Planet Nine may be Especially Faint in the red and Infrared

Comprehensive wide-band magnitudes and albedos for the planets, with applications to exo-planets and Planet Nine

Authors:

Mallama et al

Abstract:

Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B, V, R, I, RC and IC) and the 5 principal Sloan bands (u’, g’, r’, i', and z’) are presented for the 8 planets. These data are accompanied by illumination phase functions and other formulas which characterize the instantaneous brightness of the planets. The main source of Johnson-Cousins magnitudes is a series of individualized photometric studies reported in recent years. Gaps in that dataset were filled with magnitudes synthesized in this study from published spectrophotometry. The planetary Sloan magnitudes, which are established here for the first time, are an average of newly recorded Sloan filter photometry, synthetic magnitudes and values transformed from the Johnson-Cousins system. Geometric albedos derived from these two sets of magnitudes are consistent within each photometric system and between the systems for all planets and in all bands. This consistency validates the albedos themselves as well as the magnitudes from which they were derived. In addition, a quantity termed the delta stellar magnitude is introduced to indicate the difference between the magnitude of a planet and that of its parent star. A table of these delta values for exo-planets possessing a range of physical characteristics is presented. The delta magnitudes are for phase angle 90° where a planet is near the greatest apparent separation from its star. This quantity may be useful in exo-planet detection and observation strategies when an estimate of the signal-to-noise ratio is needed. Likewise, the phase curves presented in this paper can be used for characterizing exo-planets. Finally, magnitudes for the proposed Planet Nine are estimated, and we note that P9 may be especially faint at red and near-IR wavelengths.

Is Planet Nine a Captured Exoplanet?

Is Planet Nine Really a Captured Exoplanet and how Could we Tell?

Is there an exoplanet in the Solar System?

Authors:

Mustill et al

Abstract:

We investigate the prospects for the capture of the proposed Planet 9 from other stars in the Sun's birth cluster. Any capture scenario must satisfy three conditions: the encounter must be more distant than ~150 au to avoid perturbing the Kuiper belt; the other star must have a wide-orbit planet (a>~100au); the planet must be captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit Solar System bodies. Here we use N-body simulations to show that these criteria may be simultaneously satisfied. In a few percent of slow close encounters in a cluster, bodies are captured onto heliocentric, Planet 9-like orbits. During the ~100 Myr cluster phase, many stars are likely to host planets on highly-eccentric orbits with apastron distances beyond 100 au if Neptune-sized planets are common and susceptible to planet--planet scattering. While the existence of Planet 9 remains unproven, we consider capture from one of the Sun's young brethren a plausible route to explain such an object's orbit. Capture appears to predict a large population of Trans-Neptunian Objects (TNOs) whose orbits are aligned with the captured planet, and we propose that different formation mechanisms will be distinguishable based on their imprint on the distribution of TNOs.

Sedna: One of the Exoplanets in our own Solar System?

Turns out, our seemly placid star had a criminal youth of cosmic proportions.

A recent study out from Leiden Observatory and Cornell University may shed light on the curious case of one of the solar system’s more exotic objects: 90377 Sedna.

A team led by astronomer Mike Brown discovered 90377 Sedna in late 2003. Provisionally named 2003 VB12, the object later received the name Sedna from the International Astronomical Union, after the Inuit goddess of the sea.

From the start, Sedna was an odd-ball. Its 11,400 year orbit takes it from a perihelion of 76 astronomical units (for context, Neptune is an average of 30 AUs from the Sun) to an amazing 936 AUs from the Sun. (A thousand AUs is 1.6% of a light year, and 0.4% of the way to Proxima Centauri, the closest star to our solar system). Currently at a distance of 86 AU and headed towards perihelion in 2076, we’re lucky we caught Sedna as it ‘neared’ (we use the term ‘near’ loosely in this case!) the Sun.

But this strange path makes you wonder what else is out there, and how Sedna wound up in such an eccentric orbit.

link.

I Hate Self Referencing, but! Worlds Made of Dark Matter Theorized

img src here.

However, the image is NOT mine, but rather a cool picture to add some visual for this.   There are no, theorized, worlds made of neutron- and white dwarf star stuff and...dark matter.  Take a look.

Nolan's Interstellar: Looking a Little More Promising

Alien Planets (Nova)

IAU to Allow Public Naming of Exoplanets Found Before 2008

For the first time, in response to the public’s increased interest in being part of discoveries in astronomy, the International Astronomical Union (IAU) is organizing a worldwide contest to give popular names to selected exoplanets along with their host stars. The proposed names will be submitted by astronomy clubs and non-profit organisations interested in astronomy, and votes will be cast by the public from across the world through the web platform NameExoWorlds. This platform is under development by the IAU in association with Zooniverse. The intention is that millions of people worldwide will be able to take part in the vote. Once the votes are counted, the winning names will be officially sanctioned by the IAU, allowing them to be used freely in parallel with the existing scientific nomenclature, with due credit to the clubs or organizations that proposed them.

link.

Using a Starshade to See Exoplanets Directly

ESA Selects PLATO Exoplanet Telescope

A telescope to find rocky worlds around other stars has been selected for launch by the European Space Agency's (ESA) Science Policy Committee.

Known as Plato, the mission should launch on a Soyuz rocket in 2024.

The observatory concept was chosen following several years of assessment in competition with other ideas.

It is expected to cost ESA just over 600 million euros, although hardware contributions from member states will take this closer to a billion (£800m [$822 Million -me]).

Astronomers have so far found over 1,000 planets beyond our Solar System, but none as yet has been shown to be truly Earth-like in terms of its size and distance from a Sun similar to our own.

The PLAnetary Transits and Oscillations of stars mission will look to change that.

link.

Reminder: The Dragon's Gaze

My exoplanet posts have moved over to the new blog: The Dragon's Gaze.

Cloud Map of Brown Dwarf Luhman 16B on The Dragon's Gaze

Reminder.  The Dragon's Gaze is where I have all my exoplanet posts.  Luhman 16B has had its clouds(!!!) mapped.  Go see the paper!

2nd Reminder: Exoplanet Posts/Links on the Dragons' Gaze

I have moved my exoplanet posts to The Dragon's Gaze.  Please look there.

Reminder: The Dragon's Gaze

I have moved my exoplanet posts to The Dragon's Gaze.  Please look there.

Announcing "The Dragon's Gaze"

Folks, since I didn't get any suggestions on the blog name, I went with what I had in mind.

The Dragon's Gaze is the blog where I will be moving over all the exoplanet papers I come across to link to, links to other blogs about exoplanets and occasionally an original post.  I will not pull the current blog posts on The Dragon's Tales over to them, but will be discontinuing any new posts here on the subject.  The posts will be on a schedule, like I have made the Dragon's Tales, but it will be once per three hours.

Habitable Zone is Governed by Complex Rules of the Parent Stars

Habitable Zone Dependence on Stellar Parameter Uncertainties

Authors:

Kane et al

Abstract:

An important property of exoplanetary systems is the extent of the Habitable Zone (HZ), defined as that region where water can exist in a liquid state on the surface of a planet with sufficient atmospheric pressure. Both ground and space-based observations have revealed a plethora of confirmed exoplanets and exoplanetary candidates, most notably from the Kepler mission using the transit detection technique. Many of these detected planets lie within the predicted HZ of their host star. However, as is the case with the derived properties of the planets themselves, the HZ boundaries depend on how well we understand the host star. Here we quantify the uncertainties of HZ boundaries on the parameter uncertainties of the host star. We examine the distribution of stellar parameter uncertainties from confirmed exoplanet hosts and Kepler candidate hosts and translate these into HZ boundary uncertainties. We apply this to several known systems with a HZ planet to determine the uncertainty in their HZ status.

Superearth Mini Neptunes Retain Their Protoatmosphere

Origin and Loss of nebula-captured hydrogen envelopes from "sub"- to "super-Earths" in the habitable zone of Sun-like stars

Authors:

Lammer et al

Abstract:

We investigate the origin and loss of captured hydrogen envelopes from protoplanets between `sub-Earth'-like bodies of 0.1M⊕ up to `super-Earths' with 5M⊕ in the HZ of a Sun like G star, assuming their rocky cores had formed before the nebula dissipated. We model the gravitational accumulation of nebula gas around a core as a function of protoplanetary luminosity during accretion and calculate the resulting surface temperature by solving the hydrostatic structure equations for the protoplanetary nebula. Depending on nebular properties and resulting luminosities, for planetary bodies of 0.1--1M⊕ we obtain hydrogen envelopes with masses between ∼2.5×1019--1.5×1026 g. For `super-Earths' with masses between 2--5M⊕ hydrogen envelopes within the mass range of ∼7.5×1023--1.5×1028 g can be captured. To study the escape of these hydrogen-dominated protoatmospheres, we apply a hydrodynamic upper atmosphere model and calculate the loss rates due to the heating by the high XUV flux of the young star. Our results indicate that under most nebula conditions `sub-Earth' and Earth-mass planets can lose their envelopes by thermal escape during the first 100 Myr after the disk dissipated. However, if a nebula has a low dust depletion factor or low accretion rates resulting in low protoplanetary luminosities, it is possible that even protoplanets with Earth-mass cores may keep their hydrogen envelopes during their whole lifetime. In contrast to lower mass protoplanets, `super-Earths' accumulate a huge amount of nebula gas and lose only tiny fractions of their primordial envelopes. Our results agree with the fact that Venus, Earth, and Mars are not surrounded by dense hydrogen envelopes, as well as with the recent discoveries of low density `super-Earths' that most likely could not get rid of their protoatmospheres.

The Potential for Life Bearing Worlds at Proxima Centauri

On the habitability of exoplanets orbiting Proxima Centauri

Authors:

Lopez et al


Abstract:

We apply a mathematical model for photosynthesis to quantitatively assess the habitability of a hypothetical planet orbiting Proxima Centauri, inside the so called habitability zone. Results suggest significant viability for primary biological productivity, provided living organisms have evolved to reach the ability of using infrared light for photosynthesis.

We had a Hand in it...but Mostly it was Erik's: Using NERSC Supercomputers to Find Habitable Zone, Terrestrial Exoplanets

One out of every five sun-like stars in our Milky Way galaxy has an Earth-sized planet orbiting it in the Goldilocks zone—not too hot, not too cold—where surface temperatures should be compatible with liquid water, according to a statistical analysis of data from NASA’s Kepler spacecraft by Erik Petigura, a graduate student at the University of California, Berkeley (UC Berkeley).

Petigura and his colleague Andrew Howard, now at the University of Hawaii, Manoa, spent three years developing a transit search pipeline called TERRA that is optimized for finding small planets. When they used this tool on supercomputers at the Department of Energy’s (DOE’s) National Energy Research Scientific Computing Center (NERSC) to analyze nearly four years of Kepler observations, the scientists determined that our galaxy could contain as many as 40 billion habitable Earth-sized planets.

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GJ 436B has a Weird Atmosphere

THE PUZZLING CHEMICAL COMPOSITION OF GJ 436B'S ATMOSPHERE: INFLUENCE OF TIDAL HEATING ON THE CHEMISTRY

Authors:

Agúndez et al

Abstract:

The dissipation of the tidal energy deposited on eccentric planets may induce a heating of the planet that affects its atmospheric thermal structure. Here we study the influence of tidal heating on the atmospheric composition of the eccentric (e = 0.16) "hot Neptune" GJ 436b, for which inconclusive chemical abundances are retrieved from multiwavelength photometric observations carried out during primary transit and secondary eclipse. We build up a one-dimensional model of GJ 436b's atmosphere in the vertical direction and compute the pressure-temperature and molecular abundances profiles for various plausible internal temperatures of the planet (up to 560 K) and metallicities (from solar to 100 times solar), using a radiative-convective model and a chemical model which includes thermochemical kinetics, vertical mixing, and photochemistry. We find that the CO/CH4 abundance ratio increases with metallicity and tidal heating, and ranges from 1/20 to 1000 within the ranges of metallicity and internal temperature explored. Water vapor locks most of the oxygen and reaches a very high abundance, whatever the metallicity and internal temperature of the planet. The CO2/H2O abundance ratio increases dramatically with metallicity, and takes values between 10–5-10–4 with solar elemental abundances and ~0.1 for a metallicity 100 times solar. None of the atmospheric models based on solid physical and chemical grounds provide a fully satisfactory agreement with available observational data, although the comparison of calculated spectra and observations seems to point to models with a high metallicity and efficient tidal heating, in which high CO/CH4 abundance ratios and warm temperatures in the dayside atmosphere are favored.