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My God, it's full of stars
October 2, 2013 5:31 PM   Subscribe

Chandra Sky Map - Joe DePasquale runs through the process of creating the map and some helpful tips for using the interactive tool.
posted by unliteral (8 comments total) 12 users marked this as a favorite

 
I wonder if this planet is habitable.
posted by cjorgensen at 6:11 PM on October 2, 2013


The title teased me that this might be a post about champagne and I was disappointed at first, but then astronomy won me over. Barely. Because I was really looking forward to champagne. But I love Astronomy more.
posted by erisfree at 6:45 PM on October 2, 2013


I clicked on one that took me to Lyman Alpha Blobs. I won't say how I misread that title, but I am so coffee-deprived that I was thinking "I suppose it makes sense but it must be a really male-dominated field".
posted by Joe in Australia at 6:46 PM on October 2, 2013


cjorgensen: The planet is in a 2-day orbit around a Sunlike star. . . definitely not suitable for life as we know it (it's much closer to its star than Mercury is to the Sun).

From my perspective, the coolest thing about Chandra is that it provides some of the best information we have on black holes in the Universe. As gas spirals into a black hole, it heats up to tremendous temperatures -- millions of degrees Kelvin -- due to friction-like effects between the faster-moving gas closer to the center and the slower-moving gas slightly outside. Such hot gas glows in the X-ray part of the spectrum, which is what Chandra is sensitive to. Chandra's able to detect accreting black holes back to around the first billion years after the Big Bang.

The sources highlighted on this page are just the tip of the iceberg of what Chandra's seen -- that page is highlighting past press release subjects, it looks like -- but Chandra has studied many many thousands of objects over its lifespan (though most just look like a pinprick of light, not so interesting to make pictures of).
posted by janewman at 11:37 PM on October 2, 2013 [1 favorite]


Since temperature is just speed, isn't just acceleration due to gravity (no friction) high enough to get it to millions of °K when you're dealing with a black hole?

My duh moment in this came from the map itself. I was busy trying to understand the cosmic importance of the placement of nebulas and stars vs. galaxies and galaxy clusters when I had the realization, "Dude, the galaxies are all out of the plane of the Milky Way because we can't see the ones in the plane of the Milky Way."
posted by Kid Charlemagne at 2:04 AM on October 3, 2013


"Since temperature is just speed"
Well, it isn't. A fairly standard thermodynamic definition is that 1/T = (∂S/∂U)V,N, so the reciprocal of temperature is a partial derivative of the entropy with respect to internal energy. Now for a (perfect) gas you can then relate that directly to the kinetic energy of the particles in it, and find that the kinetic energy = 3/2 kT, and so you can say that the temperature goes like the square of the particle velocities. But that's only for a gas, with the particles all bumping into one another. It doesn't apply in the same way to a single object falling in. A speed alone isn't enough to make something internally hot.

For example, if I drop an egg into a black hole that is otherwise in a vacuum then on the way in it will certainly accelerate, but since from the egg's point of view it is in free-fall it doesn't notice its own speed and doesn't heat up and cook*. Likewise an atom falling in would be in free-fall and can't tell it has enough energy to emit an X-ray photon. When it hits another atom on the way in though, one that isn't taking the same trajectory, there's a collision energy and you can use that to prompt your X-ray emission. You need the messy gas flows going in to usefully have a concept of temperature and to allow the atoms to actually do the emission of photons that will ultimately end up in Chandra's detectors.

So yes, you need the friction-like effects to, in a hand-wavy sense, tell the gas how much energy it's picked up and allow it to emit.

*assuming a large enough black hole that we can ignore tidal forces and other complexities
posted by edd at 4:06 AM on October 3, 2013


To amplify a bit on what edd said: temperature corresponds to speed, but only a particular kind of speed: random motions of particles relative to each other, all going every which way. Organized motion in a vacuum doesn't change the temperature of an object.

Another way of looking at it : you can break the kinetic energy of an object into two parts: one part that describes bulk motion (which looks like 1/2 m v^2 , where v is the bulk velocity of a component) and a part that scales with temperature. If you measured the individual velocities of each particle, you would find that this equals the total of 1/2 m v^2 over all particles, but temperature allows us to describe those random motions statistically without delving into the details.
posted by janewman at 7:27 AM on October 3, 2013


When I get scrambled eggs on an airplane they are overcooked but when I make them at home they are fine is it because of kinetic energy explain plz
posted by Joe in Australia at 3:52 PM on October 3, 2013


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