Showing posts with label earth. Show all posts
Showing posts with label earth. Show all posts

Thursday, March 8, 2012

2012 DA12 In February 2013: 0.07 LD! The Truth Behind this "Cosmic Threat"

Recent talk has been accumulating around the internet and the astronomy world of a recently discovered asteroid by name of 2012 DA12. The main purpose of such a sudden news real was the patent fact of its close passing, at respectively 0.07 LD (Lunar Distances, the distance from the moon to earth). What's more shocking is that this asteroid is going to pass within the border of geosynchronous satellites and others of the kind! Although astronomers predict really no chance of this asteroid hitting the earth, it still is amazing to think we will just be 10471.869 kilometers from an asteroid in February 2013!


Discovered on February 23, 2012, by the OAM Observatory in La Sagra in Spain, 2012 DA12 is the first asteroid (or near-earth-object) ever predicted to sweep this close to earth (0.07 LD) in the history of closest-approaches predictions. Calculations have been carried out by ephemerides, and according to NASA, "there is estimated to be a cumulative 0.0067% chance (1 in 15,000) of 2012 DA14 impacting Earth sometime between 2020 and 2042."

2012 DA14 is rather small for an asteroid, around 46 meters in diameter, but the results, if an earth collision was outcome, would be close to that of a "thermonuclear bomb" Earthsky wrote. If you thought Comet Elenin was a "threat to earth" or you're thinking 2012 is "doomsday", this should seem like the end of the world; but as mentioned earlier, there is really NO chance of collision. But what about the suspected 2020 collision? We have the explanation of one of NASA's astronomers that:
These large orbit uncertainties do allow a remote possibility of an impact in 2020 – approximately one chance in 83,000 – with additional remote possibilities beyond 2020. However, by far the most likely scenario is that additional observations, especially in 2013, will allow a dramatic reduction in the orbit uncertainties and the complete elimination of the 2020 impact possibility. [as said by Donald Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory].
 
For asteroid watchers and photographers, this event looks slim. NASA explains, "On this date [February 13, 2013], the asteroid will travel rapidly from the southern evening sky into the northern morning sky with its closest Earth approach occurring about 19:26 UTC when it will achieve a magnitude of less than seven, which is somewhat fainter than naked eye visibility. About 4 minutes after its Earth close approach, there is a good chance it will pass into the Earth's shadow for about 18 minutes or so before reappearing from the eclipse. When traveling rapidly into the northern morning sky, 2012 DA14 will quickly fade in brightness." 

Earth Impact Risk Summary (from NASA)

Saturday, March 3, 2012

Mars at Opposition March 3, 2012

Ever so often, Earth, along its celestial course, travels between Mars and the Sun, or any planet, to say the least. It just so happens that on this date, March 3, 2012, Mars will be such a planet of which Earth is directly between it and the Sun, hence making Mars at opposition. What is opposition, exactly? From just glancing at the word, we can assume (based on our knowledge of Greek and Latin word roots) that "opposition" may mean "the opposite" or perhaps "against or opposing"? These two possible meanings do work together to form a rather formal definition of such a time for a planet in its orbit around the sun, relative to earth. Dictionary.com defines "opposition" to mean (in an astronomical sense) "the situation of two heavenly bodies when their longitudes or right ascensions differ by 180°." In other words, Earth is passing between Mars and the Sun: on March 3, 2012. 

Simulated Opposition for March 3, 2012

Occurring rather not-that-often, Mars reaches opposition every 780 days, or 2 years and 50 days, on the average; it will be the brightest again in April of 2014, so try to experience Mars while you can! Currently, although depending on weather conditions and urban locations, Mars is seen on a clear, dark night at approximately -1.2 magnitude, rather bright when compared to other objects, such as stars. [Venus and Jupiter are no match to Mars, though! They are currently in conjunction around -4 mag for Venus and -2 for Jupiter]. Mars can be found in Leo, as it has moved from Virgo earlier in 2012.

Jeffery D. Beish writes "opposition will occur at 20:04 UT on March 03, 2012 (78.1° Ls), with an apparent planetary disk diameter of 13.9 arcsec. Mars will remain visible for a year after opposition and then become lost in the glare of the Sun again (April 01, 2013) as it approaches the next conjunction (April 17, 2013)." Mars will be closest to earth on March 5, however. EarthSky speculates "Mars is shining brightly now for good reason. ... Presently, Mars lodges a little over 100 million kilometers (62 million miles) away. Next year, however, when Mars lies on the far side of the sun from Earth, Mars will be some 3.6 times farther away and not even one-ninth as bright.

MARCH 14 2012: JUPITER AND VENUS CONJUNCTION 
...supposed brightest in years!...

 

Saturday, February 4, 2012

Moon Halos: Heavenly Circlets

Because the full moon is just less than one week away, the moon is in prime condition: ripe for halos to result! What is a lunar halo? A halo, by definition, is an optical phenomena occurring when ice crystals (or cirrus clouds) refract light around an especially bright object, hence making a 'halo' around it. Usually before a full moon, the moon is positioned just in a way to the sun that a halo could be produced, although most common are produced as the result of cirrus clouds in the upper atmosphere.

The ween before the full moon is the best time to spot moon halos (if weather conditions are superb), becasue the moon rises at a reasonable time, meaning, by the time the moon has reached the zenith, it's now 6-9 pm, which means right before the full moon. There is a menagerie of pictures below courtesy of Spaceweather.com. Enjoy the views, and make sure you look for the moon halos!

 
The above photograph was taken from Moray, Scotland by amateur astronomer Alan C. Tough. "I intended to photograph the Moon beside the Pleiades, but the cold and cloudy conditions were better suited to capturing this spectacular halo!"



 The above picture was taken by Jim Henderson: at Kincardine O'Neil north of River Dee, Aboyne Aberdeenshire, Scotland. "Frosty evening over Royal Deeside in Scotland and strong moon halo from half moon looking west of south with Orion Belt to left and convenient aeroplane heading northwards probably landing at Aberdeen Airport some 25 miles to East. ..."

"The moon can produce interesting optical effects when conditions are right. The most common of which are moon rings, moon bows, which are similar to rainbows, moon dogs and moon pillars. A rainbow is produced when sunlight is refracted through water droplets - A similar effect is produced when moon light refracts through ice crystals. Below are a few photographs and examples about this interesting phenomena. Thanks to everyone that helped me put together this simple explanation of moon light effects" [from Special Moon Effects. Read more at this link - it's pretty interesting!]

Friday, January 27, 2012

Obscure Astronomical-Related Terms


Many words have been dedicated to the English language, and some to astronomy itself! We all know this as a fact, but some astronomy-related terms are lesser known than others, and this article is dedicated to them. In the first list, all words below are courtesy the Grandiloquent Dictionary. Definitions provided by them; copyright Grandiloquent Dictionary.

achluophobia -( ) A fear of darkness or of the night 

astrophobia -( ) The fear of stars 

barophobia - ( ) Fear of gravity

heliolater - ( ) A sun worshipper  

heliophobia - ( ) The fear of the Sun  

heliotropism - ( ) The tendency of plants to turn towards the sun  

hemeralopia - ( ) Only being able to see at night  

hemeraphonia - ( ) Able to speak only at night 

lygophobia - ( )A fear of darkness or of the night

myctophobia - ( )  A fear of darkness or of the night

nychthemeron - ( )  A period of 24-hours

phengophobia - ( ) The fear of the Sun or of sunlight 

raith - ( )  A quarter of a year 

scintillation - ( )  The twinkling of stars or small bursts of light 

selenocentric - ( )  One whose life revolves around the moon 

selenography - ( )  The science of geography of the moon 

selenomancy - ( ) Divination using the moon 

selenophobia - ( )  A fear of the moon

Below, more astronomical-related obscure terms are listed, although not necessarily from the Grandiloquent Dictionary.These are words from Dictionary.com and SeaSky Astronomical Dictionary.

Syzygy An alignment of three celestial objects, as the sun, the earth, and either the moon or a planet 

Azimuth the arc of the horizon measured clockwise from the south point, in astronomy, or from the north point, in navigation, to the point where a vertical circle through a given heavenly body intersects the horizon.

Ephemeris a table showing the positions of a heavenly body on a number of dates in a regular sequence.

Protoplanet the collection of matter, in the process of condensation, from which a planet is formed.

Zenith the point on the celestial sphere vertically above a given position or observer. 

Node either of the two points at which the orbit of a heavenly body intersects a given plane, especially the plane of the ecliptic or of the celestial equator. 

Facula an irregular, unusually bright patch on the sun's surface.

achrondite A stone meteorite that contains no chondrules.

Apastron the point at which the stars of a binary system are farthest apart (periastron).

Catena A series or chain of craters.

Ejecta Material from beneath the surface of a body such as a moon or planet that is ejected by an impact such as a meteor and distributed around the surface. Ejecta usually appear as a lighter color than the surrounding surface.

Granulation one of the small, short-lived features of the sun's surface that in the aggregate give it a mottled appearance when viewed with a telescope.

Hypergalaxy A system consisting of a spiral galaxy surrounded by several dwarf white galaxies, often ellipticals. Our galaxy and the Andromeda galaxy are examples of hypergalaxies.

Libration An effect caused by the apparent wobble of the Moon as it orbits the Earth. The Moon always keeps the same side toward the Earth, but due to libration, 59% of the Moon's surface can be seen over a period of time.

Nadir the point on the celestial sphere directly beneath a given position or observer and diametrically opposite the zenith.

Obliquity The angle between a body's equatorial plane and orbital plane.

Planemo A large planet or planetary body that does not orbit a star. Planemos instead wander cold and alone through the cosmos. It is believed that most planemos once orbited their mother star but were ejected from the star system by gravitational interaction with another massive object.

Tuesday, January 24, 2012

Mars Begins Retrograde Motion: Best Viewing 2012

The red planet, one of our favorites, has begun its literally biyearly occurrence of retrograde motion; the last time it was in such orbit, was in 2009-2010. Apparent retrograde motion is the visible, backward orbit of a planet as viewed from earth, due to the orbit of that planet. Although rather hard to explain without a visual (see the visual below for clarification), retrograde motion is due to the earth's orbit, and thus our perception on things.

On account of the fact that earth orbits quicker than other planets (particularly the outer planets; although the inner planets (Mercury and Venus) exhibit it rather differently), earth, from time to time, will "overtake" a planet of note (such as Mars), causing that planet to look as if it travels in reverse, periodically being motionless for a few days before and after the event. As earth then passes the planet again, we can see that it resumes its old orbit (which is normal: west to east).

As Earth (blue) passes a superior planet, such as Mars (red), the superior planet will temporarily appear to reverse its motion across the sky [Wikipedia]
The retrograde motions of Mars and Uranus in 2003. A composite image created by superimposing images taken on twenty-nine different dates. FROM (Tunc Tezel, apod031216)
"In the illustration above, Mars' images form a large loop, because its orbit is somewhat tilted, and it moves relatively fast. Uranus' images (the fainter line of dots above Mars) form a more compact, straight-line pattern, because it moves far more slowly in its much larger orbit, and because its orbit isn't tilted as much, relative to ours," Courtney Seligman writes in her article of Retrograde motion. The more distant planets retrograde more frequently:
  • Mars retrogrades for 72 days every 25.6 months.
  • Jupiter for 121 days every 13.1 months.
  • Saturn for 138 days every 12.4 months.
  • Uranus for 151 days every 12.15 months and
  • Neptune for 158 days every 12.07 months.
Mars will start its 2012 retrograde motion on January 25, 2012 at 01:00 UT (8:00 pm EST), as it will be closest to the earth during the period. Starting that night and a few following months, Mars' retrograde motion will bring it to its best viewing condition -- perfect for astrophotography and studying it. Rising earlier as time progresses, Mars, in late January, will rise in the evening over the eastern horizon, being up all night in early March 2012. On this January 25 day, Mars will be on the borders of Virgo and Leo, constellations, and will travel across the night sky, retrograde not really being distinguishable just yet. But, it will be noticeable as time wears on. Happy viewing!

 

 FEBRUARY 9, 2012: 


 MARS AT OPPOSITION; MARCH 3-5, 2012: