PostHeaderIcon Planetary Alignment

Question:

“I’m interested in the stars and planets. One thing I always wondered about is if the planets in the solar system ever totally align with each other, so I mean not just a few planets but ALL of them. If this happens, how often does it occur? And is there a name for it? Thank you.”

Note:

This question comes up every once in a while. Partially it’s due to random doomsayers, and partially it’s due to Lara Croft: Tomb Raider, in which there is a planetary alignment causing widespread … actually, I don’t know what it causes, I haven’t seen the movie.

Answer to “Does this happen? How often?”:

This is a difficult question to answer. First off, as an astronomer I have to point out that the planets aren’t all in exactly the same plane. If one of these alignments occured, when you looked down on the solar system from above you would see the planets in a line, if you looked from the side at the same time, some would be a little higher, and some would be a little lower.

Everything I’m reading is pointing to the fact that even that sort-of alignment probably won’t happen. On May 5, 2000, the Earth, Sun, Mercury, Venus, Mars, Jupiter, and Saturn were close to a line, but it wasn’t perfect. Check out this simulator, you’ll have to type in 2000-05-05 in the date field.

Planetary Confluence from wonderquest.com

Planetary Confluence from wonderquest.com

Phil Plait over at Bad Astronomy says this: “As it turns out, planetary alignments are fairly rare. Getting more than three lined up is difficult; getting them all lined up is rare indeed. But 5 billion years [the length of time the solar system has been around] is a long time! Alignments may be rare, but given enough time they do occur, and the Earth is still here. Even more, what most doomsayers say is an alignment is really more of a confluence, or loose gathering, of planets.”

You’d think that with the planets going around the Sun for 5-10 billion years we’d get a perfect alignment at least once, but it looks like the math just doesn’t work out.

Answer to “What is it called?”:

The article from almanac.com calls this a “great conjunction,” which is a pretty good word. Conjunction just means that from our point of view the planets end up close to each other in the sky.

Phil Plait would call these things “confluences,” since they’re not a perfect line.

The other word I can think of to describe this is “syzygy” which refers to the alignment of at least 3 celestial bodies. It doesn’t really apply though to the 5/5/2000 conjunction, because the planets aren’t in a straight line. So, save up the word and use it next time you play Scrabble.

Update 2/22/2009:

Amazingly, this is one of my most popular posts of all time. I’ve also gotten several questions recently about the “upcoming” planetary alignment. Hmm. I don’t know exactly which one y’all are interested in, but a quick web search turned up March 26th, 2009 as something the astroLOGERS seem to be interested in. Here’s what that alignment looks like according to the simulator I linked to above:

Planetary Alignment March 26th, 2009

Planetary Alignment March 26th, 2009

In case you can’t tell – Earth is an icon underlying Venus in this picture. Doesn’t mean the Earth is under Venus – it means the icons in this picture are too big. Looks like the big deal is the Earth, Venus, Sun, Mercury “line.” Good luck all – you’re not going to be able to see a thing for this one – the blasted Sun is in the way! :)

Where’d I Get My Info?

Planetary Orbit Simulator
Tomb Raider’s Science is Wrong
Phil Plait’s Article
Nothing Special Will Happen on 5/5/2000
Syzygy

Update: 6/26/2009

P.S. Here is the “alignment” of the planets on 12/12/2012:

On 12/12/2012 the planets will be in this position.

On 12/12/2012 the planets will be in this position.

Hmm.

Here’s what that looks like in Stellarium – at noon on 12/12/2012

Don't forget - that line is the ecliptic

Don’t forget – that line is the ecliptic

That looks pretty lined up – but don’t forget – the line those planets (and the Sun and Moon) are all aligned on? It’s the ecliptic. The Sun, Moon, and planets are all ALWAYS lined up along that line somewhere. Always. Even right now. Go turn on your Stellarium, turn on the ecliptic, and set it for today, right now. You’ll find every planet on that line. And the world isn’t ending. Hmm. And you won’t see it – this is during the day.

Update: 7/7/2009

Charity asked about the conjunction on 8/8/1423. Here’s what it looks like:

August 8, 1423 8pm - from Stellarium

August 8, 1423 8pm – from Stellarium

August 8, 1423 - Planetary Orbit Simulator

August 8, 1423 – Planetary Orbit Simulator

20 Responses to “Planetary Alignment”

  • Sarah says:

    I hope you will think this is funny and not obnoxiously know-it-all of me. But there are only 2 y’s in a Scrabble set, making syzygy impossible to to spell. ;-)

  • stephanie says:

    put the right planetary alignment of 2009 for once

  • alicesastroinfo says:

    Stephanie-

    Hmm. If I knew what you were asking for, I’d definitely post it or put up a comment about it – can you be more specific?

  • alicesastroinfo says:

    Timothy asks:
    Is it possible to simulate future alignments? with reference to 2012 end of mayan calander rumors of either planetary magnetic shift causing widespread havoc or melting of polar caps causing costal flooding. thanks!

    In 2012 nothing drastic will happen. All 2012 apocalypse stories are a hoax: read Universe Today

    You can use the website mentioned above (Planetary Orbit Simlator) to simlate the planetary alignment for yourself on any date you choose.

  • Abuelopaul says:

    Check out the date of 12:12:2012 and see all the planets lined up.
    During December 2012 there will be the best conjunction ever.
    Oh, and the end of the Mayan calander.
    Get Stellarium or Starry night backyard.

  • alicesastroinfo says:

    Abuelopaul,

    I’ve posted the image from Stellarium on 12/12/2012 above. Unfortunately, the alignment is not much more dramatic than what happens every day, and definitely not as close as some of the fun conjunctions we’ve had in recent years. The confluence on 5/5/2000 was much closer.

    -Alice

  • ashlynn says:

    ironic,
    my 21st birthday is 12.12.2012

  • Charity says:

    I’m interested in what you might make of the confluence of planets that happened on August 8, 1423 right around sunset (I have mine set for Manhattan at 10 ’til 7 PM pointed West in Stellarium). Is that a “one-off” event, or is it something that would happen again? If so, when?

    • alicesastroinfo says:

      Charity, sorry it took me so long to get back to you. Ooh! That looks like a cool conjunction, I would have loved to see that. I don’t feel like going all the way through the math, but I would suspect that a conjunction similar to that could happen again. I don’t know when. I’ve posted the planetary orbit simulator image of that event above.

  • About the birthday thing, i was born on March 10 1981, have a look at March 10 1982 “the Jupiter Effect”.
    I was looking at websites for the next major conjunction, syzygy, or collusion. Any idea?

    • alicesastroinfo says:

      Michael,

      I didn’t know about the book “The Jupiter Effect” … it looks fun, albeit about as accurate as Laura Croft in terms of the effect on Earth since there won’t be one.

      For the next major conjunction/syzygy or whatever, yeah, I’d play with those simulators.

      -Alice

  • Around the 10th of April 1128 is the last time this happened, i’m not sure of the exact date, but i’ve just been playing around on that website and the 10th of April looks about right.

  • esther says:

    Well my question is what will the alinment look like from New Mexico? Can anyone help out?

  • Nice de melo says:

    GOSTARIA DE SABER POSIÇÃO PARA OS ASTROS EM 12 – 12 – 2012

    GRATA

    NICE

    • Alice says:

      Ir para o site
      http://www.fourmilab.ch/yoursky/
      clicar “Set for nearby city” escolha uma cidade perto de você
      clicar “Make Sky Map”
      datilografar “2012-12-12 21:00:00″ onde diz “Universal time:”
      clicar “Universal time:”
      clicar “Update.”

      Os planetas não será alinhado em 2012/12/12. As estrelas não estarão alinhados em 2012/12/12. Nada será alinhado em 2012/12/12.

      Sinto muito, eu não falo Português. Eu só falo Inglês e Espanhol. Eu usei o Google para traduzir as instruções acima.

      Go to this website
      http://www.fourmilab.ch/yoursky/
      Click “Set for nearby city” select a city near you
      Click “Make Sky Map”
      Type “2012-12-12 21:00:00″ where it says “Universal time:”
      Click “Universal time:”
      Click “Update.”

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