help

Nighttime Sky Markers for Where We Are in the Galaxy and Local Universe

-- Bob | October 23, 2019

Question:

I don’t quite know how to pose this question, but…Are there “landmarks” in the night sky this time of year that can give a sense of “You Are Here” in our neighborhood of the galaxy?

In other words, (I’m at app. 42 deg N latitude, and you would have to specify the date and time WHEN to look)
– when you look THIS direction (toward a certain star or constellation?), you’re looking toward the dead center of the Milky Way galaxy – but 6 months later, you have to look HERE; or
– when you look THIS way, you’re looking toward the center of our Local Group; or
– when you look THIS way, you’re looking toward where we think the Big Bang occurred (is that even possible?); or
– anything that could give me a VISUAL sense of where we are in relation to the rest of the solar system at different times of the year as we go around the sun, maybe a “landmark” – or I suppose a “skymark”! – to help orient me at each of the equinoxes and solstices?

See, I told you I didn’t really know how to ask this question! I guess I’m trying to see the night sky more three-dimensionally, rather than just identifying the celestial equator, ecliptic, zodiac and other constellations and asterisms as if they’re projected onto the imaginary celestial sphere surrounding our planet.

Thank you!

-- Bob

Answer:

Here are a few sky markers that can help you orient yourself relative to our position in the Milky Way Galaxy (assuming latitude 42N):

At midnight the plane of our Milky Way Galaxy passes from SE to NW roughly overhead. The bright stars Capella, Betelgeuse, and Sirius are near this plane on the sky.
You can see the center of the Milky Way is on the southern horizon, toward the constellation Sagittarius, in the spring.
To visualize our Sun’s path through the Milky Way Galaxy, look toward the bright star Vega and you are looking in the direction that our Sun is traveling through the Galaxy. If you look toward the bright star Sirius, you are looking roughly in a direction that the Sun has traveled in our Milky Way.
Our Galaxy and the Andromeda Galaxy are two of the most massive members of the Local Group, so when you look in the direction of the Andromeda Galaxy, which is roughly overhead at midnight this time of the year, and you would be looking toward the center of the Local Group.
There is no “center” to the Big Bang (a common misconception). The Big Bang happened everywhere at the same time.

These should give you a good set of sky markers to determine the Earth’s position in the Galaxy and local universe.

-- Jeff Mangum

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