308 AU
Orbital period: 60 days
Eccentricity: <0.57
Radius: 8.74 Earths
Discovery announcement: 10 Oct 2019

Although individual masses are unknown, simple dynamic arguments suggest total masses of <28 Earth masses and <120 Earth masses for the c-d and d-b planet pairs, respectively. The densities of these planets appear to be way lower than their mature counterparts, suggesting that they're still in the process of radiatively cooling and contracting.
With data from Gaia DR1, a research team discovered that the planet candidate around HD 114762 A, one of the first 'exoplanets' discovered, is actually a red dwarf/brown dwarf in a nearly face-on orbit, and not a planet.

HD 114762 b
Semi-major axis: 0.353 AU (wikipedia)
Orbital period: 83.9151 days (wikipedia)
Eccentricity: 0.3354 (wikipedia)
Inclination: 6.23 degrees (0 deg = face-on, 90 deg = edge-on)
Mass: 107 Jupiters
Discovery announcement: May 1989
A research paper posted on 14 Oct 2019 further refined the orbit of Epsilon Indi Ab using astrometry, revealing its inclination and thus true mass.

Epsilon Indi Ab
Semi-major axis: 11.55 AU
Orbital period: 45.20 years
Eccentricity: 0.26
Inclination: 64.25 degrees (0 deg = face-on, 90 deg = edge-on)
Mass: 3.25 Jupiters
Confirmed: March 2018

In Orion's Arm, this object corresponds to a planet known as...III. A MesoJovian. I believe we should name these planets soon, hah, and so I've posted my proposal in this thread.

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