galaxy

Alright, startswithabang-ers, Ben, my most avid commenter, saw me online while I was eating breakfast this morning, and pointed me to this new press release. Now, before you get started clicking on everything, the guy who the release is about is Brian Gaensler, who's a really nice guy, lives in Australia, whom I met at the AAS (American Astronomical Society) meeting in Austin, TX last month. Bryan's also brilliant. Basically, what he did was he said, "well, we know what the rough density of hot gas in our galaxy is, and we can measure the timing of these pulsars to extraordinary accuracy."…

Last week, Pamela Gay over at Star Stryder pointed me to a press release which claimed that, among other things, perhaps dark matter wasn't necessary. So I wrote a guest post on her blog explaining why it was. Apparently, some people still aren't convinced. So I will lay out for you all the reasons I can think of why we need it, and explain what happens if you try to do without it. 1. Cluster Velocity Dispersions. When we take a look at galaxies, we often find hundreds or even thousands of them clustered together, like in the Coma Cluster. We can measure how quickly those galaxies are moving…

Last week, Jamie (my significant other) came home from work and told me about a conversation she had with her coworker, Chris. This week she asked another one, Miguel, whether he had any questions about Astronomy, Physics, space, etc. This week's question comes from Miguel: What is a galaxy, anyway? Why does it look like a big bright fuzzy star? And why are there different types of galaxies; shouldn't they all be the same? This might come as a surprise, but 100 years ago, it was pretty much accepted that we were the only galaxy in the Universe. In fact, there was a great debate in 1920 on…

Last year, I had just finished my Ph.D. studies, and had moved to Madison, WI to teach introductory physics at the University of Wisconsin. I was working on this paper, and when I submitted it, I got a phone call from New Scientist magazine's space division. Fast-forward two weeks, and I find this article online, where I got to see my name in print: Now, scientists led by Ethan Siegel of the University of Wisconsin, in Madison, US, have come up with a new way to potentially reveal blobs of dark matter drifting nearby and perhaps even pin down what it is once and for all. And I thought to…

I got a great question earlier today from my buddy Zrinka, and decided to figure out the answer for her, and also for myself. She asks: Ethan, is it possible to know, or better to say to imagine somehow how our galaxy looks from outside? What a simple-sounding question! After all, we know what the Earth looks like from the outside: we just go outside of it and photograph it. But the galaxy is too big to do that to; it would take tens of thousands of years moving at the speed of light to get that far away! So we're left with the option of looking at our galaxy from inside of it, and trying to…