We are bathing an uncertain universe. Astrophysicists generally accept that about 85% of all the mass in the universe comes from exotic, yet hypothetical particles called dark matter. Our Milky Way galaxy, which appears as a shiny flat disk, lives in a gigantic sphere of the stuff – a halo, which becomes especially dense towards the center. But the very nature of dark matter dictates that it is elusive. It does not interact with electromagnetic forces like light, and any potential clash with matter is rare and difficult to spot.
Physicists ignore these probabilities. they have detectors designed on Earth based on silicon chips, or liquid argon baths, to directly capture these interactions. They watched how dark matter can affect neutron stars. And they search for him as he floats near other celestial bodies. “We know we have stars and planets, and they’re just dotted all over the halo,” says Rebecca leane, astroparticle physicist at SLAC National Accelerator Laboratory. “By simply moving around the halo, they can interact with dark matter.”
For this reason, Leane suggests that we look for them in the vast collection of exoplanets in the Milky Way, or those outside our solar system. Specifically, she thinks we should be using large sets of gas giants, planets like our own Jupiter. Dark matter can get stuck in the gravity of planets, like in quicksand. When this happens, the particles can collide and annihilate, releasing heat. This heat can build up to make the planet very hot, especially those near the dense center of a galaxy. In April, Leane and her co-author, Yuri Smirnov from Ohio State University, published a paper in Physical examination letters who proposed that measuring an array of temperatures of exoplanets towards the center of the Milky Way could reveal this telltale trace of dark matter: unexpected heat.
Their article was based on calculations, not observations. But the temperature spikes Leane and Smirnov predict are noticeably large, and we’ll soon have a cutting edge thermometer: the new one from NASA. James webb Space telescope is expected to launch this fall. The JWST is an infrared telescope and the most powerful space telescope ever built.
“It’s a very surprising and inventive approach to detect dark matter,” says Joseph bramante, a particle physicist from Queen’s University and the McDonald Institute in Ontario, who was not part of the study. Bramante has already studied the possibility of detecting dark matter on planets. He says the detection of unusually hot planets pointing towards the center of the Milky Way “would be a very compelling dark matter signature.”
It has been less than 30 years since astronomers detected the first exoplanets. Because they are much darker than the stars on which they gravitate, they are difficult to see for themselves; they usually turn out to be just barely darken the light of those stars. Astronomers also find and measure exoplanets with tips like micro lens. (The gravity of one star distorts our view of the light of another star, and a planet in between creates a this effect.) The count of exoplanets is now to 4375, but some 300 billion could be there.
Dark matter generally moves freely among these islands of “normal” matter, which means it slides past objects without interacting. But when a dark matter particle pushes ordinary particles like protons, it slows down by a smidgeon. “Just like pool balls,” Leane says. “He just walked in, literally hits him, then bounces back. But it can bounce back with less energy. “
Accumulating enough of these collisions slows them down too much to escape the gravity of a planet. Physicists expect that when this “scattering” and capture occurs, dark matter particles can collide and annihilate. The once energetic dark matter decays into other particles – and heat. “When they break up together,” Leane says, “it puts energy into the planets.”