How Do Scientists Measure Size Of The Ever Expanding Universe?

How Do Scientists Measure Size Of The Ever Expanding Universe?

Mapping out the universe isn’t easy, even with the most advanced equipment humans currently have. It’s a known fact that the universe is constantly expanding, though its rate of expansion is unknown. To calculate the distance of very distant objects, scientists use a method known as the cosmic distance ladder.


The concept uses different objects as rungs on a ladder to calculate distances. It helps astronomers observe the movement of stars and look at pulsating stars known as cepheid variables and Type Ia supernovas.

Determining The Precise Distance

These objects help researchers determine large distances, but they should be calibrated to each other to provide precise results. Cepheid variables’ brightness changes with time and these changes are correlated to their actual brightness. Scientists can determine how far a star is by comparing its pulsing to its apparent brightness.

To determine the distance of more distant objects, astronomers use Type Ia supernovae, as they have nearly the same level of brightness that allows them to compare the true brightness to the apparent brightness and determine how far they are located.

But to determine the distance precisely, researchers need to see if the distances measured based on supernovae and cepheids are calibrated with each other.

UGC 9391 Comes To The Rescue

Well, galaxies such as UGC 9391 feature cepheid and have hosted a Type Ia supernova are ideal for the job. Recently, the legendary Hubble Space Telescope captured an image that leverages this distance-measuring method.


“UGC 9391 helped astronomers improve their distance estimates by providing a natural laboratory in which to compare two measuring techniques – supernova explosions and Cepheid variables,” the Hubble team noted. “Improving the precision of distance measurements helps astronomers quantify how quickly the universe is expanding – one of Hubble’s key science goals.”

Hubble, James Webb At It Again

The Hubble Space Telescope and the James Webb Space Telescope recently also captured images of the spiral galaxy IC 5332 which is located more than 29 million light-years away from Earth. The spiral galaxy IC 5332 is one-third of the Milky Way galaxy’s size; however, it is an ideal target for astronomers thanks to its perfect spiral arms.

James Webb used its MIRI instrument to snap the skeletal-like structure of the IC 5332 galaxy’s spiral arms. Hubble’s image, on the other hand, shows cosmic dust as dark patches that are preventing light from passing through the galaxy’s arms.

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