Today I was trolling astro-ph looking for articles on subjects that interest me and/or articles written by people I know.  I noticed an article entitled “New evidence for determining of the date of adoption of Christianity as a state religion in Georgia” I was like “uhh… what does that have to do with Astronomy?”  Come to find out, it actually does.  Abstract:

At present it is considered that Christianity was declared a state religion in Georgia in circa 326 AD, during the reign of King Mirian and Queen Nana. In the Georgian Chronicle [1] (Kaukhchishvili, 1955) it is stated that this event is connected with the adoption of Christianity by King Mirian. Once he was hunting somewhere between Mtskheta (the ancient capital of Georgia) and Khashuri, near Mt. Tkhoti in dense woodland. It rapidly got dark and the Sun disappeared from the sky. Mirian began to ask his traditional pagan gods, but to no avail. Then he addressed the god whom Nino from Cappadocia believed in (subsequently she became Saint Nino, a woman whose name is inseparably linked with the spread of Christianity in Georgia) and there was a miracle; the darkness suddenly disappeared and the Sun began shining in the sky again. Then Mirian turned to the East and thanked “Nino’s god”. In the authors’ opinion, the eclipse seen by King Mirian happened on the evening of 6 May, 319 AD. Later, in May 320 AD, cypress crosses were made and raised. Thus, we have answered the question raised 70 years ago by the Georgian historian Ivane Javakhishvili about the occurrence of a total solar eclipse in Georgia in the fourth century. The eclipse seen by King Mirian happened on the evening of 6 May, 319 AD. Later, in May 320 AD, cypress crosses were raised and Christianity was become the state religion of Georgia.

I haven’t read the article because I’ve been really busy today, but I just wanted to post this because I thought it was a fun, random connection to astronomy of which I was not previously aware.

:)

M67, now with H-alpha emission!

M67 CMD with H-alphaI've still been working on the M67 data, but trying to balance that with NGC2516 and working on the paper.  And studying.  I did generate a CMD of M67 that has the H-alpha emission information included.  There aren't as many stars as there were in the previous CMD I showed, because the narrowband field didn't pick up as many stars as the broadband, so when I correlated them some of the stars were lost.  You can sill see the main sequence, though.

Kevin pointed out to me that the colorbar doesn't have the correct values on it, which I will fix eventually.  But first I want to focus on the very obvious color gradient in the activity values from low to high magnitudes.  It is likely due to the fact that the uncertainty changes with magnitude, so you can't use a blanket sigma cutoff across the entire range.  We discussed this possible issue with NGC2516 but didn't end up having to do anything about it because once we did a 3-sigma cutoff on the activity it took out a lot of what were probably spurious values, leaving pretty much only the M dwarfs active.  For M67 I will probably end up having to bin by magnitude and find the sigma for each bin.  It shouldn't be too hard though, because I already wrote a lot of code for it when I wanted to try doing that on NGC2516.

M67 progress…

Before Christmas break happened I was working on the M67 data and I generated a CMD for group meeting (finishing it at the 11th hour and grabbing it off the printer as I was headed to the meeting). It looked like this:
Original attempt at a CMD for M67

This CMD is really crappy. It is pretty much a bunch of field stars. There is maybe one or two that may be cluster stars. Plus the mags aren't calibrated either. I'm actually kind of embarrassed that I brought it to group meeting at all, but I felt like I needed to have something to prove that I had been working.

Today we had group meeting for the first time this semester. It was a lot of fun! However I was still concerned about having something to show to "prove" I had been working. Unfortunately I spent most of my "working" time during the break writing this grant proposal, so I hadn't been working on my research that much. However, since I got back I had done some things, one of which was returning to the M67 data to try to improve on my previous "results". I made another CMD for group meeting today that looked a little something like this:
Successful attempt at M67 CMD!

As you can see, this is actually a CMD. You can see the main sequence, and the turnoff point, and everything. It's beautiful. I was super happy with it. Now I just need to get the H-alpha data on there and I will be done with M67 for a while, because I need to go back to NGC 2516 and work on a few things in order to get this paper out. But, yay for an awesome CMD!!!

:)

Two Suns? Popular press does it again.

My friend sent me an article today along with the comment "i love reading about astronomy after the popular press has mangled it beyond recognition." The article was entitled Two Suns? Twin Stars Could Be Visible From Earth By 2012 and is found at http://www.huffingtonpost.com/2011/01/20/two-suns-twin-stars_n_811864.html

The accompanying illustration shows a Tatooine-esque sunset with two large glowing orbs instead of the singular sun we are used to. I thought they were saying that the solar system was going to pass through another star system and the sun and that star would become gravitationally bound, but no, it's just a possible supernova of a nearby star. Apparently the star Betelgeuse is losing mass which could be indicative of its collapse. Astronomers claim it could happen as soon as 2012. I kind of hope it does. I want to see it. Because, it could also happen in a million or so years, and I definitely won't be around for that.

The article also contained the laughable statement "a neutrino shower could be beneficial to Earth." Ah, bad science writing at its best (worst?).

See also: Tatooine's twin suns - coming to a planet near you just as soon as Betelgeuse explodes

:)

MHD simulations reveal crucial differences between solar and very-cool star magnetic structures

Today I was reading a new article I saw on astro-ph that relates to the research I might be doing next year if the NSF gives me money (fingers crossed). The article is called "MHD simulations reveal crucial differences between solar and very-cool star magnetic structures" and can be found at http://arxiv.org/abs/1101.3848. From the abstract:

Our numerical simulations show for the first time a qualitative difference in the magneto-convection between solar-like stars and M dwarfs. Owing to higher surface gravity, lower opacity (resulting in higher density at optical depth unity), and more stable downflows, small-scale magnetic structures concentrate into pore-like configurations of reduced intensity. This implies that in very cool stars magnetic surface structures like plage regions and starspots significantly differ from the solar example. Such a difference would have major impact on the interpretation of Doppler imaging data and the analysis of M dwarf spectra. (emphasis added)

The article is very short--only a couple pages of actual text and lot of illustrations--but nevertheless interesting. Beeck et al. apparently did some MHD simulations modeling different stars and found--GASP!--that M dwarfs have significantly different magneto-convection than stars of earlier spectral types. As an M dwarf scientist this does not really surprise me, but it's nice to see it qualitatively. One thing they saw was that "While solar magnetic structures appear as bright features, the magnetic structures on M-dwarfs tend to be rather dark."

The explanation for this is:

In the case of the Sun, magnetic structures create a strong depression of the optical surface with hot side walls that can radiatively heat the interior of the magnetic structure. This mechanism is much less efficient for the magnetic structures in M-dwarf atmospheres: owing to the much higher densities, the depressions formed by the magnetic structures are very shallow and their side walls have small excess temperatures due to a shallow temperature gradient. Since the magnetic field suppresses convective energy transport, the structures cool down.

Thus, the so-called "plage regions" (a "plage" is a brighter, hotter patch in the chromosphere of the Sun, and a region of particularly strong magnetic field) on M dwarfs might not might not show bright points as they do on the Sun but rather “pores” and small “star spots” of reduced intensity. This has all sorts of implications on the correct interpretation of M dwarf observational data.

Awesome article, short, and very readable. It's just in draft form right now so I'll probably read it again when it gets accepted for publication.

:)

Happy New Year

It's a new year and I have a lot of research to do. I spent a great majority of Christmas break writing up a grant proposal for an NSF supplemental grant to do some research combining my current topic of stellar activity with exoplanets. I love exoplanets, so this would be a great opportunity. If I do get the grant I will be spending a year working on the project in Copenhagen, Denmark, which is a great city that I love to visit. Fingers crossed.

I wrote up my research goals for this semester and they are:
1. Write calibration paper
2. Finish reducing M67 data
3. Better calibration of instrumental mags (I just did a kind of quick-and-dirty thing last year and I need to be a bit more rigorous)
4. Start on the next cluster
5. Update this research blog daily

Stay tuned to see how I am doing. I may also post some articles that aren't necessarily related to my specific research, but are scientifically interesting to me.

:)

Research goals

Just before the semester started, I attended the Cool Stars conference in Seattle, WA.  It was awesome!  Definitely one of the best experiences of my graduate career so far.  I finished all the of NGC 2516 data for my Cool Stars poster.  Now that I am back, and school has started again, I plan to start with reducing the rest of the data.  My goals so far are:

  • start reducing M67 data
  • email Michael--one of my collaborators--to ask him about a few questions we had
  • check out Jackson and Jeffries' catalog and compare their 2516 data with mine
  • make a more specific plan of exactly what I am going to do, and when, for the next set of reductions (with deadlines)

:)

Hello world!

Welcome to my research blog!  :)