Alien Sunsets   33 comments

Watching the sunset on another world 150 light years from Earth….

What would it look like?


HD 209458 b (Osiris) is a large exoplanet or extrasolar planet that orbits the Sun-like star HD 209458 in the constellation Pegasus, some 150 light-years from Earth’s solar system. First discovered on November 5, 1999 during “Spectroscopic studies.”

Osiris_HD 209458bOsiris

Osiris is a 7th magnitude world, visible from Earth with good binoculars or a decent telescope. Osiris (HD209458b), 150 Ly from Earth orbits very closely to its sun. Measured by the Spitzer Infrared Space Telescope on March 23. 2005 it had an atmospheric temperature of around 1,000 degrees Celsius (1,800 degrees Fahrenheit) it’s year lasts just 3.5 Earth days long. Very bad for the aging process!

Osiris Firsts:

First PrizeHD 209458 b was the first transiting extrasolar planet discovered:

  • Known to have an atmosphere
  • Observed to have an evaporating hydrogen atmosphere
  • Found to have an atmosphere containing oxygen and carbon
  • One of the first two extrasolar planets to be directly spectroscopically observed
  • The first extrasolar planet found to have water vapour in its atmosphere. (April 2007)

(Sunset On HD 189733 – Osiris)

Sunset on HD209458b (reconstructed from the HST/STIS transmission spectrum): Image: Frederic Pont of the University of Exeter: based on data form a camera on-board the Hubble Space Telescope)

Osiris doesn’t actually have as surface on which to sit peacefully watching an alien sunset but for the purposes of this post we will pretend it does. What it does have however is an atmosphere, which when passed through by the light from its star (sun) – it does this every so often when Osiris passes between Earth and its own sun (transits)– allows the scientific types here on sunny Earth to figure out in a scientific way mostly beyond the understanding of the average Earthling, exactly which colours its sun would set in, should Osiris have a surface – as already stated it doesn’t but… and we were spending a happily romantic evening sitting on the (make-believe) surface.

I said it HASN’T got one!!! So don’t try it!! It won’t be any good for you!!

In the image to the right Osiris’s sunset can be seen as it would appear if having travelled at light speed to reach it, you were floating 6,200 miles/10,000 km above the planetary surface – preferably not in a deckchair unless you’re wearing a heavy duty space suit 😉 a space station would do nicely.

Floating 6,200 miles above the planetary surface...The Osirisian sun- HD 209458– it’s star, is, much like Earth’s Sun, white – yes I know…The Sun is yellow…but if there was no atmosphere it would look white – not that we would see it because without an atmosphere life on Earth would have survived for approx. 20 seconds before exploding into instant extinction.

An alien sunset on Osiris really does look alien – unlike Earth’s. Osiris’s atmosphere consists of sodium which when starlight (sunlight) zips through it, absorbs the red light. (think prisms and colours of rainbows when white light is split) This results in the remaining starlight appearing blue. It makes perfectly good sense if you were paying attention in your school science lessons. If you weren’t then it’s your own fault and you should be thoroughly ashamed of yourself!!

As back home on Earth the blue light from the star is scattered (“Rayleigh scattering,” a mechanism also responsible for the Earth’s sky being blue) creating a progressive change through the blue end of the spectrum through to a pretty green and later a deep, dark shade of green as its star dips further beneath the horizon.

The more sensible approach to watching the Osirian sunset...In such colours you should be able to get a good view of Osiris’s sun without going instantly blind in which case you will notice it looks oddly flat around the southern half. The same effect occurs when we watch the sun setting from Earth. This is the consequence of diffraction (light bending) and nothing to worry about..

Osiris, Eygptian god of the Underworld_Credit Jeff DahlWhilst you are relaxing in the Osirisian sunset you can reflect on the little snippet of mythology attached to it’s title… Osiris was an Egyptian god, usually identified as the god of the afterlife, the underworld and the dead. He was classically depicted as a green-skinned man with a pharaoh’s beard, partially mummy-wrapped at the legs, wearing a distinctive crown with two large ostrich feathers at either side, and holding a symbolic crook and flail. His green skin is symbolic of new birth. This image is based on New Kingdom tomb paintings.



    Sunset on HD 189733 bSunset on HD 189733 b looks like an especially awesome Earth sunset when the sky is very clear and there is only a small amount of dust in the atmosphere. HD 189733 b is much closer to its star (sun) than Earth is to our Sun so its star looks considerably bigger 25 times larger than Earth’s sun when viewed at sunset compared.

Soaking up the atmosphere on HD 189733b

HD 189733 b’s sun is orange and nowhere near as hot as Earth’s Sun and consequently is coloured orange as oppose to the white of our Sun. Instead of undergoing a gradual change of colour as it sets, this alien sun transforms straight from its original orange colour to deepest red in the thick layers of the lower atmosphere.

Jupiter and HD 189733 b size comparison

HD 189733b discovered in 2005 is an extrasolar planet of similar size to Jupiter. It orbits a star (it’s sun) in a binary system called HD 189733 in the constellation of Vulpecula in two Earth days. The aging process on this world would be terribly fast in our terms and those wrinkles would appear in a frighteningly super-smart short time!! The star system itself one of the closest planet-star systems known making it extremely hot. It is located near the Dumbell Nebula, approximately 62 light years from Earth and is known as a “Hot Jupiter.”

HD 189733 and M27, the Dumbbell Nebula. Credit: Daniel Jaroschik

HD 189733b shares many similar characteristics as HD 209458b (a.k.a. “Osiris) Although HD 189733b’s atmosphere isn’t thought to be evaporating like Osiris’, atmospheric gases extend far beyond it and out into space. This is significant in that starlight can also pass through meaning that scientists have been able to figure out that the atmosphere contains water and methane resulting in the probability that HD 189733b may have a blue hue, reminiscent of Uranus.

The atmosphere also contains iron, silicate and aluminium oxide particles. These would seem to collect in HD 189733b’s upper atmosphere, forming a thin, hazy, reflective cloud in the exosphere. This leads to the natural conclusion that the weather on HD 189733b is hot and cloudy.

Thanks to the Spitzer telescope it was discovered in February 2007 for the first time that the atmosphere of exoplanet HD 209458b (Osiris) is relatively dry, thick and dusty. Osiris even contains grains of sand (silicates).


Although it is not suitable for the existence of alien life it is an exciting step on the road to discovery of such worlds.


Prof. Frédéric Pont

33 responses to “Alien Sunsets

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  1. Merhaba benim sevgili arkadaşım Buz 🙂
    size güzel bir haftasonu diliyorum.
    kendine iyi bak güzel arkadaşım
    iyi geceler ve tatlı rüyalar
    çok kucak dolusu sevgiler yolluyorum
    öptümmmmmmm 🙂

    • Merhaba canım ve güzel arkadaşım Seçil 🙂
      Seni burada gördüğüme çok mutluyum!
      Ben çok iyi
      teşekkür ediyorum.
      Bu Kutsal Hafta zamanı – İngiltere’de Paskalya
      ve ben bunun için çok meşgul hazırlıyorum 🙂
      Nasıl benim güzel arkadaşım vardır?
      Ben hayatı çok iyi umuyoruz
      ve ben güzel bir hafta diliyorum
      Aşk ve kucaklamak
      öptümmmmmmmmmmmmmmmmmmmmmm 😀

  2. Very pretty. So one couldn’t stand on the surface? Then how do the aliens do it? Do they float? Are they jealous of us and pointing their giant death ray at us because we have our nice ground to stand on? 😉

    • Unless you like floating on gas clouds standing on the “surface” might be a little bit difficult…as it doesn’t have one 😉 How the aliens do it I should imagine depends on what form they take…and just how very jealous they are! lol…maybe they’re gassy creatures themselves and swim through the gas 😉 On the other paw, if they’re pointing a giant death ray at us they’re probably from a planet much closer to home…like Mars!! 😀

  3. I hope humans don’t find other habitable worlds.

    • They certainly could be a liablity if they do! But if it’s a toss up between extinction and survival… 🙂

      • why should other life forms suffer the way we have at the hand of humans?

      • Protocol in these matters usually states that it should be an uninhabited world not already possessing of sentinent life forms.
        Also alien bacteria from humans or alien lifeforms could easily be lethal to the other and wipe us or them out. So an uninhabited world would be a far safer and logical choice.
        The other thought is that if there was a sentinent race there already there is no saying it wouldn’t either be far more advanced and deal very swiftly with the erradication of intruding humans, or it would more primitive but far better equipped both in familiarity with the world in question and also in the use of whatever form of native weaponary necessary to protect itself from dangerous “animals”
        So! Humans might just have to keep themselves to themselves and keep their heads down for a change!

  4. Cool stuff… I’ve been an astronomy geek since childhood, though not recently, alas… but, this was a fun read, with well reasoned,if speculative conclusions based on strong scientific grounds…. Fun for us geeks, anyway…. 😆

    • Oooh! A man after my own heart! I’m not sure about the geek bit though 😉 Astronomy has been a lifelong fascination…the day I mistook the Moon for Venus and ran round telling everyone with great excitement lol was perhaps a slightly embarrasing moment lol but apart from that…well, besides the moment I realised it was the Moon not Venus!! A day in my astronomy career that will haunt me forever and to this day causes great Wolfie cringiness and red-facedness!! lol 😀

  5. So very interesting, although I’ll take your advice and not attempt sunset viewing in a deck chair. Would be outstanding to view for real, although I would be rather concerned about that rapid aging process. Go and view it for one day and come back old and wrinkled. I think you need to find us another planet where aging is reversed. That way, if we go on a trip to both, we could at least return to earth at the age we left.

    • I like your reversed aging theory lol 😉 Only pitfall with it to my Wolfie mind is that we’d be so old and decrepit at Osiris’s aging rate lol that we’d be deceased long before we made it back to the age reversing planet!!! Or so wrinkly that even the best and most expensive anti-aging cream wouldn’t stand a chance lol causing us to be far too self concious to show our wrinkled, ancient faces on another planet 😉 Resulting in the long deceased state to kick in remarkably quickly…oops! That had already happened hadn’t it? lol… not much hope for us really! Best get the factor 500 sun tan lotion with extra UV protection built in and hope for the best in our deck chair sunset viewing 😀

  6. I love space travel, Icewolf, and these are two worlds I haven’t come across yet in the vast infinity of the Universe! Fascinating post… and I love a good sunset. With Osiris not having a surface, is it a gaseous planet, or a liquid one? I think a nice swim at sunset sounds very appealing, so I hope it’s a water world!
    Have a good weekend, Icy!

    • Better tell your mansion not to take you to Osiris Aquatom…remember you will grow remarkably ancient and wrinkly incredibly fast! And your hair might turn grey and fall out!!! Worse still, no swimming in the sunset 😉 Osiris is a giant gas planet like Jupiter…no surface for an ocean to exist on 🙂 You might want to try floating in the gas clouds instead…but very quickly! You’ll be terribly, dreadfully old by the time you get back to your deck chair otherwise! lol 😉

  7. Your story line, humor and great pictures held my interest Wolfie. And I thought we live in a strange world!
    These places are just a little too distant for a weekend jaunt. But the information is useful in as much as it is the universe we live in and it is always good to learn more about it. Thank you for the extensive work you did.

  8. Now who dos’t like sunsets. I Just love Earths sunsets. But most of them occur behind my back, while I am watching the sunrise.
    interesting post Timid one.
    O SIR IS an Egyption god is he mmmmm…. 🙂

    • “O SIR IS”… lol 😀
      It will be much safer for you not to watch Osiris’s sunset at all…just think of all those wrinkles Osiris’s speed mad year will inflict on you whilst you’re doing so! Best you stay cosily in your deck chair floating an awfully long way from it wearing the ultra hi-power sun tan lotion with added extra UV protection 🙂 Unless you’ve metamorphed into an Egyptian god of course! 😀

  9. Pingback: Dragon’s Loyalty Award | MisBehaved Woman

  10. I like all the graphics on this one Icywolfy
    and you tell your story so well, now all we
    need is a rocket and a nice hamper for all
    the gang when we get there 🙂 I think that
    it will be safer eating in the capsule on this
    mission but hey with strawberry pancakes
    for afters who cares? 🙂 🙂 Have a snow-free
    Monday Icywolfy and have fun 🙂 xxxx

    • Don’t forget the deck chairs! And the anti-aging cream! And better make the strawberry pancakes long life ones to be sure of countering the super wrinkly aging effects!

      I assume I am missing all your posts now as I haven’t received a single notification for it through the reader or via email since my last visit…not even via the mobile. I can’t usually read your posts on the mobile because your background causes white spaces on it and no writing but at least I’d know there was a post to check out! I’ll try to drop in over the next few days and check 🙂

  11. Schöne Bilder liebe Wölfie und Grafiken und ein toller Bericht wie immer sehr spannend.Ich wünsche dir von Herzen eine gute neue Osterwoche und viel bunte Eier.Grüße dich lieb und Freundschaft.Gislinde

    • Vielen Dank für Ihren schönen Kommentar Gislinde 🙂
      Ich wünsche Ihnen einen schönen Ostern und ich hoffe, es bringt dir viel Segen
      wie wir die wahre Bedeutung von Ostern und daran erinnern, warum es sich um eine der Karwoche
      Wolfie Umarmungen 🙂

  12. This is fascinating! It would be fun to visit other worlds, if only it were a bit easier!

  13. A fascinating read thank you for all this knowledge my wolfie friend! But I think I am going to stick with earthly sunsets


  14. Now I wouldnt mind sitting on the red chair out in the Cosmic Sunsets of some far distant planet…. Seems Mars may not now be the right place as a holiday destination! as I read somewhere it was scheduled in the future for a hit by a meteorite …. LOL..
    Have a Beautiful Day Wolfie.. and loved all the info here.. Hugs Dreamwalker

    • Yes…Mars could be in for a little battering! Lol…NASA are keeping an eye on that situation but too early to tell what if any action maybe needed…I won’t be sharing a deckchair with Curiosity though!

  15. Awesome post 🙂

    • Thanks! It was fun to work with! I might even get a signal for my internet service from a deck chair up there – no atmospheric interference and incoming cut off the connection and no inbox full of blog updates I can’t respond too! Reading blogs by the light of an alien sunset…umm!!

  16. This is fascinating – completely fascinating!! Really broadens my view of ‘it all’.

    Great listing your sources too.

    • Thank you! Oh yes…the sources…lol it took some time…a long time actually! lol to realise that it might be a good idea to include them and that not doing so was probably very rude and and inconsiderate of me!! Not to mention it could bring angry individuals or companies crashing down on my Wolfie head in wrath and indignation! 😉

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