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.

A Thanksgiving Astrobite!

In a funny coincidence, when the latest three-month schedule for Astrobites was put together I ended up being scheduled for both Thanksgiving and Christmas Eve. I got my Thanksgiving post up two days ago, and amusingly the title (“Mirach’s Ghost and Mirach’s Goblin: A New Galaxy Found Near the Local Group”) sounds a bit like I mis-scheduled a post intended for Halloween.

I'd actually intended to write this post for the queue and write about a different paper for my scheduled Thanksgiving post, but I ended up being extremely busy this week (details below) and since I'd already started working on this post I ended up using it instead. Oh well. Maybe I'll write the other one up for the queue. The paper I ended up writing about is fascinating in its own right, about the discovery of a new, extremely faint dwarf galaxy just beyond the boundary of the Local Group.

The reason I was so busy this week is that I was attending SciCoder 2018, an intensive week-long workshop in scientific programming. This was, however, an almost-literally last-minute decision, as the course had filled up so quickly upon being announced a few months ago that I only made it on the waiting list (and knew there was at least one other person who was on it ahead of me). Sunday night at about 7:30 PM I got an email from the conference organizer letting me know there was an opening and asking if I wanted to attend, and after half an hour or so of working out just how much that would impact my week I accepted.

And when I say intensive, it was just that; 9 to 5 each day (or 8:30 on the first day), at the University of Melbourne (necessitating an hour of train and tram travel for me each way), and throughout a veritable avalanche of information. I was fortunate to already have some familiarity with some of the concepts presented, and even I left each evening feeling like I'd just spent the day doing the mental equivalent of drinking out of a fire hose. It was good, don't get me wrong, but also quite exhausting.

Somehow during the week I also managed to squeeze out enough time (not that it took much) to work on a little personal project: Astrobites has had an offer, through its parent association the American Astronomical Society, for a logo revamp by a professional design firm. In place of the current logo which uses a photograph of Mars (with a bite taken out of it), one of the concepts they've provided was a stylized representation of Mars (with a bite taken out of it).

I'm a huge sucker for stylized representations of things, and liked the general idea, but there were a few details of the proposal that I wasn't 100% satisfied with so I quickly made a slightly different version of my own based on their template to illustrate the shortcomings I saw…and then had a fanciful idea to make a whole solar system of stylized-planets-with-bites-out for logos. I've got enough experience with Inkscape now that it only took me an hour or two, and I really like how it came out (as did a few fellow students when I showed them).

At this point I've changed Mars enough that the only thing I'm really copying from the proposal is the “bite and crumbs” motif each planet has. I doubt these will show up in an official capacity, so I thought I'd show them off here as a personal project. That's it for today though, I need to go catch up on my sleep now. A hui hou!

A Year Down Under and an October Astrobite

As of September 29th I've been in Melbourne for a full year now. It's been a long year of working on my PhD, I've moved twice, and I miss Hilo's climate pretty often, but I've also made some amazing friends and discovered a facility for and enjoyment of painting I didn't know I had (about which I promise a post in the next few weeks). I've had artwork exhibited in a public exhibition, and learned that stars and CCDs are infinitely more complicated than I ever dreamed (or wanted to know).

I've done an excellent job of hiding my telescope model behind a pillar in this photo.

In other news I put out a new Astrobite today, on a paper talking about finding the mass of the closest known white dwarf by measuring its gravitational redshift (basically, how much its light is redshifted climbing out of its gravitational well). This one was pretty interesting for me, as the authors used the Hubble Space Telescope and spent some time detailing all the tiny systematic errors in its spectrograph's CCD. Detailing tiny systematic errors in CCDs is pretty much my PhD (or at least it feels like at times) so I could really empathize with what they went through to get a good measurement. I also got some nice comments from two of the paper's authors, so that was cool.


That's it for now! A hui hou!

An August Astrobite

Grad school and other things have kept me intensely busy this past week, which is why I'm just posting about an Astrobite I wrote on the 8th. I'll say upfront that I don't think this is my best work; not that it's particularly bad or under my standards for writing, I just realized over the course of writing it that I wasn't quite as interested in the subject matter as I thought when I started.

It's still reasonably interesting however, the subject matter being that when the authors examined a baker's dozen supernovae type Ia (that's “type one-A,” not “type eee-AA!”) which had been caught very early in their brightening stage they found evidence for two distinct populations when looking at the color of their spectra. “Color” in this case is an astronomical term for summing up the flux in two different filters that cover different spectral ranges and subtracting them, leaving a single number to represent the color. Most commonly the “Blue” and “Visible” filters are used to get what's known as a \(B-V\) color (visible here meaning roughly “green”), but any two filters in any part of the spectrum can work. Basically, some of the supernovae looked “red” and some looked “blue,” though the differences disappeared after about four or five days since the explosion.

Most supernovae aren't caught this early, which is why they had so few to work with despite there being hundreds of known type Ia supernovae. Interestingly, in a bit of a personal connection to the paper, one of the supernovae they looked at was SN 2011fe—which I actually got a picture of while in Hawaii! I didn't realize this until after I'd chosen the paper and started writing it up.

Messier 101 with SN 2011fe marked with the green dots.

If there's one thing I learned while doing background research on supernovae type Ia for this Astrobite, it's that we still have much to learn about these enigmatic explosions. A hui hou!

Another (Unexpected) July Astrobite! Structured Satellite Galaxies

So just a few days after my previous Astrobite summarizing the ASA meeting I got a surprise when I woke up to an email from the Astrobites scheduler saying that he'd posted my Astrobite I wrote for the queue back in February. This one deals with an interesting problem I'd never heard of before called the “Satellite Planes of Galaxies problem.” Observations of he Milky Way, the Andromeda Galaxy, and Centaurus A show that a significant fraction of the satellite galaxies around them tend to orbit in correlated planes. Yet similar-looking structures are vanishingly rare in simulations, to the point where it would be exceedingly unlikely to find them around three galaxies so close to each other. It's pretty interesting as while we've had hints of theses planar structures around the Milky Way for a few decades and Andromeda for a little less it's only recently that we've really been able to confirm them and discover the one around Centaurus A.

Something amusing I found in this paper was the name for the structure around the Andromeda Galaxy, which is called the “Great Plane of Andromeda.” This sounds like a reference to a very old name for the Andromeda galaxy, several hundred years ago when it was known as the Great Nebula in Andromeda. I just like the idea that anything associated with the galaxy becomes known as the “Great ____ in/of Andromeda.” A hui hou!

July Astrobite: Summarizing the ASA Meeting

My Astrobite for July came out yesterday, a short summary of the Astronomical Society of Australia (ASA) meeting last week. Well, I say “short,” but as it's not a normal paper summary I allowed myself another hundred words or so beyond the usual thousand-word-limit. I think there were a hundred and forty talks total, so to summarize I just picked one from each day from a range of topics and by people from different universities. Even then I didn't have room to cover some of the things that came up such as a good number of talks about radio astronomy which covered things like using measurements of pulsar timing across the Milky Way to make a very sensitive gravitational wave detector on a galactic scale.

One thing I did notice over the course of last week, though, was that there weren't any other talks or posters related to my area of research in varying constants. There were quite a few areas where there were multiple talks/posters on similar subjects (like gravitational waves, or pulsar timing, or the challenges of big data), but nobody else presenting anything like what I'm doing. (That I saw at least; there were parallel session each afternoon of which I could only watch one, but from reading the talk titles I don't think I missed anything obviously related.) Certainly there are other people working in this area, but it was interesting to have presented what felt like a pretty unique talk. Anyway, that's enough for now or I'll end up writing another thousand-word summary. A hui hou!

May Astrobite, or “How Is a Pixel Like a Bucket?”

Just a quick post tonight to point out my most recent Astrobites article which came out on the 22nd. This one was very interesting to write. It's about a paper which I read when it first came out back in February on the arXiv. (It's pronounced “archive,” and it's a website where most papers in physics and astronomy and several over sciences are hosted freely available; it's undoubtedly revolutionized the areas it serves by making it easier to communicate results, and I can't imagine trying to do research without it.) I'd been stockpiling recent papers that looked interesting for a week or two before sitting down to write, but none of them really seemed to call to me, till I finally remembered this interesting paper I'd read about CCD systematics.

CCD stands for charge-coupled device, which is the technology behind most digital cameras nowadays. Astronomers adopted them very rapidly back in the 1970s soon after they were invented, and they're responsible for a very wide variety of astronomical research since then. Despite coming up on fifty years old, the authors of the paper I wrote about managed to find a new, never-before-seen form of subtle systematic errors in sixteen out of twenty-two instruments they investigated. The thing that really blew my mind while browsing the abstract and got me to read the paper? They noticed an effect that was proportional to the number of 1's in the binary representation of the value of various pixels in the image.

If you just said “What‽” out loud like I did upon reading that, check out the paper! It's really well written and does a good job of explaining their findings with some really good, high-quality graphs. If you don't know what that means or why it sounds so weird, maybe check out my astrobite—I spent several hours wrestling with an analogy involving grids of buckets and sprinklers in an attempt to render the technical details more approachable, so hopefully I've explained it there in a way that makes sense.

Basically, the top part should be a flat line at zero, not…this.

The results of this paper, while not necessarily highly problematic, are likely to be very far reaching and will affect a lot of people and their science, so now that it's been officially published as of May 11th I expect we'll start seeing some more papers popping up on arXiv related to the issue it reveals. (arXiv allows people to upload “preprints” of papers that have been submitted to journals and are in the process of peer review, which is how I was able to read it back in February.) That's it from me for now though, a hui hou!

April Astrobite, a Supercomputer Tour, and Other News!

So this is a few days late, but I wrote another post for Astrobites this month back on the 12th. It covers a really cool paper about the largest flare yet observed from Proxima Centauri, the closest star to the Sun. Proxima Centauri is a red dwarf, the most common type of star in the universe, but also the faintest; it emits a mere 0.17% of the light the Sun does, and despite being the closest star at just over 4 light-years away normally sits at about magnitude 11.13, or over a hundred times fainter than can be seen with the naked eye. However, during the flare reported in the paper, the authors calculate that it would have briefly reached up to magnitude 6.8, making it just barely visible to the naked eye from a very dark site for a few minutes! Pretty nifty! I even got an email from the lead author on the paper saying he'd enjoyed my summary of it, so that was nice.

---

In other news, I was fortunate enough to tag along on a tour of Swinburne's new supercomputer. (We are the “College of Astrophysics and Supercomputing,” after all!) It's called OzStar and replaces an older supercomputer called G2, though that one will still be in operation for most of the rest of the year to give people time to switch over.

OzStar, CAS's new supercomputer. I don't actually have reason to use it myself, sadly.

---

Going through all my photos in my panorama series, I've been struck by just how many photos of random birds I take. So have another one of some really colorful parrots I found in a eucalyptus tree near where I live one day while walking!

Parrots! Really colorful ones, too. These pictures are all from my new S9+, by the way.

---

And finally, one thing I haven't been able to find here in Australia is my favorite salad dressing, Hidden Valley Ranch. You can get Ranch dressing here, but there's usually only a single kind on sale. One of my friends from church was in the US for a few weeks as part of a school trip and very kindly brought me back the ambrosia below:

Just can't beat the original.

---

I also gave my first public Astrotour at Swinburne last week! We have a 3D theater that is used primarily for public outreach with grad students and faculty who volunteer giving talks to both school groups and the general public. I signed up last year, and gave my first talk to a small public audience last Tuesday. I felt rather rusty and disjointed as it's been so long since I gave a public talk about astronomy, but all that practice at the VIS paid off and it seems to have gone well. I've got another scheduled for the 30th of April, though I think this one is a school group, so that'll probably be a very different experience.

And I think that's all so far for this surprisingly busy month. Oh yes, last week I finally managed to write some code that collated some information on atomic transition lines that we've been trying to get together for a few months now, and this week we sent them off to some collaborators to do some calculations for us. So that's a huge weight off my chest. A hui hou!

Unexpected Accolades

Something pretty incredible happened to me today, but to have any chance of properly explaining it I'm going to have to quickly jump back to…

…2012, when I was working at the Visitor Information Station on Mauna Kea. Among the videos we had to play for the public was one starring an astronomer named Phil Plait, author of the popular Bad Astronomy blog, dedicated to debunking all the crazy ideas people come up with regarding astronomy, or just explaining astronomy to the public in general. In the video he engages in charming Myth Busters-esque hijinks, like trying to stop a scale-model comet of dry ice and water ice by shining a laser on it, or investigating whether shooting an asteroid with a nuke would be a good idea (it's not). He's written a book (called “Bad Astronomy”), he's been on TV, he's got over 600,000 followers on Twitter, the point is that he's pretty good at communicating science effectively.

Jumping forward in time to this past January, I wrote my first article for Astrobites. I picked a paper from 2016 about some astronomers who accidentally observed the wrong star, then discovered it was a previously-unknown solar twin. It made for a great story about serendipity in science, and it fit with my Ph.D. project. I wrote and re-wrote it for a period of several weeks, and was pretty happy with the result.

Fast forward to this afternoon, when I discovered (via a colleague) that Phil Plait had come upon the same paper, thought about writing about it on his blog, discovered my Astrobite, and thought it good enough to simply retweet rather than write his own post:

I found an article about the accidental discovery of a solar twin, a star almost exactly like the Sun. I was going to write it up for the blog, but AstroBites already did a great job! This is pretty cool: https://t.co/0zxmfXm7R8

— Phil Plait (@BadAstronomer) March 6, 2018

I don't really have much more to say about this other than: wow. This made my day. Soli Deo gloria! A hui hou!

January Astrobite and Australia Day

Well this is a few days late due to a busy week, but I posted my first Astrobite this week over at the Astrobites site. It's on the accidental discovery of a so-called solar twin, a star extremely similar to our Sun, and is a heavily-edited version of my initial application submission (though it's much better now than it was originally!). I had some fun figuring out when to post it due to being pretty much the first Astrobites author in Australia as far as I know, but it worked out in the end.

I've also taken on the modest task of designing some new logo variations for the Astrobites store that I (and quite a few other authors, and not just the new ones) found out about a few weeks ago, so I may have some stuff to show off in that regard in a bit.

Other than that not much to say; it's a long weekend here due to today being Australia Day so I've got some more time to be creative. A hui hou!