# Age of the sun in galactic years

## Main Question or Discussion Point

The Solar System is traveling around 155 miles a Second around the Milky way Galaxy.

There are 31,556,926 seconds in a year.

We will round off the Age of our sun from 4.76 Billion to 5 Billion Years for easier figuring.

If we Multiply 31,556,926 seconds by 5 Billion Years we get 157,784,630,000,000,000 seconds in 5 Billion years.

Now if we multiply that by 155 Miles a Second we get 24,456,617,650,000,000,000 miles that our Sun has traveled since its birth.

Which results is a distance of 1,275,543 Parsecs or 4,160,350 Light Years arc distance

Somewhere at 4,160,350 Light Years arc distance away out our Star was born.

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Do you know how many Galactic years our Solar System has traveled since our Stars Birth? this is not in solar system years but Galactic Years.

Where's the Math, if not, I will provide it.

Vogue said:
The Solar System is traveling around 155 miles a Second around the Milky way Galaxy.

There are 31,556,926 seconds in a year.

We will round off the Age of our sun from 4.76 Billion to 5 Billion Years for easier figuring.

If we Multiply 31,556,926 seconds by 5 Billion Years we get 157,784,630,000,000,000 seconds in 5 Billion years.

Now if we multiply that by 155 Miles a Second we get 24,456,617,650,000,000,000 miles that our Sun has traveled since its birth.

Which results is a distance of 1,275,543 Parsecs or 4,160,350 Light Years arc distance

Somewhere at 4,160,350 Light Years arc distance away out our Star was born.
If we review what I posted here then we can continue to find out approximately how many Galactic Years old our Star is.

We'll use an a round figure for our Milky Way Galaxy to be around 100,000 Light Years in diameter and multiply that by pi, 3.1415926535897932384626433832795, Now we find out that the Milky Way Galaxy has a circumfrence of just over 314,159 Light Years, Then we divide that figure with the 4,160,350 Light Years arc distance our Sun has traveled since its birth and we get 13 Galactic Years or in other words our Sun has made approximately 13 trips around the Milky Way's Galactic center.

Hi SpaceTiger.

I like your program: Unicalc0 - Calculations with automated unit conversion but have you tried Convert.exe, It has many conversion techniques including custom Conversions and even more in the latest version.

It allows you you to convert from one math format to another, If you know of a better program please let me know and I will excite it as far as I can for you.

SpaceTiger
Staff Emeritus
Gold Member
Vogue said:
We'll use an a round figure for our Milky Way Galaxy to be around 100,000 Light Years in diameter
There are a lot of mistakes in this calculation. Let's start by thinking about exactly what "size" we want to use. We want to count the number of times the sun has been around the galaxy, so we don't want the total radius of the galaxy, but rather the radius of the sun's orbit. This is 8 kpc or ~25,000 light years.

and multiply that by pi, 3.1415926535897932384626433832795
That's far more precision than you'll need for the calculation, but the most important problem here is that the circumference of a circle is $2\pi r$, not $\pi r$.

The conventional values for the other parameters in your calculation:

Age of the sun - 4.5 billion years
Speed of the sun - 220 km/s (137 mi/s)

The final equation to determine the number of orbits the sun has made since its birth is then:

$$N_p = \frac{v_{\sun}*t_{\sun}}{2\pi r_{\sun}}$$

This gives about 20 galactic years. Incidentally, you can just plug the following into Unicalc0 to get this result:

"220 km/s * 4.5 Gyr / (2*c_pi*8 kpc)"

do we know if the orbit is anywhere near round ?
or if it was stable for any fraction of the time ?
do we travel along with the currently close stars?
or are they moving in different orbits
that just happent to be near us now
with a new set of stars in a revolution?

tony873004
Gold Member
I believe the orbit is close to round. It bobs up and down through the galactic plane, more than twice per orbit! That's one more difference planets orbiting a star and stars orbiting a galaxy.

The galaxy's halo contains older stars, so I believe over time, the Sun's inclination will increase.

I would guess that 20 orbits is enough to stir things up so that most of the stars that were part of the Sun's birth cluster are too far to be seen. But if we had a way to tell which ones they were, there's probably still a few lingering within reach of a backyard telescope. We do share a similar motion around the galaxy as our stellar siblings.

I would guess that the constellations are completely re-worked each galactic orbit. If we went back in time 200 million years, we would not recognize the sky.

Just my guesses.

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"217 km/s * 5.43 Gyr / (2*c_pi*8 kpc)"

What angle on the current galactic plane relative to current position will this event occur?

How much time until this plane angle position is reached?

Reference:
http://qonos.princeton.edu/nbond/unicalc/calculator.php [Broken]

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DaveC426913
Gold Member
tony873004 said:
I would guess that the constellations are completely re-worked each galactic orbit. If we went back in time 200 million years, we would not recognize the sky.
If we went back a puny 100,000 years, we would not recognize the sky.

Well, it'd be the same stars, just all out of sorts.

SpaceTiger
Staff Emeritus
Gold Member
Orion1 said:
None that I can see, the sun is only 4.5 billion years old and will only live about that much longer.

That should be 5.43 Gyr.

"217 km/s * 5.43 Gyr / (2*c_pi*8 kpc)"

Reference:
http://qonos.princeton.edu/nbond/unicalc/calculator.php [Broken]

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