Nov 30, 2010

The outstanding beauty of the Milky Way

The Milky Way over Haleakala Crater on Maui. Click for a larger version. Photo by Wally Pacholka via National Geographic


Astronomers turn their telescopes to the unbounded beauty of the Milky Way.

Our galaxy is far larger, brighter, and more massive than most other galaxies. From end to end, the Milky Way's starry disk, observable with the naked eye and through optical telescopes, spans 120,000 light-years. Encircling it is another disk, composed mostly of hydrogen gas, detectable by radio telescopes. And engulfing all that our telescopes can see is an enormous halo of dark matter that they can't. While it emits no light, this dark matter far outweighs the Milky Way's hundreds of billions of stars, giving the galaxy a total mass one to two trillion times that of the sun. Indeed, our galaxy is so huge that dozens of lesser galaxies scamper about it, like moons orbiting a giant planet.

As a result of its vast size, the Milky Way can boast at least one planet with intelligent life. Giant galaxies like the Milky Way and the nearby, even larger Andromeda galaxy possess the power to create and retain a rich supply of iron, oxygen, silicon, magnesium, and other elements heavier than helium. Forged by the Milky Way's abundant stars, such heavy elements are the building blocks of terrestrial planets.

Nov 29, 2010

Clash of the Titan Galaxies

NGC 520 — also known as Arp 157 -- is actually a mashup of two gigantic galaxies. Credit: ESO
 Is this galaxy exploding? Although that’s what it might look like, this is actually two gigantic galaxies crashing into each other. NGC 520 — also known as Arp 157 — is a mashup of two huge galaxies, now combining into one. We can’t really watch the process, as it happens extremely slowly — over millions of years, and the whole process started about 300 million years ago. Apr 157 is about 100,000 light-years across and is now in the middle stage of the merging process, as the two nuclei haven’t come together yet, but the two discs have. The merger features a tail of stars and a prominent dust lane. NGC 520 is one of the brightest interacting galaxies in the sky and lies in the direction of Pisces (the Fish), approximately 100 million light-years from Earth.

This image was taken by the ESO Faint Object Spectrograph and Camera attached to the 3.6-metre telescope at La Silla in Chile.
You’d need a about a 4-inch telescope to see this 12th magnitude object yourself. Here’s the location: RA: 1h 24m 35.1s, Declination: +03° 47? 33?. Or put in those coordinates in Google Sky to see it there.
Source: ESO

Nov 26, 2010


Total lunar eclipse
WHEN: 21 December, 05:00 to 08:30

During totality the Moon is completely in the Earth's umbral shadow

A TOTAL ECLlPSE of the Moon takes place in the early hours of 21 December. Such an event can only happen when the Sun, Earth and Moon are perfectly aligned, Viewing the eclipse will be tricky since the Moon will be setting as the eclipse really gets underway.
The Earth's shadow has two parts due to the fact that the Sun isn't a point source of light as seen from Earth. The main 'dark' or umbral shadow is in the form of a cone stretching out behind the Earth in the opposite direction to the Sun, as shown in the diagram. Surrounding this is another region of less intense shadow known as the penumbra. Look back at the Sun from within the penumbral shadow and you'd see only part of the Sun's disc covered. In the umbral shadow, the entire Sun appears covered.
At the distance of the Moon, the cross-section of these two shadows appears as two concentric circles: all inner dark umbral circle about three times the apparent diameter of the Moon, surrounded by a fainter penumbral circle about five times the apparent diameter of the Moon. The Moon enters this bull's-eye cross-section on the morning of 21 December.
The penumbral eclipse starts at 05:27 GMT when the Moon is about 23° up in the west as seen from the centre of the UK. However, because the penumbral shadow isn't very dark, it doesn't much change the visual appearance of the Moon. Having said that, the left-hand edge of the Moon will begin to take on a subtly darker shade just before the Moon enters the darker umbral shadow at 06:32.
The main umbral part of the eclipse begins with the Moon 14° above the horizon, and this marks the start of the partial phase of the eclipse. Totality occurs at 07:40, when the Moon's entire disc will be immersed in the umbral shadow. Its altitude at this time will be just 5° and the sky will be starting to get bright.
The Moon never goes completely dark because some light from the Sun is refracted, or bent, as it passes through the Earth's atmosphere. The blue component of this light gets scattered, leaving mainly red to fill in the umbral shadow. The result will be a reddened Moon, close to the northwestern horizon. Mid-eclipse occurs at 08:12 and from the centre of the UK, the Moon sets soon after.

Geminid meteors
WHEN: Peak on 13/14 December 

THE GEMINIDS is  probably the finest meteor shower of the year with a dependable Zenithal Hourly Rate (ZHR) of around 100 meteors per hour. They all appear to emanate from a point in the sky known as the radiant, which in the case of the Geminids lies close to the star Castor, as shown in the chart. The shower is active from 6-19 December, with peak rates occurring in the early hours of 14 December, close to when the radiant is at its highest point in the sky.
The best way to observe the shower is to lie on a sunbed and look up at a large area of sky. Being December, it's important to make sure you wrap up warm before venturing outside for any length of time. Choose the darkest location you can find away from any lighting, lie back and wait. The only thing you need to enjoy the Geminids is your eyes and plenty of patience! Although you could see a meteor anywhere, looking in the direction of Orion for a couple of hours after midnight and then switching to look at Leo until dawn would be our recommendation.
The first quarter Moon will look gorgeous on the night of 13 December, sitting just 6° north of mag. -2.3 Jupiter. However, its light will drown out some of the early meteor. Thankfully, the Moon sets at around 00:30 on 14 December, and from this time until dawn is the best period to view the Geminids. The shower produces medium to slow meteors with a good proportion of bright trails. This means that the Geminids make excellent photographic subjects.

Asteroid 7 Iris and M67
WHEN: Visible all December; view around midnight 

THE ASTEROID 7 IRIS  will be located in the constellation of Cancer the Crab throughout December and will pass quite close to the mag. +6.9 open star cluster M67. A collection of stars loosely held together by their mutual gravity, this object is one of the more ancient open clusters in our Galaxy, and is thought to be around 4 billion years old.
lris brightens from mag. +8.9 at the start of December to +8.3 by the end and should be easy to pick out with binoculars or a small telescope using a low-power eyepiece. This is a fairly sparse region of the sky so it shouldn't be too difficult to spot Iris as it moves from day to day among the background stars. The best way to confirm you've seen it is to observe the suspected region several days apart, drawing or photographing the main 'stars' you can see. If one of those stars moves between your observations then that should be Iris.
The asteroid's track swings quite close to M67, taking it within a degree of the cluster's centre between 13- 25 December. At its closest approach on 2L December, it sits about 45 arcminutes from the cluster's centre, unfortunately coinciding with the full Moon!

Nov 25, 2010

Viewing the aurora from space: Earth aurora and Saturn Aurora

All images via NASA

You’ve seen amazing images of the Aurora Borealis and its counterpart, the Aurora Australis, but now you have a chance to see them as never before: from space. If you think the view down on Earth is incredible beyond words, wait until you see what these natural light phenomena look like from the International Space Station and through the lens of the Hubble Telescope.

Auroras are created when charged particles from the sun, called the solar wind, interact with the magnetic shield that surrounds our planet (and other planets as well). On Earth, this magnetic shield, called the magnetosphere, protects us from radiation by pushing the solar wind around it. Electromagnetic waves and electric fields are created, then transfer their energy into electrons that interact with oxygen and nitrogen to create the beautiful natural light display we know as Aurora.

Beautiful Aurora Borealis
The Aurora Borealis was named by Pierre Gassendi in 1621 after Aurora, the Roman goddess of dawn, and Boreas, the Greek name for north wind. The Cree called it the “Dance of the Spirits.” 

< In this picture of the Aurora Borealis, the Manicouagan Impact Crater, located in northern Canada, can be seen 300 km below. International Space Station Science Officer Don Pettit said that “changing auroras appeared to crawl around like giant green amoebas” in orbit.

Auroras become more visible the closer one gets to either the north or south poles. At these extreme ends of the Earth, they may appear high up in the sky overhead, but farther away, they seem to rise up from the horizon as a green glow with tinges of red, like the “red crown” of Aurora Australis, seen in the picture below. This image almost looks like a treasure map: follow the trail and get to what looks like a legendary castle from space.
Follow the Trail

Another image of the southern lights almost looks like loops of light created by huge glow sticks (Below); 
Loop de loop

and here’s the amazing view that the astronauts at the International Space Station get to see:
An Astronaut’s View

In the image below, the view of the Aurora Borealis from the International Space Station includes the shining lights of Finland, Russia, Estonia and Latvia. The Praesepe or Beehive Cluster in the constellation Cancer can be seen to the lower right of the moon, with Saturn to the right of that.
Take Me To the Moon

And if you thought Auroras were spectacular on Earth, check out these two pictures of amazing light shows on Jupiter and Saturn:

Auroras on Jupiter and Saturn

Aurora on Jupiter
Aurorae on Saturn  

 This incredible image of Saturn features its famed rings and Auroras at either end of the planet.

Nov 22, 2010

Beginners' guide to: Your first five sights

Beginners' guide to ...
  Your first five sights

Tooled up and ready to go, but don't know where to aim your scope? Here's our list of the top sights.

What are the best objects to aim at for your first nights at the telescope? Where you need to look in the night sky to find them. How you can get the most out of your first Foray into stargazing

The long winter nights mean it's a great time of year for stargazing, with the sky filled with some real celestial gems. If you've just bought a telescope or have asked for one, you'll no doubt want to get out there and start using it. However, faced with the countless points of light in the night sky, it can be a daunting task to decide what to aim your telescope at first.
To make sure you're suitably impressed, we've highlighted five top sights that arc around at the moment. We've explained where and when to search for them, and what to look for. This list will also give you a good taste of the range of objects you can point your telescope at.
Heading up our list is the Moon – the best place for any fledgling astronomer to start is our nearest celestial neighbor, You haven't really seen this familiar celestial body until you've viewed it with a telescope; its rugged, crater- marked surface will keep you coming back to your new scope for more.
You'll then need to bag yourself a planet and Jupiter, the largest of them all, will be a stunning sight. We then take you to deep space and the famous Orion nebula, a huge cloud of gas and dust hanging in Orion's Sword. Indeed, a relatively cheap telescope with an aperture of 3 to 6 inches will show you a wide variety of astronomical objects, and our final two targets are a distant galaxy and a pair of star clusters.
You could just rush outside and get going. But, with a little preparation, your session can be even more enjoyable. Once you're at the scope, with your eye properly adjusted to the dark after 20 minutes or so outside, you're ready to go.
What you won't see are grand, colorful objects that look like the stunning space images you see in books. However, what you do get is an amazing feeling as you find the e incredible objects for yourself. 

Your first telescope targets

Ready? Take aim ... Go! Read on to find the top five astronomical objects for beginners

The moon
Constellation: It doesn't stay in the same place but it's hard to miss
When to view: 8 to 17 December and 8 to 17 January
These dotes cover the waxing phases of the Moon in the evening skies, from the date when it is first seen as a thin crescent emerging after sunset. The reason you want to look at this time is because the terminator is visible. This is the line between the lighted side and the dark side of the Moon and the place where the Sun's light catches the craters and mountain ranges, thus casting amazing shadows across the lunar surface.

Constellation: moving from Aquarius into Pisces in the south
When to view: as soon as it's dark
Jupiter is unmistakable as there are no bright stars in the area where it sits. Through a small telescope, you can see the planet as a disc with several dark bands of its atmosphere. You may also see Jupiter's four largest moons as points of light either side of the planet.

Constellation: Orion
When to view: from 9pm at the start of December
Orion Nebula
The Orion Nebula, numbered 42 in the famous Messier Catalogue of deep-sky objects, is a 'must' for observing the winter skies. The Orion Nebula is just visible to the unaided eye as a misty patch, but even the smallest of scopes will start to reveal the sweeping structure of this stellar nursery. You will see it as a wonderful curving cloud of dust and gas.

Constellation: Andromeda
Andromeda Galaxy M31
When to view: as soon as it's dark, high in the sky
M31 is found by star-hopping from the nearby asterism, the Great Square of Pegasus. This will appear as a misty patch to the eye but is actually a giant, spiral island of stars, similar to our own Milky Way Galaxy. What is so impressive about the Andromeda Galaxy is that what you are looking at sits at around 2.75 million light-years away - a staggering distance.

Constellation: Perseus
When to view: as soon as it's dark
The Sword Handle will be very high in the east and moves almost overhead through the night. To find the Sword Handle, locate the 'W'-shape of Cassiopeia and work from there. In a darker location, it's just visible with the unaided eye. With a small telescope it's a wondrous sight of two amazing, roundish concentrations of hundreds of stars.

Nov 21, 2010

ISS crew captures spectacular view of earth’s atmosphere

A breathtaking new image taken by astronauts on the International Space Station clearly shows the various layers of Earth's atmosphere during sunset over the Indian Ocean.   

A brilliant sequence of colors in the image denotes each of the layers of Earth's atmosphere, which are visible here because the picture was taken while the space station had an edge-on, or limb, view of the Earth. From this vantage point, the Earth's curvature can also be made out.
The troposphere — the lowest layer of Earth's atmosphere and the one in which humans dwell and weather occurs — appears in deep oranges and yellows. The troposphere can extend from the planet's surface to a height between 3.5 to 12.5 miles (6 and 20 km).
This lowest layer contains more than 80 percent of the mass of the atmosphere and almost all of the water vapor, clouds, and precipitation.
Several dark cloud layers are visible within this layer in the image. Variations in the colors are due mainly to varying concentrations of either clouds or aerosols (airborne particles or droplets).
Next up is the stratosphere, which appears as a pink to white region above the clouds. This atmospheric layer generally has little or no clouds and extends up to approximately 30 miles (50 km) above the Earth's surface.
The stratosphere is also home to the layer of ozone that protects the Earth's surface and the creatures that live on it from the sun's harmful ultraviolet rays.
Above the stratosphere, blue layers mark the upper atmosphere (including the mesosphere, thermosphere, ionosphere, and exosphere) as it gradually fades into the blackness of outer space.
The astronaut aboard the space station was facing west when they snapped this picture. Astronauts in low-Earth orbit see 16 sunrises and sunsets every day due to their high orbital velocity (more than 17,000 mph, or 28,000 kph).

Nov 14, 2010

Aurora Alert! Solar Flare Heading Our Way!

This image shows a three and a half hour (0000 - 0330 UT) time lapse movie of the flare and filament event. Credit: NASA/SDO

An active sunspot (1123) erupted on (Nov. 12th), producing a C4-class solar flare and apparently hurling a filament of material in the general direction of Earth. Coronagraph images from the Solar and Heliospheric Observatory (SOHO) and NASA’s twin STEREO spacecraft show a faint coronalsun-Earth line. The cloud could deliver a glancing blow to Earth’s magnetic field sometime on Nov. 14th or 15th. High latitude sky watchers could see auroras on those dates. 
New sunspot 1123 in the Sun's southern hemisphere is crackling with C-class solar flares. Credit: SDO/HMI.

 Here’s a look at the two sunspots currently visible on the Sun.'s Most Recent Observing Stories blog

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