Stars Getting Kicked out of the Milky Way can Help us map its Dark Matter Halo

Dark matter is notoriously difficult to study. It’s essentially invisible to astronomers since it can’t be seen directly. So astronomers rely on effects such as the gravitational lensing of light to map its presence in the universe. That method works well for other galaxies, but not so well for our own. To map dark matter in the Milky Way, we rely mostly on the motions of stars in our galaxy. Since dark matter attracts regular matter gravitationally, the method works well for areas of the galaxy where there are stars. Unfortunately, most of the stars lie along the galactic plane, making it difficult to map dark matter above and below that plane. But a recent study proposes a way to map more of our galaxy’s dark matter using runaway stars.

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A new Simulation of the Universe Contains 60 Trillion Particles, the Most Ever

Today, the greatest mysteries facing astronomers and cosmologists are the roles gravitational attraction and cosmic expansion play in the evolution of the Universe. To resolve these mysteries, astronomers and cosmologists are taking a two-pronged approach. These consist of directly observing the cosmos to observe these forces at work while attempting to find theoretical resolutions for observed behaviors – such as Dark Matter and Dark Energy.

In between these two approaches, scientists model cosmic evolution with computer simulations to see if observations align with theoretical predictions. The latest of which is AbacusSummit, a simulation suite created by the Flatiron Institute’s Center for Computational Astrophysics (CCA) and the Harvard-Smithsonian Center for Astrophysics (CfA). Capable of processing nearly 60 trillion particles, this suite is the largest cosmological simulation ever produced.

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One Star Could Answer Many Unsolved Questions About Black Holes

A supermassive black hole (SMBH) likely resides at the center of the Milky Way, and in the centers of other galaxies like it. It’s never been seen though. It was discovered by watching a cluster of stars near the galactic center, called S stars.

S stars’ motions indicated the presence of a massive object in the Milky Way’s center and the scientific community mostly agreed that it must be an SMBH. It’s named Sagittarius A*.

But some scientists wonder if it really is a black hole. And one of the S stars could answer that question and a few others about black holes.

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Searching for Dark Matter Inside the Earth

Dark matter remains one of the greatest mysteries in science.  Despite decades of astronomical evidence for its existence, no one has yet been able to find any sign of it closer to home.  There have been dozens of efforts to do so, and one of the most prominent just hit a milestone – the release and analysis of 8 years of data.  The IceCube Neutrino Observatory will soon be releasing results from those 8 years, but for now let’s dive in to what exactly they are looking for.

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A Dark Matter map of our Local Cosmic Neighborhood

Since it was first theorized in the 1970s, astrophysicists and cosmologists have done their best to resolve the mystery that is Dark Matter. This invisible mass is believed to make up 85% of the matter in the Universe and accounts for 27% of its mass-energy density. But more than that, it also provides the large-scale skeletal structure of the Universe (the cosmic web), which dictates the motions of galaxies and material because of its gravitational influence.

Unfortunately, the mysterious nature of Dark Matter means that astronomers cannot study it directly, thus prevented them from measuring its distribution. However, it is possible to infer its distribution based on the observable influence its gravity has on local galaxies and other celestial objects. Using cutting-edge machine-learning techniques, a team of Korean-American astrophysicists was able to produce the most detailed map yet of the local Universe that shows what the “cosmic web” looks like.

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Dark Matter Could Change the Temperature of Exoplanets, Allowing us to Detect it

Ah, dark matter, you continue to allude us. The stuff is incredibly difficult to study. It doesn’t interact with light, so our evidence of it is based upon its gravitational effects on light and visible matter. And the biggest difficulty is that we still don’t know what it is. Efforts to detect dark matter directly have come up empty, as have indirect methods such as looking for evidence of dark matter through things such as excess gamma-rays in the Milky Way. But astronomers continue to think up new ways to detect the stuff, such as a recent study published in Physical Review Letters.

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New All-Sky Map of the Milky Way’s Galactic Halo

The outer reaches of the Milky Way galaxy are a different place.  Stars are much harder to come by, with most of this “galactic halo” being made up of empty space.  But scientists theorize that there is an abundance of one particular thing in this desolate area – dark matter.  Now, a team from Harvard and the University of Arizona (UA) spent some time studying and modeling one of the galaxy’s nearest neighbors to try to tease out more information about that dark matter, and as a result came up with an all new way to look at the halo itself.

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One Idea to Explain Dark Matter – Ultralight Bosons – Fails the Test

Dark matter continues to resist our best efforts to pin it down. While dark matter remains a dominant theory of cosmology, and there is lots of evidence to support a universe filled with cold dark matter, every search for dark matter particles yields nothing. A new study continues that tradition, ruling out a range of dark matter candidates.

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