The annual Geminid meteor shower may be already strong in the night of December 13/14 (Sunday/Monday) and at its best in the evening of December 14.
See the end note about enlarging illustrations.
Whereas most meteors are dust and small fragments shed from comets, the Geminids derive from a 6-kilometer-wide asteroid, 3200 Phaethon, which has a very short orbit of only 1.52 years and goes nearer to the Sun than any other named asteroid. So, tending to be rocky rather than dusty, Geminids as they burn up in the atmosphere are often bright and without trails. The meteors, following the asteroid’s orbit appproximately, cross inward close over Earth’s orbit almost sideways – from only slightly to the front, and slightly to the north. They appear to come at us from near Castor in the constellation of the twins, and from this “radiant” point their paths streak to any part of the sky. The radiant is up for almost all of the long (northern) winter night, highest at 2 AM.
In this view from ecliptic north, the broad arrow shows Earth’s flight along its orbit in 3 minutes, and an arrow on its equator shows its rotation in 3 hours. America is coming around into a view of the Geminid radiant higher in the sky.
The predicted time of maximum this year is Dec. 14 around half an hour before midnight by Universal Time; which, for North America, is 5:30 PM in the Eastern time zone, 4:30 PM in the Central zone, and so on. However, rather than having a short sharp peak like some other showers, the Geminids seem to have a “plateau” of around 22 hours. And and outlying members of the stream may be seen from about Dec. 4 to 17.
At the time and place of our horizon scene, the radiant has just risen into view. It will keep climbing (parallel to the celestial equator) as the long night goes on.
The ZHR, or zenithal hourly rate, of the Geminids is given as 120; this is what an alert observer might count under ideal conditions if the radiant were overhead. Actual rates are liable to be less. This is arguably the best shower of the year – it does not produce wild storms like the Leonids, but since about 1960 it is said to have superseded the famous Perseids of August as the most reliable.
And this year is favorable because that spoiler of meteor displays, the Moon, is well out of the way. It is New at almost the same time. – And will eclipse the Sun: watch this space.
Mixed metaphor of the week
Josh Tetrick, of a company called Eat Just, said: “I think the approval is one of the most significant milestones in the food industry in the last handful of decades. It’s an open door and it’s up to us and other companies to take that opportunity. My hope is this leads to a world in the next handful of years where the majority of meat doesn’t require killing a single animal or tearing down a single tree.” – The Guardian, Dec. 2.
A milestone in a handful can open a door?
But yes, this news could make anyone splutter with enthusiasm. Singapore (“an innovation hotspot”) has become the first country to approve the sale of meat cultured from cells – identical to “real” meat except for being free of chemical additives, drugs, antibiotics, growth hormones, and bacteria from animal waste. When the system is scaled up and worldwide, it will reduce the slaughtering of animals (800,000 cows, 1,500,000 sheep, 4 million pigs, 130 million chickens every day), and the 80% of all farmland used for growing their fodder, and the methane and other pollution they generate, and the headlong destruction of soil by intensive farming. Reminder: by mass, 36% of mammals are humans, 60% are livestock grown for human use, and only 4% are wild.
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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
Sometimes I make improvements or corrections to a post after positing it. If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version.
This weblog maintains its right to be about astronomy or anything under the sun.
Of course our San Francisco weather forecast for the peak is for clouds and a chance of rain. We need the rain, so I won’t complain.
This past Monday evening December 7 was exceptionally clear. I was skywatching on Bernal Hill. At 1853 PST a really bright earth-grazer passed fairly slowly from the northeast to the southwest. About magnitude minus 2 or 3! Bright white and a little puffy, left a white train about 20 degrees long that only lasted for a few seconds. So I think I’ve officially seen this year’s Geminid meteor shower.
If cultured meat or plant-based meat substitutes like the impossible burger get more people to eat fewer dead animals, that would be a very good thing in many respects. An easy low-tech alternative already exists: just eat a plant-based diet. Even just replacing meat and dairy with grains, legumes, and veggies a few times a week would make a big difference.
That could have been a very early Geminid, a large rock on the outer edge of the stream – though doesn’t solar radiation pressure mean that smaller particles are likely to be farther out? Perhaps Alastair McBeath can explain. Could you see enough of the stars to figure whether it was coming from Gemini? You might check with Sky & Telescope whether anyone else recorded it and whether a path has been calculated.
Experts say that cutting down on meat and dairy is the most effective action individuals can take against climate decline. When cultured meat becomes available I’ll try it out of curiosity, but I’ve enjoyed a meatless diet long enough that I don’t even miss the taste of meat – what Tilly cooks is better. Gaining that command over cheese is going to take longer…
I was on the darker west side of the hill, so I couldn’t see Gemini, and the radiant would still have been below the horizon anyway. But the path was at least roughly from the Geminid radiant. I like thinking it was probably an early Geminid, but who knows? I definitely saw a lone Geminid during a break in the weather around 2140 last night.
I have the same challenge with cheese. It’s just too good. Northern California has a lot of small organic dairy farms and some excellent cheesemakers. Vegan cheese products don’t even come close. A few months ago I started having hummus every other day, so I’ve cut my dairy consumption in half.
Hummus and tahini taste so good that, yes, they could make one cease to regret cheese.
After two days of clouds and intermittent rain, the weather cleared yesterday evening. I saw a few Geminids before bed, and a really bright one before dawn this morning. Not bad in a sky with a limiting magnitude about 3.