New Insights on How Spiral Galaxies Get Their Arms

Spiral galaxies are some of the most beautiful and photogenic residents of the universe. Our own Milky Way is a spiral. Our solar system and Earth reside somewhere near one of its filamentous arms. And nearly 70 percent of the galaxies closest to the Milky Way are spirals.

But despite their common shape, how galaxies like ours get and maintain their characteristic arms has proved to be an enduring puzzle in astrophysics. How do the arms of spiral galaxies arise? Do they change or come and go over time?

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(Source: christinetheastrophysicist)

“A sense of wonder is not our only starting point. It can also be our destination.”

Sharman Apt Russell | Anatomy of A Rose: Exploring the Secret Life of Flowers

Must Watch: Neil deGrasse Tyson Moderates a Debate on Nothingness

Its been said that something cannot come from nothing, but is “nothing” even conceivable?

If you’ve got two hours to kill on nothing, this is the video for you.

(Source: divineirony, via fyeah-degrasse-tyson)

(Source: facebook.com)

Galaxy Collisions: Simulation vs Observations

The folks over at NASA apod just put up an awesome galaxy collisions, simulations and observations video for the public. I made a little gif set to go along with the video which can be found here.

What happens when two galaxies collide? Although it may take over a billion years, such titanic clashes are quite common.

Images Credit: NASA, ESA; Visualization: Frank Summers (STScI);

Simulation: Chris Mihos (CWRU) & Lars Hernquist (Harvard).

Since galaxies are mostly empty space, no internal stars are likely to themselves collide. Rather the gravitation of each galaxy will distort or destroy the other galaxy, and the galaxies may eventually merge to form a single larger galaxy.

Expansive das and dust clouds collide and trigger waves of star formation that complete even during the interaction process. Pictured above is a computer simulation of two large spiral galaxies colliding, interspersed with real still images taken by the Hubble Space Telescope.

Our own Milky Way Galaxy has absorbed several smaller galaxies during its existence and is even projected to merge with the larger neighboring Andromeda galaxy in a few billion years.

(Source: ikenbot)

Alien Planet Documentary

— Explore an Earth-like alien planet 6.5 light years away, named Darwin IV, with two well equipped robotic probes called Leo (the risk-taker) and Ike (the more cautious one).

Above are only a few of the exciting creatures you will encounter.
— Watch it here

(Source: the-science-llama)

What is Magnetar?

A magnetar is a type of neutron star with an extremely powerful magnetic field, the decay of which powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays. The theory regarding these objects was proposed by Robert Duncan and Christopher Thompson in 1992, but the first recorded burst of gamma rays thought to have been from a magnetar was detected on March 5, 1979. During the following decade, the magnetar hypothesis has become widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs).

Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter and have a greater mass than the Sun. The density of the interior of a magnetar is such that a thimble full of its substance would have a mass of over 100 million tons. Magnetars are differentiated from other neutron stars by having even stronger magnetic fields, and rotating comparatively slowly, with most magnetars completing a rotation once every one to ten seconds, compared to less than one second for a typical neutron star. This magnetic field gives rise to very strong and characteristic bursts of X-rays and gamma rays. The active life of a magnetar is short. Their strong magnetic fields decay after about 10,000 years, after which activity and strong X-ray emission cease. Given the number of magnetars observable today, one estimate puts the number of inactive magnetars in the Milky Way at 30 million or more.

Starquakes triggered on the surface of the magnetar disturb the magnetic field which encompasses it, often leading to extremely powerful gamma ray flare emissions which have been recorded on Earth in 1979, 1998, and 2004.

Magnetars, the Most Magnetic Stars In the Universe

“We only know of about 10 magnetars in the Milky Way galaxy.” remarked Dr. Peter Woods of the Universities Space Research Association. “If the antics of the magnetar we are studying now are typical, then there very well could be hundreds more out there.” NASA research has suggested there may be far more magnetars than previously thought.

Observing the explosions from these celestial bodies has been tricky. The answer lies in the timing. So how do the researchers observe what has never been seen? Leave it to NASA to develop the perfect piece of equipment to handle the job.

The Rossi X-ray Timing Explorer (RXTE), launched in December 1995 from Kennedy Space Center, Fla., was designed to observe fast-moving neutron stars, X-ray pulsars and bursts of X-rays that brighten the sky and disappear.

Some pulsars spin over a thousand times a second. A neutron star generates a gravitational pull so powerful that a marshmallow impacting the star’s surface would hit with the force of a thousand hydrogen bombs.

Magnetars, the most magnetic stars known, aren’t powered by a conventional mechanism such as nuclear fusion or rotation, according to Dr. Vicky Kaspi. “Magnetars represent a new way for a star to shine, which makes this a fascinating field,” said Kaspi.

Although not totally understood yet, magnetars have magnetic fields a thousand times stronger than ordinary neutron stars that measure a million billion Gauss, or about a hundred-trillion refrigerator magnets. For comparison, the Sun’s magnetic field is only about 5 Gauss.

Image 1 | Artist’s conception of a magnetar, with magnetic field lines

Image 2 | Magnetar SGR 1900+14 is in the exact center of the image, which shows a surrounding ring of gas seven light-years across in infrared light, as seen by the Spitzer Space Telescope. The magnetar itself is not visible at this wavelength, but it has been seen in X-ray light.

Image 3 | On 27 December 2004, a burst of gamma rays arrived into the Solar System from SGR 1806-20 (artist’s conception shown). The burst was so powerful that it had effects on Earth’s atmosphere, at a range of about 50,000 light years.

(Source: atomstargazer, via atomstargazer)

Galactic Habitable Zone

One of our Sun’s unusual features is its orbit around the center of the galaxy, which is significantly less elliptical (“eccentric”) than those of other stars similar in age (and therefore metallicity, or proportion of an object’s chemical composition other than hydrogen and helium) and type and is barely inclined relative to the Galactic plane. This circularity in the Sun’s orbit prevents it from plunging into the inner Galaxy where life-threatening supernovae are more common. Moreover, the small inclination to the galactic plane avoids abrupt crossings of the plane that would stir up the Sun’s Oort Cloud and bombard the Earth with life-threatening comets.

In fact, the Sun is orbiting very close to the “co-rotation radius” of the galaxy, where the angular speed of the galaxy’s spiral arms matches that of the stars within. As a result, the Sun avoids crossing the spiral arms very often, which would expose Earth to supernovae that are more common there. These exceptional circumstances may have made it more likely for complex life and human intelligence to emerge on Earth. According to Guillermo Gonzalez (an astronomer at Iowa State University), fewer than five percent of all stars in the galaxy enjoy such a life-enhancing galactic orbit. Other astronomers point out, however, that many nearby stars move with the Sun in a similar galactic orbit.

The Sun resides in a pancake region of the Galaxy called the “disk” with a strong concentration of stars (and gas and dust) within 3,000 light-years (ly) of the galactic plane, which includes the so-called “thin disk” that has more relatively younger stars within 1,500 ly of the plane (more on stellar population groups in our Milky Way Galaxy). This region contains relatively young to intermediate-aged stars that within around five billion years old with relatively higher average metallicity than other galactic regions located outside of the galactic core, in a circular band that broadens with time. Generated by the deaths of older stars, the greater availability of elements higher than hydrogen and helium in this galactic region favor the formation of rocky inner planets as large as Earth, or bigger (Gonzalez et al, 2001). Moreover, the galactic orbits of stars in this region tend to be relatively circular — with low to moderate eccentricity. According to one recent definition of the galactic habitable zone, as much as 10 percent of all stars in the Milky Way may have experienced chemical and environmental conditions suitable for the development of complex Earth-type life over the past eight to four billion years for evolutionary development (press release; and Lineweaver et al, 2004, in pdf). (Further discussion of the different galactic regions and their distinctive stellar populations is available from ChView’s “The Stars of the Milky Way.”)

In recent millenia, the Sun has been passing through a Local Interstellar Cloud (LIC) that is flowing away from the Scorpius-Centaurus Association of young stars dominated by extremely hot and bright O and B spectral types, many of which will end their brief lives violently as supernovae. The LIC is itself surrounded by a larger, lower density cavity in the interstellar medium (ISM) called the Local Bubble, that was probably formed by one or more relatively recent supernova explosions. As shown in a 2002 Astronomy Picture of the Day, located just outside the Local Bubble are: high-density molecular clouds such as the Aquila Rift which surrounds some star forming regions; the Gum Nebula, a region of hot ionized hydrogen gas which includes the Vela Supernova Remnant, which is expanding to create fragmented shells of material like the LIC; and the Orion Shell and Orion Association, which includes the Great Orion Nebula, the Trapezium of hot B- and O-type stars, the three belt stars of Orion, and local blue supergiant star Rigel.

Top Image credit: Yeshe Fenner, STcI, AURA, NASA, ESA

(Source: stellar-indulgence, via atomstargazer)

Desert Varnish – Signs of a shadow biosphere?

(Source: invaderxan, via invaderxan)

Are you suffering a long Monday? Click the image to put the concept of time in context and relieve this pain by yourself.

More: exploringtime.org

This is awesome.

(Source: scienceisbeauty, via invaderxan)

To celebrate Commander Chris Hadfield’s return to earth today, Monday, May 13, Scientific American has collected the Top 10 Commander Hadfield Videos from the International Space Station. Excellent watching all around.

Above: the most popular video on their list, Wringing out Water on the ISS - For Science. And a just-released bonus vid below, the Commander’s version of David Bowie’s 1969 Space Oddity:

It’s the first music video made in space.

(Source: thekidshouldseethis.com)

What Matters About Antimatter

Just like the dog that didn’t bark in the night time, the absence of antimatter in the universe worries us. Why there isn’t more of it is one of the biggest mysteries in particle physics, and one which my experiment (LHCb, at Cern’s Large Hadron Collider) was built to explore. On April 24 this year the LHCb experiment unveiled its latest findings. I want to explain here why these results matter, why they are a triumph, and why, despite them, we are little nearer that precious understanding of why and how this has happened.

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(Source: christinetheastrophysicist)

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astrodidact:

A truly giant neutrino detector recently began full operation in Antarctica. The IceCube Neutrino Observatory uses a cubic kilometer of ice as its detector material; a network of sensor chains has been embedded in the ice. The colored dots on the photo above mark the location of a vertical string of sensors. A neutrino interacting with the ice produces a charged particle called a muon that in turn gives off blue light as it traverses the detector. IceCube’s chains of sensors register that light and allow physicists to track the arrival direction of the neutrino.