A Christmas Eve Astrobite

I've put up a final post on Astrobites this year, on Christmas Eve, of all days! Especially after posting one on Thanksgiving. This is actually the post I wanted to write for Thanksgiving, but time constraints and the fact I already had one half-written changed that.

This paper is about how our Sun is so incredibly stable in brightness over time compared to other stars. In fact, its variability is so much lower than other stars that it's been a long-standing puzzle in solar physics. To explain it briefly, the authors of the paper I wrote about did some simulations of Sun-like stars while varying a few key parameters such as the proportion of elements besides hydrogen and helium and the star's effective temperature. What they found is that the Sun sits in a very special place in phase-space where it ends up being almost perfectly constant in brightness over the course of its solar magnetic cycle. Changing the metallicity or temperature by extremely small amounts (relatively speaking)—in any direction—causes the variability over a star's magnetic cycle to shoot up dramatically.

(The mechanism I thought was pretty interesting: magnetic activity in stars causes two types of phenomena, starspots which are darker than average, and faculae which are brighter than average. Most stars are dominated by one or the other over the course of a magnetic cycle which changes their brightness, but the Sun's parameters cause the relative numbers of sunspots and faculae to almost perfectly balance in such a way that its average power output as seen from Earth is almost constant.)

This is actually final astrobite as a scheduled author; going into my second year of my PhD I've decided to retire from the active rotation to be able to focus more on my research. However, I'm not done writing just yet! I'll be able to write posts for the queue, and I still intend to, which just means I won't know when they'll go out. I no longer need to write one every month or so, so the number may go up or down depending on how many interesting papers I come across. Honestly, that's the part I'm looking forward to the most: some of my posts were on papers I found genuinely fascinating and loved explaining and I'm really proud of them, while a few of them were written just because I had a deadline and were the most interesting least boring papers I could find recently. Being able to write only when I'm really motivated (kinda like I do here…) is quite an exciting prospect!

I feel like that may have ended up more melancholy than I intended, so how about some Christmas presents? For the featured image for my posts I used the painting below, which I painted last Thursday as a present for my adviser:

“A Solar Twin,” by me.

(Unfortunately I miscalculated when he was going on vacation so he'll find it when he gets back in January, I guess. Some of my friends were ribbing me that I'm setting unrealistically high expectations for the other students now!)

Painting a star turned out to be so much fun that I painted another one the next night, a pulsar for my associate adviser:

“A Pulsar,” also by me.

Ignore the ugly shadow cast by my easel at the top of the picture. Which, I realized, I haven't mentioned yet, so yes, I bought an easel! I feel like a real artist now. An easel makes painting so much easier. I picked one that's quite portable and folds up nicely so I can bring it home (as I've done over the break, along with my painting supplies). It's sitting in the corner with my current work on it, and I must say, an easel with a painting in progress on it really classes up the room it's in!

Anyway, that's enough for tonight. Merry Christmas everyone, and I hope to be back with some more posts soon now that I'm on vacation.

Transit of Venus: Reloaded: Director's Cut

Remaking and rebooting things seems to be all the rage these days, so I figured it was time for me to join the bandwagon and take a shot at redoing one of my old videos from 2012 about the transit of Venus. Well, actually I was recently reminded of its existence and decided that I could do better now. The original video was from before I'd started really working at video editing, and was probably made in Windows Movie Maker. I wouldn't call it bad, and you can already see some of the hallmarks of my video editing style even back then, but I think this one's a bit better overall. I've gone back and replaced the old version from 2012 with this one, as Blogger's video hosting abilities have always felt a bit shaky to me—one of the reasons I didn't upload many videos prior to getting a YouTube channel. (Two, actually, one for gaming that I introduced in the previous post and a second more general one seen here for everything else.)

(Fun fact, the title in the thumbnail there was recycled from the original video.)

Transit of Venus Video (At Long Last!)

Well, I have finally recovered enough from the wonderful back-to-back combination of virulent head-cold and raging sunburn to finish my long-promised video of the transit of Venus. And it only took me over a month.

First, a quick explanation: this video does not show the beginning or end of the transit. The beginning I didn't catch because I had other duties to attend to which prevented me from getting set up in time, and when I finally did I had some unexpected problems focusing. Because of this, the video doesn't start until 2:26 PM, almost two and a half hours after the transit started. The ended wasn't captured because it wasn't visible from my location, as the Sun set behind hills to west. The last frame I captured was at 6:00 PM, about 40 minutes before the transit ended. In between I took a shot every minute, for a total of 188 frames. With that said, enjoy.

Edit (1/13/2018): Remaking and re-releasing videos seems to be all the rage these days, so I thought I'd join the fun! Actually, I was reminded of this video a while back and after watching it was dissatisfied with the quality—this was years before I started seriously pursuing video editing, and was made in Windows Movie Maker. Plus now that I've got a YouTube channel it can reside there instead of relying on Blogger's somewhat shaky video hosting abilities.

Transit of Venus Redux

Well, the transit of Venus came and went, and I survived. I wasn't entirely sure I would with all the stress building up to it, but here I am. I've been quite fortunate in getting four days off in a row to recuperate, and I felt rested enough by the third day to finally make myself the belated birthday cake that I've been meaning to do for two weeks now.

I also recovered enough of my creative drive to put together this collage from pictures I took with my camera through one of our 14-inch scopes. This picture was taken around 3:37 in the afternoon, and you can clearly see Venus as the round dot and a couple of sunspots as the irregular faint black spots.

Transit of Venus, June 5, 2012.

It's kind of strange to consider, but this is now a rather historic picture. I can't really say that I've ever done anything historic before. Making some assumptions about the future, it's possible that someone over a hundred years from now could find this picture while researching ancient coverage of previous transits of Venus. Kinda makes you stop and think, doesn't it?

To paraphrase a famous quote from the previous pair of transits, “And what will be the state of science in that far distant future when the December snows are falling in 2117, God only knows.”

Another Sun Panorama

Just another picture of the Sun, this one taken last Saturday when I was finally able to get it between the clouds after three days of shut-out. Or rather, when I was finally able to get the six different pictures that I stitched together to make it. This version is only 1200 by 1200 pixels, but the full picture is 4500 by 4500!

Just like my picture from last year with the planets, this picture was made using the 11-inch solar telescope we have at the Vis – though unlike last year's, this picture was made by directly connecting my camera to the telescope, rather than shooting through an eyepiece. This caused the Sun to overflow the field of view of my camera, which allowed me to take multiple photos and combine them into this panorama.

It's a bit disappointing in this picture, but that sunspot group near the bottom was one of the largest I've ever seen when I first set eyes on it on Wednesday. By Saturday as you can see it had diminished somewhat – although it's still larger than all the inner planets, and probably larger than the ice giants Uranus and Neptune too.

As a side note, while combining the pictures that make up the final image, I discovered an incredibly useful and easy way to do so. Simply setting the mode of a picture on top to "difference" allowed me to easily see how much, well, difference there was between two photos. The difference mode subtracts one photo from the other pixel by pixel. If the pixels are identical in color to each other, you'll get black. If not, you'll get something that depends on how different they are.

For something fairly featureless like the Sun in white light, it's then a simple matter of moving the upper photo around to minimize the difference as much as possible (which in practical terms, means maximizing the blackness, since the closer the two photos are to each other, the more they cancel each other out and make black). Once you have the maximum amount of black you can set the mode back to normal, and marvel at how closely the photos merge together (although I still spent the better part of an hour manually smoothing and blending the edges). I'm sure this is probably standard panorama-making procedure that people learn about in Photography 101, but I'm really happy to have stumbled upon it. Can't wait to try it on my next set of Moon panorama photos!

Stella Nostra

Today I'd like to share with you a picture of the Sun that I took last week using the imager at the Vis while testing out one of our new solar filters that we got for the upcoming transit of Venus in June (which you will hear much, much more about as we get closer to it).

Our Star.

There's not too much detail to see, but you can make out a sunspot (probably about the size of Earth) in the upper-middle. When I came back to work this week, the Sun had a humongous sunspot complex on it that was probably about the size of Jupiter, which just goes to show how fast it can change. In fact, I would bet that it was that sunspot group that was responsible for the massive solar flare that hit Earth this morning. I'll try to get a picture of it if I can, but it's been very cloudy up here the last few days. It has a suspicious tendency to cloud over whenever I grab my camera...

If you're wondering about the title, that's simply Latin for "Our Star".

Our Star

Have you stopped to ponder just how mind-blowingly huge the Sun is lately?

Last week while volunteering up at the Vis I took a picture of the Sun through the solar telescope on a whim. I noticed a large sunspot group on it, but didn't think anything else of it until this week when I learned that said sunspot group (called Active Region 1339) is one of the larger ones on record. I'd also heard somewhere along the line that it was larger than Earth, so I decided to do some visual comparing of my own. After seeing how Earth and Jupiter looked against the Sun, I decided to go all the way and add the rest of the planets. This image is the result. It shows the 8 planets of our Solar System against the Sun with AR 1339, all of them correctly sized relative to each other. (The distances between the planets are not to scale, due to the way I set up the picture.)

Our Solar System.

Look at this image, and let it sink in for bit. The Sun accounts for a whopping 99.86% of all matter in the Solar System. It's big. For fun, see how many other sunspots you can spot in this picture that are larger than Earth.

Edit (11/25/11): One other thing I like about this picture that I forgot to mention the first time is the sense of security it gives, when you really think about it. Stable orbits, despite their ubiquity in nature, are still nothing to take for granted, and it's sort of comforting seeing just how huge the Sun is compared to the Earth, and just how firmly we're caught in its gravitational embrace.

“Tremble before Him, all the Earth; indeed, the world is firmly established, it will not be moved. Let the heavens be glad, and let the Earth rejoice” -- 1 Chronicles 16:30-31a