When you look up at the 200 billion trillion (ish) stars, you probably don't think about adding another – but NASA aims to launch an artificial "star" over the USA before the end of the decade.

From Earth, stars appear to have variable brightness based on a number of factors, including how distant they are, what type of star they are, and what stage those stars are at in their life cycles. Getting very precise measurements of these parameters can help us figure out, for example, how fast the universe is expanding by looking at how far away they are, and how much the light has become redshifted on its journey to us.

For these sorts of projects, you need to know very precisely how bright a star is, and this is where having an artificial star comes in handy. The Landolt mission – named for astronomer Arlo Landolt – will provide one for us when it launches in 2029, as it places a calibrated light source into orbit at a distance of 35,785 kilometers (22,236 miles) from the Earth. 

“The goal is to be able to figure out, for other planets orbiting other stars, whether they too could have oceans where life could presumably arise and live,” Jamie Tayar, assistant professor of astronomy at the University of Florida,  explained in a statement. “For each star, you need to know exactly how much energy is coming from the star, and exactly how far away the planet is, and so on.”

The artificial star, really a CubeSat, will be in a synchronized orbit over the US during its first year. The idea is that the "star" will send send a known emission rate of photons back to telescopes on Earth. Here, astronomers will observe the artificial star next to the space object they are interested in, allowing them to assess its brightness.

"The Landolt mission will allow us to re-calibrate the brightnesses of millions of stars," Peter Plavchan, Associate Professor of Physics and Astronomy at George Mason University, explained in a paper on the project. "Such measurements can only be achieved by a space-based orbiting artificial star, where the physical photon flux is accurately known. Consequently, Landolt will enable the refinement of dark energy parameters, improve our ability to assess the habitability of terrestrial worlds, and advance fundamental constraints on stellar evolution."

It is hoped that the mission could help identify habitable zones around stars, with the ultimate goal of finding another planet harboring life.

“There are so many big questions in astronomy: How did we get here? Are there other planets like ours? Do aliens exist?” Tayar added. “But those are really hard questions, and so to answer them the measurements have to be really good, and they have to be right.”