Space Shuttle Atlantis Over The Andes Mountains.

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Image Credit: NASA
Flying above the Andes Mountains near the border of Argentina and Chile, the space shuttle Atlantis is shown making its relative approach to the International Space Station. This image was taken from ISS, during the STS-132 shuttle mission on 16 May 2010. 

Atlantis was named after the RV Atlantis, an exploration sailing ship of the Woods Hole Oceanographic Institute. 

In it's lifetime, Atlantis had travelled almost 126 millon miles or 203 millon km, which is nearly 525 times the distance from the Earth to the Moon.

Light Pillars, An Optical Phenomenon Beyond Imagination.

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  Light pillars over Laramie, Wyoming, USA in a winter night. Photo by Christoph Geisler/ CC BY 
Sometimes nature creates more spectacular scenes than anything we can dream up in science fiction and Light pillars are definitely one of them.

Usually visible during very cold weather, light pillars are an atmospheric optical phenomenon where columns of light can be seen beaming directly upwards from a light source.

  Light Pillars in North Bay Ontario, Canada. Photo by Timmyjoeelzinga/ CC BY
This majestic phenomenon occurs when lights, both from natural and artificial sources interact with the numerous flat ice crystals in the atmosphere. These flat crystals are hexagonal in shape and float horizontally in the air close to Earth’s surface.

Photo by V1adis1av/ CC BY
Together the surface of million of tiny crystals act as a mirror and reflect light downwards to our eyes or camera. As the ice crystals float in the air at different heights, it creates a light column from the source.

Let's interpret this with a simple example, have you ever used a torch or flashlight in a dusty place? if yes, then you surely have seen the light beam emanating from the torch.

In a clean room we don't see this phenomenon but in not so clean room we do. It occurs only in dusty places because the dust floating in the air reflect the light and create a column. 

 Light Pillars during a cold January winter night in Stockholm, Sweden. Photo by Raitisfreimanis/ CC BY
That's the same thing happens in Light pillars, just, in this case, ice plays the role of dust. One more plus point of ice is it reflects the exact same colour of the light source, which makes light pillars more alive.

Top 12 Most Astonishing Images Taken by Cassini.

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A still image from Cassini's Grand Finale film. Credit: NASA/JPL-Caltech/Space Science Institute
Launched on October 15, 1997, Cassini entered Saturn's orbit after a long interplanetary voyage on July 1, 2004. For the last 13 years, NASA's Cassini spacecraft has returned thousands of stunning images and made many scientific discoveries about the giant planet, its rings, moons and atmosphere. As Cassini begins its #GrandeFinale, here are top 12 most astonishing images highlighting its epic journey. 

12. A Giant Red Rose. 

Image Credit: NASA/JPL-Caltech/Space Science Institute
The spinning vortex of Saturn's north polar storm resembles a deep red rose surrounded by green foliage. This false-colour image was made by using a combination of spectral filters sensitive to wavelengths of near-infrared light.

11. Bull's-eye Moons.
Image Credit: NASA/JPL-Caltech/Space Science Institute
Like a cosmic bull's-eye, Enceladus and Tethys line up almost perfectly for Cassini's cameras. The image was obtained at a distance of approximately 2.1 million kilometers from Enceladus and 2.6 million kilometers from Tethys.

10. The Yin and Yang moon.
Image Credit: NASA/JPL-Caltech/Space Science Institute
In 2007, the Cassini captured this high-resolution view of the bright trailing hemisphere of Iapetus. Iapetus has also called the yin and yang of the Saturn moons because its leading hemisphere is dark and its trailing hemisphere is bright.

09. The Triple crescent Moons.
Image Credit: NASA/JPL-Caltech/Space Science Institute
A single crescent moon is a familiar sight in Earth's sky, but with Saturn's many moons, we can see three or even more. The three moons shown here are Titan Mimas and Rhea.

08. Tethys tops Saturn.
Image Credit: NASA/JPL-Caltech/Space Science Institute
An illusion of perspective, Saturn’s moon Tethys seems to hang above the planet's north pole. The image was taken with the Cassini's wide-angle camera on Jan. 26, 2015.

07. An Ice World with an Ocean.
Image Credit: NASA/JPL-Caltech/Space Science Institute
Dramatic plumes, both large and small, spray water ice and vapour from many locations along the famed 'tiger stripes' near the south pole of Saturn's moon Enceladus. 

06. A Glorious view.
Image Credit: NASA/JPL-Caltech/Space Science Institute
Cassini delivered this glorious view of Saturn, on October 17, 2012, while the spacecraft was in Saturn's shadow. Since images like this can only be taken while the sun is behind the planet, there are only two times Cassini has captured a view like this.

05. Saturn approaching its northern Summer.
Image Credit: NASA/JPL-Caltech/Space Science Institute
This Natural view shows Saturn's northern hemisphere and its shadow on the rings as Saturn’s season advances toward northern summer. Saturn's year is nearly 30 Earth years long, and during its long time there, Cassini has observed winter and spring in the north, and summer and fall in the south. 

04. The Uranus from Saturn’s orbit.
Image Credit: NASA/JPL-Caltech/Space Science Institute
On April 11, 2014, Cassini captured this rare image of the blue ice-giant planet Uranus [indicated by a arrow] in the distance beyond Saturn’s rings. When this view was obtained, Uranus was nearly at a distance of 28.6 astronomical units from Saturn.

03. Catching the Tail.

Image Credit: NASA/JPL-Caltech/Space Science Institute
On February 25, 2011, Cassini captured this true-colour view where the huge storm was moving through the atmosphere in Saturn's northern hemisphere formed a tail that wrapped around the planet.

02. Earth as seen from Saturn.
Image Credit: NASA/JPL-Caltech/Space Science Institute
The tiny blue light indicated by the arrow is Earth as seen from Saturn, 1.44 billion kilometres [898 million miles] away. This iconic image was taken on July 19, 2013, by the wide-angle camera on Cassini spacecraft.

01. Saturn in a moment of Solar eclipse.
Image Credit: NASA/JPL-Caltech/Space Science Institute
As Saturn eclipsing the sun, Cassini captured this majestic moment on September 15, 2006, from its orbit. The night side of Saturn is seen to be partly lit by the light reflected from its own ring system. The rings themselves appear quite bright and slightly scattering the sunlight. Far in the distance, visible on the image left just above the bright main rings, [covered by a black box] is the almost ignorable presence of our home planet Earth. 

On this historic moment NASA also released a short animated video describing Cassini's Grand Finale.

When Science Meets Nature, This Happens.

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When science meets with nature, it always creates something special and this time it's created a rainbow.

The beautiful phenomenon happened during the RS-25 engine test conducted by NASA on Feb. 22, 2017, to collect performance data of the rocket engine which will help power the new Space Launch System [SLS] rocket to launch astronauts aboard the Orion spacecraft, deeper into space than ever before.

Shown mostly from the viewpoint of a drone, NASA also released a video of the test on its youtube channel.

article reference:-'s Marshall Center
credit:- NASA

10 Amazing Facts about the Ultimate High-Altitude Hike, Spacewalks.

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Image Credit: NASA
Spacewalks, which technically known as Extra-vehicular Activity [EVA] are the finest examples of human innovation and courage. During a spacewalk, astronauts witness a breathtaking view of Earth below them as they soar over the mountains, deserts, city lights, rivers and oceans experiencing a sunrise and a sunset in every 90 minutes. 

Spacewalks are mainly performed to carry out space station maintenance and science experiments outside the station, but sometimes it has also done to repair spacecraft and telescopes that are in space. So, here are the ten amazing facts about the ultimate high-altitude hike, spacewalks:-

1.Long training on Earth- 
Before launching to space, astronauts train for months and practice their spacewalks several times in an underwater simulated environment. Another way astronauts practice spacewalks is by using virtual reality. It's simulation looks and feels just like a spacewalk.

SM4 EVA Astronauts John Grunsfeld and Andrew Feustel practice installing Hubble’s new panchromatic imaging instrument, the Wide Field Camera 3, during final underwater training at the Neutral Buoyancy Laboratory at the Johnson Space Center in Houston, Texas. Image Credit: NASA.
2.Spacesuits, you can't dare to wear- 
During spacewalks, astronauts wear a spacewalking suit called Extravehicular Mobility Unit or EMU which acts as a life support system and protects them from the hazardous environment of space. While in space it weighs nothing, but on Earth these suits weighs around 280 pounds [127 kg], without the astronaut in it.

3.Preparation before a spacewalk takes hours- 

It takes almost 45 minutes to wear an EMU and even after putting it on, to get adapted to the lower pressure of the suit, an astronaut has to spend few more hours breathing pure oxygen before going outside of the space station. Breathing only oxygen also helps to get rid of all the nitrogen in an astronaut's body, which could cause body pain during the spacewalk.

4.How long they walk in space?
Usually, spacewalks last between 6 to 7 hours but can be extended to 8 hours, if necessary. The work timeline is designed to fulfil as many tasks as possible, as the astronauts have limited life support systems in the spacesuit.

Astronauts Steven L. Smith and John M. Grunsfeld are photographed during an EVA during the December 1999 Hubble servicing mission of STS-103. Image Credit: NASA.
5.Eating and Drinking- 
Before a spacewalk astronauts eat light, usually something like a protein bar, some fruits and water. Their spacesuits also have a drink bag inside, with a bite valve that allows ready access to water.

6.Why spacesuits only come in white?

The reason that spacesuits are white because white colour reflects heat in space as the same it does here on Earth. During spacewalks astronauts face a wide variety of temperatures. In direct sunlight, the temperature can go up to 275°F [135°C] and in Earth orbit, conditions can be as cold as -250°F [-121°C].

Astronauts F. Story Musgrave, left, and Donald H. Peterson float in the cargo bay of the Earth-orbiting space shuttle Challenger during their April 7, 1983 extravehicular activity on the STS-6 mission. Their "floating" is restricted via tethers to safety slide wires. Image Credit: NASA.

7.Safety during the walking-
Astronauts use safety tethers to stay close to their spacecraft. One end of the tether is hooked to the astronaut, while the other end is attached to the spacecraft. The safety tethers protect astronauts from floating away into space.

8.And the best part, they also have Jetpacks-

To move around freely in space without any safety tethers astronauts use a jetpack-like device called the Manned Maneuvering Unit [MMU]. It uses small jet thrusters to move and has a control on the armrest to direct.

Astronaut Dale A. Gardner, getting his turn in the Manned Maneuvering Unit, prepares to dock with the spinning WESTAR VI satellite during the STS-51A mission. Image Credit: NASA.
9.The first and the longest spacewalks-
The first person to go on an EVA was cosmonaut Alexei Leonov from Russia. It took place on March 18, 1965, and was 10 to 12 minutes long. The longest EVA was 8 hours and 56 minutes, performed by Susan J. Helms and James S. Voss on March 11, 2001.

10.The first spacewalk for an in-flight repair-

The first EVA where an astronaut performed an in-flight repair of a space shuttle was by American astronaut Steve Robinson on Aug. 3, 2005, during STS-114. Robinson removed two protruding gap fillers from space shuttle Discovery's heat-shield while the shuttle was docked to the International Space Station.

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What Happens When A Star Hits A Supermassive Black Hole?

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Supermassive black holes, with masses ranging from millions to billions of times the mass of our Sun, have such a huge gravity that once matter or energy gets close enough, it can not escape their grip and get pulled in. 

According to Einstein's general theory of relativity and also, most astronomers believe that black holes are cosmic singularities with no physical surface area, surrounded by an invisible gravitational barrier known as the event horizon.

While the supermassive black holes are thought to exist at the heart of almost all galaxies, including our own, there is another opinion based on modified theories of general relativity, suggest that instead of a black hole there is a central massive object that has somehow managed to avoid gravitational collapse to a singularity and have hard surface area.

When a star hits a black hole.
So, what happens when a star falls into a supermassive black hole? Does it swallowed entirely by the black hole or crash into the hard surface of a massive object and get destroyed. 

Pawan Kumar an astrophysicist from the University of Texas at Austin along with his team, come up with a test to determine which theory is correct. "Our whole point here is to turn this idea of an event horizon into an experimental science, and find out if event horizons really do exist or not," said Pawan Kumar.

The researchers tried to figure out what would be the scenario if a star hit the hard surface of a supermassive object at the center of a galaxy, the star’s gas would envelope the object, shining visibly for months or perhaps even years. Once they knew what to search for, the team calculated how often this should be seen in the nearby galaxies.

Then they searched a recent archive of telescope observations made by Pan-STARRS telescope in Hawaii. During a period of 3.5 years, the telescope scanned half of the northern hemisphere sky, looking for 'transients', things that glow for a while and then fade. 

Their aim was to find transients with the expected light signature of a star falling toward a supermassive object and hitting a hard surface. "Given the rate of stars falling onto black holes and the number density of black holes in the nearby universe, we calculated how many such transients Pan-STARRS should have detected over a period of operation of 3.5 years. It turns out it should have detected more than 10 of them if the hard-surface theory is true," explains one of the team, Wenbin Lu.

So, did they find any?
No, they did not find any transients with that expected light signature of a star hitting a supermassive object. It means that when a star falls into a supermassive black hole, it just simply pass the event horizon and vanishes completely.

"Our work implies that some, and perhaps all, black holes have event horizons and that material really does disappear from the observable universe when pulled into these exotic objects, as we've expected for decades. General Relativity has passed another critical test," says one of the researchers, Ramesh Narayan from the Harvard-Smithsonian Center for Astrophysics.

The researchers are now proposing to improve the test with a larger telescope, the Large Synoptic Survey Telescope, presently under construction in Chile. LSST will perform surveys like the Pan-STARRS telescope, but with much greater sensitivity.

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image credit:- nasa/jpl caltech
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