Sunrise on Gliese 876d

On planet Gliese 876d, sunrises might be dangerous.

Although nobody really knows what conditions are like on this close-in planet orbiting variable red dwarf star Gliese 876, the above artistic illustration gives one impression. With an orbit well inside Mercury and a mass several times that of Earth, Gliese 876d might rotate so slowly that dramatic differences exist between night and day.

Gliese 876d is imagined above showing significant volcanism, possibly caused by gravitational tides flexing and internally heating the planet, and possibly more volatile during the day. The rising red dwarf star shows expected stellar magnetic activity which includes dramatic and violent prominences.
In the sky above, a hypothetical moon has its thin atmosphere blown away by the red dwarf's stellar wind. Gliese 876d excites the imagination partly because it is one of the few extrasolar planets known to be in or near to the habitable zone of its parent star.

New 6-8 Earth-mass planet Gliese 876d (rendered by artist Trent Schindler at the National Science Foundation.)

Sources:
- Exoplanets.org
- Wikipedia
- APOD

Originally posted by elevenaugust
Gliese 876d might rotate so slowly that dramatic differences exist between night and day.

Gliese 876d is imagined above showing significant volcanism, possibly caused by gravitational tides flexing and internally heating the planet, and possibly more volatile during the day.

And so my first thought is Crematoria, from the Vin Diesel movie Chronicles of Riddick.

How is it within the "habitable zone"? I would think it is far too close to its sun for that.

One criteria for a star's goldilock's zone is the presence of stellar temperature that allows for liquid water on the surface of the planet. With as close as this planet is to the star, the odds tend to run for it to be either tidally locked to the star or to have a 3/2 resonance with the star, both situations run into having a planetary surface area exposed for too long of a period of time to the star's radiation. To further complicate matters, being that close to the stellar surface, you will have more severe problems with solar flares. Ones that perhaps would often intersect with the planet's orbital path.

Dont let Gilese 876d, shown in this article, get confused with Gilese 667cc.

Of the 2 Gilese 667cc is far more interesting.

Concept art of 667cc

www.eso.org...

"Gliese 667 Cc performed very well in a habitability assessment undertaken by the Habitable Exoplanet Catalog (HEC), ranking as the planet with the greatest habitability potential of all discovered exoplanets to date.
A quick refresher of the HEC metrics in the context of Cc: ESI is the ‘Earth Similarity Index’ and consists of several planetary characteristics, namely radius, density, escape velocity, and surface temperature that are used to determine the relative similarity of the planet to Earth on a scale from 0 (completely dissimilar) to 1 (identical). An ESI 0f 0.82 represents an ‘Earth-like’ world, but the large mass (5.2 as the mean expected mass) of Cc has negatively affected this value.

SPH is the Standard Primary Habitability, a measure (from 0 to 1), calculated from surface temperature and humidity, of the ability of the planet to support terrestrial primary producers. In the case of SPH, Cc outranks even the Earth! Its position half-way between the very centre of habitable zone and its inner edge, represented here by the metric HZD, means that it is extremely favourable to supporting a ecosystem of primary producers similar to those on Earth. However, as a red dwarf, Gliese 667C emits much of its radiation in the red, near-infrared (NIR) and infrared (IR) portion of the electromagnetic spectrum. Red dwarfs like Gliese 667C are also known to be more variable and prone to flaring. The affect of this shift in wavelength would have very negative repercussions for Earth-based photosynthetic mechanisms which utilise visible light, but the possibility of photosystems evolved to exploit lower-energy NIR/IR radiation is hypothetically possible."

The danger is that with all these different planets, with obscure classifications, all being released by competing organisations the interesting stuff is getting lost in the noise.

Nice renderings....I wish i could draw like that......

OK....Question (of which I have no Clue to the answer).

Our Sun is Bright white in the noon sky, Many magnificent Stars we see at night are also bright white.

Our Sun sends us bright white light, which we know is made up of a spectrum of colours ROYGBIV. All these colours mixed together make white.
All life on Earth has various colours that reflect a particular spectrum of light.eg Yellow flowers reflect Yellow, Purple flowers reflect purple. etc etc.

Q. With all the "Red" Dwarfs around, do Red Dwarfs only give off the Red Spectrum of light (as well as other ultra/micros etc), which means any life can only absorb red ligh?.
Or do Red Dwarfs give off white light, like our Sun? So it encompasses all colours.

Would any Life on the near red dwarfs, see/live/survive etc, in only Red light?
Would they be invisible in our White Light?

Just wondering...

reply to post by Schkeptick


This may have been answered already, but it is in the habitable zone because the temperature of the star at the center of the system is not as hot as our own sun. They call it a habitable zone because the planet exists at a distance from the star that may allow for the formation of liquid water on the surface. If there is water, so the theory goes, there is life. I would bet there is already a ship enroute to check it out. .