Edit I copied the question to the Astronomy site (https://astronomy.stackexchange.com/questions/36947/is-it-true-that-we-see-the-center-of-the-milky-way-for-only-half-of-the-year), as suggested in one of the comments. Thanks!.

I'm not an astronomer, please excuse my non-formal language.

Since we are located in one of the arms of the Milky way, the center of the galaxy should be in one direction from our location, while in the other direction, we stare into the "other side".

Does this mean we only see the milky way half of the year?

In the below diagram, the small circle is our year-orbit around our sun. Red dot is the earth place on day 0 of the year and the green dot is the earth location at day 180 of the year.

I know that as we are orbiting our sun, it also orbits the galaxy, but since it is so slow, it is negligible.


Is this reasonable?

  • $\begingroup$ I think this is better suited for Astronomy $\endgroup$
    – Jack
    Commented Jul 15, 2020 at 8:36
  • $\begingroup$ @riorio ... but you are aware what "a year" and "a day" is? Because it looks like you think "a year" is earths tour around the center of milky way .. but it is actually a tour around sun .... and while we make this (around sun) tour every 365.25 days, earth is spinning around itself once a day (not going into detail with siderical and star day etc...). So we have "access" half the day from a single point on earth. To "see" the center, it still has to be dark ("night") at the position of the observer... To Sum up, as long as the center is not behind sun, there is always a spot to see the center $\endgroup$
    – CallMeTom
    Commented Jul 15, 2020 at 8:52
  • $\begingroup$ @CallMeTom I think he has denoted it correctly. The smaller circle on the side around which red and green circles are there, represents sun. So basically, what he is asking is when we are on one side of the sun for half a year, can we still see the center of the milky way which lies on the other side? I think what this doesn't consider is that sun is also revolving around some barycenter. Everything is revolving around something, so I am not sure how the combined dynamics plays out. $\endgroup$ Commented Jul 15, 2020 at 9:30
  • $\begingroup$ The Sun needs about 240 million years around the center of milky way... So we can consider this as static in terms of "we see ... half of the year" $\endgroup$
    – CallMeTom
    Commented Jul 15, 2020 at 10:00
  • $\begingroup$ @CallMeTomI updated the question. $\endgroup$
    – riorio
    Commented Jul 15, 2020 at 10:09


Browse other questions tagged or ask your own question.