11 May 2009

Near-Earth Astronomy: Iridium Flares

For quite a while I have been captivated by the sight of the International Space Station (ISS) whenever it is visible in the evening or morning sky. It is a big object, about 100 meters across and highly reflective. In the sky it looks as bright as Venus but it moves as swiftly as an airplane and in a very beautiful arc across the sky. Last week I was introduced to another near-earth satellite, actually a group of satellites known as Iridium Satellites. These are a collection of 66 communications satellites that circle the globe from a higher orbit than the ISS, but nonetheless light up quite brightly when viewed from just the right orientation. When sunlight glints off the antenna panels they create a very bright beam of light known as an "Iridium Flare."

I had never taken the time to look for one of these flares so I consulted a website known as Heavens Above (also permanently linked from this blog). There you can enter your location on a Google map and get a listing of the next 7 days of Iridium Flares. I did this and yesterday saw an amazingly bright flare from my front steps.

Iridium Flares are very localized events - that is, when a flare is visible at a particular moment and in a particular location, you won't see it nearly as bright (or at all) 10 or 20 miles away. So if you want to see one, take the time to carefully select your location on the map and then jot down the exact times and locations of the next few flares in your neighborhood. They are indeed impressive and you will be glad you took a moment to see one. They are astronomy - from my point of view - because you are looking carefully at the sky and seeing something that is outside of our own atmosphere.


Doug Wyllie said...

Heard you on KFOG this morning (my wife listens every day, and she called me in to hear you talk because she knows I love this stuff). Checking out the site and have saved you to my favorites. Glad to have discovered you... going to discover an Iridium Flare next!
~ dw

The Urban Astronomer said...

Hi Doug - glad that you like the site. There is always something to discover in the sky - besides the Iridium Flares, check out "Spaceweather" (link on the blog). Pretty cool stuff. Enjoy!

Drive-by Astronomy said...

Followed the ISS the other night from a dark site through my telescope almost from horizon to horizon. A beautiful sight. I still love the anticipation and observation of a bright Iridium flare too.

Enjoyed listening to your radio spot. We also do rooftop observing from the rooftop of the Buffalo Museum of Science at a tremendously fun event- "Starlight, Drinks, and Bites" http://www.sciencebuff.org/news/25/

Always a fun crowd to show some celestial wonders to. At times, plentiful adult beverages and astronomy are a perfect marriage. Ones first look through the eyepiece at Saturn in a mildly inebriated state has elicited some wonderful expletives.
Have fun at your event this year!

The Urban Astronomer said...

Hi Mike - San Francisco can sometimes disappoint. As the weather gets warmer the fog starts to roll in and last night it covered the City -- meaning that the Iridium Flare was invisible and (more than likely) telescopes at the CAS were not happening. I'll try again next week.

I like your blog. Nice to read about astronomy enthusiasm in Buffalo. I agree, a nice party and astronomy mix well!