NASA Astronomy Picture of the Day 2015 April 20

Total Solar Eclipse over Svalbard

Going, going, gone. That was the feeling in Svalbard, Norway last month during a total eclipse of the Sun by the Moon. In the featured image, the eclipse was captured every three minutes and then digitally merged with a foreground frame taken from the same location. Visible in the foreground are numerous gawking eclipse seekers, some deploying pretty sophisticated cameras. As the Moon and Sun moved together across the sky – nearly horizontally from this far north – an increasing fraction of the Sun appears covered by the Moon. In the central frame, the Moon’s complete blockage of the disk of the Sun makes the immediate surroundings appear like night during the day. The exception is the Moon itself, which now appears surrounded by the expansive corona of the Sun. Of course, about 2.5 minutes later, the surface of the Sun began to reappear. The next total eclipse of the Sun will occur in 2016 March and be visible from Southeast Asia.


Two Photographers Set Out To Capture the Lost Night

Have you ever seen the Milky Way with your own eyes? You really should. It’s an experience both awesome and marvelous in the truest sense of those words. Sadly, thanks to light pollution, most people can’t just step outside at night, look up, and gaze through the streaking arm of our galaxy.

Filmmakers and astrophotographers Gavin Heffernan and Harun Mehmedinovic (featured here before) have launched a Kickstarter project called SKYGLOW that sets out to educate people on the ill effects of light pollution to our species and others, while inspiring us to reconnect with the same stars that have inspired our species for eons.

In the video above, a beautiful composite of stellar and urban time lapses, the pair imagine what the skies over Los Angeles would look like if we could see more than the glow of sodium vapor and aircraft strobes. That’s fantasy, sadly, but so is the idea of truly dark skies in most parts of the world: 

“For a lot of people, the idea of an incredible night sky is becoming more science fiction than ever before.”

According to Heffernan and Mehmedinovic, half of the light that we humans produce is pointed up at the night sky. This wastes energy. It wastes resources. It wastes the very splendor of the night sky. It’s as if we’ve taken an eraser made of photons and rubbed out each jewel in Earth’s starry canopy one by one. 

Most of us today live beneath skies that are only half night, and as Earth’s population grows in number and consumption there are fewer and fewer dark sky sanctuaries left. Let’s save them, so people like you and me and Heffernan and Mehmedinovic have something to look up to.

To learn more about the dark sky movement and the effects of light pollution, check out the International Dark-Sky Association. And to find out how you can support the SKYGLOW Kickstarter, check out the video below: 

In the Grip of the Scorpion’s Claw

Gripped in the claw of the constellation Scorpius sits the reflection nebula DG 129, a cloud of gas and dust that reflects light from nearby, bright stars. This infrared view of the nebula was captured by NASA’s Wide-field Infrared Survey Explorer, or WISE.

Viewed in visible light, this portion of the sky seems somewhat unremarkable. But in infrared light, a lovely reflection nebula is revealed. DG 129 was first catalogued by a pair of German astronomers, named Johann Dorschner and Joachim Gürtler, in 1963.

Credit: NASA/JPL-Caltech/UCLA


Space-X’s dramatic second barge landing attempt.

Seen here from two different perspectives, it’s agonisingly apparent how close the reusable Falcon 9 Rocket came to actually landing. Landing in quite a stable manner the rocket slowly teeters on the edge before sadly toppling over. 

Afterwards Gwynne Shotwell, Space-X’s president, mentioned the next landing attempt will probably be attempted on land to give the rocket more stability. 


Close Asteroid Flyby Tonight

Asteroid 2015 HD1 will pass by Earth tonight at 4:00 AM EDT.

I quote Bob King’s UT article, “a 50-foot-wide asteroid will hurdle just 0.2 lunar distances or 45,600 miles over your bed.

This asteroid was only discovered a few days ago and is now a member of a group of what people like me call “AHHH!-steroids”.

In all seriousness though, were HD1 to hit Earth, would it cause any damage?

Almost certainly not. It’s just not large enough. Friction with Earth’s thick atmosphere would cause it to burn and burst overhead. The most likely outcome of this would be a beautiful meteor shower.

(Image credit: Gianluca Masi)

A galactic cloak for an exploding star

The galaxy pictured here is NGC 4424, located in the constellation of Virgo. It is not visible with the naked eye but has been captured here with the NASA/ESA Hubble Space Telescope.

Although it may not be obvious from this image, NGC 4424 is in fact a spiral galaxy. In this image it is seen more or less edge on, but from above you would be able to see the arms of the galaxy wrapping around its centre to give the characteristic spiral form .

In 2012 astronomers observed a supernova in NGC 4424 — a violent explosion marking the end of a star’s life. During a supernova explosion, a single star can often outshine an entire galaxy. However, the supernova in NGC 4424, dubbed SN 2012cg, cannot be seen here as the image was taken ten years prior to the explosion. Along the central region of the galaxy, clouds of dust block the light from distant stars and create dark patches.

To the left of NGC 4424 there are two bright objects in the frame. The brightest is another, smaller galaxy known as LEDA 213994 and the object closer to NGC 4424 is an anonymous star in our Milky Way.

Credit: ESA/Hubble & NASA
Acknowledgement: Gilles Chapdelaine

Climate scientists join search for alien Earths

NASA initiative seeks to bolster interdisciplinary science in hunt for extraterrestrial life.

By Jeff Tollefson

The hunt for life beyond the Solar System is gaining new partners: NASA climatologists. After more than 30 years of studying Earth, a team at the NASA Goddard Institute for Space Studies (GISS) in New York will adapt its global climate model to simulate conditions on potentially habitable exoplanets. The effort is part of a broader push to identify Earth-like worlds that NASA will launch on 20 April at a meeting in Washington DC.

Already, the agency’s space-based Kepler telescope has pinpointed more than 1,000 alien planets by observing the brief interruption of starlight that signals a planet passing in front of its parent star. At least five of these planets are similar in size to Earth and located in the ‘habitable zone’, where liquid water could persist. The next step would be to detect light passing through exoplanet atmospheres, which could hold clues to conditions on these distant worlds.

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How to stop an asteroid:

It’s a question on many minds but contrary to common belief, stopping an asteroid from hitting Earth is actually surprisingly simple.

Step 1: Make a huge mirror

Step 2: Launch mirror into space

Step 3: Use mirror to reflect sunlight directly at target asteroid

Step 4: Profit

Why this works:

Einstein (who else?) discovered that light has momentum. This momentum allows light to push things, however lightly. With constant sunlight, things can be moved quite a bit.

Solar sails take advantage of this by reflecting light off their sails and gliding through space on the stolen momentum.

By altering an asteroids orbit gradually, it’s direction can be changed enough so that it will fly past Earth harmlessly.


This technique requires knowledge of the asteroid beforehand as the power of solar momentum lies in that it would be a constant force on the asteroid, the force in any given instant is too small to make any large, sudden changes to the asteroid’s path.

(Image credit: NASA/JPL)

Dark Matter May Be Less Mysterious Than We Thought

“Astronomers have been struggling for nearly 80 years to figure out what makes up the mysterious dark matter that pervades the universe. 

 A new paper appearing in Monthly Notices of the Royal Astronomical Societyargues that dark matter particles within a galaxy cluster known as Abell 3827, about 1.4 billion light-years from Earth, are responding to a force other than gravity.” 

Read more from National Geographic.