Thursday, March 12, 2009

Cloudy Plan

It happens to each of us sooner or later. Our stargazing plans are thwarted by clouds.

It doesn’t matter how much time or thought you put into creating your observing list for the evening, how lovingly you cleaned your binoculars and eyepieces in preparation, or how long you dark adapted. Sometimes, the sky gods are simply not smiling.

Those of us who design and deliver night-sky education programs learn pretty quickly that we always have to have a “cloudy plan.” A cloudy plan is the set of indoor activities you roll out in a hurry when the weather goes south and there isn’t a sucker hole in sight.

What’s your cloudy plan? When the promise of deep-space photons doing the can-can on your retinas is heartlessly revoked by foul weather, how will you drown your sorrows? With a carton of fudge ripple ice cream? With a marathon of Trick My Truck episodes? Or…might I suggest an alternative?

When the cosmos rains on my parade, I simply boot up my computer and head out into cyberspace (well, OK, after I kick my rocker box and set my observing list on fire in the gas grill). With the cornucopia of astronomy websites now available on the internet, I can usually find just the right pick-me-up for my dejected eyeballs.

Here are my lucky-seven picks for cosmic-eye-candy websites on which to while away a cloudy night. If there is an antidote for what ails you, you might just find it here.

1) Astronomy Picture of the Day
I don’t know about you, but I regularly break my resolution to visit this site daily. So I’m always playing catch up via the "Archive" link. On a cloudy night, this can be a good thing, as I can saturate my rods and cones with a dazzling variety from “the largest collection of annotated astronomical images on the internet.” The image captions are highly readable for non-scientists and peppered with hot links to other web pages for deeper reading.

Orion Nebula: a star factory in the Milky Way
Source: ESO

2) ESO Image Gallery
Supported by 14 European countries, the European Southern Observatory (ESO) comprises several telescopes in Chile, one of the premiere locales on Earth for ground-based astronomy. Choose images from such categories as solar system, stars, star clusters, nebulae, galaxies, and galaxy clusters. Try more exotic fare from categories like quasars and black holes, and cosmology. Click on each thumbnail image for a larger image with accompanying explanatory text.

Solar prominence (eruption) on our Sun
Source: SOHO (ESA & NASA)

3) SOHO Image Gallery - Best of SOHO
An amazing, astounding, and awe-inspiring collection of images of our nearest star, the Sun. The images were captured by the space-based Solar & Heliospheric Observatory (SOHO). Each thumbnail click reveals a brief caption and a choice of viewing the image at several resolutions.

You’ll never look at El Sol quite the same way again.

4) Spitzer Space Telescope Image Gallery
This space-based observatory enables us to see celestial objects in a new way— in the infrared spectrum, outside the narrow band of visible light we humans operate within. Choose from categories such as galaxies & the universe, other Milky Way objects, and protoplanetary & debris disks.

Tycho’s Supernova Remnant in the Milky Way
Source: Chandra and Spitzer Telescopes
Credit: X-ray: NASA/CXC/SAO, Infrared: NASA/JPL-Caltech; Optical: MPIA, Calar Alto, O.Krause et al.

5) Chandra X-Ray Observatory Photo Album
Through the oeuvre of this space-based observatory, we can again venture outside our comfort zone of visible light into the mysterious X-ray universe. There are no thumbnails, so to view images, you’ll select individual files grouped under category headings.

The Northern Lights
Copyright 1995-2003 Jan Curtis

6) The Aurora Page by Jan Curtis
For a change of pace, let’s move a little closer to home and wander through this spectacular gallery of aurora images shot in Alaska. Auroras, also known in the Northern Hemisphere as the Northern Lights, are colorful sky displays that occur primarily in polar regions when particles from the solar wind slam into Earth’s atmosphere and excite the gasses there.

The star-packed heart of the Milky Way
Credit: NASA and The Hubble Heritage Team (STScI/AURA)

Acknowledgment: J. Trauger (Jet Propulsion Laboratory)

7) Hubble Heritage Image Gallery
No survey of premium cosmic-eye-candy sites would be complete without a trip to the “Oracle,” aka the Hubble Space Telescope site. This prolific space-based observatory has revolutionized astronomy world-wide— not just for professional scientists but for every man, woman, and child on the planet.

The mission of the Hubble Heritage Project is to emphasize particularly compelling Hubble images and, in doing so, to build a bridge between the endeavors of scientists and the general public.

On the website, you’ll select images from a sea of thumbnails grouped under object types and Hubble instruments. Once each image has loaded, choose “Caption” or “Fast Facts” from the menu for, respectively, a full-length text explanation or a bare-bones data sheet that includes object name, constellation, distance, and dimensions.

Do you have a favorite cosmic-eye-candy site you like to savor on cloud-bound nights? By all means, post a comment and share it with us.

And bon appetit!

Astronomy Essential: The reason for the seasons is Earth’s tilted axis.

It’s a common misconception among the peoples of the world that the Earth’s proximity to the Sun determines our seasons. Not so. In fact, here in the Northern Hemisphere, we’re closer to the Sun when it’s coldest— in winter!

Earth’s tilted axis is the real culprit. The axis is the imaginary straight line that connects the North and South Poles and around which the Earth turns. Instead of sitting upright in the saddle as we gallop around the Sun, our axis “slouches” a bit— listing 23.5 degrees. When it’s tilted toward the Sun, more direct sunlight falls on the Northern Hemisphere; we call this “summer.” At the opposite end of our orbit, when the axis is tilted away from the Sun, we receive less direct sunlight and it’s “winter.”

To think about this another way, consider how much higher in our sky the Sun appears to be in the summer versus the winter. Since we’re tilted towards it in the summer, it’s over our heads, blazing down on us. And since we’re essentially leaning back away from it in the winter, it hangs low in our sky with sunlight hitting us weakly, at a narrowly acute angle.