28 January 2010

Mars and the Biggest Full Moon of 2010

The next few days offer a chance to see Mars and the full Moon together while each celestial body passes through its closest point to the Earth in their orbit. When Mars and Earth line up in their orbits around the Sun, we call that "opposition" and it represents the closest approach between the two planets. This takes place approximately every two years and when it does, Mars appears brighter than usual and is larger in a telescope. Also at opposition, Mars rises just as the Sun sets and is up all night. Mars is at opposition on Friday January 29th.

The Moon has an elliptical orbit around the Earth and as such, each orbital period (approximately 29 days) it is a bit closer to Earth (called Perigee) and then a bit farther from Earth (called Apogee) This month, the Moon is full and is at Perigee on the same date, Friday January 29th. It is also next to Mars so when you look outside on Friday evening, you'll be seeing a nice lineup of a couple of our nearest neighbors. When the Moon is at Perigee, it is a considerably bigger object in the sky than usual. The website Spaceweather.com highlights this nicely in their article.

I have written about the biggest full moon of the year in a previous blog post, if you want to get more information about that subject.

Regarding Mars and opposition, there was a great deal of hype in August 2003 when Mars had a particularly close opposition and was inaccurately stated as "being as big as the Full Moon." That won't ever happen, of course, but it certainly inspired a lot of people to take a look at Mars that summer. This week Mars will be less bright and big compared to 2003 but still a worthy binocular or telescope target. The next close encounter that will rival the 2003 lineup will be in 2018. For an extremely detailed chart and description of the Mars opposition phenomenon, visit the seds.org site.

16 January 2010

Jupiter and a Young Moon

Despite the cloudy weather here in San Francisco these last few days, bright Jupiter shines through from time to time as it slowly works its way down the western sky after sunset. The next few days offer a chance to see one of my favorite views, that of the young Moon and a bright planet. In this case the waxing crescent Moon slides across the south-western horizon each night for the next few nights. With Earthshine illuminating the dark portions of the Moon, the visual effect is quite striking. If clouds part in the next few days, find a good western horizon for this beautiful scene.

11 January 2010

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!

06 January 2010

International Space Station coming to a city near you!

The International Space Station (ISS) is one of the brightest satellites visible in the sky, and for the next few evenings it is making a particularly good set of passes over the USA and Canada in the evening. If you have not seen it fly over, it is worth a few minutes out of your day to use an online tool such as the Simple Satellite Tracker from spaceweather.com or the NASA Satellite Tracker.

Here in San Francisco we can look forward to four consecutive evenings of good fly overs. Wednesday 6th it is visible from 6:36 to 6:38 pm, Thursday 7th it is visible from 5:59 to 6:02 pm, and Friday 8th it is visible from 5:44 to 5:47 pm.

The ISS looks like a fast-moving airplane, but the light is perfectly smooth (not blinking, not red and white) and the path is a very clean arc from west to east. Given the current orientation of the ISS as it orbits Earth, the upcoming passes across North America will generally be from the west to east and from the south to north.

01 January 2010

Mars arrives in the evening sky

Mars is back on display, now visible shortly after sunset in the eastern sky. During the month of January it will reach "opposition" when it appears exactly opposite the Sun in the sky. At opposition Mars is also at closest approach to Earth (and is therefore at its brightest for the year). It shines a distinctive red-orange color especially when compared to the stars in Leo and Cancer that surround it. Through binoculars or a telescope Mars appears as a small colorful dot of light. This week the Moon serves as a guide for locating Mars.