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 20, 2012: Saw a Lyrid Meteor

I was out around midnight, not at home. I realized the sky was quite dark (not like the light pollution by my house), and there were no clouds. I decided to stop and survey the sky for a few minutes — not only because it was so dark, but also because it was a bit later than I’ve been going out, so I hoped to see a different area of the sky. It was also a bit unexpected because earlier in the week, AccuWeather’s stargazing forecast had predicted poor conditions tonight, but great conditions tomorrow. Now it looks like it will be cloudy tomorrow night, though clear tonight.

The revised forecast is disappointing because tomorrow night is when the Lyrids peak. The Lyrids are a meteor shower, moderate intensity. From our viewpoint, they seem to originate from the direction of the constellation Lyra, hence the name. There will be a new moon, which means the skies will be very dark, setting up ideal conditions for meteor watching. Unfortunately, clouds will block all of that for me. If it will be clear where you live, then you might get a good view. Look for the bright star Vega in Lyra, to the east. It will rise around midnight, so any time in the hours after that should give you a decent view.

Diagram showing where to see the Lyrids

This diagram, from spaceweather.com, shows where to see the Lyrids.

Back to tonight: I was enjoying the dark sky, and I tried to familiarize myself with some of the constellations in this part of the sky. Bootes was bright, and I was able to see some of the stars of Hercules. I also could pick out the rough shape of Draco. Vega and Deneb were also in view.

Although I wasn’t planning for any methodical or detailed viewing, I did attempt to pick out Monoceros, the constellation I had studied yesterday (I’m trying to read about one every day or two). Apparently, I’ve been mispronouncing it in my head. It’s pronounced “muh-NAH-ser-us” — that makes sense, since it would rhyme with “rhinoceros”. I never knew that. Probably because I’ve never seen it before. Probably because it’s a very dim constellation. With the help of Pocket Universe on my iPhone, I could see that most of Monoceros would have already set. I picked out Procyon (α CMi), and could see that ζ Mon should have been just to the left (east). I struggled to see it, but nothing was there. I can’t say I’m surprised — ζ Mon’s magnitude is only 4.35, and at that time it was only around 15° above the horizon. Even nearby Procyon, at around the same altitude but with magnitude 0.40, was relatively dim.

And then I was looking over at Saturn, currently in Virgo, when I saw the unmistakable streak of a meteor between Virgo and Corvus. I almost thought I imagined it, but I traced its path back towards Lyra. So even if I don’t end up seeing any meteors tomorrow, at least I got to enjoy one tonight!

Also, I’m beginning to really like Corvus. It’s a nice tight little geometric constellation. I never really knew it before.

April 17, 2012: An eclipsed star, and two artificial satellites!

I discovered that AccuWeather.com offers forecasts for stargazing. It’s a nice quick glance at the week ahead, and it showed me that tomorrow, Thursday, and Friday were rated a “1” (poor). Today was a “9” (excellent) so I decided to go out as soon as it was dark enough.

My goal today was to again continue familiarizing myself with the overall layout of this section of the sky. Like yesterday, I was observing outside my front door. The conditions are certainly not optimal, with lights, buildings, trees, and cars. But not only will this be the easiest place for me to pop out for a few minutes to take in the sky, but also I want to get used to trying to pick out fainter objects under challenging conditions. My other goals were to study Perseus a bit more and to see if I could identify stars in a constellation I didn’t previously know.

Saturn, Mars, and Venus were all in the sky. Saturn and Spica make a nice bright pair, with Saturn looking softer and Spica harsher. Mars almost looks like a part of Leo, but its red color makes it a misfit among Leo’s stars. Venus is incredibly bright, with a magnitude of −4.35. It’s gorgeous, but its brightness was almost a distraction as I tried to study Perseus. Perseus was pretty low (altitude around 26°), so buildings blocked it and the thickness of the atmosphere and light pollution at that low elevation really concealed it. With difficulty, I could make out η Per (magnitude 3.75).

But I really struggled to see Algol (β Per, usual magnitude 2.05). I finally did manage to see it, but only if I kept my gaze about 10° to the side. I thought that perhaps because it was so much closer to the horizon (altitude around 18°), that was why it was so dim. But looking at my charts later, I read that Algol is not a single star, but rather a triple-star system (Beta Persei A, B, and C). From our point of view on Earth, we are in the same plane in which β Per A and β Per B orbit, so periodically the dimmer β Per B eclipses the brighter β Per A. According to Wikipedia, “Thus, Algol’s magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every two days, 20 hours and 49 minutes during the roughly 10-hour long partial eclipses.” I then found a page on Sky & Telescope that showed that there was brightness minimum today at 21:44 CDT (4/18/2012, 0244 UT), which was right around the time I was observing it. Fascinating! — I can’t wait to see it during a period of normal brightness to compare.

High up in the sky, close to the zenith (altitude 80°), I was able to make out 38 Lyn (magnitude 3.90). That’s the dimmest star I identified tonight. I was not familiar with Lynx, nor with the adjacent Leo Minor, nor with the two nearby stars (λ UMa and μ UMa) that are part of Ursa Major but far from the Big Dipper asterism. It took me a long time to figure out what stars I was looking at.

But one of the highlights of the evening was seeing a slowly moving point of light traveling just below Arcturus (α Boo) and ε Boo in Boötes. I recognized it as an artificial satellite, and described the path into the Voice Recorder app on my iPhone so that I could identify it later. With help from the fantastic site Heavens Above, I was able to identify it as Cosmos 2082 Rocket. NASA’s page informs us that it was a surveillance/military satellite launched by the former U.S.S.R in May of 1990.

Then, a few minutes later, I noticed another moving point, this time in Ursa Major. Again, with the help of Heavens Above, I identified it as Tiangong-1, a Chinese space module that’s a prototype for docking capabilities for a future Chinese space station. It was launched last September.

In retrospect, it wasn’t only chance that I happened to see those two artificial satellites. During the day, the sky is too bright to see practically any satellite. At night, the Earth is between the satellite and the sun; in Earth’s shadow, they’re dark. But close to dawn and dusk, the sun may be below the horizon for us, but a satellite is high up enough that it can still get hit by sunlight.