Category: Astronomy

Some of the most extreme objects that we know of in the Universe are magnetars. These are small neutron stars with insanely powerful magnetic fields – they could erase your credit cards from millions of kilometres away. They occasionally have outbursts, blasting out radiation visible from across the galaxy. Now researchers think they have a better handle on where these outbursts are coming from. What’s causing them? That’s still a mystery.

Back in 2003, astronomers watched as a previously unknown neutron star brightened by a factor of 100, briefly becoming visible to a collection of powerful observatories. After detecting pulsations of radiation coming from its surface, astronomers realized they were dealing with a magnetar.

Magnetars were once stars at least 8 times as massive as our own Sun. After the star exploded as a supernova, all that remained was the tiny – but massive – core. The entire mass of the Sun was packed into an object no larger than about 15 km (9 miles across).

Large mass packed into a small area makes it a neutron star, but a tremendously powerful magnetic field puts it into the magnetar class.

The analysis of this new magnetar, known as XTE J1810-197, allowed astronomers to trace the recent outburst to a region just below its surface. In fact, they were able to narrow down the region to an area about 3.5 km (2 miles) across. They could also determine that the magnetic field on the object is about 6 trillion times more powerful than the Earth’s magnetic field.

The process that actually created the outburst is still a mystery. Astronomers are certain that the magnetic field helped trigger the explosion, but they’re not sure what the mechanism is.

Original Source: ESA News Release

The Milky Way is surrounded by a cloud of smaller dwarf galaxies in various stages of destruction. Our galaxy’s gravity is tearing them apart and adding their stars to the galactic halo. The two largest and most familiar are the Large and Small Magellanic Clouds; only visible from the Southern Hemisphere. According to new research, this might be the first time these objects have ever met the Milky Way. After we’re done with them, it won’t be a pretty picture.

The Magellanic Clouds were first named after the explorer of the same name. To the unaided eye, they look like large glowing clouds. They’re both irregular galaxies; the larger is about 1/20th the size and has tenth the mass of the Milky Way, and the smaller cloud is even, well, smaller.

Astronomers from the Harvard-Smithsonian Center for Astrophysics recently calculated the three-dimensional velocities of the two galaxies with greater accuracy than ever before, and found they were strangely high. There can really only two explanations for this: either the Milky Way has more mass than astronomers believe, or the clouds aren’t actually gravitationally bound to our galaxy.

In other words, the two galaxies are on their first pass by the Milky Way.

This new result creates problems, though. The Milky Way is known to have a significant warp in its disk. Astronomers explained this warp through the gravitational interaction between our galaxy and the Magellanic Clouds. But if this is their first pass through, it doesn’t explain the warp. Another problem is a long trail of hydrogen gas streaming behind the clouds. Once again, if this is the first interaction, it couldn’t explain how a tidal stream of hydrogen could be stretched out.

The researchers are next planning to focus on the origin on the stream of hydrogen, trailing behind the clouds. If they can find a different source, it gives strength to the theory that the clouds are here for the first time.

Original Souce: CfA News Release

Astronomers using NASA’s Swift and Rossi X-ray Timing Explorer satellites have discovered a very bizarre object. It only has about 7 times the mass of Jupiter, but instead of orbiting a star, it’s orbiting a pulsar. Oh, and it’s not a planet. It’s all that’s left from a star after the pulsar siphoned away most of its material.

The ghastly duo was discovered on June 7 when Swift picked up a burst of X-rays and gamma rays coming from the direction of the galactic centre. Rossi turned to gaze at the source as well, and confirmed that it’s pulsing out X-rays 182.07 times a second. These are the classic characteristics of a pulsar – the rapidly spinning remains of a massive star.

Normally a pulsar like this is slowing down over time, releasing energy that decreases its rotational velocity. However, in the case of SWIFT J1756.9-2508, it’s actually speeding up. This means that some source is supplying the pulsar with additional material to increase its spin rate.

The researchers were able to detect that a low mass object is orbiting the pulsar, tugging it back and forth, towards and away from the Earth. Astronomers were then able to calculate that this binary companion has somewhere between 7 and 30 times the mass of Jupiter.

The system probably formed billions of years ago as a very massive star and a smaller companion with 1 to 3 solar masses. The massive star evolved quickly and then detonated as a supernova. The smaller star eventually died as well, becoming a red giant, and encompassing the pulsar. This slowed down their orbits enough to begin them spiraling inward.

Today they’re so close that the pulsar produces a tidal bulge on the surface of the dead star, siphoning material away. Sometimes there’s so much mass accumulated that it piles up and explodes as the outburst that led astronomers to the discovery in the first place.

Don’t think of the companion as a planet. “Despite its extremely low mass, the companion isn’t considered a planet because of its formation,” says researcher Christopher Deloye of Northwestern University. “It’s essentially a white dwarf that has been whittled down to a planetary mass.”

Original Source: NASA News Release

A new image taken by the Japanese/European space telescope AKARI turned up huge regions of star formations on the outer edges of galaxy M101. That’s strange. Normally galaxies will have the rapid star formation going on near their centres, and not out at the edges. Astronomers think that it’s all thanks to a recent collision.

M101 is a spiral galaxy in the constellation Ursa Major, and lies about 24 million light-years away. Its diameter is 170,000 light years across, and it has roughly double the mass of the Milky Way. In a galaxy like this, you would expect to see star formation near the middle and along its spiral arms. But in this latest image captured by the AKARI satellite, astronomers have discovered vast regions of star forming regions right out to its outer edges – they’re the bright red blobs in the picture.

It’s not alone out there. Astronomers know that M101 interacted with another galaxy recently, tearing out vast quantities of gas with its gravity. This gas is now falling onto the outer edges of M101, triggering the active star formation. Astronomers have turned AKARI towards several other galaxies nearby, so they hope studying them will help put the puzzle together.

Original Source: JAXA News Release

Canadian and US astronomers have located what is thought to be the closest neutron star ever seen. The exotic object, nicknamed Calvera after the villain in the movie “The Magnificent Seven”, is located in the constellation Ursa Minor, somewhere between 250 and 1,000 light-years away. It’s a member of a rare group of isolated neutron stars – they lack binary companions – and could be just the tip of the iceberg.

The discovering astronomers pored over a gigantic catalog of 18,000 X-ray sources captured by the German-American ROSAT satellite, which was operational between 1990 and 1999. They compared these X-ray sources to objects visible other wavelengths of light, such as infrared, visible light, and radio waves. One object, 1RXS J141256.0+792204, stood out as being visible only in X-rays.

Then they targeted the object with NASA’s Swift satellite, and performed more detailed observations. Swift was able to find the source, and confirmed that it was putting out as much X-ray energy today as had been captured by ROSAT. Then they pointed one of the most powerful telescopes on Earth, the 8.1 Gemini North Telescope in Hawaii, and couldn’t find a single optical light object down to the faintest magnitudes. It was only shining in X-rays.

According to the researchers, there are no widely accepted alternate theories for objects like Calvera, which are bright in X-rays, but faint in visible light. Either it’s an unusual example of a neutron star, or it might be a completely new kind of object. Another mystery: it’s high above the plane of the Milky Way Galaxy. It must have formed in the plane, but then somehow migrated up to its current position.

With the discovery of Calvera, astronomers think there could be many objects like this. It’s close enough that astronomers will be able to perform detailed observations with many instruments. It should yield interesting results for years to come.

Original Source: PSU News Release