Image of the Day: Mercury

This image of Mercury was taken yesterday, September 29th, 2009.


credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Here was Messenger flying past Earth in 2005: http://dwarmstr.blogspot.com/2006/04/messenger-departing-earth.html

And Mercury transiting across the face of the Sun from Earth: http://dwarmstr.blogspot.com/2006/11/mercury-transit.html

More Mercury science releases

The Messenger science team produced some great press release images and the Planetary Society Blog has a great analysis. Make sure you take a gander at the Mercury departure movie.

Mercury's unseen hemisphere

NASA/JHUAPL/Carnegie
Mercury from Messenger's closest approach, edited to highlight the terminator from the stock release image.

Messenger reaches Mercury

The Messenger spacecraft is now 17 hours away from closest approach to Mercury, the first spacecraft to visit the tiny, dense, and baked interior planet in 30 years. Only about half of Mercury is currently mapped. It only passes by this time; it will flyby twice again, then finally enter orbit in 2011. See an orbital movie here. You might also remember this Earth flyby movie, mentioned almost two years ago here.

Some useful astronomy charts

For the current Mercury and Venus evening apparitions, here are two useful graphics from Curt Renz, plus the lunar phases for June:

June moon calendar
Mercury evening apparition
Venus evening apparition

See via Chicago Astronomer's forum

Mercury, the Moon, and Venus

As I mentioned in my last post, more images from the evening of May 17th.

You can see the Moon--but look closely at the support wires on the left side of the crane--see Mercury?


Through the telescope, the autofocus picks up the high contrast of the crane--and makes Mercury a round blur.


Forcing the focus to Mercury.


Venus, much higher up in the sky, but still subject to atmospheric dispersion.


You can see the turbulence by viewing this video of Venus here (753kB, 0:17 WMV).

The wide view.

The young moon

The 29 hour-old moon was beautiful last night, and just a few degrees away was a suprisingly bright Mercury.




Composite of two images.

Both were taken through the Ryerson 6-inch refractor and a Canon A540 camera. I have more images--will post them as soon as I finish processing them.

followup on the compact fluorescent story

A long followup on the compact fluorescent story from Pharyngula. My previous calculations about mercury in compact fluorescents.

Mercury in compact fluorescents

Ah drat. A slashdot article appeared about some poor lady in Maine broke a compact fluorescent lamp and freaked out about the small amount of mercury in it. A questionable journalist wrote an article about the freakout.

I had a draft article about the issue: Compact fluorescents contain mercury. How does this amount compare to the amount of mercury released by using a standard incandescent lamp? So enjoy my sketchy calculations below.

Lamp Amount (mg.)
Pre 1988 T-12:~45
Post 1988 T-12: ~11.6
Typical T8: ~4 to 5
Low Mercury T8: ~3
CFL: ~4 to 5

Type Mercury content mg/unit*
Fluorescent lamp: 10
Straight fluorescent with diffusion barrier coating: 6
Compact fluorescent lamp: 4 - 23 W: 5
26 - 55 W: 10
Source: http://www.helcom.fi/Recommendations/en_GB/rec23_4/

26 watt CF: 8 hours a day, per year uses 75.92 kWh. At roughly 10 cents/kwh (new IL prices), $7.59 a year.
100 watt incandescent 8 hours a day, per year: 292 kWh. $29.20.

every 1000kWh produces 619lbs CO2 for ComEd power, which was 27% coal. (12 months prior to march 2004) Excelon environmental release
(Although recently it's been very highly nuclear, up to 92% in fall 2006).
2/3 of mercury in coal escapes to air http://www.epa.gov/mercury/control_emissions/index.htm

0.17ppm average Hg content in US Coal http://igs.indiana.edu/Geology/coalOilGas/mercuryInCoal/index.cfm
Indiana coal varied from 0.31ppm to 0.02ppm

# The thermal energy content of coal is 6,150 kWh/ton. Even though coal-fired power generators are very efficient, only about 40% of the thermal energy in coal converts to electricity. So the electricity generated per ton of coal is (0.4 ton)(6,150 kWh) = 2,460 kWh/ton.
(ISA: Maximize energy buck with efficient bang)

For our 100W incandescent, it burns 292kWh per year, of which 27% is coal, which means 64lbs (29kg) of coal is burned in IL. 0.17ppm of that is 4.93mg Hg, which 66% escapes: 3.29mg Hg.

Our compact fluorescent will produce 26% of that much mercury, or 0.86mg Hg. At 8000 hours lifetime, that's roughly just short of three years of 8hrs/day. So we'd release 2.37mg of Hg for the lifetime of the bulb, while the incandescent would release 9mg over that same time period. Add the existing 4 to 5mg per CFL, and the CF still is releasing less mercury into the environment.

This calculation gets worse and worse the more coal your power is made from. Illinois has the highest production of nuclear power of any state, so using compact fluorescents reduce the release of mercury into the environment, if you ignore renewables like hydroelectric. The nation as a whole uses 50% coal as its power source.