A Deep Look into a Dark Sky

"Can you count the number of bright dots in this picture? This crowded frame is a deep-field image obtained using the Wide Field Imager (WFI), a camera mounted on a relatively modestly sized telescope, the MPG/ESO 2.2-metre located at the La Silla Observatory, Chile.

This image is one of five patches of sky covered by the COMBO-17 survey (Classifying Objects by Medium-Band Observations in 17 filters), a deep search for cosmic objects in a relatively narrow area of the southern hemisphere’s sky. Each one of the five patches is recorded using 17 individual colour filters. Each one of the five COMBO-17 images covers an area of the sky the size of the full Moon. [read more]”

Credit: ESO/COMBO-17

The Sun is better than art

This incredible image was produced using data from NASA’s Solar Dynamics Observatory (SDO) taken on January 17, 2003. This is the sun photographed as it was building towards a major eruption.

SDO carries imaging instruments that photograph different wavelengths of light released from the sun. If you remember your physics, there is a relationship between the wavelength of light, the frequency of the light, and the energy of the light, so SDO images basically reflect the temperature of the sun.

The colors in this shot are 3 different wavelengths of light. Temperature across the sun’s surface and in its corona varies as gases are moved around by convection and by the sun’s powerful magnetic field. Images like this are both gorgeous and help scientists understand the forces churning beneath the surface of the body at the heart of the solar system.


Image credit: NASA Goddard/SDO

"Maybe we’re on Mars because of the magnificent science that can be done there - the gates of the wonder world are opening in our time. Maybe we’re on Mars because we have to be, because there’s a deep nomadic impulse built into us by the evolutionary process, we come after all, from hunter gatherers, and for 99.9% of our tenure on Earth we’ve been wanderers. And, the next place to wander to, is Mars. But whatever the reason you’re on Mars is, I’m glad you’re there. And I wish I was with you.

— Carl Sagan

There are two great mysteries that overshadow all other mysteries in science. One is the origin of the universe. That’s my day job. However, there is also the other great mystery of inner space. And that is what sits on your shoulders, which believe it or not, is the most complex object in the known universe. But the brain only uses 20 watts of power. It would require a nuclear power plant to energise a computer the size of a city block to mimic your brain, and your brain does it with just 20 watts. So if someone calls you a dim bulb, that’s a compliment.

Spiral Galaxy NGC 1232

This spectacular image of the large spiral galaxy NGC 1232 was obtained on September 21, 1998, during a period of good observing conditions at the European Southern Observatory. The colors of the different regions are well visible : the central areas contain older stars of reddish color, while the spiral arms are populated by young, blue stars and many star-forming regions. Note the distorted companion galaxy on the top side, shaped like the greek letter “theta”.

NGC 1232 is located 20º south of the celestial equator, in the constellation Eridanus (The River). The distance is about 100 million light-years, but the excellent optical quality of the VLT and FORS allows us to see an incredible wealth of details. At the indicated distance, the edge of the field shown corresponds to about 200,000 light-years, or about twice the size of the Milky Way galaxy.

Credit: ESO/VLT



Astronomers have created the first realistic virtual universe using a computer simulation called “Illustris.” Illustris can recreate 13 billion years of cosmic evolution in a cube 350 million light-years on a side with unprecedented resolution.

The computer simulation began a mere 12 million years after the Big Bang. When it reached the present day, astronomers counted more than 41,000 galaxies in the cube of simulated space. 

The model requires a huge amount of computing power: running it on even a state-of-the-art desktop computer would take almost 2,000 years. Even run across more than 8,000 processors, the simulation still took several months.



The Astro Alphabet
By Ethan Siege

A is for Aurora, the Earth’s polar lights,
as the Sun’s hot electrons help color our nights.

B is for Black Hole, a star’s collapsed heart,
if you cross its horizon, you’ll never depart.

C is for Comet, with tails, ice, and dust,
a trip near the Sun makes skywatching a must!

D is for Dark Matter, the great cosmic glue
that holds clusters together, but not me and you!

E is for Eclipse, where the Moon, Earth and Sun
cast light-blocking shadows that can’t be outrun.

F is for Fusion, that powers the stars,
as nuclei join, their released light is ours!

G is for Galaxies, in groups and alone,
house billions of planets with lifeforms unknown.

H is for Hubble, for whom Earth’s no place;
a telescope like this belongs up in space.

I is for Ions, making nebulae glow;
as they find electrons, we capture the show.

J is for Jets, from a galaxy’s core,
if you feed them right, they’ll be active once more!

K is for Kepler, whose great laws of motion
keep planets on course in the great cosmic ocean.

L is for Libration, which makes our Moon rock,
it’s a trick of the orbit; it’s tidally locked!

M is for Meteors, which come in a shower,
if skies are just right, you’ll see hundreds an hour!

N is for Nebula, what forms when stars die,
this recycled fuel makes cosmic apple pie.

O is for Opaque, why the Milky Way’s dark,
these cosmic dust lanes make starlight appear stark!

P is for Pulsar, a spinning neutron star,
as the orbits tick by, we know just when we are.

Q is for Quasar, a great radio source,
accelerating matter with little remorse.

R is for Rings, all gas giants possess them,
even one found in another sun’s system!

S is for Spacetime, which curves due to matter,
this Universe-fabric can bend but won’t shatter!

T is for Tides, caused by gravity’s tune,
our oceans bulge out from the Sun and the Moon.

U is the Universe, our goal’s understanding,
with billions of galaxies, as spacetime’s expanding!

V is for Virgo, our nearest great cluster,
with thousands of galaxies, it’s a gut-buster!

W is for Wavelength, the energies of light,
that tell us what atoms are in stars just from sight!

X is for X-rays, high-energy light,
where bursts of new stars show an ionized might.

Y is the Year, where we orbit our Sun,
each planet’s is different; the Earth’s is just one.

Z is for Zenith, so gaze up at the sky!
The Universe is here; let’s learn what, how and why.

Source: Starts With A Bang!
Image credit: Galaxy Zoo’s writing tool


New Galactic Supercluster Map Shows Milky Way’s ‘Heavenly’ Home

A new cosmic map is giving scientists an unprecedented look at the boundaries for the giant supercluster that is home to Earth’s own Milky Way galaxy and many others. Scientists even have a name for the colossal galactic group: Laniakea, Hawaiian for “immeasurable heaven.”

Image 1: Scientists have created the first map of a colossal supercluster of galaxies known as Laniakea, the home of Earth’s Milky Way galaxy and many other. This computer simulation, a still from a Nature journal video, depicts the giant supercluster, with the Milky Way’s location shown as a red dot. Credit: [Nature Video](https://www.youtube.com/watch?v=rENyyRwxpHo)

Image 2: This computer-generated depiction of the Laniakea Supercluster of galaxies, which includes the Milky Way galaxy containing Earth’s solar system, shows a view of the supercluster as seen from the supergalactic equatorial plane. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France

The scientists responsible for the new 3D map suggest that the newfound Laniakea supercluster of galaxies may even be part of a still-larger structure they have not fully defined yet.

"We live in something called ‘the cosmic web,’ where galaxies are connected in tendrils separated by giant voids," said lead study author Brent Tully, an astronomer at the University of Hawaii at Honolulu.

Galactic structures in space

Galaxies are not spread randomly throughout the universe. Instead, they clump in groups, such as the one Earth is in, the Local Group, which contains dozens of galaxies. In turn, these groups are part of massive clusters made up of hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls. The colossal structures known as superclusters form at the intersections of filaments.

The giant structures making up the universe often have unclear boundaries. To better define these structures, astronomers examined Cosmicflows-2, the largest-ever catalog of the motions of galaxies, reasoning that each galaxy belongs to the structure whose gravity is making it flow toward.

"We have a new way of defining large-scale structures from the velocities of galaxies rather than just looking at their distribution in the sky," Tully said.


Gravity wells - 

A Gravity well or gravitational well is defined as “a conceptual model of the gravitational field surrounding a body in space.”

The more massive the body, the deeper and more extensive the gravity well associated with it. The Sun is very massive, relative to other bodies in the Solar System, so its gravity well appears “deep” and far-reaching.

(picture a very heavy object sinking deep into a bed mattress; the more mass the object has the deeper it sinks in and creates a deeper sinkhole; a deeper sink hole will pull in any nearby objects towards the centre object with greater influence. Objects of  mass bend the fabric of spacetime this way also as the theory of general relativity explains) 

a video example

How did scientists determine our location within the Milky Way galaxy—in other words, how do we know that our solar system is in the arm of a spiral galaxy, far from the galaxy’s center?

There is no short answer to this question, because astronomers have followed many lines of evidence to determine the location of the solar system in the Milky Way. But some of the general techniques can be outlined briefly.

Finding one’s location in a cloud of a hundred billion stars—when one can’t travel beyond one’s own planet—is like trying to map out the shape of a forest while tied to one of the trees. One gets a rough idea of the shape of the Milky Way galaxy by just looking around—a ragged, hazy band of light circles the sky. It is about 15 degrees wide, and stars are concentrated fairly evenly along the strip. That observation indicates that our Milky Way Galaxy is a flattened disk of stars, with us located somewhere near the plane of the disk. Were it not a flattened disk, it would look different. For instance, if it were a sphere of stars, we would see its glow all over the sky, not just in a narrow band. And if we were above or below the disk plane by a substantial amount, we would not see it split the sky in half—the glow of the Milky Way would be brighter on one side of the sky than on the other.

The position of the sun in the Milky Way can be further pinned down by measuring the distance to all the stars we can see. In the late 18th century, astronomer William Herschel tried to do this, concluding that the earth was in the center of a ‘grindstone’-shaped cloud of stars. But Herschel was not aware of the presence of small particles of interstellar dust, which obscure the light from the most distant stars in the Milky Way. We appeared to be in the center of the cloud because we could see no further in all directions. To a person tied to a tree in a foggy forest, it looks like the forest stretches equally away in all directions, wherever one is.

A major breakthrough in moving the earth from the center of the galaxy to a point about 3/5 away from the edge came in the early decades of this century, when Harlow Shapley measured the distance to the large clusters of stars called globular clusters. He found they were distributed in a spherical distribution about 100,000 light-years in diameter, centered on a location in the constellation Sagittarius. Shapley concluded (and other astronomers have since verified) that the center of the distribution of globular clusters is the center of the Milky Way as well, so our galaxy looks like a flat disk of stars embedded in a spherical cloud, or ‘halo,’ of globular clusters.

In the past 75 years, astronomers have refined this picture, using a variety of techniques of radio, optical, infrared and even x-ray astronomy, to fill in the details: the location of spiral arms, clouds of gas and dust, concentrations of molecules and so on. The essential modern picture is that our solar system is located on the inner edge of a spiral arm, about 25,000 light-years from the center of the galaxy, which is in the direction of the constellation of Sagittarius.

Credit: Laurence A. Marschall in the department of physics at Gettysburg College