Monthly Archives: October 2008

light pollution, stargazing

Counting Stars and Seeing the Light

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The Great World-wide Star Count

Want to help track the effects of light pollution?  Can you see the night sky from your location?  Can you count?  If you can answer “Yes” to all three questions, the Great World-wide Star Count needs you.

It’s the second year of this effort to use stars to tell how much light pollution is obliterating the night sky view. Scientists use the data that comes from schoolchildren, families and citizen scientists over the period of October 20 through November 3 about which constellations they can see.

It’s pretty simple to do.  First, visit the Great Star Count web site and read the instructions about what to look for and how to report your counts to Star Count HQ. Anybody can do it, and I read last year about how student teams ranging from public and private schools to home-schoolers did the count as part of their classwork.

Those of you in the Northern Hemisphere will look for the constellation Cygnus, while folks in the Southern Hemisphere will look for Sagittarius. Once you find your assigned constellation, you match what you see with charts you download from the Great World Wide Star Count site.

You can observe from the comfort of your back yard or make your way to dark-sky sites where more stars are visible. If you happen to get cloudy nights during the observation period, you will share data about cloud conditions instead.  Every bit of data is important.

Why do this?

Bright outdoor lighting at night is a growing problem for astronomical observing programs around the world and it has an effect on quality of life for people and nature. By participanting in the Great World Wide Star Count you will be able to comparew what you see with what others see. It gives a very clear picture about how star visibility varies from place to place and how light pollution affects all of us (including astronomers). It’s one step toward controlling light pollution (and saving energy in the process).

Hubble Update: According to CNN, there have been some problems implementing the Side B switchover on Hubble Space Telescope. This means that the planned restart of science observations is put off for the time being until engineers figure out how to get around the problems.

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U.S. Readers: Please register and vote.

exoplanets

Hot Times at New Planet High

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Sizzling Newborns Easier to Spot

Early Earth
Early Earth (courtesy of Donald J. DePaolo, University of California, Berkeley)

When you’re an astronomer looking for Earth-like planets around other stars, you might strike pay dirt among newly formed planets.  Such baby rocky worlds come out of the planetary system birth process with hot, molten surfaces. As it turns out, an astronomy team equipped with instruments sensitive to that glow could pick it out entirely separately from the glow of the bright nearby parent star.

At the Division of Planetary Sciences meeting in Ithaca, New York this week, MIT planetary scientist Linda Elkins-Tanton discussed the possibilities for discovering new worlds not long after they’re born.  It’s all a matter of catching them at the right time, while they’re still giving off that after-birth glow.

For a few million years after their initial formation, Earth-like planets (i.e. made of rock) may be slathered with a surface magma ocean (think: molten rock) that would glow brightly enough to make them stand out as they orbit neighboring stars.

Comparisons of the Sun and planets sizes
Comparisons of the Sun and planets' sizes (NASA).

Elkins-Tanton suggests that the “magma ocean” stage for Earth-sized planets may last a few million  years, much longer than previously estimated. What’s more, even after the surface solidifies, it could stay hot enough to provide an infrared glow for more than 10 million years.

The big problem for astronomers hoping to detect planets around other stars is that there’s a huge difference in brightness between the star and a planet. The planet shines only by reflecting light from its parent star and the planet is pretty tiny compared to the relative monstrosity of a star. Just look at the relative sizes of the Sun and the terrestrial planets of our own solar system and you’ll see what I mean.

Lava cooling after it flowed from Kileaua Volcano on the Big Island of Hawaii. Copyright 2007, Carolyn Collins Petersen
Lava cooling after it flowed from Kileaua Volcano on the Big Island of Hawai'i.(Copyright 2007, Carolyn Collins Petersen)

But, when the planet is relatively young and still has a molten surface, or is in its cooling-down stage, the difference in brightness in infrared wavelengths for a glowing, molten planetary surface would be much less.

If you knew what to look for, you could tell the difference between the star and the planet. Elkins-Tanton’s work suggests a neat new way that astronomers using future high-resolution instruments will be able to spot and identify newborn Earth-like planets. This, in turn, will help them understand just how long planetary surfaces stay molten, how long they take to cool down, and give them some surprising insights into the heating sources and surface evolution processes that make rocky planets.  What’s really interesting is that watching this process on newborn Earth-like worlds will also help us understand what our own home planet was like during its babyhood.

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Planetarium Hoo-rah Update: I received some notes from folks today about the last of the presidential debates here in the U.S. and the continuing misstatement of the McCain campaign about the Adler Planetarium’s projector. At this point, I’m not inclined to blog about it again, since I and many others have already pointed out publicly the flaws and errors in the McCain campaign’s reasoning and fact-checking. Please visit my previous postings (and links to other posters) to see for yourself what the hoo-rah is all about. Just for the heck of it I created a t-shirt and mug over at my CafePress store (see left sidebar). Check ’em out!

Also, if you haven’t registered to vote and there’s still time, please do register–no matter who you support.