Saturn and the nearest star

By Phil Plait | August 5, 2010 7:00 am

The Cassini probe is orbiting Saturn, taking devastatingly beautiful pictures all the time. But sometimes one comes along, and while at first glance it looks like just another routine shot, when you look more closely you realizing you’re gazing into awesomeness.

Cassini_alpcentauri

This picture [click to enjovianate] looks like just another shot of the edge of the planet, doesn’t it? You can see the layering of the atmosphere, which is cool, but it’s otherwise unremarkable. But wait! What’s that weird double blip above the horizon?

That’s Alpha Centauri, the nearest star system to the Sun!

How freaking cool is that? Cassini was about 530,000 km (330,000 miles) from Saturn when it took this shot, but those two stars were 80 million times farther away!

Cassini_alpcentauri2That picture is no accident. One thing scientists like to do is watch bright stars go behind the planet Saturn itself. As the planet’s atmosphere dims and eventually blocks the star’s light, astronomers can determine all sorts of things about Saturn’s air: its composition, distribution and density with height, and much more… so they tracked the famous duo as they passed behind the planet itself.

I had the privilege of seeing Alpha Centauri two years ago this month, on my trip to the Galapagos. It was an amazing experience. I had read about that star system all my life, but to actually see it, to have photons that traveled all that distance fall into my eyes, be interpreted by my brain directly… well. It was very touching, and to me, very poetic.

I feel the same way to see this image, too, even though those photons weren’t seen by me directly. But they were detected by our robotic proxy orbiting the solar system’s most beautiful planet a billion kilometers away. And that may seem like a distance most terrible and remote, but it’s practically a warm hug compared to the emptiness that lies between us and this nearest, yet still so forbiddingly distant, star system.

Tip o’ the Zefram Cochrane to Gavin O’Brien. Image credit: NASA/JPL/Space Science Institute

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (60)

  1. Every time I have been far enough south to see the Centauri AB system, I forget to look (never having taken a VACATION there…). I guess I have an excuse that I have to go back. :)

    Again, science and reality is so much cooler than made up fairy tales! Pure awesome.

  2. I love stuff like this, I never would have gotten how cool this was without your description.

  3. IVAN3MAN_AT_LARGE

    That should be encronianate, not “enjovianate”. :P

  4. I remember being in a summer art class in elementary school where I wound up not finishing any projects for two days because I found an old National Geographic in the teacher’s junk pile talking about Cassini (still in the planning phase at the time) and all the wonderful things that we would learn from it.

    Now seeing all these great pictures coming out of the project nearly twenty years later I’m taken back to those early days of wonder. Thanks for highlighting these shots!

  5. Messier Tidy Upper

    Wow! I absolutely *love* that superluminous superb photo! Thankyou once again Cassini team & BA. :-D

    I’m amazed that Cassini‘s camera is good enough – obviously telescopic in capability – to see Alpha Centauri as two stars rather than one. I wouldn’t have thought it had the resolution to split binary stars even easy ones like Alpa Centauri. Impressive. Very.

    I can see Alpha Centauri anytime of any night – from here in Adelaide, South Australia it is circumpolar. Well, make that almost any night – its too cloudy at present much to see any stars & has been overcast and very cold here for a few weeks now.

  6. How did they make the photo? I would think that the light from the ring would burn the photo if it would be exposed too much, or if one could see the ring, then the star wouldn’t be visible (like the photos of the space station or other spacecraft). Is it a high dynamic range camera?

  7. Any exoplanets orbiting Alpha Centauri?

  8. Pi-needles

    But .. the nearest star is our Sun! Proxima & the two stars of Alpha Centauri are the second, third and fourth nearest. :-)

  9. Bob

    Yet – the Jupiter 2 is still lost….

  10. Brian Schlosser

    @6 blakut: thats not a ring, its the upper layers of Saturn’s atmosphere. The image was taken on purpose to get information about the composition of said atmosphere.

  11. Ketil Tveiten

    *Enjovianate*, v. ‘to jupiterize’.

  12. Shoeshine Boy

    Clearly faked. There are no stars in the photogra…..oh, nevermind.

  13. DrFlimmer

    In the (hopefully) likely but not confirmed case that I can visit the southern “skies” later this year, I definitely know what I need to bring along: a star chart! Just to know what I’m looking at, and to know WHERE I have to look to see all of the awesomeness down there!

  14. @Mark (#7): We don’t know. As best as we can tell, there are no gas giant type planets. Given the orbits of the two main stars (still not sure Proxima is part of the system or not, it may just be passing by on a parabolic path), it would indicate that both A and B can support a stable orbit for smaller type planets that are closer to the star (in the approximate habitable zone for both stars).

  15. Messier Tidy Upper

    @7. Mark Says:

    Any exoplanets orbiting Alpha Centauri?

    I think I recall reading something here that suggested there were very likely rocky exoplanets orbiting Alpha Centauri B at least. I’ll see if I can find it & link it here for you.

    There was (if I’m not mistaken) some talk quite a few years ago of an exoplanet candidate observed around Proxima Centauri but this has been disproved since I think.

    If a planet had been observed around Alpha Centauri I think we’d know about it although I still think (and honestly expect!) one or five to be found orbiting one or both stars of Alpha Centauri aka Rigil Kentaurus aka Toliman aka Bungula – or all three stars incl. Proxima Cen. eventually! ;-)

    A study back in 1964 by the Rand Corporation (?) suggested Alpha Centauri was the best bet for hosting habitable planets – see :

    Dole, Stephen, Habitable planets for Man, Santa Monica: Rand Corporation report, 1964

    &

    Dole, Stephen, & Asimov, Isaac, Planets for Man, New York, Random House, 1964.

    Isaac Asimov wrote a great science fact book on Alpha Centauri – Alpha Centauri : The nearest star, (Lothrop, Lee & Shepard Company, 1976) – as well which I’d recommend even though it is also now quite out of date :

    Plus there was an excellent article on the possibilty of life on any planets around Alpha Centauri in Astronomy magazine decades ago now :

    Croswell, Ken, “Is there Life around Alpha Centauri?” (Article in) Astronomy magazine, April 1991, Kalmbach publishing Co.

    Which was one of the first astronomy articles I read and still one of my favourites. Hope that’s of some interest &/or help to folks. :-)

  16. Messier Tidy Upper
  17. Messier Tidy Upper

    @ 13. Larian LeQuella Says: [August 5th, 2010 at 9:11 am]

    @Mark (#7): We don’t know. As best as we can tell, there are no gas giant type planets. Given the orbits of the two main stars (still not sure Proxima is part of the system or not, it may just be passing by on a parabolic path),

    If Proxima *is* truly a member of the Alpha Centauri system then as Robert Heinlein noted in his SF novel Friday (New English Library, 1982) :

    ” .. that dim star, while a hair closer today will soon be further away – just hold your breath a few millennia. Being ‘ballistically linked’ it averages the same distance from Earth as the other two in the triplet.”
    – Page 364, Heinlein, 1982.

    However, there does seem reason to doubt Proxima is really attached to the Alpha Centauri system as a study in March 1993 by British astronomers Robert Matthews and Gerard Gilmore :

    “… calculated that Proxima could only be in orbit around Alpha if the stars velocities though space were within one percent of each other’s. And [sic] some velocity measurements show this may not be so – Proxima seems to be moving too fast for Alpha’s gravitational pull to keep it in orbit.”

    – The Astronews column in Astronomy magazine August, 1993.

    In that case, instead of being chained at an average distance of 13,000 AU to the Rigel Kentaurus twins in an orbit taking around a million years, Proxima is really an independent and solitary star holding a singular distinction of being the closest star and deserving its name!

    The fact that Proxima is also a flare star is further evidence of its youth and suggests that it is younger and thus unrelated to the Alpha Centauri duo as well.

    Proxima is a flare star with its own variable star designation of V645 Centauri, indeed it is the most active flare star known. However whether “flare star champion” or not, a lot of patience is still required to spot a flare, just finding the star might prove difficult, it isn’t even in the same telescopic field as it’s companions Alpha Centaurio A & B. Once you found it, you may need be in for a long wait, as variable star observer Fraser Farrell explains :

    “.. you have to watch it continuously for at least 4 hours to have a reasonable chance of seeing a flare. Just the job for an automatic telescope! I have seen one flare in 20 years – they last only 10-15 minutes visually and a bit longer at radio wavelengths.” (Personal communication, Fraser Farrell, cited with permission.)

    As well as radio, flare stars (incl. Proxima I thnk) have detected in the ultraviolet and even X-ray wavelengths. (Astronomy magazine, August, 1991.) These flares which resemble Solar flares are extremely bright and hot with temperatures of 20 million degrees measured by the ASCA X-ray satellite. (Astronomy Now, August 1995.)

    Finally, on the question of Proxima’s putative planet there’s this quote from The New Challenge of the Stars by Sir Patrick Moore and David Hardy, (Hutchinson, 1977.) :

    “There have been suspicions that Proxima, too, may have a planet … The evidence at present is slender, but the planet may exist … relatively near its weak, red sun, around which (it is calculated) it orbits in 10-12 days … [From that purported world, you would apparently see that :] ” .. the limb of Proxima is not sharp but is clearly diffuse.”
    – Pages 44-45, Moore and Hardy, 1977. (Brackets original.) [brackets added.]

    Since then, the hypothetical planet has disappeared possibly being put down as a instrument flaw.

    ****

    NB. Parts of this comment adapted from an article I wrote on Proxima Centauri back in June 1996.

  18. Saturn and the nearest star

    Phil, I’d expect better of you. Isn’t the Sun the nearest star?

    When I saw the image, before reading the rest of the text, I wondered why the Sun made a double image.

    And isn’t Proxima Centauri closer?

  19. Info on Proxima Centauri from Wiki:

    “The mixing of the fuel at Proxima Centauri’s core through convection and the star’s relatively low energy production rate means that it will be a main-sequence star for another four trillion years,[13] or nearly 300 times the current age of the universe.”

    WOW! So that’s it, we need to find an Earth2 around a low mass star. We’d have it made for trillions of years. :)

    So mind bogglingly awesome. Astronomy, that is.

  20. Messier Tidy Upper

    @^ Lewis : Well, we cvertainly would have a long time to exist there, but we may find such red dwarf worlds to be NOT so habitable because :

    1. Tidal locking means the planet would likely be half freezing, half-frying with the red dwarf Sun fixed in the one constant position in the sky. Thus there’d be no sunrise or sunset and day or night would depend on where you are located.

    2. Flares – as noted earlier red dwarfs like Proxima seem prone to be variable with sudden massive flares which may make things very interesting for climate /radiation environment. Think of UV Ceti aka Luyten’s Flare star or this one :

    http://blogs.discovermagazine.com/badastronomy/2008/05/19/the-red-dwarf-that-roared/

    EV Lacertae as mentioned on the BA blog.

    &

    3. The light would be quite different – mostly emitted in infra-red rather than at visible wavelengths and not at all like our familiar sun(‘s)light. This may possibly have biological implications for humans as we know them adapting and thriving. Remember how we get our vitamin D – or was that vitamin E?

    Then again, Ken Croswell has an article here :

    http://kencroswell.com/reddwarflife.html

    that argues the case in the red dwarfs favour life-wise. So, who knows, perhaps I could be being too pessimistic here. :-)

    For those unfamiliar with the southern sky or new to astronomy who might not already know this; may I just quickly note that Alpha Centauri is located as the lower of the two bright “pointers” to the Southern Cross.

    The upper pointer is Beta Centauri (aka Hadar or Agena) which I always *used* to tell people was about 460 light-years distant compared with Alpha Centauri’s 4.3 light year distance. That was, until they had to go & refine Beta Centauri’s location to just 330 or so ly and spoil it for me! ;-)

    More good basics on Alpha Centauri can be found via stellar expert James Kaler’s Stars website here :

    http://stars.astro.illinois.edu/sow/rigil-kent.html

    PS. Just stepped outside now (3 am~ish local time) and the skies have cleared – very cold but great sky – except .. Wouldn’t you know it Alpha Centauri is now hidden by trees from my place! ;-)

  21. It can be amusing to look up Alpha Centauri in computerized star mapping software. Since it’s a wide double, it should come up as two stars (if your magnitude limit is set so that you don’t get Proxima), or one star if the double isn’t resolved. But it also has high proper motion, which causes star catalogs to disagree with each other, and I’ve seen it come up as five stars!

  22. Chris

    @17 Lewis
    Good in theory but a red dwarf would need to have a planet really close to be warm enough then it’d tend to be tidally locked like our Moon is. Also a lot closer, more solar radiation and I think red dwarfs tend to have more flare activity. So possible but I don’t think it’d work.

  23. Vat

    So, are both stars of the Alpha Centauri system actually resolved there or is it a trick of the camera?

  24. Rory Kent

    “[…] but to actually see it, to have photons that traveled all that distance fall into my eyes, be interpreted by my brain directly… well. It was very touching, and to me, very poetic.”

    This is precisely the reason I don’t do astrophotography very much. The feeling, for me, is amplified hugely when looking at Andromeda so very far away.

  25. Cool, but no Pandora to be found. Oh well.

  26. Mark Hansen

    Not sure if Phil has changed the text but I think some people are not reading it correctly. It says “the nearest star system to the Sun!” So Phil hasn’t made the all-too-common mistake of saying the Centauri system is the closest star.

  27. «bønez_brigade»

    That was more like a mini-encronianation (or mini-centaurianation), but neat-o, nonetheless.

  28. #22 Mark: Try the headline of the post :)

  29. Ah yes, the “I can’t believe that point of light I’m looking at is a star a few trillion km away, and I could visit it if I could just cross the distance in between us…” feeling. I know it well. Wrote about it a few days ago in fact as I went on a long walk in a dark park on the way home and stared up at the sky most of the time.

    http://www.pagef30.com/2010/07/space-is-not-about-space-answer-to.html

    I really believe this is the focus we need to have when advocating space to others that otherwise aren’t that interested. That is, we’re not really interested in space itself, we’re interested in what’s in it. Far too many think we’re interested in space because travelling endlessly in LEO is so much fun for us. LEO is better than nothing, but not even close to our ultimate goal.

  30. Beautiful post, beautiful pictures – took my breath away. Thank you :)

  31. Emery Emery

    I am always amazed when someone offers the music of Beethoven as an example of what beauty religion has given us and then I read one of Phil’s descriptions of the stars and I am moved to tears like no music ever has.

    In fact, Beethoven’s music alone is very nice and for some, quite emotional, but lay it beneath a slideshow of the images Phil has introduced us to, and you have something visceral and truly moving.

    Nature moves me in profound ways.

  32. David

    @Messier Tidy Upper where abouts in Adelaide are you? I’m from Stirling in the hills, nice to see a fellow south australian on BA forums!

  33. Messier Tidy Upper

    @^ David :

    Likewise! :-)

    I’m in the hills too – Glenalta halfway between Blackwood & Belair. If it’s any help or interest I was also a contestent on The Einstein factor last year – special subject : stars. :-)

    @26. Mark Hansen : Well the title above still says “nearest star” for Alpha Cen. It is a fairly common trick question – I think I recall Isaac Asimov writing he fell for it once with a bright kid. :-)

    @ 21. Michael Covington Says:

    It can be amusing to look up Alpha Centauri in computerized star mapping software. Since it’s a wide double, it should come up as two stars (if your magnitude limit is set so that you don’t get Proxima), or one star if the double isn’t resolved. But it also has high proper motion, which causes star catalogs to disagree with each other, and I’ve seen it come up as five stars!

    Myabe that’s it’s review ranking? Wide spectacular double like two headlights seen through even a modest scope, third brightest star and nearest star after the Sun (& possibly Proxima) five stars out of five! ;-)

  34. Messier Tidy Upper

    This link is my Einstein Factor page :

    http://www.abc.net.au/einsteinfactor/txt/s2702296.htm

    if folks are curious its a TV quiz show – I won the first heat but one of the contestants in the second show was too quick for me.

  35. Nigel Depledge

    This is so cool.

    It reminds of this passage:

    Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the street to the chemist’s, but that’s just peanuts to space! . . .

    And yet that star system is our nearest stellar neighbour.

  36. bassmanpete

    …orbiting the solar system’s most beautiful planet a billion kilometers away.

    I have to disagree; I think Earth is the solar system’s most beautiful planet.

    Living in far north Queensland I can see Alpha Centauri any night I like – providing it’s not cloudy of course. Also the Magellanic Clouds, the Coal Sack, etc., etc. Working as a tour guide I’m just trying to make northern hemispherians envious so that they’ll come here and keep me in a job. :)

  37. Drew

    “Our SUN is the neartest star”……REALLY?!?!?! Well, thanks for pointing that out to all of us unejukated idiots round hyar!! How much of a douchebag ARE you to be such a killjoy. I’m pretty sure the author already assumes we all know that our nearest star is the sun and that most of us are capable of making the next leap of logic and get beyond that point. Shouldn’t you be counting your comic book collection in your parent’s basement or getting ready to spend the day on world of warcraft?

  38. BigBob

    Nice pic, but why are these the only two stars in the sky?

  39. Khyron

    One thing I realized, many years ago, was that Alpha Centauri is the only star system we have VERY accurate distance measurements for. The +/- on the measurements I’ve seen is about 2.5 light-days.

    This inspired a vacation plan for an anniversary of sorts: Whenever it’s been 4 years, 133 days since you got married/engaged/had a child, go on a week vacation somewhere with a good view of Alpha Centauri. Do some stargazing every night. At some point during that week the light that hits your retina just finished a trip that started during the day you’re celebrating. Happy Light-Anniversary!

  40. I was curious if Alpha Centauri can ever be seen in the USA. Per my venerable STARRY NIGHT astronomy program, it looks like, if you were a little south of Miami, say, Key Largo or Key West, on the beach looking south, you could see it in early March around 5 AM/early April around 3 AM/Early May around 1AM / early June around 11 PM / early July around 9 PM.

  41. Tribeca Mike
  42. Elliot Nixon

    Good to see Phil Plate finally used the word “Awesome” appropriately.

  43. whit

    Pi-Needles had it right…how easily we are lulled into believing…that’s political science!
    Do we have to go to Wiki for the “truth”!

  44. All right, the more I look at this, the more I’m unclear what I’m looking at. At first glance, you might assume it’s a ring of Saturn, but the various text here and on NASA’s site mentions both a ring and the atmosphere of Saturn.

    But the more I look at it, I just see layers of atmosphere. We’ve got the upper black part, i.e., space, where Alpha Centauri is visible. Then a little hazy area, then a big white area, then several layers of darker and lighter areas, and then the bottom black area. Which, is we were looking at a ring, is more space, but I think it’s more likely that it’s the planet itself in shadow.

    But if that’s the case, where’s the ring come into play?

  45. BHarris

    Planettom: There is an astronomy star party usually around the new moon in February called the Winter Star Party. It is held about 35 miles north of Key West. It is very popular because one of the draws is being able to see southern sky objects like Alpha centauri and the southern cross from the U.S.

  46. don gambill

    Lolz @ Shoeshine

  47. @45. planettom

    You don’t actually see the rings in this picture. That bottom black area? That’s the shadow of the rings.

  48. Jon Hanford

    Speaking of Cassini imaging of deep sky objects in Centaurus, has anyone mentioned Cassini’s movie and still of the great globular cluster Omega Centauri slewing thru an image of the rings: http://photojournal.jpl.nasa.gov/catalog/PIA12788 ? An awesome image in its own right. :D

  49. MAC

    Wouldn’t it be great if, near the end of its life, Cassini could be maneuvered to orbit just above the rings? We have some idea of their composition, but it would be so much better to confirm it photographically. And of course there’s always the serendipity effect; they might have a few surprises in store.

  50. Messier Tidy Upper

    @ ^ MAC : Agreed & seconded by me. Hopefully the radiation (or age or whatever else) won’t have killed the cameras by then.

  51. Joe

    Wow, that is just mind-blowing. Makes me want to go down south just to see it myself… and maybe bring a telescope with me to separate the two stars.

    And on the whole red dwarf argument, and tidal locking: Couldn’t a moon of a big planet in the habitable zone, such as Gliese 581 d prevent the effects of tidal locking on a star? The planet would still be tidally locked, but the moon could be locked to the planet, and would then have a day-and-night system.

  52. Xrogg

    I’ve been to the Alpha Centauri solar system and I can say that its much better here.

  53. planettom

    BHarris: That Winter Star Party in the Florida Keys (where Alpha Centauri can be observed) sounds fun. Here in Google Earth: 24 38.975 N 81 18.575 W http://www.scas.org/wsp.html Although their disclaimer that basically reads, “Despite our best efforts, you will be eaten alive by fire ants” is ominous.

  54. Messier Tidy Upper

    @51.Jon Hanford : Thanks. :-)

    I hadn’t heard of that – superluminously (beyong merely brilliant) magnificent image. I hadn’t realised that Cassini‘s cameras could take such telescopic views. I’ve posted that to my facebook page and my local astronomy groups fb page too. :-)

  55. Nigel Depledge

    Drew (39), presumably in response to Pi-needles (8), said:

    “Our SUN is the neartest star”……REALLY?!?!?! Well, thanks for pointing that out to all of us unejukated idiots round hyar!! How much of a douchebag ARE you to be such a killjoy. I’m pretty sure the author already assumes we all know that our nearest star is the sun and that most of us are capable of making the next leap of logic and get beyond that point. Shouldn’t you be counting your comic book collection in your parent’s basement or getting ready to spend the day on world of warcraft?

    Wow!

    A) Way to miss the joke, Mr Grumpy.

    B) You reveal a lot about your own prejudices with this rant, and I fail to see what you hoped to achieve by it.

  56. I’m sure some day humans will visit the Alpha Centauri system, I wonder how they’ll feel looking back at our sun as a tiny point of light in the far distance.

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