Tuesday, August 31, 2010

New Blog: Astronomy Computing

I see that Bruce Berriman has started a new blog, Astronomy Computing. I know him of course from IPAC, and before that I knew of him for his early work with Neill Reid. I read his papers on M dwarfs very carefully as a graduate student, even if he seems to remember only a failed project!

He has a very good post on Was it hard to return to astronomy and research? and another called How I survived in astronomy.

He also has some important thoughts on computation, as the name of the blog hints. I'm looking forward to learning.

New Paper: M Dwarfs in the Mid-Infrared

I've submitted a paper to the Astronomical Journal called M Dwarfs in the Mid-Infrared AKARI/IRC Sky Survey.

AKARI is a Japanese satellite that took pictures of most of the sky at wavelengths of 9 and 18 microns. For comparison, visible light is around 0.5 micron.

I found that about a thousand nearby -- that means within about 70 lightyears -- late-K and M dwarfs were detected. These are stars that around about half the mass of the Sun. For the most part, the brightnesses at 9 microns, where AKARI detected most of the them, are exactly what astrophysicists predicted backed on the brightnesses measured at 2 microns in the 2MASS Survey.

However, I do find a few of the M dwarfs are about 30% brighter than they should be. This may just be random error -- that is, we expect some measurements to be off just by poor luck. On the other hand, if the excess is real, it's very interesting.

One explanation for such an excess is that the M dwarf is surrounded by dust grains that about 300-500K. How would you get grains -- small particles -- around an M dwarf? The grains could be debris form collisions between asteroids. If this is the case, these M dwarfs have Super-Asteroid Belts much more massive and denser than our Solar System's. Also, the asteroids would be near the "habitable zone" where liquid water can exist on planets. Obviously, it's difficult to imagine life existing on asteroids that are constantly colliding with each other, but it's an exciting possibility.

Unfortunately, we really need independent measurements of the mid-infrared brightnesses before we can believe there really are excesses. The Spitzer Space Telescope no longer can make these measurements, because it ran out of coolant as scheduled last year, but perhaps the SOFIA observatory can. I'm looking forward to it, whether I or someone else make the measurements

Saturday, August 21, 2010

Earth and Moon, from a distance

NASA's MESSENGER mission took this image of the Earth and Moon as seen from 114 million miles away. That's more that the distance between the Earth and the Sun. Notice that they're lit up nicely since they (we!) are being viewed from the inner solar system.The image credit is NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

That reminds me of another nice NASA photo, this one from Cassini. In this one, the Earth and Moon are visible through Saturn's rings. This is the view from the outer solar system. The upper left has a blow-up of our home since it's just a small blip in the full image.

Friday, August 13, 2010

Too true

From xkcd:

Astronomy Decadal Survey out

The Astronomy Decadal Survey press release is out:

The report identifies space- and ground-based research activities in three categories: large, midsize, and small. For large space activities -- those exceeding $1 billion -- an observatory the report calls the Wide-Field Infrared Survey Telescope (WFIRST) is the top priority because the space telescope would help settle fundamental questions about the nature of dark energy, determine the likelihood of other Earth-like planets over a wide range of orbital parameters, and survey our galaxy and others. For large-scale, ground-based research initiatives that exceed $135 million, the first priority is the Large Synoptic Survey Telescope (LSST), a wide-field optical survey telescope that would observe more than half the sky every four nights, and address diverse areas of study such as dark energy, supernovae, and time-variable phenomena...

Along with WFIRST, other priorities in the large-scale space category recommended in the report are an augmentation to the Explorer program, which supports small- and medium-sized missions that provide high scientific returns; the Laser Interferometer Space Antenna (LISA), which could enable detection of long gravitational waves or "ripples in space-time"; and the International X-Ray Observatory, a large-area X-ray telescope that could transform understanding of hot gas associated with stars, galaxies, and black holes in all evolutionary stages.

Other recommended ground-based research projects include the formation of a Midscale Innovations Program within the National Science Foundation (NSF), which would fill a funding gap for compelling research activities that cost between $4 million and $135 million. In addition, the report recommends participation in the U.S.-led international Giant Segmented Mirror Telescope, a next generation large optical telescope that is vital for continuing the long record of U.S. leadership in ground-based optical astronomy. The next priority is participation in an international ground-based high-energy gamma-ray telescope array.

For midsize space-based activities, the first priority is the New Worlds Technology Development Program, which lays the scientific groundwork for a future mission to study nearby Earth-like planets. Top priority for ground-based midsize research is the Cerro Chajnantor Atacama Telescope (CCAT), which would provide short wavelength radio surveys of the sky to study dusty material associated with galaxies and stars.

You can read it online for free:

Majoring in "Astronomy" at the University of Delaware

Potential students often find the information on astronomy for undergraduates at the University of Delaware confusing so I am writing this post.

Astronomy can be viewed as a branch of physics, and in order to go graduate school in astronomy you certainly need an understanding of physics similar to a physics major. Therefore, you will find that at U.S. colleges various Bachelor of Science (BS) degrees with names like "Astronomy" or "Astronomy and Physics." Our program is called "Physics with a concentration in Astronomy/Astrophysics." Regardless of the name, you'll notice they have more physics classes than astronomy classes and are almost identical to a physics major. There will also be lots of math. This major will prepare you for graduate school in astronomy -- or physics or another science for that matter. The course catalog for our major is here.

We also now have a minor in "Astronomy", just as you can minor in physics. Students majoring in engineering, math, and similar programs may find the astronomy minor suits their needs.

The fact that U.D. information guides list "Astronomy" as a minor but not a "major" is misleading because what could be called an astronomy major is instead called Physics with a concentration in Astronomy/Astrophysics.

If you are interested in this topic please contact me via the information at John Gizis's work webpage.