Saw Saturn and Titan

A very nice man had a telescope set up right in the middle of Waikiki. I stopped to chat with him about astronomy for a bit, and I looked in his telescope.

I saw a surprisingly clear view not only of Saturn, but I also saw Titan. What a treat! I’ve always wanted to see Titan.

I also was really impressed with what he was doing. He wasn’t charging, but just taking donations, and he was spreading interest in astronomy. We need more people like him.

What is that mess of stars

I’m in Hawaii. Even from my light-polluted balcony, I could see a good portion of the southern sky. I almost didn’t recognize Leo, high in the sky at an absurd angle. Saturn and Spica are still paired. I don’t know Virgo well enough to disapprove of its position. To the southeast, though, I saw a whole bunch of stars. They were bright and grouped, and clearly looked like a constellation. I had no idea what, though.

“What is that mess of stars?” I muttered rhetorically to my wife. It didn’t look familiar at all. I tried to think of what could be there. I couldn’t pick out the end of Scorpio’s tail, nor the teapot of Sagittarius. But I was determined to try to figure it out without pulling out my phone.

And then I saw the district kite shape of the Southern Cross. And that meant Centaurus was next to it. Would that mean I could see Alpha Centauri? At my home latitude of 42 N, I would never be able to see it. I had to check my phone since I’m not familiar with Centaurus. Yes, that was definitely Alpha Centauri. And wow, was it bright! Well, that makes sense, since it is the alpha star after all. It was awesome seeing the closest star system to our planet.

Also, as I type this on my phone, I keep mistyping “Alpha” as “Aloha”. Clearly my subconscious has something it wants to say.

April 26, 2012: Focus on Algol (Beta Persei) and Lynx

It was rather chilly out, and the sky was a bit hazy, but it also looks like today will be the best viewing day for the next several days, so I popped out for a few minutes. A few days ago, I focused on α Persei, so today I decided to focus on β Persei. Not only is it the beta star, but it’s also the lowest from my position so I’m catching it shortly before setting.

I wrote about Algol (β Persei) a few days ago. It’s actually a triple star system (β Persei A, B, and C). As I noted before, we’re in the plane of the orbits of β Per A and B around each other. β Per B is dimmer, and when it passes in front of β Per A, the combined star magnitude drops from 2.1 to 3.4. A and B are only 0.06 astronomical units (the distance from Earth to Sun) apart! That’s closer than Mercury is to the Sun, and only some thirty times the distance from the Earth to the Moon. C is 2.7 AU away, about as far as our asteroid belt is from the Sun.

Computer simulation on how Algol may rotate

Computer simulation on how Algol may rotate

This type of eclipsing binary star, where we happen to be in the orbital plane and so one star periodically eclipses the other, is now called an Algol variable.

I also really tried to see Camelopardalis, the constellation I read about yesterday. No luck — it’s just too faint. Monoceros has a new friend. I also tried to see Lynx, and I was able to just make out α Lincis — the other stars are all too faint. That’s fine — I don’t mind having a single star represent the constellation.

Terminology: Constellations and stars

One of the things I love about astronomy is you don’t actually need to know anything to appreciate the night sky. But if you want to communicate with others about what you saw or learn what’s out there, you have to have names.

Ever since humans have seen the stars, they’ve seen patterns. These patterns are called asterisms and they can be whatever you want. Some are common and have established names, such as the Big Dipper and Orion’s Belt. It’s important to remember that even though stars appear close to each other in the sky, they’re (usually) not actually connected. Since the stars are so distant, they all look equally far away, but they’re not. It would be like standing in New York City and thinking that because Chicago and San Francisco both lie in the same general direction, that they were closely connected.

Ptolemy formalized 48 of these as constellations. The International Astronomical Union (the international authority for astronomy) modified and expanded this list (including adding constellations that can only be seen from the southern hemisphere) into the modern official 88 constellations. Furthermore, constellations are now defined as areas of the sky, not as patterns of stars. This means that every point in the sky is part of some constellation. The bright stars may form patterns that help us to identify it, but they are not the constellation per se. I like to think of the stars as cities, and the constellations as states or countries. In the United States, some states have several large cities, others may have none. But every point in the United States is part of some state.

Star chart of Orion

Star chart of the constellation Orion. Note that the Orion includes the entire unshaded area, not just the bright stars and connecting lines. The Greek letters are Bayer designations (see below). (IAU/Sky&Telescope/Wikipedia)

The names of stars are bit more complex, since there are an estimated 3 sextillion stars in the observable universe (3 × 1023, or almost a trillion trillion stars)! Clearly, we need some naming scheme. I’ll normally use Johann Bayer’s method. To each star in a constellation, he assigned a lower-case letter from the Greek alphabet, usually following brightness and location characteristics. (After he ran out of Greek letters, he switched to lower-case Latin letters — our alphabet — and then upper-case letters). In his designation, the name of the star consists of the letter followed by the constellation name in the “genitive case” (a possessive form). Either the Greek letter can be used or it can be spelled out as an English word, and either the full constellation name or the standard three-letter abbreviation can be used. So for example, take Rigel, in the constellation Orion. This star will be called Beta Orionis, or β Orionis, or β Ori for short. Many stars also have their own names (like Rigel!). For the twenty or so brightest stars, their individual names are commonly used, but for the rest, Bayer designations are most common. There are stars that Bayer didn’t list, and for those I’ll use John Flamsteed’s names: they’re similar to Bayer’s method, but use a number instead of a Greek letter (for example, 40 Eridani, one of the stars in Eridanus).

For a more thorough discussion, see Sky & Telescope’s excellent Names of the Stars.

April 22, 2012: Happy Earth Day, and focus on Perseus (Alpha Persei)

Earth Day flag from Wikipedia

Earth Day flag, from Wikipedia.

Happy Earth Day! I tried to make the most of this day by spending time outdoors: I went for a 4.5–mile run this afternoon, then went out for an extended observing session at night. I located a nearby park and drove over to check it out. It’s pretty convenient: no streetlights and no obstructing trees or houses next to me, though the houses adjacent to the park do have some lights, and occasional cars drove by.

I focused again today on Perseus. I’m really starting to recognize it as well as its position in the sky. Its low in the sky these days, so I want to study it before it disappears for the season (or more precisely, before the sun moves towards Perseus so that daylight obscures it [or even more precisely, before Earth proceeds further in its orbit so that the sun comes between us and Perseus]). It’s quite easy for me to make out δ Per, α Per, and γ Per. I saw Algol (β Per) pretty clearly earlier tonight. I later picked out η Per, ε Per, and even ν Per (3.75m).

View of Alpha Persei Cluster

Simulated view of the Alpha Persei Cluster, created in Stellarium (Wikipedia).

I’ve also been thinking about trying to focus on one star each day. That way I can try to systematically learn the sky, as well as log the stars I’ve seen. And I can read about the star, too. I selected the brightest star in Perseus for today: Alpha Persei (α Per). Also called Mirfak, it’s a second-magnitude star (1.8m) from our distance, though its absolute magnitude of −5.1 shows it to be a rather bright star. It’s 510 light years away. It’s part of an open cluster of stars called the Alpha Persei Cluster. Apparently you can see the cluster with binoculars. I’ll have to try that out some time.

I know I mentioned this before, but I’ve come to really like Corvus. It’s such a nice shape. Monoceros, however, is my new nemesis. The brightest star in it is still only magnitude 3.9. I stared and stared at the locations where its stars should be, but I saw nothing. I few times I could barely imagine I saw a hint of a glimmer, but I couldn’t convince myself that it was real.

April 16, 2012: Overall sky survey

Diagram of Cassiopeia

Cassiopeia (IAU/Sky & Telescope)

I spent around 15–20 minutes outside today, just studying the overall sky. I was just out in front of my house, which is convenient, but there is a lot of light pollution from street lights and house lights. The trees and other buildings also obstruct much of the sky. But since the view from outside my front door is going to be the most convenient place to stargaze, I want to be familiar with it. Fortunately, the sky was completely clear, and it wasn’t too cold (about 43°F/6°C, with no wind).

My best view is to the south, with good views to the east and west, but obstructions to the north. The nice thing about tonight’s viewing was that the visible constellations represented a part of the sky with which I’m relatively familiar. The first thing I noticed was Mars nice and high in Leo, Sirius visible just above the horizon, and Venus close to setting. Orion, my favorite constellation, was setting. I could see Betelgeuse (α Ori) and the belt (ζ Ori, ε Ori, and δ Ori).

I’ve been trying to start systematically becoming familiar with the constellations, going quadrant by quadrant. I’ve started with “NQ1”, the eighth of the sky between right ascension 0h and 6h and above 0° declination. Most of the stars in this quadrant aren’t really visible at this time of year, since the sun is currently in this quadrant. I did try to focus on Cassiopeia, but it was close to setting. I could clearly see the five bright stars of the “W” asterism: ε Cas, δ Cas, γ Cas, α Cas, and β Cas. I also tried to study Perseus, since it’s a constellation with which I am really not familiar. I could make out four stars that were more or less parallel to the horizon, at about an altitude of 20°; reviewing my charts now, I assume these are δ Per, α Per, γ Per, and η Per. I’ll hope to recognize Perseus better once it’s more visible.

Overall, I think η Per was the dimmest star I saw tonight — it has an apparent magnitude of 3.75, making it a fourth-magnitude star. It’s not bad given the amount of light pollution.

Purpose

Welcome to my new blog. I’ve loved astronomy since I was young, though more as an armchair astronomer, reading about stars and galaxies. Several years ago, I started developing an interest in actually observing the night sky, trying to match what I saw to what I knew. That interest has waxed and waned over the years, but I never stopped looking up whenever I was outside at night.

I’ve always been a casual observer, a dilettante. When I think of the term “amateur astronomer”, I envision someone with more dedication, knowledge, and sophistication than I. But recently I’ve been wanting to take stargazing a bit more seriously. In particular, I can only recognize a handful of constellations, and I’d really like to become familiar with the entire night sky. Even without looking at a star chart, I would like to be able to look up and find my way around the sky (a task made harder by light pollution and view obstruction where I live). And eventually, I’d like to be able to do more than pick out the brightest stars in the most salient constellations.

I was browsing Sky & Telescope’s How to Start Right in Astronomy, and one of the author’s suggestions was to keep an astronomy diary. The more I thought about it, the more I liked this idea. What better way to learn the sky than by recording what I’ve seen? I decided to start keeping a log in my notebook, but I also liked the idea of keeping a blog as a companion to my log. I hope to share some of my thoughts and perspectives, and perhaps some of my observations as I explore the night sky.

I’m still at a beginner’s level, so I welcome commentary from all levels — it would be nice to have experience from more advanced astronomers and questions from other beginners. Exploring the night is more fun, and more rewarding, if you can explore with others.