What Can We Do About Light Pollution?
Published May 9, 2012
The brightest areas of Earth are the most urbanized, but not necessarily the most populated. (Compare western Europe, China, and India.) Cities tend to grow along coastlines and transportation networks. Even without the underlying map, the outlines of many continents would still be visible. Image Credit: Marc Imhoff of NASA GSFC, Christopher Elvidge of NOAA NGDC, Craig Mayhew and Robert Simmon, NASA GSFC.
With truly dark skies (Bortle Class 1) becoming an endangered species, many parks and cities across the globe are doubling their efforts to become “dark sky preserve” sites. Often times though, these efforts conflict with housing developments, mining efforts, and other side-effects of the rapidly developing world.
In some cases, cities, parks, and dark sky preservationists clash with new developments, as it’s very easy for developers to throw up lighting without any concern for night skies or lighting efficiency. Recent studies have shown that increased levels of artificial lighting at night can have a detrimental effect on birds, insects, and even humans. New studies by the EPA have also led to a correlation between high smog levels in the lower atmosphere and high levels of artificial lighting at night.
In the debate between providing adequate light at night, and protecting our night skies, opponents often cite security and cost as the main factors for not utilizing “dark sky safe” lighting methods. That being said, many cities are now seeing tremendous cost-savings from reducing their nighttime lighting levels, along with a corresponding reduction in crime! Seems like criminals don’t like carrying flashlights! Also consider with energy costs rapidly rising, the value of reclaiming countless millions of tons of coal, and barrels of oil wasted on unnecessary outdoor lighting. With the heightened concerns over energy usage and global climate change, it is a logical conclusion to reduce energy usage through the use of properly configured, energy efficient outdoor lighting.
What other factors affect our night skies, and what can be done to help take back the night?
Product Review: Orion SkyQuest XT8 Classic Dobsonian Telescope
Published January 16, 2012
Orion SkyQuest XT8 Classic Dobsonian Telescope.
Shown with Telrad finder (sold separately ). Image Credit: Ray Sanders
The Orion XT8 dobsonian is a mid-range reflector telescope. There are a few smaller and less expensive models available in Orion’s classic dobsonian series, and there are a few larger, more expensive models as well. The XT8 offers a good balance between portability, price and performance. In this review we’ll look at the build quality of the XT8, along with how it performs at planetary and “dark sky” objects.
For starters, let’s look at the raw specifications for the XT8. The XT8 features an 8” (203mm) primary mirror. With a focal length of 1200mm, this gives a focal ratio of f/5.9. Advanced observers will enjoy the XT8′s 2” focuser, which allows for larger eyepieces, or even a “T” adapter for short-exposure astrophotography. New observers (or those on a budget) will find the included 2” to 1.25” eyepiece adapter allows the use of 1.25” eyepieces with no noticeable wiggle/slop.
The XT8 does come with a 25mm 1.25” Plossl eyepiece which performs well as a medium-power eyepiece in the XT8. The XT8 features Orion’s EZ Finder II sight. While the EZ Finder II isn’t a terribly bad “red-dot” finder, some observers may see fit to replace the stock finder with something like a “correct image” finder scope, a laser pointer, or even a Telrad non-magnified finder.
Orion ships the XT8 in two boxes. One for the optical tube, and a second for the dobsonian mount base. The shipping box for the mount base was well thought out, minimizing potential damage to the base components. The shipping box for the optical tube was adequate, but as with any piece of delicate equipment – there can never be enough padding.
Featured Sponsor: The Chop Shop
Published December 12, 2011
I’m sure by now, many of you have notices the spiffy new banner ad running on for the past week or so. The ad is for The Chop Shop – a novelty t-shirt company specializing in some pretty awesome (and geeky) t-shirt designs.
This month I’m testing out a new program where I feature a monthly site sponsor. As mentioned above, this month’s featured sponsor is The Chop Shop. I chose The Chop Shop for a few reasons. One, I like their shirts, especially their badass “space exploration” shirts. Secondly, The Chop Shop donates a portion of the proceeds from some of their shirts to The Planetary Society.
Basically, if you are looking for a geek gift this holiday season, I encourage you to visit http://chopshopstore.com/ and check out The Chop Shop’s offerings.
With regards to advertising and site sponsors, rather than throw random ads on the site, with the hopes of covering costs ( site hosting, telescope giveaways, etc.) I’ve been a bit more selective about the ads ran on the site. Instead of seeing ads for online casinos or mortgage refinancing, you see ads for telescopes, think geek gadgets, etc. Also of note is that the ad placement is rather inobtrusive and I don’t resort to pop-ups, interstitials, or any of the other annoying ad techniques. While I do have site costs (and expenses) to cover, keep in mind that my plan will always be to do so in the least obtrusive manner possible.
Thank you all for continuing to read “Dear Astronomer”
Update: 2011 Blogging Scholarship Results
Published November 30, 2011
The voting deadline for the 2011 Blogging Scholarship has passed and it seems that John McAuliff over at http://roadtripofpassage.com/ is the winner.
Please take a minute to stop by his blog and give him some well-deserved congratulations.
It was an honor to be one of the finalists this year, and I’d like to thank every one of my readers for helping to grow the Dear Astronomer site into what it is today. I’ve only been doing this for about two years now, but my readership has grown each month.
For most of you it’s clear that I run this site out of my love for astronomy and science literacy. This isn’t a business, (I do have to pay for hosting and the telescopes I give out) but I do take this site as seriously as my family, education, and “day” job.
Thank you all for visiting my little corner of the Internet – the best is yet to come!
Astronomy Question: Why isn’t Pluto a Planet Anymore?
Published October 20, 2011
Solar System Diagram. Image Credit: Wikimedia
Michelle asks,
Dear Astronomer, Why isn’t Pluto a planet anymore?
Great question Michelle, one that still sparks debate over five years after the controversial decision by the International Astronomical Union (IAU). For the benefit of those who don’t know the full backstory, this will be a pretty in-depth explanation.
Discovered by Clyde Tombaugh in 1930, Pluto is certainly an interesting case. During the early 1900′s there was speculation of another planet lurking past Neptune. After many years of studying Pluto, the determination was made that Pluto was not massive enough to be the cause of perturbations in the orbits of Neptune and Uranus. The determination was also supported by revised estimates of Neptune’s mass.
Pluto, Charon, Nix, Hydra and newly discovered "P4".
Image Credit: NASA/HST
As astronomers discovered more about Pluto, the less of a “fit” with the rest of the solar system became clear. Even when I was in grade school (in the late 70′s/early 80′s), textbooks and even some planetarium presenters described Pluto as more of a “giant comet”, than a planet.
Further adding to the confusion is Pluto’s moon ( for lack of a better term ) Charon. Technically speaking, Pluto and Charon are a “binary” system – the only one known to exist in our solar system. Additionally, three more objects orbiting Pluto have been discovered. Nix, Hydra and an unnamed object now designated “P4″. Given these objects, one could describe the Pluto system as a loosely bound “cloud” of icy objects.
So how does all this fit in with “planetary status” ?
Consider that most people like to organize things in similar groups. We don’t put plates in the silverware drawer, nor do we put shoes in our refrigerator. A quick glance at our solar system shows three readily apparent classes of planets; Terrestrial planets ( Mercury, Venus, Earth, Mars), Gas giants (Jupiter, Saturn), and “Ice” giants ( Uranus and Neptune ). Out past Neptune (out to a distance of almost a light year from our Sun!) there are many icy/rocky objects, few of which have been studied in great detail.
Eris and Dysnomia.
Image Credit: NASA/HST
While studying the region past Neptune, astronomer Mike Brown and his team discovered an object that at its furthest point orbits at nearly twice the distance from our Sun as Pluto. The object, first dubbed 2003UB313 (now known as Eris) was estimated to be nearly the same diameter as Pluto and additional studies of this object and its moon revealed a mass roughly 25% more than Pluto’s.
Brown’s discovery raised some interesting questions. If Eris, being much further from the sun was the same diameter and had more mass than Pluto, had a new planet been discovered? If more objects like Eris were to be discovered past Pluto’s orbit, would they also be planets?
A controversial decision by the International Astronomical Union in 1996 set out to provide an “official” set of criteria for planetary status. The IAU states an object is a planet if it:
In order to classify objects like Pluto and Eris (as well as Makemake, Ceres, and Haumea) which meet the first two criteria, the IAU adopted the term “dwarf planet”. Based on studies of the outer solar system, estimates of how many dwarf planets exist range between a few dozen and a few hundred.
On August 24th 2006, the IAU’s proposal passed a vote, and thus, Pluto no longer was considered a full-fledged planet, but instead the first of the dwarf planets. Many people to this day criticize the vote and the decision, however science is not dictated by popular opinion. With the discovery of many additional objects past Neptune’s orbit that share similar characteristics with Pluto, the IAU’s decision appears to make sense, for the time being.
Interesting Facts About Pluto
Published August 24, 2011
Image credit: The International Astronomical Union/Martin Kornmesser
Fraser Cain at Universe Today writes:
Pluto isn’t a planet any more, but it’s still a very interesting dwarf planet in the Solar System, worthy of our fascination and interest. Here are 10 facts about Pluto. Some you might already know, and others will be completely new.
1. Pluto has an atmosphere
Even though Pluto’s average temperature averages a mere 44 degrees above absolute zero, the dwarf planet has an atmosphere. Not an atmosphere as we know it, but an atmosphere, none the less.
It was first discovered back in 1985, when astronomers watched as Pluto passed in front of a star. They were able to calculate a slight dimming as its atmosphere passed in front of the star, before Pluto itself blocked the star entirely. From those observations, they were able to calculate that it has a thin envelope of nitrogen, methane and carbon dioxide.
As Pluto moves away from the Sun, this atmosphere gets so cold that it freezes onto the surface. And then as the dwarf planet warms again, the atmosphere evaporates again, forming a gas around it.
2. Pluto has 3 4 moons
You might have heard that Pluto has a large moon called Charon (more on that later), but did you know that it actually has 3 moons in total. Charon is the large one, with a mass of roughly half that of Pluto’s.
Two additional moons, Nix and Hydra, were discovered by astronomers using the Hubble Space Telescope on May 15, 2005. They were originally called S/2005 P1 and S/2005 P2, and then given their final names on June 21, 2006.
They took a long time to discover because they’re so tiny. Nix is only 46 km across, while Hydra is 61 km across.
Update:A fourth moon, dubbed “P4″ was recently detected by the Hubble Space Telescope.
3. Pluto hasn’t cleared out its orbit
Although Pluto orbits the Sun and it’s round, it’s not a planet. And that’s because Pluto hasn’t cleared out its orbit of material. This was the reason that the International Astronomical Union chose to demote it from planet to dwarf planet in 2006.
Just to give you an idea, if you added up the mass of all the other objects in Pluto’s orbit, Pluto’s mass would only be a tiny fraction of that total. In fact, it would only be 0.07 times as massive as everything else. For comparison, if you did the same thing with all the other material in the Earth’s orbit, our planet would be 1.5 million times as massive.
And that’s why Pluto’s not a planet.
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