Hunting for dark matter, the invisible substance that makes up about 85 percent of all the mass in the universe, is no easy feat. It’s nearly undetectable because, if it interacts with light at all, it does so extremely weakly. Still, its presence is believed by most astronomers to be almost everywhere, shaping galaxies and stars with its gravitational force.

A new study published in Physical Review Letters suggests a surprising twist. Dark matter might not be entirely invisible after all. Instead, clumps of it could be acting like “lampshades,” dimming the light from stars just enough that our current telescopes can pick up the difference. Melissa Diamond is a coauthor of the study and works at Queen’s University in Canada. In a statement to Space.com, she said:

“While we usually say dark matter does not interact with light at all, making it totally transparent and invisible, the truth is, it is allowed to interact with light a tiny bit. Dark matter might form large clumps or clouds, often called MACHOs. There may be enough dark matter in these MACHOs that their weak interactions with light collectively block light from passing through the cloud, like how a lampshade blocks some but not all light from getting through.”

For years, scientists have focused on a leading theory that dark matter is made up of invisible particles known as WIMPs (Weakly Interacting Massive Particles). These hypothetical particles don’t emit or interact with light, and they’re believed to clump together under gravity to shape cosmic structures.

Despite ongoing experiments, WIMPs remain elusive, and so far, no one has detected them.

This latest study turns attention to another contender known as MACHOs (Massive Astrophysical Compact Halo Objects). These could include dense objects like neutron stars or black holes, which are made of ordinary matter and typically emit little or no light. This would make them hard to spot, unless they’re acting like a cosmic lampshade that is.

Scientists have used a method called microlensing to detect MACHOs before. Microlensing happens when a massive object bends the light of a more distant star like a natural telescope, making it appear brighter.

But there’s a drawback. If the object isn’t dense or compact enough, its gravitational effect might be too weak to notice. That’s where the lampshade idea comes in. Even a loosely structured cloud of dark matter might still dim the star’s light in a tiny but detectable way. Diamond goes on to explain:

“This is where the lampshade effect can make a big difference. While the clump might be too puffy to make for a good lens, it can still block some starlight, causing the star to dim instead of brightening.”

Using this “lampshade method,” astronomers can search for these dimming events using existing data sets with no need for new telescope technology. Surveys like the Optical Gravitational Lensing Experiment (OGLE) could help identify these MACHOs.

“This technique lets us get new use out of existing data, and lets us look for new types of MACHOs that microlensing surveys might not otherwise be sensitive to,”

If confirmed, these findings would bring us one step closer to understanding what dark matter truly is. And even if they don’t turn up results, refining what doesn’t work narrows down the possibilities.

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