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Space NASA

The 'Great' Conjunction of Jupiter and Saturn (nasa.gov) 62

Posted by BeauHD from the end-of-year-treat dept.
On Monday, December 21, Jupiter and Saturn will merge in the night sky in an astronomical event known as a "Great Conjunction," appearing closer to one another than they have since Galileo's time in the 17th century. NASA reports: The planets regularly appear to pass each other in the solar system, with the positions of Jupiter and Saturn being aligned in the sky about once every 20 years. What makes this year's spectacle so rare, then? It's been nearly 400 years since the planets passed this close to each other in the sky, and nearly 800 years since the alignment of Saturn and Jupiter occurred at night, as it will for 2020, allowing nearly everyone around the world to witness this "great conjunction."

The closest alignment will appear just a tenth of a degree apart and last for a few days. On the 21st, they will appear so close that a pinkie finger at arm's length will easily cover both planets in the sky. The planets will be easy to see with the unaided eye by looking toward the southwest just after sunset. From our vantage point on Earth the huge gas giants will appear very close together, but they will remain hundreds of millions of miles apart in space. And while the conjunction is happening on the same day as the winter solstice, the timing is merely a coincidence, based on the orbits of the planets and the tilt of the Earth.

For those who would like to see this phenomenon for themselves, here's what to do:

- Find a spot with an unobstructed view of the sky, such as a field or park. Jupiter and Saturn are bright, so they can be seen even from most cities.
- An hour after sunset, look to the southwestern sky. Jupiter will look like a bright star and be easily visible. Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter until December 21, when Jupiter will overtake it and they will reverse positions in the sky.
- The planets can be seen with the unaided eye, but if you have binoculars or a small telescope, you may be able to see Jupiter's four large moons orbiting the giant planet.
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The 'Great' Conjunction of Jupiter and Saturn More

The 'Great' Conjunction of Jupiter and Saturn

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  • Specific events, where many operators will be observing the same phenomenon, would be a good time to test the significance of photobombing by Starlink satellites; it would be interesting (to me, at least) to see how many make their way within 1 degree of the target from various vantage points around the globe, over the course of the next few nights. Unfortunately, my immediate vicinity is typically too polluted with light sources to do any meaningful astronomy.
  • From my location, 32.9 degrees South, they're below the horizon not long after sunset. And it's been cloudy for the past week with more rain forecast. Good thing there's Stellarium to simulate the view :)

  •   "nearly 800 years since the alignment of Saturn and Jupiter occurred at night, as it will for 2020, allowing nearly everyone around the world to witness this "great conjunction."
    "

    Its always nighttime somewhere on this planet

    • But if the earth happens to be on the opposite side of the sun during the conjunction, most people on the nighttime side won't be able to see it.

      • I'm curious to be sure I understand what you're saying.

        > if the earth happens to be on the opposite side of the sun during the conjunction [ so the conjunction is on the day time side, and on the other side of the sun] *most people on the nighttime side* won't be able to see it.

        Only a few people would be able to look through both the Earth and the sun to see it?

        Are you trying to say the following, or something else I'm missing?:

        If the conjunction of planets isn't nearly opposite the sun, it'll only be vi

        • Re: (Score:2)

          by shanen ( 462549 )

          Really? This isn't clear enough? The Ptolemaic system isn't being taught anywhere that I know of.

          Actually the only interesting aspect of this dumb thread would involve the next one, but none of us are going to be here in 400 years to check it out. Obviously we can't see such a conjunction if it appears close to the sun, but I doubt that the three planets and the sun ever form a perfect line. Therefore someone in a space station orbiting the earth should be able to see a conjunction even if it occurs on the

    • Re: (Score:2)

      by jimmosk ( 620403 )
      If the planets in the conjunction also happen to be in the same part of the sky where the Sun is -- as was the case with Jupiter and Saturn 400 years ago -- then nobody can see the conjunction (without special equipment anyway). This time, those two planets are about 30 degrees east of the Sun, so are still above the horizon after the Sun sets. So everyone gets to see them together on the evening of conjunction day (even if most places won't see them at the exact minute of closest approach).

    • Its always nighttime somewhere on this planet

      The earth rotates. The sky doesn't.

      The conjunction will be visible in the night sky just after sunset regardless of where on earth you live.

    • My goodness, even for Slashdot 2020, that's a really dumb thing to say. Are you a flat earther? Or maybe you believe in the Ptolemaic system and you think Jupiter and Saturn are orbiting the earth rather than the sun? So are you enjoying the music of the spheres, too? I'm certainly ready to bet you're an American. Probably a believer in "He whose name need not be spoken", to boot.

      No mention anywhere in the summary or discussion of such esoterica as splitting the optical double. The FP was bad enough,but thi

  • The Great Conjunction Comes! (Score:3)

    by Aethedor ( 973725 ) on Saturday December 19, 2020 @05:34AM (#60847890)
    The Great Conjunction is the end of the world... or the beginning. End, begin. All the same! Big change! Sometimes good, sometimes bad!

    • Thank you, kind person. I have no mod points, else I'd upboat you +1 Funny, so please accept my gratitude for referencing "The Dark Crystal" and Aughra.

  • Already a cool sight (Score:5, Informative)

    by JoeRobe ( 207552 ) on Saturday December 19, 2020 @08:19AM (#60848124) Homepage

    They're already pretty close to each other in the sky, so take a look in early evening if you have clear skies now. No matter what celestial bodies they are, I think it's cool to see two of the brightest objects in the sky so close.

    Some fun facts: while this is the closest they've appears since 1623, it wasn't visible. The last time they were this close together and visible was 1226!

    https://blogs.nasa.gov/Watch_t... [nasa.gov]

    The last time they actually eclipsed each other was 6857 BC. The next eclipse will happen in 7541.

    Also, they won't be this close again until 2417. Imagine what humans 400 years in the future will think of it. Will they look up from a nuclear wasteland? Or will they admire the "Earth-Jupiter" conjunction from one of Enceladus colonies? (Or both?)

    https://en.m.wikipedia.org/wik... [wikipedia.org]

    Reminds me that there's a whole, changing universe out there that has nothing to do with my little world.

    • Also, they won't be this close again until 2417. Imagine what humans 400 years in the future will think of it.

      When’s the next alignment as viewed from mars again?

    • They're already pretty close to each other in the sky, so take a look in early evening if you have clear skies now. No matter what celestial bodies they are, I think it's cool to see two of the brightest objects in the sky so close.

      Some fun facts: while this is the closest they've appears since 1623, it wasn't visible. The last time they were this close together and visible was 1226!

      https://blogs.nasa.gov/Watch_t... [nasa.gov]

      The last time they actually eclipsed each other was 6857 BC. The next eclipse will happen in 7541.

      Also, they won't be this close again until 2417. Imagine what humans 400 years in the future will think of it. Will they look up from a nuclear wasteland? Or will they admire the "Earth-Jupiter" conjunction from one of Enceladus colonies? (Or both?)

      https://en.m.wikipedia.org/wik... [wikipedia.org]

      Reminds me that there's a whole, changing universe out there that has nothing to do with my little world.

      The most important reason to look now is the weather could change before (and after) the 21st.

  • So what? Maybe if there were some control on light pollution, we could actually see the night sky in urban areas in the US.

  • I live in the heart of Austin and we can see no stars, Nary a one We can see the moon Venus and possibly Mars. Jupiter, maybe. If it's really clear. I miss seeing stars, but I ain't moving for that. Plenty of countryside here abouts for that.

  • Be on the lookout for sketchy gelflings.

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