26 July 2011

Daytime Astronomy: Sunspots

Summer nights are short, making it more challenging to enjoy the night sky. But days are long, and the Sun often provides some fireworks to make things interesting. Right now, the Sun is moving into a period of maximum solar activity. Maximum solar activity comes as part of an 11 year cycle in which we observe peaks and valleys in the number and size of Sunspots, with the next peak in 2012.

Sunspots are areas on the surface of the Sun where magnetic fields have caused a disturbance in the normal flow of heat from the core of the Sun , and the areas appear black through Earth-based solar telescopes. These areas are "cooler" than the surrounding surface of the Sun (I'm not sure if the term "cooler" applies to the surface of a 10,000 degree star!), which means that Sunspots check in at about 5000 degrees. With a well filtered telescope, the areas look black by contrast to the extremely bright solar surface, known as the Photosphere. It's one of nature's truly fascinating phenomenon, and a wonderful thing to see directly through a telescope.

Our eyes are sensitive light sensors, and are completely overwhelmed when you look directly at the Sun. The heat from the intense radiation of the Sun can cause blindness in a matter of seconds. Fortunately we instinctly look away from the Sun and preserve our vision naturally. Experienced astronomers, however, can safely use solar filters on telescopes to cut the brightness of the Sun to the brightness of the Full Moon, and hence use a standard telescope with a filter to enable daytime astronomy. In San Francisco, you sometimes find a Sidewalk Astronomer showing off the Sun during the day. With the increase in Sunspots during 2011 and into 2012, I'll be out on the sidewalk doing this from time to time, and even if you don't have access to a solar telescope, you can check out Sunspots on the solar surface daily at the excellent website SpaceWeather.com. This website has some very amazing images of the Sun and other space-related "weather" items.

Remember: only view the Sun with properly designed filtering intended for safe solar viewing.

Image courtesy of SpaceWeather.com.

16 July 2011

One Year on Neptune

We passed a landmark moment this month, the one-year anniversary of the discovery of the Blue Planet, Neptune -- one Neptunian-year, that is, which is 165 of our Earth-years. This gem of a planet is something that an urban astronomer has to work a bit harder to see, but once spotted it is a lovely blue point of light in the sky, a fine payoff for those with the persistence to track it down against the backdrop of stars in the heavens.

During its long trek around the Solar System, Neptune has periodic close encounters with other planets, as it did during the "Triple Conjunction of 2009" with Jupiter. However, this year it stands alone in the constellation Aquarius, more challenging to find because we don't get Jupiter as a beacon leading us to find the elusive blue planet. However, using this star chart, a pair of binoculars, a dark backyard location, and some patience, I am sure you can find it. I will be looking from time to time over the coming months as Neptune moves from the morning sky into the evening sky, scanning for its dim blue glow in the vastness of the night sky.

08 July 2011

KFOG Podcast - July 8, 2011

Today was the final launch of the Space Shuttle. KFOG's Irish Greg and I talk about this historic event, about the wonders of the Summer night sky, and about upcoming Star Parties in the San Francisco Bay Area. All in 5 minutes! Listen here.

05 July 2011

Moon in Descent

The Moon traces out a path across the sky that is slightly offset from the path of the planets and Sun (the well-known "ecliptic" path). The orbit of the Moon is inclined to the ecliptic by 6 degrees, meaning that at any given point in a month, the Moon might be found in the sky just at the ecliptic, or moving below the ecliptic (up to 6 degrees away from it), or above the ecliptic. As it travels in its 29 day journey around the Earth, the Moon passes through the ecliptic twice, once going down (descending node) and once going up (ascending node).

Since we just finished an Eclipse Season, the Moon's nodes are very near to the points in space where we have New Moon and Full Moon, enough that from the New Moon a few days ago, to the First Quarter Moon later this week, we see the Moon traveling past the descending node and moving well below the ecliptic. Visual proof of that this week comes in the form of Saturn and Spica (see image), both of which are nearly on the ecliptic. The daily change in location of the Moon shows us just where the Moon is in relation to the ecliptic, this week skirting just south (below) this imaginary line in space.