Astronomy Science
sb admin | November 24, 2007(I know I'm not doing this any more, but I couldn't resist.)
An article in New Scientist reports on musing by two reasonable and respected cosmologists— indeed, ones whom I've met myself— that our discovery of dark energy may have shortened the life of the Universe.
To which I can only say "foo". And I say "foo" on two levels. Primarily, on the sensational way in which this is described by New Scientist. But secondarily, on the interpretations of quantum mechanics that respectable cosmologists are promoting.
First of all, for a bit of perspective. The actual research paper on which this…
sb admin | October 10, 2007Astronomers have long assumed that supernovae are the source of at least most of the cosmic rays that hit Earth.
Woah, slow down... cosmic rays? Right, you hear the term all the time, but do you really know what they are? They are charged particles that rain down on Earth from space. Really! Kinda cool, huh? There are charged particles— mostly protons, or hydrogen nuclei, but with some heavier ions mixed in— smacking into our atmosphere all the time. Some of them have extremely high energies, higher energies than those to which we can accelerate particles in our best particle physics…
sb admin | September 27, 2007Every so often you will come across somebody who has a "killer" list
of "problems" with the Big Bang. While there remain unknowns and
questions about the Big Bang— just as there do with biological
evolution— the basic picture of the Big Bang is rock
solid— just like evolution.
Nearly two months ago, I received a query from somebody who found my
name through the
Clergy
Letter Project "expert database" regarding one of the websites that
lists these objects. I've been through quite a number of life changes
in the last 6-8 weeks, and my blogging rate has suffered as a result…
sb admin | August 18, 2007This is mostly just an MLP ("Mindless Link Post"), and it's nearly two weeks late, but there's a post by Julianne over at Cosmic Variance that I think is of crucial importance. People who are outside the field of science very often lose sight of the huge amount of important science that is done, but doesn't produce the "amazingly sexy discovery" news headlines, or, say, the Gruber prize. Also, people working in one field of science often don't appreciate the value of other fields of science when it doesn't obviously overlap theirs... even though, as Julianne points out, all of that other "…
sb admin | August 14, 2007Following the talk I gave in Second Life about the discovery of the accelerating Universe, we held a couple of Q&A sessions. The original plan was to have questions right after the talk, but the Second Life main grid crashed right at that moment. We all got online about half an hour later, and I held one Q&A session for the people who came back. There was another one the next day.
Troy McLuhan (his Second Life avatar name) logged the session, and has done the hard work of formatting and lightly editing it for web publication. You can find the transcript of the Q&A session…
sb admin | July 31, 2007I managed to get through my 15-20 minute "talk," and just as I threw it open for questions Second Life had a database problem and everbody in-world had to be logged out.... We got back in 40 minutes or so later, and I answered questions for a while for people who came back. However, if you were at the talk and wanted to ask questions but didn't come back, I'll be doing a follow-up Q&A session tomorrow (Wednesday August 1) at 10AM PDT at the same location.
Below, I've got a transcript of the talk I gave. Other than fixing some typos and merging things into paragraphs, I haven't edited…
sb admin | July 31, 2007Just a reminder: I'm giving a talk / Q&A session about the discovery of the accelerating Universe today in Second Life. The talk is at 10:00 AM PDT / 12:00 Noon CDT / 1:00 PM EDT / 17:00 UT. Find it by going to this location: Spaceport Bravo (120,65,278).
Also, for those of you who don't know: a basic Second Life account is completely free! Go to the site and register for an account, and download the client to run on your computer. After you get in-world, you'll go through an "orientation island" that teaches you how to move about and look about. The Basic Account lets you get in…
sb admin | July 26, 2007Next Tuesday, July 31, at 10:00AM PDT (17:00 UT), I'll be giving a talk and Q&A session in Second Life about the discovery of the accelerating Universe.
The talk is being hosted by Troy McLuhan of the Science Center Group. I t will be located at Spaceport Bravo (120,65,278).
And now, for no adequately explained reason, I include a picture of my Second Life self wearing M51 on my head:
sb admin | July 17, 2007This is really cool. Several years ago, the Gruber Foundation established a prize in cosmology. Last year (2006) the award went to John Mather and the COBE team; you may recall that Mather was one of the two winners of this year's Nobel Prize in Physics. This year the award is being split four ways: (1) Saul Perlmutter, leader of the Supernova Cosmology Project (SCP); (2) Brian Schmidt, leader of the High-Z Supernova Team (HZT); (3) the members of the SCP who were on the Perlmutter '99 paper; and (4) the members of the HZT who were on the Riess '98 paper. These two papers were the…
sb admin | June 22, 2007NGC 5135 is a barred spiral, similar in some ways to NGC 1365. Both galaxies are members of the IRAS "Bright Galaxy Sample," meaning that they are very luminous in the infrared as a result of vigorous star-forming activity. Both have very strong bars. Both harbor an active galactic nucleus at their core. (All large galaxies are believed to have a supermassive black hole at their core, but only a small fraction of those black holes are actually being fed; it is the feeding of the black hole that triggers the AGN.) And, both have been observed by Katie Chynoweth and I as part of our (sadly…
sb admin | June 8, 2007The image below is an image taken in 1994 with the Hubble Space telescope of galaxy NGC 4526:
Image: NASA, ESA, The Hubble Key Project Team, and The High-Z Supernova Search Team
The bright spot in the lower left is the supernova known as SN1994D. This is a Type~Ia supernova, type type of supernova that has been used by several times (initially two, the one that I was in, and the one that this image is credited to) to measure the expansion history of the Universe, and to discovery that the expansion is accelerating (requiring that there be that which we now call "Dark Energy" filling the…
sb admin | May 25, 2007VV114 is a very interesting galaxy. It's a major merger of at least two big galaxies. If I might go out on a limb, it may even be an advanced merger (on the left) currently strongly interacting with another galaxy (on the right).
The left galaxy is extremely dusty. Sunsets are red because particles in the atmosphere preferentially scatter away the bluer light. Redder light penetrates the dust better. Just before the Sun sets, we're looking at it through as much atmosphere as we ever see it, so it has to go through the most number of particles in the atmosphere. similarly, very dusty…
sb admin | April 27, 2007Are you ready for this? This week's Friday Galaxy is Mk509:
DSS2 image from Skyview
Admittedly, the image of this galaxy does not rank very high on the "wow, what a cool and pretty looking galaxy" scale. However, this is an interesting galaxy because of what's going on at the nucleus. Like all large galaxies, there is a supermassive black hole at the core of this galaxy. The black hole in this galaxy is being fed, giving rise to what we call an Active Galactic Nucleus (AGN). If you drop gas down into an accretion disk near a supermassive black hole, a tremendous amount of…
sb admin | April 16, 2007Here are images of two more galaxies. These weren't taken during the current run, but in a previous run. Last November, I was also down at CTIO with some students. I was doing blazar work on the 1.0m telescope (not to be confused with the 0.9m telescope I'm using right now), and shot off some images of the galaxies that Katie was observing spectroscopically. The two galaxies below are those galaxies.
The first is NGC 1614:
This galaxy has what we in the biz call a "disturbed morphology." It's not just a clean spiral galaxy, and it's certainly not an elliptical galaxy. Sticking off…
sb admin | April 14, 2007I apologize for my silence of the last few weeks; real life gets busy at times. This time, I was in a crunch finishing up things before running off to an observing run at the CTIO Observatory in Chile. That's where I am right now. I'm at the 0.9 meter telescope doing imaging of "blazars," a class of active galactic nuclei that sometimes vary on timescale of minutes (which is surprising if you know how big galaxies are). My graduate student Katie Chynoweth is observing on the 1.5 meter telescope, doing spectroscopy of infrared-luminous galaxies.
Below is an image — really, a composite of…
sb admin | March 20, 2007I don't do this any more, but in the past I did what many astronomy professors do when teaching introductory astronomy: tell the tale of Tycho, Kepler, and Newton, as a way of introducing and describing planetary orbits. It's such a great story, as it shows the concrete struggle we as a race went through to fully codify and understand the heliocentric, Copernican picture of the Solar System. It also highlights the contributions of three very different sorts of scientists.
We have Tycho, the observer. We have Kepler, the phenomenologist. And, we have Newton, the theorist. Each played a…
sb admin | March 13, 2007"Redshift" is a term that astronomers use a lot. This is particularly true if they are extragalactic astronomers or (especially) cosmologists, but even galactic astronomers use it, and it is absolutely central to the method use to discover most of the extrasolar planets known today.
This post is going to be divided into three parts. First, I am going to explain that redshift itself is just a definition of an observable or measurable quantity, without any need to reference what caused it. Second, I'm going to talk about the more familiar source of redshift -- the Doppler shift. Finally, I'…