Detect Dark Matter’s Mark From Your Backyard
If you’re wondering what dark matter is, you’re not alone. Astronomers don’t know. But they’ve determined that this invisible material must be far more abundant than the stars and nebulas that they can see. They’ve surmised as much from observing the gravitational effects of all this perplexing dark stuff, launching a decades-long campaign to understand its nature. I recently learned that it is…
Dark matter remains an enigma for astronomers, yet its presence is inferred from gravitational effects on observable matter. A recent breakthrough allows backyard enthusiasts to detect the elusive substance using a compact radio telescope, such as the Discovery Dish featured in a prior article. The key to this detection lies in identifying the distinct radio emissions from interstellar clouds of neutral hydrogen, which span the Milky Way and offer insights into the galaxy's dynamics.
The author outlines the construction of a homemade radio telescope using a pyramidal-horn antenna, an online design calculator, and inexpensive materials like $25 roof flashing and a one-gallon paint-thinner can. This antenna, enhanced in size for better angular resolution, employs a Nooelec SAWBird+ H1 device and an RTL-SDR V4 dongle to pick up signals from hydrogen clouds.
While the hardware setup is straightforward, interpreting the data involves analyzing the Doppler effect to gauge the speed of these clouds as they orbit the galaxy's center.
The crux of the method is understanding that the orbital speeds of clouds should remain constant regardless of their distance from the galactic center if dark matter were absent. However, if substantial amounts of dark matter are distributed throughout the galaxy, their gravitational pull would maintain uniform orbital velocities, regardless of distance. Radio observations, which can measure Doppler shifts in hydrogen cloud signals to determine their speeds, provide a direct way to test this hypothesis.
By pointing the radio telescope at various galactic longitudes (0 to 90 degrees) and using trigonometry, the author can calculate the orbital speeds of interstellar clouds. Comparing these speeds with those previously measured by the astronomical community reveals whether the observed velocities align with predictions of a galaxy containing hidden dark matter.
The results, plotted in comparison to existing data, demonstrate the feasibility of this approach, offering a new avenue for backyard astronomers to contribute to the ongoing quest to understand dark matter.
Written by urgent.news from IEEE Spectrum's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
