December 12, 2017

AstroEvent: An Equinox, a Full Moon, and a Perigee.

NOTE: The post that follows was written and loaded for timed release before the March 11th earthquake & resulting tsunami  off of the coast of Japan. We decided to relase it early to combat much of the pseudo-science that was already afoot about the “Super-Moon…” To re-iterate much of what follows, perigee is perigee, and varies little (<4.5%) from lunation to lunation.  Astronomers are not predicting earthquakes, Nibiru, or Sheen-zombie apocalypse as a result of an apsidal Full Moon…  


All hail the rising Worm Moon… (Photo by Author).

A perfect storm of astronomical events is transpiring at the end of the week, one that will no doubt trigger the worldwide Woo and break with much shoddily composed pseudo-science journalism. But you’ve arrived here at Astroguyz in search of astronomical knowledge, so we’ll give you the straight up-low down on the street; [Read more...]

Astro Event: The Closest Full Moon of the Year.

(Editor’s note: Due to a flurry of astronomical events, February’s events of the week will be released on an accelerated schedule; hang on!)

Amid the opposition of Mars, two launches out of the KSC and the Cape next week, and an exceptionally fine elongation of Mercury in the early morning skies, this weekend brings us a special treat; the closest Full Moon of the year. This Moon, known also as the Full Wolf Moon, is technically full at precisely 06:00 Universal time on Saturday morning, the 30th of January. This comes only 3 hours prior to perigee, when the Moon is closest to Earth in its orbit. At this time, the Moon will be only 217,862 miles distant, and appear 34.1’ arc minutes in size, as opposed to 29.3’ arc minutes at apogee. An added plus is that this Full Moon occurs at a very northerly declination in the constellation Cancer, and hence will be riding high for northern hemisphere viewers all night. And don’t forget ruddy Mars, just 7° degrees north of the Moon!

The astro word for this week is albedo. Think that bright silvery Full Moon is bright? Science says otherwise. Albedo is the measure of the percentage of light reflected back by an astronomical object; 100% is a full mirror, optimal reflection, and 0% is pitch black. On Earth, fresh snow reflects about 85% of the light that falls on it, and the average albedo of Earth is about 30%, depending on the amount of cloud cover and the percentage of land versus ocean presented to the Sun. In fact, this phenomenon of reflectivity may play a key role in a lesser known effect impacting global climate; that of global dimming. Now for the real shocker; the average albedo for the Moon is about 10%, slightly less than worn asphalt! Ask the Apollo astronauts; the Moon is in fact, a very grey-to-black place! The reason that this weekend’s Full Moon looks bright is that you are seeing the sum of 5% of the Sun’s reflected light crammed into an area tinier than a fingernail at arm’s length. In fact, anyone who has stood under a 99% percent eclipsed Sun, as occurred earlier this month, will tell you that even 1% of the sun’s output is still pretty bright!

AstroEvent: A Very Looong Annular Eclipse!

One of the more unique celestial events on the calendar for 2010 occurs on Friday, January 15th; an annular eclipse of the Sun, and the longest for the millennium! An annular solar eclipse occurs when the moon is at or near apogee (its most distant point from the Earth) and/or the Earth is at or near perihelion (its closest approach to the Sun)… these happened on January 17th and January 2nd respectively, setting us up for a visually large Sun and correspondingly small Moon, small enough that it won’t completely cover the Sun’s disk.   The maximum possible duration for an annular eclipse is 12 minutes and 24 seconds and the actual maximum for this eclipse is 11 minutes and 7.7 seconds, which occurs off of the southwestern coast of the Indian subcontinent.

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Event of the Week: 20.07.09: A VERY long solar eclipse!!!



The astronomical event of the year is about to take center stage this Wednesday. A total eclipse of the Sun, the longest possible for a VERY long time! Those lucky enough to have secured a ticket or live along the Pacific/Southeast Asia corridor will see an eclipse of a duration of up to 6 minutes and 39 seconds, near the maximum 7 minutes and 31 seconds possible. This is a consequence of the Earth passing aphelion a few weeks ago (read: a visually small Sun) and the a large New Moon very near perihelion (remember the year’s smallest Full Moon a few weeks back?) [Read more...]

Astro Event of the Week: January 26th-February 1st, 2009; An Annular Eclipse.

This week’s event is a rare annular eclipse of the Sun. The first eclipse of the year, this one traverses Borneo, Sumatra and the Mid-Indian Ocean. Folks from India and Southeast Asia to South Africa, Antarctica, and Australia will see varying degrees of partiality.

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AstroEvent of the Week, January 10th-18th: The Largest Full Moon of the Year!

Does that Full Moon rising this weekend look a little larger than usual? It’s not totally an illusion, although much has been written about the “large Moon on the horizon” effect. The first Full Moon of the year will also be the largest of 2009. This is because the Full Moon on the 11th at 3:28UT (Saturday evening for the US east coast) is still occurring pretty near perigee, which happens on the the 10th at 10:53 UT 16 hours prior. I know, Decembers’ Full Moon last month was the largest of last year, as well…any collectors of obscure astronomical phenomena know how often the largest Full Moons of the Year happen back to back? Of course, it would have to be in December-January, as happened in 2008-9. This months’ Moon is also known as the Full Wolf Moon. This sets the Moon up for an annular Solar eclipse in two weeks time, as it will be very near perigee and hence too small to completely cover the Sun. The Earth itself just passed perigee for the year on January 4th; all this translates into a big eclipsed Sun/small New Moon scenario!

This weeks’ Astro-word of the week is the lunar Maria. One of the first things a lunar observer notices are these dark, flat planes that cover roughly half of the lunar nearside. Galileo mistook them for seas (that’s how poor his first handmade optics were!) and the Latin name stuck. Noticeable to the naked eye, they form the famous “man in the Moon” illusion. One of the big surprises of the space age was the near total absence of mare (the plural) on the lunar far-side! Obviously, the gravitational influence of the Earth has had something to do with their formation, but their origins still aren’t entirely clear. These Maria are now known from sample returns to be basins filled in with accumulated basaltic ejecta and dust. The Moon may look shinny and bright to a dark adapted eye, but check out some of the Apollo photos snapped from the surface sometime; the Moon is a very dark place! Astronauts returning from the surface have remarked that remnants “tracked in” to the Command Module looked like coal dust and smelled like gunpowder. So much for Swiss cheese!



Astro Event of the Week 9-16th, 2008.

Welcome to a new weekly feature here at Astroguyz… each Monday, our goal will be to present some new and interesting celestial event that you can see from your own backyard. If the event is happening anytime from Monday evening, US East Coast time, up through early next Monday, you’ll read about it here. We’ll also tie in a vocabulary “astro-word of the week.” So, as Fat Albert says, “If you’re not careful, you just might learn something before it’s done!”

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