TESS discovers habitable zone planet in GJ 357 system

Posted: August 3, 2019 by oldbrew in Analysis, Astrophysics, Fibonacci, News, Temperature
Tags: , ,

Credits: NASA’s Goddard Space Flight Center/Chris Smith

Following the report we analyse the orbital data for evidence of resonances.

A planet discovered by NASA’s TESS has pointed the way to additional worlds orbiting the same star, one of which is located in the star’s habitable zone, reports SciTechDaily.

If made of rock, this planet may be around twice Earth’s size.

The new worlds orbit a star named GJ 357, an M-type dwarf about one-third the Sun’s mass and size and about 40% cooler that our star. The system is located 31 light-years away in the constellation Hydra.

In February, TESS cameras caught the star dimming slightly every 3.9 days, revealing the presence of a transiting exoplanet — a world beyond our solar system — that passes across the face of its star during every orbit and briefly dims the star’s light.

“In a way, these planets were hiding in measurements made at numerous observatories over many years,” said Rafael Luque, a doctoral student at the Institute of Astrophysics of the Canary Islands (IAC) on Tenerife who led the discovery team. “It took TESS to point us to an interesting star where we could uncover them.”

The transits TESS observed belong to GJ 357 b, a planet about 22% larger than Earth. It orbits 11 times closer to its star than Mercury does our Sun. This gives it an equilibrium temperature — calculated without accounting for the additional warming effects of a possible atmosphere — of around 490 degrees Fahrenheit (254 degrees Celsius).

“We describe GJ 357 b as a ‘hot Earth,’” explains co-author Enric Pallé, an astrophysicist at the IAC and Luque’s doctoral supervisor. “Although it cannot host life, it is noteworthy as the third-nearest transiting exoplanet known to date and one of the best rocky planets we have for measuring the composition of any atmosphere it may possess.”

But while researchers were looking at ground-based data to confirm the existence of the hot Earth, they uncovered two additional worlds. The farthest-known planet, named GJ 357 d, is especially intriguing.

“GJ 357 d is located within the outer edge of its star’s habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun,” said co-author Diana Kossakowski at the Max Planck Institute for Astronomy in Heidelberg, Germany. “If the planet has a dense atmosphere, which will take future studies to determine, it could trap enough heat to warm the planet and allow liquid water on its surface.”

Full article here.

NASA video (2 mins)…

– – –
Talkshop analysis

The orbits of the planets, with distance from the star, are:
GJ 357 b – 3.93056 days (0.034 AU)
GJ 357 c – 9.1258 days (0.085 AU)
GJ 357 d – 55.66 days (0.204 AU)
(data: exoplanet.eu)
14 b = 55.02784 d
6 c = 54.7548 d
1 d = 55.66 d

Conjunction data:
8 b-c (14-6) = 55.2344 d
5 c-d (6-1) = 54.5773 d
13 b-d (14-1) = 54.9797 d

So this system has, or is very close to, 5:8:13 synodic ratios and these resonances are Fibonacci numbers.

The distance (AU) numbers from the star show:
b:c = 2:5
c:d = 5:12
b:d = 1:6
– – –
A paper describing the findings was published on Wednesday, July 31, in the journal Astronomy & Astrophysics and is available online.

  1. oldbrew says:

    On a musical note…

  2. Gamecock says:

    That it is in a ‘habitable zone’ is right up there with saying it is “green.”

  3. JB says:

    JUST 31ly distant and beckoning… And a planet that is too hot even for baking pizza.

    I wonder what interesting things can be derived by tabulating all these exoplanets’ Fibonacci relations? Star mass, planet mass, orbital scaling and rates, companion star. Would other patterns emerge from large scale system profiling?

  4. oldbrew says:

    JB – somebody, a team even, would have to do a systematic trawl through all the multiple-exoplanet data (i.e. stars with > 2 planets), and have a suitable method.

    I don’t plan to do that myself – life’s short enough as it is. But if/when multiplanet systems turn up in the new discoveries I’ll try and check them out. Tallbloke did suggest using some software, but good luck to the person writing it. Exoplanet.eu does have a query language which is quite useful: http://exoplanet.eu/query_language/

    As far as other patterns go, they do exist but apart from occasional Lucas numbers it’s hard to see any pattern in the patterns* as it were. Planetary theory (ours and some others that is) says that stability is behind the resonances and Phi/Fibonacci ratios offer the best chance of that, although other arrangements do exist.

    [*except for being able to find ratios of small numbers of conjunctions]

    BTW – GJ 163 contains a Lucas-based resonant system (I believe) so that might feature soon.
    – – –
    Update – found this…

    A fast method to identify mean motion resonances

    Based on the geometrical meaning of the resonance variable, an efficient method is introduced and described here, by which mean motion resonances can be easily found without any a priori knowledge of them.

    [2018 – Published by Oxford University Press on behalf of the Royal Astronomical Society]

    But: ‘You do not currently have access to this article.’ :/

    They probably mean orbital resonance but we always look for synodic resonance, which is not the same thing although related.

  5. oldbrew says:

    At the edge of chaos: New method for exoplanet stability analysis
    July 30, 2019 , American Institute of Physics

    ‘”Earlier studies pointed out that Kepler 36b and 36c is a very special system, because from the direct simulation and the numerical integrations, we see the system is at the edge of the chaos,” Kovács said. “Sometimes, it shows regular dynamics, and at other times, it seems to be chaotic.” ‘


    88b = 75c = 13 conjunctions
    See: http://exoplanet.eu/catalog/

    Not seeing the chaos 🤔

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