astronomy

What’s the closest galaxy to us?

Apart from the Milky Way of course… the answer is surprising.

Most people would probably answer the Andromeda Galaxy, but this would be totally wrong.

A little over a decade ago my school co-conducted a survey with another to detail the night sky around us.

Among many of the discoveries made in this survey was that there was something strange going on about 25,000 lightyears from Earth. The stars in that area were unusually dense.

In addition, the collection of stars was elliptical-shaped.

The incredible part?

It’s inside the Milky Way.

Canis Major Dwarf Galaxy, a small galaxy of a billion stars, is now thought to be the closest (non-Milky Way) galaxy to Earth at a mere 25,000 lightyears away from Earth.

It was likely an independent galaxy until our much larger one ate it. It’s since  been leaving a trail of stars as it orbits around the middle of the Milky Way.

This means, like the Galapagos, you’d better go there soon if you want to see what it’s like. In a few billion years its stars may all have been stolen by the gravity of the Milky Way.

(Image credit: VncntM)

Mars - Not All Red

The permanent ice cap at the south pole of Mars shows that not everything on the Red Planet is red. Made of frozen water and carbon dioxide ice, the cap ranges from nearly pure white to a ruddy mixture of colors. It also features variation in terrain, with layers of material, wind-carved canyons and melting fringes.

The southern ice cap is up to 3 kilometers (1.8 miles) thick and spans about 350 kilometers (217 miles). When winter reaches the region, a thinner ice cap forms over the top of the permanent ice, expanding the size of the polar cap until spring arrives.

The cap is displaced north of the geographic south pole of the planet by about 150 kilometers (93 miles). The topography of the region may play a role in this shift, with strong winds being funneled by features like the Hellas Basin, the largest impact structure on Mars. At 7 kilometers (4 miles) deep and 2,300 kilometers (1,429 miles) across, the basin can actually create a mix of low and high-pressure systems. These pressure differentials can cause variations in the rate at which frozen carbon dioxide sublimates, resulting in the offset, lopsided structure of the cap.

This image comes the European Space Agency’s Mars Express, which has been imaging Mars since 2003.

-JF

Image credit: ESA/DLR/FU Berlin/Bill Dunford

Source

Some galaxies have extremely bright cores, suggesting that they contain a supermassive black hole that is pulling in matter at a prodigious rate. Astronomers call these “active galaxies,” and Hercules A is one of them. In visible light, Hercules A looks like a typical elliptical galaxy. In X-ray light, however, Chandra detects a giant cloud of multimillion-degree gas (purple). This gas has been heated by energy generated by the infall of matter into a black hole at the center of Hercules A that is over 1,000 times as massive as the one in the middle of the Milky Way. Radio data (blue) show jets of particles streaming away from the black hole. The jets span a length of almost one million light years.  

Credit: X-ray: NASA/CXC/SAO, Optical: NASA/STScI, Radio: NSF/NRAO/VLA

husseyshy asked:

Is there any chance of earth getting destroyed by asteroid soon or later ?

Big time! Every day roughly a hundred tons of meteoroids enter Earth’s atmosphere. Most of these things don’t present a danger but every now and then a huge one, like the one that hit Earth around Chelyabinsk, Russia can cause incredible damage.

Obviously all it takes is one impact from one large object and the entire surface of the Earth could be liquified into roiling oceans of lava. Some of the fragments of Earth thrown into the air and space will have been superheated into fragments of glass which would then rain down all over the Earth.

Nothing like this has happened for a long time but remember… it only takes one…

Which is why everyone should support the Planetary Society’s effort to create a grant for astronomers that will fund a search for dangerous Near Earth Objects (NEOs). If we’re successful then everyone on Earth will benefit from this early-warning system. If we know there’s something out there coming towards us soon enough, we can do something about it! :)

If you’re interested in helping us or finding out more, click here.

Feature: Testing Einstein’s theory in the galaxy’s toughest neighborhood

Like an Olympic athlete, the general theory of relativity has passed many tests in its century-long career. Its string of successes began in 1915, when Albert Einstein’s picture of gravity as curved spacetime neatly explained shifts in the orbit of Mercury that had vexed astronomers for more than half a century. In recent decades it has faced more exotic and extreme tests, such as explaining why pairs of superdense neutron stars whirling around each other appear to be gradually spiraling toward collision. Here, too, general relativity triumphed: The stars are losing energy at exactly the rate expected if, as the theory predicts, they emit gravitational waves.

Yet physicists remain unsatisfied. The tests so far have been too easy, they say. The gravitational fields involved have been fairly weak, coming from single stars and bending or slowing light only very slightly. If the theory is going to show cracks, it will be under more extreme, high-field conditions. That matters because—on paper, at least—general relativity isn’t the only game in town. Theorists have put forward alternative models for gravity, but in low fields they look identical to Einstein’s theory. In strong fields, they begin to change.

Now, searching for a tougher test, researchers are looking toward the center of our galaxy. There, shrouded in dust, lurks a bright, compact source of radio waves known as Sagittarius A* (Sgr A*) for its position in the sky, near the edge of the constellation Sagittarius. Because of the way stars move in its vicinity, astronomers think that Sgr A* marks the dark heart of the Milky Way: a supermassive black hole weighing as much as 4 million suns but crammed into a space smaller than the distance between the sun and Mercury. That black hole produces the most intense gravitational field in our galaxy and so provides a unique laboratory for testing the predictions of general relativity. Over the next few years, using a range of new instruments tuned to infrared light and radio waves—radiation capable of penetrating the clouds of dust and gas around the galaxy’s core—astronomers are hoping to see whether Sgr A* is bending relativity beyond the breaking point.

Two teams of astronomers—one led by Andrea Ghez of the University of California, Los Angeles (UCLA), and the other by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany—are staring at the center of the galaxy more intently than anyone before them. They are tracking a handful of stars that swoop close to the center—one of them to a distance equal to that between the sun and the edge of the solar system. Meanwhile, a unique new radio telescope array—still being assembled—is gearing up to carry the scrutiny right up to the edge of the putative black hole itself. In each case, the mission is the same: to spot discrepancies that Einstein’s formulae cannot explain.

General relativity has “never before been tested at the high-field limit,” says astrophysicist Abraham Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts. Elsewhere in the galaxy, astronomers have observed stars apparently caught in the grip of smaller black holes. But the stars close to Sgr A* “are 100 times closer to the event horizon [the boundary of a black hole] and the mass scale is a million times greater,” Ghez says. “Does general relativity work down at scales 100 times closer? You’re getting into the realm of basic physics: What is gravity? That’s why people care.”

read more 

NGC 602

Lying some 200,000 light-years away in the outskirts of the Small Magellanic Cloud (SMC), NGC 602 (sometimes referred to as N90) is home to some young new stars. This Hubble Space Telescope image peers into the youthful star cluster, revealing details that give hints about the history of star formation in this stellar nursery.

The hot young stars in NGC 602 are Sun-like stars, with masses ranging from 0.6 to 3.0 solar masses. Their energetic outflows are carving out the inner regions of the molecular cloud they were born in, creating ridges and swept back plumes. Studies conducted with the Spitzer Space Telescope have shown that as the radiation and shock waves move outward, they compress regions of the cloud, creating a second population of even younger stars. The central stars in the cluster are the oldest, but are still just some 5 million years old. Farther out, embedded in nebular material, are Young Stellar Objects (YSOs) that are only 1 million years into their very long life cycles.

Because this star cluster lies at the tenuous outer reaches of the SMC, Hubble can see through the satellite galaxy, revealing many distant background galaxies.

-JF

Image credit: NASA, ESA and the Hubble Heritage Team

Sources: 1, 2

A Galactic Rose

This image of a pair of interacting galaxies called Arp 273 was released to celebrate the 21st anniversary of the launch of the NASA/ESA Hubble Space Telescope.

The distorted shape of the larger of the two galaxies shows signs of tidal interactions with the smaller of the two. It is thought that the smaller galaxy has actually passed through the larger one.

Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)
Source: http://www.spacetelescope.org/images/heic1107a/

Auroral Corona over Norway  : Higher than the highest mountain lies the realm of the aurora. Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from energetic electrons and protons striking atoms and molecules in the Earth’s atmosphere. Somewhat uncommon, an auroral corona appears as a center point for a surrounding display and may occur when an aurora develops directly overhead, or when auroral rays are pointed nearly toward the observer. This picturesque but brief green and purple aurora exhibition occurred last month high above Kvalya, Troms, Norway. The Sessyfjorden fjord runs through the foreground, while numerous stars are visible far in the distance. via NASA