Showing posts with label Astronomy. Show all posts
Showing posts with label Astronomy. Show all posts

Monday, May 14, 2012

Powerful Cosmic force would have destroyed Earth

http://www.messagetoeagle.com/beamatearth.php
 

A very interesting, but also frightening event took place back some years ago when satellites and observatories suddenly registered an extremely powerful cosmic force that almost destroyed Earth. The explosion, coming from the Bootes constellation was firing material directly toward Earth traveling at almost the speed of light.
 

The explosion formally named GRB 080319B was detected at 2:13 a.m. EDT on March 19, 2008. It came from the constellation of Bootes.
 

The event, called a gamma-ray burst, became bright enough for human eyes to see.
In a scientific report, Judith Racusin of Penn State University and a team of 92 coauthors state that observations across the spectrum began 30 minutes before the explosion and followed its afterglow for months.
 

The team concludes the burst's extraordinary brightness arose from a jet that shot material directly toward Earth at 99.99995 percent the speed of light. 


At the same moment Swift saw the burst, the Russian KONUS instrument on NASA's Wind satellite also sensed the gamma rays and provided a wide view of their spectral structure. A robotic wide-field optical camera called "Pi of the Sky" in Chile simultaneously captured the burst's first visible light.
The system is operated by institutions from Poland.
Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes.
It briefly crested at a magnitude of 5.3 on the astronomical brightness scale.
Incredibly, the dying star was 7.5 billion light-years away.

Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away.

TORTORA, a robotic wide-field optical camera operated in Chile with Russian-Italian collaboration, also caught the early light. TORTORA's rapid imaging provided the most detailed look yet at visible light associated with a burst's initial gamma-ray blast.






 

A powerful jet from the Bootes constellation was directed at Earth. Image credit: NASA
Immediately after the blast, Swift's UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event.
Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star's core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.
The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider.

 
Gamma-ray bursts are the Universe's most luminous explosions.
Image credit: NAS
"It's this wide jet that Swift usually sees from other bursts," Racusin explained. "Maybe every gamma-ray burst contains a narrow jet, too, but astronomers miss them because we don't see them head-on."
 

Such an alignment occurs by chance only about once a decade, so a GRB 080319B is a rare catch.
 

Could then such a gamma-ray destroy life on Earth? That depends on the nature of the burst and its location.
 

There are two type of gamma-ray bursts. 

There is a longer, brighter burst and a "short-hard" burst, which lasts less than a second but seems to give off more radiation than a longer burst.
 

If a gamma-ray happened inside the Milky Way, its effects on Earth would be much longer lasting.
 

These bursts of radiation reach the Earth's atmosphere and cause free oxygen and nitrogen atoms to bang together, and some recombine into ozone-destroying compounds called nitrous oxides.
Short gamma-rays could be caused by dense neutron stars or colliding black holes.
According to researchers, such stellar collisions might occur once every 100 million years in any given galaxy. At this rate, Earth would have been hit by several of these short-hard events over the course of its 4.5-billion-year history.
It is possible that a short gamma-ray was responsible for at least one planet-wide extinction event in the past.
We do not know with certainty what would have happened if the powerful jet from the Bootes constellation would have hit our planet, but we can be thankful it missed our planet.

Monday, November 7, 2011

Important Astronomical Events in 2012

 
March 3 - Mars at Opposition. The red planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Mars. 

March 14 - Conjunction of Venus and Jupiter. The two bright planets will be within 3 degrees of each other in the evening sky.  

April 15 - Saturn at Opposition. The ringed planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Saturn and its moons.  

May 20 - Annular Solar Eclipse. The path of annularity will begin in southern China and move east through Japan, the northern Pacific Ocean, and into the western United States. A partial eclipse will be visible throughout parts of eastern Asia and most of North America. (NASA Map and Eclipse Information)    

June 5, 6 - Transit of Venus Across the Sun. This extremely rare event will be entirely visible throughout most of eastern Asia, eastern Australia, and Alaska. A partial transit can be seen in progress at sunrise throughout Europe, western Asia, and eastern Africa. A partial transit can be seen in progress at sunset throughout most of North America, Central America, and western South America. The next transit will not take place until the year 2117. (NASA Transit Information | NASA Transit Map)        

August 24 - Neptune at Opposition. The blue planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view Neptune. Due to its distance, it will only appear as a tiny blue dot in all but the most powerful telescopes.  

September 29 - Uranus at Opposition. The blue-green planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view Uranus. Due to its distance, it will only appear as a tiny blue-green dot in all but the most powerful telescopes.  

November 27 - Conjunction of Venus and Saturn. These two bright planets will be within 1 degree of each other in the morning sky. Look to the east around sunrise.  

December 3 - Jupiter at Opposition. The giant planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Jupiter and its moons.  

December 21 - December Solstice. The December solstice occurs at 11:12 UTC. The South Pole of the earth will be tilted toward the Sun, which will have reached its northernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the northern hemisphere and the first day of summer (summer solstice) in the southern hemisphere.

    Wednesday, October 12, 2011

    Mini-moon: Smallest full moon of 2011 rises tonight

    Mini-moon: Smallest full moon of 2011 rises tonight

    Moon
    Bigger isn't always better.
    So tonight, why not get outside and look up at what astronomers say will be -- or rather, will appear to be -- the smallest full moon of 2011?
    According to astronomy expert Joe Rao, the smallest full moon of 2011 will be 12.3% smaller than the largest full moon of 2011, which occurred in March.
    The difference in perceived size is due to the moon's elliptical orbit. In March, the moon turned full just minutes away from the perigee of its orbit, or the point at which the moon is closest to Earth. Tonight's full moon will reach its fullness peak at 7:06 p.m. PDT; just a few hours later, at 5 a.m., the moon will hit the apogee of its orbit, or point at which the moon is the farthest from Earth.
    The perigee and apogee of the moon's orbit change each month, but in March the moon was 221,565 miles from Earth when it appeared to be full; tonight, the moon will be 252,546 miles from  Earth when it appears full.
    For those who don't have a calculator handy, that's a difference of 30,981 miles.
    So will we be able to notice the difference?
    "I really should say no, because 12% is just not that much of a change,"said Steve Edberg, an astronomer at the Jet Propulsion Laboratory in an interview with The Times. "But to someone who was paying close attention and remembered what the moon looked like in March, there's a difference. And there is quite a noticeable difference in pictures."
    The October full moon is traditionally called the hunter's moon, and like the harvest moon -- which occurred in September -- will appear to be full for longer than normal. All this light could have helped hunters in their pursuit of prey.
    One thing we're wondering: What does one call the smallest full moon of the year? News outlets dubbed the largest moon of the year a super-moon.  Perhaps we should call tonight's underwhelming lunar display a mini-moon.
    http://latimesblogs.latimes.com/nationnow/2011/10/mini-moon-smallest-full-moon-of-2011-rises-tonight.html