March 22, 2019

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 release 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…

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 youíve arrived here at Astroguyz in search of astronomical knowledge, so weíll give you the straight up-low down on the street; [Read more...]

Astro Event: The Closest Full Moon of the Year.

(Editorís note: Due to a flurry of astronomical events, Februaryís 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 34.1í arc minutes in size, as opposed to 29.3í 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 donít forget ruddy Mars, just 7į 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 weekendís Full Moon looks bright is that you are seeing the sum of 5% of the Sunís reflected light crammed into an area tinier than a fingernail at armís 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 sunís output is still pretty bright!

21.10.09:IBEX: The Unsung Hero.

Amidst the recent water on the Moon hoopla, one key player was largely missed by the media; IBEX, NASA’s Interstellar Boundary Explorer. Launched in October 19th, 2008, IBEX travels in a highly eccentric Earth orbit that takes it from a perigee of 4,000 miles to an apogee of 150,000 miles in 3 days. This enables IBEX to dip in and out of Earth’s magnetosphere and bow shock, panning its 7 degree field of view camera in an all sky survey to map the heliopause, the boundary of our solar system with interstellar space. The cameras, dubbed IBEX Hi & Lo respectively, are the most sensitive neutron detectors ever flown, and span the sky looking for particles moving in access of 161,000 miles per hour. When it was first turned on & checked out earlier this year, engineers got a start; a nearby, large source of neutral atoms nearly filling the field of view. That was none other than our own Moon, reflecting the solar wind off of the lunar soil. The Earth’s magnetic field protects us from this onslaught, which hits the daytime side of the Moon unimpeded. The signature and percentage of particles seen lends credence to the water mixed in with the lunar soil theory, embedded mostly as hydroxyl compounds. In fact, the heliopause itself has shown signs of shrinking as of late due to the ongoing solar minimum… the just released image above released by the IBEX team sheds light on the overall structure of the heliopause as our solar system moves through the interstellar medium. Most interestingly, it shows that a large ribbon of Energetic Neutral Atoms (ENA’s) flowing between Voyager 1 & 2, our farthest soon-to-be intergalactic outposts. Just what would life in the interstellar medium be like, should it be pressed down or swept back interior to Earth’s orbit, as has been hypothesized in the distant past? Watch for more news on IBEX to come!

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; November 10th-16th; The Launch of STS-126.

One of the very few remaining shuttle launches will be occurring this week; STS-126 is scheduled to launch on November 14th at 7:55 P.M. EST (yes, another spectacular night launch!) and dock with the ISS on Day 3.

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