|Posted on November 3, 2011 at 9:45 AM||comments (0)|
Perhaps you have heard some chatter about an asteroid passing between Earth and the Moon on Tuesday, November 8th?
Just the sound of such an event conjures up fantastical scenes of impacts, tsunami’s and terrestrial destruction from Hollywood doomsday movies. But this time there is nothing to worry about. In fact, NASA has calculated the orbit of Asteroid 2005 YU55 for the next 100 years and this asteroid poses no threat of hitting Earth.
However, it is a rare occasion happening in our astronomical backyard, and worth sharing some interesting facts about.
The one-quarter mile, spherical shaped cosmic interloper in the spotlight is Asteroid 2005 YU55. Except, “in the spotlight” would be an overstatement, unless one is using a telescope 6” or larger trained on it, and even then….
This space rock is very dark in color and is not visible to the bare eye. It has a less than 1% reflectivity of sunlight due to the carbon based material it is composed of, making it dark much like coal.
The visual magnitude of 2005 YU55 is 11. In backyard viewing terms, that means you can’t see it unaided. A visual magnitude of 6 is about the limit of visibility of a sky object for the human eye. Unless one lives in the suburbs washed in ambient light, then perhaps 3 or 4 magnitude is the limit of visibility.
To put in terms relevant to backyard star-gazing, a bright star is about 0 or -1 visual magnitude. Yes, we are in negatives, low and negative number means bright and brighter.
Jupiter shines at magnitude -3 and the Moon is -12.7.
Under clear skies Tuesday evening facing ESE just before 6:30 pm the Moon, two days shy of full phase, and Jupiter cannot be missed. Silently and unnoticed a stealth visitor tumbles through our Earth-Moon neighborhood far above in the SSW direction of sky.
Observationally, it will be travelling by the star Altair in the constellation Aquila and onward through the constellations of Delphinus, and Pegasus.
At 6:28 pm EST, 2005 YU55 will pass closest to Earth at almost 202,000 miles; 85% of the lunar distance of 250,000 miles.
But, before panic breaks out, this small carbonaceous object will have no effect on gravitational pull or tides on Earth.
In 1976 an asteroid did make such an approach but it was not known in advance. An object this large passing so close is not expected to happen again until 2028 when a different asteroid with an even longer name will pass at about 6% of the lunar distance.
Considering all of the rocky objects out there in our solar system - most located in the asteroid belt between Mars and Jupiter (see image below) we should welcome the opportunity to usher this 1,300 foot intruder in and out of our Earthly neighborhood...Some visitors you just enjoy more after they leave!
The following links will offer additional information and graphics of 2005 YU55:
Merri Niland-Bare copyright 2011
|Posted on October 31, 2011 at 6:00 PM||comments (0)|
There’s no trick about it, Halloween observances are steeped in a cauldron of practices marking endings and new beginnings.
The celebrations practiced long ago were to observe the end of the Sun’s warmth and bounty of harvest as it gives way to the onset of the cold season.
Some ancient customs have persisted and morphed into traditions of costume and candy ~ the modern-day association with this last day in October.
This date has been called Halloween, All Hallow’s Eve, Samhain, All Soul’s Day, Day of the Dead. Call it what you may, actually this day marks the astronomical beginning of the second half of the fall season. That is, halfway from the Autumnal Equinox (September 22,) to the Winter Solstice (December 21) – the beginning of winter season in northern hemisphere.
It seems fall decided to join in the revelry and dress up as winter this year for Halloween in the northeastern U.S., bringing significant snow just halfway through the fall season.
Though it is of little consolation, in urban areas effected by power outages from the storm, the sky will be darkened with the wash of ambient light diminished. It may offer a rare opportunity to view our Milky Way galaxy from the inside looking out from otherwise light polluted locations.
image best viewed from 40 degrees N. Latitude
The Moon this Halloween is a waxing crescent and will be visible hovering just left of the nebulous swath of the Milky band arching across the sky ~ spanning from SW to NE horizons.
The Moon will offer little moonlight to illuminate one’s path out treating this Halloween, and will be setting in the west minutes after 10:30 p.m.
If you are looking for the storybook full Moon to cast its eerie glow o’ver the land on this spooky night, the next time the Moon will be in full phase on Halloween will be in the year 2020.
With 10½ hours of sunlight per day now and shrinking, the daylight’s disappearing act is assisted by the trick and play of light hours on the clock.
Daylight saving time ends and standard time resumes at the end of this week as the clocks are set back one hour at 2:00 a.m. on the first Sunday of November. November 6 this year.
Some may recall this time-trickery in the fall as being earlier than this, and it was. Prior to the Energy Policy Act of 2005 taking effect in November 2007, daylight saving time ended the last Sunday in October.
The trick is that daylight is not saved, it is just shifted and that trick will be uncloaked when the Sun sets – by the clock – just after 5:00 p.m. eastern standard time next Monday.
Happy Halloween ~ Be Safe! And look up, there really is half a season left until Winter begins!
Merri Niland-Bare copyright 2011