The Astronomy Thread

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carl stromberg
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The Astronomy Thread

Post by carl stromberg »

This is the new astronomy thread.

A satellite is going to crash into the Earth tomorrow.

http://www.bbc.co.uk/news/science-environment-15021323

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22 September 2011 Last updated at 15:53


Nasa refines satellite crash time

By Paul Rincon Science editor, BBC News website



The US space agency (Nasa) says that its out-of-control climate satellite is expected to crash to Earth sometime on Friday evening (GMT).

There is still much uncertainty over when and where the satellite will re-enter the atmosphere.

Experts say they will get a more precise idea in the last 12 hours before the satellite is due to return.

The US space agency says the risk to life from the Upper Atmosphere Research Satellite (UARS) is 1 in 3,200.

Satellite and space expert Dr Stuart Eves stressed the large uncertainties involved in tracking the "decay" of satellite orbits (their slow fall back into the Earth's atmosphere).

Using the most recent determination of UARS' orbit - taken in the early hours of this morning - Dr Eves and a colleague have come up with their own projections of the satellite's final descent. But he explained that a spacecraft's orbit lifetime could only be estimated to about 10% accuracy.

This translates to a six-hour window either side of the expected decay which, based on a range of probabilities, would see the spacecraft splash down in the Southern Ocean.

But given the 10% accuracy figure, and the fact that UARS takes about one-and-a-half hours to complete an orbit of Earth, the satellite could come down during one of four possible orbits of Earth on Friday evening/Saturday morning.

And a number of different estimates could be produced depending what software is used to model the satellite's decay, Dr Eves explained.

Satellite decays can be affected by a number of different factors, such as the shape of the satellite and its unpredictable tumbling, as well as heating of the Earth's atmopshere by ultraviolet radiation from the Sun.

This can make the atmosphere expand, causing UARS to fall to Earth faster than expected.

But other conditions could see the satellite stay in space for longer than anticipated.

Nasa says that debris could fall across an area 400-500km (250-310 miles) long.

In its latest update, the space agency said only that the spacecraft would "not be passing over North America" when it is expected to be pulled through the atmosphere to Earth.

The spacecraft could pass over Britain during its final passes over the planet.

Given that some 70% of the Earth's surface is covered by water, a splash-down for the debris seems most likely. But there remains a real possibility that some debris could fall on land.

UARS could land anywhere between 57 degrees north and 57 degrees south of the equator - most of the populated world.

The 1 in 3,200 risk to public safety is higher than the 1 in 10,000 limit that Nasa aims for.

But agency officials stress that nobody has ever been hurt by objects re-entering from space. And Dr Eves points out that meteorites were falling to Earth all the time.

The US satellite was deployed in 1991 from the space shuttle Discovery on a mission to study the make-up of Earth's atmosphere, particularly its protective ozone layer.

Nasa has warned members of the public not to touch any pieces of the spacecraft which may survive the re-entry, urging them to contact local law enforcement authorities.
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Re: The Astronomy Thread

Post by Capt. Sir Dominic Flandry »

Someone in Italy (I don't think it was Alessandra) has made some neutrons go faster than the speed of light.
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Re: The Astronomy Thread

Post by Harvey Wallbanger »

8)
http://www.space.com/13383-spellbinding ... hotos.html

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Spectacular Northern Lights Display Leaves Skywatchers Spellbound
by Tariq Malik, SPACE.com Managing Editor
Date: 25 October 2011 Time: 10:13 AM ET
A dazzling aurora light show amazed skywatchers across North America, from Canada to Arkansas, and other northern regions Monday night (Oct. 24), painting the sky with striking green and even rare red hues.

The aurora display, also known as the northern lights, was touched off by a wave charged particles unleashed by a massive sun storm on Saturday, which took two days to reach Earth, according to the Space Weather Prediction Center operated by the National Weather Service and NOAA.

"These were the most vibrant I've ever seen," Canadian skywatcher Colin Chatfield of Saskatoon, Saskatchewan told SPACE.com in an email. "I was also able to see red with the naked eye, which I've never seen before either. Simply put, they were amazing."

A dazzling aurora light show amazed skywatchers across North America, from Canada to Arkansas, and other northern regions Monday night (Oct. 24), painting the sky with striking green and even rare red hues.

The aurora display, also known as the northern lights, was touched off by a wave charged particles unleashed by a massive sun storm on Saturday, which took two days to reach Earth, according to the Space Weather Prediction Center operated by the National Weather Service and NOAA.

"These were the most vibrant I've ever seen," Canadian skywatcher Colin Chatfield of Saskatoon, Saskatchewan told SPACE.com in an email. "I was also able to see red with the naked eye, which I've never seen before either. Simply put, they were amazing."

Auroras are caused when charged solar particles hit Earth's atmosphere, causing a glow as the particles collide. The particles are funneled down over Earth's poles causing the northern lights, or aurora borealis, in the north. Aurora displays over the South Pole are known as the Southern Lights, or aurora australis. [See the spellbinding October aurora photos]

Photographer Shawn Malone in Marquette, Mich., expected a good aurora light show, but was still surprised by the sheer brilliance of Monday night's northern light show.

" had taken a few pics, went back to the car to change lenses, and when I looked up the sky was on fire," Malone said. "To the north there was this huge curtain that sent beams overhead to a corona in which I had to turn to the south to photograph. That's when I noticed the reds and pinks starting to happen. From there the lights were every which direction. It was hands down the best northern lights I've seen since the great storm of November 2004."
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Re: The Astronomy Thread

Post by carl stromberg »

There is a blue moon this evening - but it is cloudy!
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Re: The Astronomy Thread

Post by mcbride007 »

Thick cloud cover here in the UK so I did not see the Blue Moon. :(
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