What little we know about the Milky Way Galaxy might surprise you.
After all, scientists now estimate that there are well over 100 billion galaxies in the observable universe, and we know they create an interconnected web. We even know that our closest galactic neighbor, Andromeda galaxy, will collide with our own Milky Way. Still, figuring out just the size and shape of our home galaxy has been a frustratingly long process. But, a recent discovery of five “Cepheid” stars by researchers in Japan and South Africa might change that.
First it’s important to understand why we don’t know the Milky Way’s dimensions. Imagine trying to fix your hair without a mirror. You can do your usual routine and imagine exactly how you look, only to see a mangled knot on your head when you pass an office window. The same difficulty exists for astronomers because we are in the Milky Way galaxy.
Until we ask aliens in nearby Andromeda to mail us a photo, our visuals of the Milky Way will have to be computer-generated estimates or pictures of galaxies that may look like ours (the picture posted above is Galaxy NGC 6744).
So how can the five Cepheids help us with this issue?
Because Cepheid stars are great for revealing celestial distance and these Cepheids happen to be at the very edge of the Milky Way. Cepheids are yellow supergiant stars that produce a lot of light. More than that, they pulsate, expand and contract in a way that changes the light the star emits.
That pulsation period gives us a measure of the star’s luminosity that can be compared with how it looks from Earth, and like magic we get the distance.
These stars are so distant that at first scientists thought they were part of Sagittarius Dwarf galaxy, which our Milky Way is callously destroying with its gravity. However, these Cepheids belong to the Milky Way’s outer edge. Measuring the star’s distance will give scientists a point of reference on the galaxy’s perimeter, which will ultimately lead to better methods of estimating size and shape.
One problem: There are only five that the researchers observed. Having only five small spots on a perimeter so large boggles the mind.
This discovery will open up the possibility of larger scale surveys to search for more Cepheids.
But why is understanding the dimensions of the galaxy important? Because understanding the galaxy means understanding our own future, albeit distant future. In our future, the Milky Way will cease to exist as we know it when it eventually collides with Andromeda. Also thanks to our understanding, we don’t have to be afraid of that event because there is so much space between solar systems that actual collisions will be incredibly rare.
Measuring galactic dimensions may seem abstract and distant from the problems of the Earth today, but who knows what a greater knowledge of the Milky Way will produce tomorrow.