The Changing Sky: Mira, a Variable Star

When observing the night sky, I enjoy the slow changes of the seasons and the stars as they arrive into the evening sky. The Moon and planets change their positions regularly, sometimes quite quickly. And transient events such as meteor showers and eclipses bring some drama to the sky. But the backdrop of stars is supposed to be constant and unchanging. And that brings me to the motivator for this blog post, the variable star Mira.

Stars have billion-year life cycles, so for us to witness a star's brightness changing over days and weeks is a rare thing. Astronomers study this special class of stars that regularly vary in brightness, and there is an association, the American Association of Variable Star Observers (AAVSO) that collaborate on research in this field. There's even a cool iPhone app that developer John Rachlin introduced me to. It's called Variable Stars, and it is free.

Mira is a well known variable star, and lately it has been changing its brightness very fast and over an extreme range, so that this star that is normally invisible to the naked eye is suddenly visible in the evening sky. I stepped outside this evening and found it near Jupiter, just a "thumb and a little finger away" as described by astronomy writer Tony Flanders in this Sky & Telescope article. I'm pleased to have found this special star that is now 1000s of times brighter than usual. If you feel up for a challenge, try to find it tonight.

Image courtesy of Sky & Telescope Magazine.

Seeing the Milky Way in City Skies

Summers bring pleasant viewing and a wealth of richness in the heavens. As the Summer Triangle rises and dominates the night sky, two of my favorite Zodiac constellations, Scorpius and Sagittarius, are visible deep in the southern sky. These big, bold constellations combine with the Summer Triangle to guide the urban star-gazer to the Milky Way.

For anyone who has seen the spectacle of the Milky Way in dark skies, you know just how profound this band of light looks as we view our own galaxy from within. And I know how disappointing it is after a few days in dark skies, to return to the city and realize that the beauty of the Milky Way is missing. But don't despair, for even in urban settings, you can still see many of the wonders of the Milky Way. To do this, you need to use a telescope or binoculars. Using Scorpius and Sagittarius as your anchor on the southern horizon, and the Summer Triangle high above, point the telescope or binoculars into the sky and move slowly from the south slowly overhead. You are looking into the Milky Way, and with the magnification and light-gathering of a telescope or binoculars, you cut through the glow of the city lights and enhance the light from space. And that will be a rewarding moment under the sky. No need for a fancy star chart or an iPhone app. All you need is a sense of wonder and a comfortable chair.

Review of iPhone Astronomy Apps: ISS Visibility and Iridium Flares

Two of my favorite iPhone apps are ISS Visibility and Iridium Flares, apps that help you to locate satellites very precisely. I use these two apps extensively, anytime I have clear skies and want to enjoy the spectacle of dazzling satellites crossing the sky, even here in the bright city lights of San Francisco. Continuing from my previous post on iPhone apps, here are two more reviews.

ISS Visibility does exactly what it promises by telling you when and where to look to see the International Space Station. Transits of the ISS across the evening or morning sky are impressive, whether the viewing is of the space station crossing a broad arc across the sky, or a short appearance that ends in the impressive flickering and fade of the ISS as it crosses the Earth's shadowline from daylight to night. At a price of $1.99, ISS Visibility gives you simple-to-use charts based on your location, and shows you where to look along with a nice 2D map showing the location of the ISS over Earth as it passes your viewing site.

Iridium Flares are bright lights in the sky that shine when Iridium Satellites in orbit around Earth reflect sunlight back toward the planet and produce a particularly bright glint of light in the sky for a few seconds. I find iridium flares wonderful to watch because at their best they flare up to -7 or -8 magnitude, many times brighter than Venus or Jupiter at their brightest. Also, being able to predict these special events is quite a lot of fun. I love to show off iridium flares to friends when the conditions permit. The Iridium Flares iPhone App costs a mere $0.99 but will pay back many times over.

Enjoy these two apps to see things in the sky that will certainly impress you.

KFOG Podcast - October 26, 2010

Today's Urban Astronomer talk with Irish Greg of the KFOG Morning Show features the North Star, Meteor Showers in November and December, some early shopping tips for the holidays, cool iPhone Apps, Jupiter and more. It's always a treat to talk with KFOG and share some astronomy tips with the listeners. Click here to listen.

Review of iPhone astronomy apps: iSolarScape and Planets

My admiration for the iPhone grows as I add more astronomy apps to it. Continuing from my last review of iPhone apps here on the Urban Astronomer blog, I review two more apps that I enjoy using.

iSolarScape: This is an impressive app for $0.99. It provides a broad range of information for the star gazer, from fun facts and figures about the Solar System, to up-to-date information about sunrise, sunset, Moon phase, the location of Jupiter's Galilean Satellites, and more. iSolarScape is the first app I reach for when I want the basics before an evening of stargazing.

The core views of the app are: Sun, Moon, Planets, Asteroids and Zodiac. I use the Sun and Planets selections the most, because they offer me important timing information and wonderful facts and figures about the objects in the Solar System. When I am conducting a star party, iSolarScape has answers to the typical questions (and also the fun and unusual questions) being asked: how far away is a planet, how hot (or cold) is it on the Moon, how many moons does Saturn have, and so on. I marvel at the range of information and ephemeris data I can find throughout the app.

For a great visual tour visit the iSolarScape website.

Planets: This fine app provides a wealth of information and given that the price is free, just load it up and enjoy! A recent upgrade added the "Sky 3D" view, an excellent map of the constellations of the night sky, something that is easy to use and yet quite complete, especially for an Urban Astronomer like me that can only see the brightest stars in constellations most nights. Another view is "Visibility," a planet-by-planet display of when a particular planet is visible in the sky (with back-side data and fun-facts about each object in the Solar System). The "Globe" view is a very cool 3D display of each planet in the Solar System and of course a beautiful Earth map that can be spun around and tilted in any direction allowing you to see the lit side or night side of the Earth.

The publisher of Planets, Dana Peters of QContinuum Software, has a very simple website. For much more vivid illustrations of the Planets app visit the iTunes Store.

I'll have more iPhone asrronomy app reviews in the coming months. Happy viewing!

iPhone apps: Star Walk, Moon Map Lite

I love my iPhone. There are many reasons for this, not the least of which are the nifty astronomy apps that are available for the iPhone. These apps bring a universe of information (pun intended) to my fingertips anytime and anyplace.

I've been using these apps while enjoying the rare clear evenings here in San Francisco this summer and will start posting short write-ups of these apps. Although these are not definitive, elaborate product reviews, I wanted to offer some cursory thoughts on a selection of astronomy apps for the iPhone. Here are two, Star Walk and Moon Map (Lite).

Star Walk: ($4.99) I am delighted with this application and have put it to work under different circumstances and in different settings, high on Mt. Tam, in the coastal redwoods where the skies were dark, and in my own backyard in San Francisco under the glow of city lights. Dan Schroeder has an excellent website with a complete review of Star Walk including screenshots.

My personal experience is that the application provides the detail needed while enjoying an evening under the stars. I used it extensively to accurately locate all the stars of constellations when I simply want to know the exact configuration of Bootes or Virgo or Centaurus (as noted in my Mt. Tam blog post). I also used Star Walk with binoculars to find Messier objects in Canis Venatici and Ursa Major this evening and the level of detail was just sufficient to help me to correctly identify these objects.

As with any iPhone application, there is tremendous flexibility to zoom in and out, something that makes map reading feasible on such a small screen. Having all of this detail in my pocket, ready to go at any time, is a very powerful tool for the casual observer as well as the seasoned amateur. My test of technology, hobby toys and computer applications is whether I actually get them out and use them when I should. With Star Walk, I find I am using it more and more often to give me deeper insights into the night sky.

Moon Map Lite: This is a free application (there are standard and "pro" versions that cost a few dollars) and it does just what it claims, providing a nice detailed map of the moon that you can scroll and zoom. The creator of Moon Map has a nice webpage showing all three versions of the application with short demo videos.

Earlier this week the full moon dominated the sky and I spent some time trying to use Moon Map Lite to help me identify some of the major features of the moon. I've not tried to identify more than just a few features of the moon in the past, so I figured this would be a chance to see if I could learn some new craters and seas.

To my dismay, I found this to be considerably more challenging than expected, primarily because the full moon is illuminated in a way that "drowns out" some of the key features of craters and makes them look quite a bit different than the excellent maps in Moon Map. However, I don't blame the Moon Map application for this, but rather my limited attempt to use it during only one phase of the moon. I will try using Moon Map to learn more of the moon's features when the moon is at different points in its orbit, looking for additional details through the telescope that might be easier to see when the sunlight strikes the moon from different angles. And who knows, I might just spring for $2.99 to get Moon Map Pro :-)

Coming soon: I'll review more iPhone apps including Distant Suns, Iridium Flares, ISS Visibility and iSolarScape. If you want to read an excellent group of reviews of star-map applications and see a very helpful comparison chart, look at Dan Schroeder's webpage comparing seven different iPhone apps.