Interview: Juan Collar and Detecting Dark Matter (MP3, 28.3MB, 41:10, Show Notes)

Check this sh!t out:

Credit: Brant Robertson, Spitzer Fellow, KICP/UChicago

This interview is quite long so we’ve uploaded low and high rez versions. The low rez version is the one in the RSS feeds.

If you subscribe to the feed, the audio is probably already on your box. Or you can check out the show notes or download the MP3 file directly:

Slacker Astronomy podcast interview with Brant Robertson (low rez) (MP3, 24.7MB, 1:11:20)

Slacker Astronomy podcast interview with Brant Robertson (high rez) (MP3, 65.6MB, 1:11:20)

Black holes are the most likely source of the mysterious ultra high-energy cosmic rays that bombard the planet… Observations at the world’s largest cosmic ray detector suggest the particles are emitted by huge black holes in the middle of nearby galaxies. 

Cosmic rays are a pain in the ass for spectroscopy, astrophotography and other CCD-based astronomy. Especially spectroscopy is plagued by cosmic rays. There are 3 kinds of cosmic rays that I’m aware of, electrons, protons and Helium nuclei (or alpha particles). The cosmic rays discussed in this article are high-energy and create a shower of interactions when they slam into the earth’s atmosphere.Pretty cool that we are starting to see results out of the Pierre Auger Observatory.

The BBC reports: Dark matter clues in oldest stars:

“In cold dark matter the particles move very slowly; in warm dark matter they move very quickly,” he explained.

“We found that if the dark matter consists of these fast moving particles, then the first stars form in very long, thin filaments…Some of the stars that formed within the filaments would have had a relatively low mass, which is of interest to astronomers as they have a long lifespan and could still survive today.

Dr Theuns added: “In stark contrast, what happens in (the simulation with) cold dark matter is very, very different. Here, the first stars formed in little lumps of dark matter, and just one star per dark matter lump. And these stars are probably very massive as well: 100 solar masses. Because these stars are so massive, they die very quickly; so you wouldn’t find such stars in the Milky Way today,” he said.

Everything I’ve read about the “1st stars” (or Population III stars) is that they would have been very massive because they lack metals (elements heavier than Helium). The stars that followed them (Pop. II and Pop. I) had access to heavier elements created by the supernovae of the Pop. III stars and evolved differently as a result.

What’s important here, as I read it, is that we have a “1st stars” option which creates low-mass stars that could still exist today. So finding such stars could tell us something about dark matter.

MACHO, and its sequel, SuperMACHO, are projects that have directly detected dark matter. Dark matter is dark, yet we can observe it through a variety of clever techniques. One such technique involves measuring the brightness of stars and looking for the effects of gravitational microlenses — stars which get brighter for a brief time, once and only once, as the dark matter passes in front of it.

Dark matter is a funny term because it encompasses all the matter we can’t see. Dark matter is not one thing, it is all the things we can’t see but can detect due to their gravity. The dark matter detected by MACHO is likely things like planets, brown dwarfs, white dwarfs or low-mass black holes, if such things exist.

Dr. Doug Welch is one of the researchers involved with the MACHO project. In this podcast interview with Michael Koppelman, Doug talks about all things MACHO.

If you haven’t already subscribe to the podcast or just listen now.