Something small, dark, and heavy lurks at the heart of the Milky Way Galaxy. Most astronomers say it’s a black hole. But a recent study says “not so fast”- it could be a clump of dark matter.

The central object is called Sagittarius A-star. It’s about 4.3 million times the mass of the Sun. A few years ago, astronomers took a picture of its “shadow” against a glowing background.

Sagittarius A-star is encircled by stars and dusty clumps in tight orbits. They’re accelerated to millions of miles per hour by the gravity of the central object.

The new study suggested that object could be a knot of dark matter particles known as fermions. Dark matter produces no detectable energy, but its gravity pulls on the visible matter around it. It appears to make up about 85 percent of all the matter in the universe, but its nature remains unknown. The clump could account for many of the observed qualities of the central dark object.

Other studies have suggested that dark matter could produce fountains of gamma rays that shoot from the galaxy’s core. Dark-matter particles could produce the gamma rays when they ram together and cancel each other out.

The dark-matter model doesn’t explain all of the evidence of a black hole. But future instruments should be able to discern between the two models – providing a definitive explanation for the darkness at the galaxy’s heart.

More about dark matter tomorrow.

Script by Damond Benningfield