Astronomy Archives

September 17, 2007November 7, 2016 by Fraser Cain

The Magellanic Clouds are Here for the First Time

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

September 12, 2007December 26, 2015 by Fraser Cain

Pulsar Has Almost Completely Devoured a Star

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 isnâ€™t considered a planet because of its formation,” says researcher Christopher Deloye of Northwestern University. “Itâ€™s essentially a white dwarf that has been whittled down to a planetary mass.”

Original Source: NASA News Release

September 11, 2007January 24, 2021 by Fraser Cain

Hubble Looks at Four Dead Stars

Planetary nebulae are some of the most beautiful objects in the Universe. Don’t let the name confuse you, though, they have nothing to do with planets. They’re all that’s left behind when stars at the end of their lives cast off their outer layers into space. Here’s a nice image released from the Hubble Space Telescope, containing 4 different planetary nebulae.

As a star like our Sun reaches the end of its long life, its ejects its outer layers in a series of dramatic events. The ultraviolet light from the star illuminates the material, causing it to glow like we see in this Hubble photograph. This same ultraviolet light also disperses the cloud of material, pushing it outward so that it eventually fades away into the vacuum of space.

Although the star might have lived for 10 billion years, its planetary nebula lasts for just a moment – only 10,000 years.

In this Hubble image there are 4 planetary nebula.

At the top left is He 2-47, nicknamed the “starfish” because of its shape. It has six different lobes, which indicates that the original star shed material three different times in three different directions. With each ejection event, the star blasted out twin jets of material.

At the top right is NGC 5315, which seems to have an x-shaped structure. As with the previous nebula, it suffered two different ejection events, casting away its outer layers and firing out jets in opposite directions.

IC 4593 is on the bottom left, and it’s in the northern constellation Hercules. My good friend Phil Plait actually did a cool write up about this object, so I link you to his site for the scoop.

And finally, NGC 5307 is down at the bottom right, and has a beautiful spiral pattern. The dying star might have had a serious wobble as it was expelling gas, creating the complex shapes in the picture.

Original Source: Hubble News Release

September 7, 2007December 26, 2015 by Fraser Cain

AKARI Sees Star Formation on the Edge

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

September 6, 2007December 26, 2015 by Fraser Cain

Hubble Sees Ancient Galactic Building Blocks

Let’s go back, way back, to an earlier time when the Universe was a fraction of its current age. Tiny galaxies, just a fraction of the mass of the Milky Way came together, piece by piece, building up larger and larger galaxies. Well, we don’t have a time machine, but we’ve got the next best things: Hubble and Spitzer, which were called upon to look back into the distant Universe, to watch this process unfold.

The new data gathered by the Hubble Space Telescope and the Spitzer Space Telescope reveal a collection of the smallest, faintest, most compact galaxies ever seen. These aren’t the majestic spiral galaxies we know and love, but primordial building block galaxies that played an important role in the evolution of the structure of the Universe. The two great observatories saw these galaxies when they were just a billion years after the Big Bang; in other words, the galaxies are more than 12 billion light years away.

The images from Hubble are key. It saw galaxies that only contained blue stars just a few million years old. These young, hot stars haven’t had a previous generation before them. They’re using the pure raw material of the Big Bang – mostly hydrogen and helium – as their fuel, unpolluted by heavier elements. Spitzer came in after and helped make accurate measurements of the galaxies’ masses.

“These are among the lowest mass galaxies ever directly observed in the early universe,” says Nor Pirzkal of the Space Telescope Science Institute and the European Space Agency in Baltimore, Md.

Three of the galaxies look distorted, with the familiar tadpole shape of a galaxy in a gravitational tangle with another galaxy. And this is how it started. These tiny galaxies merged with one another, growing into larger and larger objects, and eventually spirals like our own Milky Way.

The earliest time of the Universe is gradually coming into focus, thanks to these observatories.

Original Source: Hubble News Release

August 31, 2007December 26, 2015 by Fraser Cain

Supernovae Blowing Superbubbles in the Small Magellanic Cloud

At a distance of only 200,000 light years, the Small Magellanic Cloud is one of the Milky Way’s closest galactic neighbours. Thanks to its brutal treatment by our galaxy’s gravity, the galaxy has massive regions of active star formation, and regular supernova explosions. Astronomers studied the region with the Chandra X-Ray Observatory, and saw superbubbles formed by stars and supernovae working together.

The region that Chandra focused in on is known as LHa115-N19, or N19 for short. It’s an area in the Small Magellanic Cloud which is rich in ionized hydrogen gas. There are many massive stars forming in the region, and many more supernova remnants – all that remain from the short-lived stars that formed in this rich nursery.

Astronomers combined images from Chandra with data gathered in other wavelengths. And when they did this, they found evidence for so-called superbubbles. These are formed when smaller cavities created by stars and detonating supernovae combine together to create gigantic cavities.

In just one small region, the Chandra data reveals three supernovae explosions clustered together; well, the supernova remnants, anyway. There are even hints in the data that the stars were associated with one another, forming together from the same interstellar cloud, and then dying together.

Original Source: Chandra News Release

August 22, 2007December 26, 2015 by Fraser Cain

Google Earth… for Astronomy

All right, this is the coolest thing ever. You know Google Earth, that cool software application that lets you explore satellite photography of the whole planet. Well, some clever Google engineers have flipped the software inside out, letting you explore the Universe with a similar interface.

This new addition to Google Earth is called “Sky in Google Earth”. It allows you to zoom around the heavens, with various Hubble Space Telescope images highlighted. You can click on the special objects, like the Orion Nebula, and then see the Hubble photograph of the region.

The images of the entire sky are made up from the Digitized Sky Survey and the Sloan Digital Sky Survey. The Digitized Sky Survey covers almost the entire sky, contains about a million objects. The Sloan Digital Sky Survey only has about 25% of the sky covered, but in much more detail, comprising hundreds of millions of images.

For all the images captured by Hubble, you can see bigger versions of the images, and then link out to press releases and additional resources on the web.

I’ve got to say, I’m really impressed with the way this project has started out. I can envision a future where more and more sky surveys are put into the program, and maybe even different observatories, so you can see what the sky looks like in X-rays, infrared, etc.

I think this will also help highlight how little of the sky has actually been captured in any detail. Perhaps this will spur on the development of additional robotic sky surveys to continue capturing the Universe in greater and greater detail. Still, it’s an amazing start – nice work Google.

To get a copy of Google Earth, go to http://earth.google.com/. The latest version of the software, 4.2, contains the additional sky watching features.

Original Source: Hubble News Release

August 20, 2007December 26, 2015 by Fraser Cain

Closest Neutron Star Discovered

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

August 17, 2007December 26, 2015 by Fraser Cain

Dead Star Found Polluted By Earthlike Planet

Astronomers have found a burned out white dwarf star with the remants of an Earthlike planet orbiting it. This chemical fingerprint gives hope that terrestrial planets, like the ones in our Solar System, could be common across the Universe. Now we just need to find some that havn’t been pulverized into planet powder.

The white dwarf star surrounded by planetary remains is called GD 362, and it’s located about 150 light-years from Earth. Although it’s a dying star, it has a ringlike structure around it like Saturn. During their observations, astronomers from UCLA captured the distinct signature of a rocky asteroid interacting with the white dwarf.

At some point in the recent past, an asteroid was torn apart by the powerful gravitational forces around the compact object, and the dust has polluted the white dwarf’s atmosphere. The relative abundances of elements match the chemical constituents of the planets in the inner Solar System.

Here’s a comment from Michael Jura, a UCLA professor and co-author of the research:

“What we have here is a composition of the white dwarf that is fairly similar to that of the inner planets of our solar system. Are there other terrestrial planets like Earth in other solar systems? This white dwarf’s fingerprint is a significant advance in demonstrating that something like terrestrial planet formation occurred around this other star and probably occurred around other stars as well, because it suggests the Earth’s composition is not unique.”

With this discovery, astronomers have evidence that the kinds of forces that made the Earth and planets in our Solar System happened around GD 362, back when it was a newly forming star. And it gives us a glimpse into the future fate of our planet.

In approximately 5 billion years, when our Sun starts to run out of hydrogen fuel, it will expand out enormously, consuming the inner planets, and maybe even the Earth. The change in the Sun’s density will affect the orbits of all the remaining planets. Some may spiral inward and be consumed by the Sun. Others may spiral outward into interstellar space. Others may collide into smaller and smaller objects. Eventually, our Sun may have its own ring of leftover planetary material. And one of those chunks might be a piece of the Earth.

Original Source: UCLA News Release

August 16, 2007December 26, 2015 by Fraser Cain

Galaxy Cluster Collision Creates a Dark Matter Core

This strange photograph is a composite image of Abell 520, a massive cluster of galaxies in the process of colliding with one another – it’s one of the most massive structures in the Universe. Several different instruments and observatories came together to produce the image, and the final result gave astronomers a big mystery: its dark matter is behaving strangely.

When galaxies collide, three ingredients come into play: individual galaxies and their billions of stars, hot gas in between the galaxies, and the mysterious dark matter that actually makes up the bulk of the mass. Optical telescopes can see the light from the stars in the galaxies, and X-ray observatories, like Chandra can see the radiation pouring out of the superheated gas. But the presence of dark matter has to be calculated by the way it warps light from more distant objects.

During gigantic collisions like this, astronomers believed that the dark matter and galaxies should stay together, even during the most violent collisions. And this was seen in another galaxy collision: the so-called Bullet Cluster. But in the collision of Abell 520, something surprising was seen.

They found a dark matter core, containing hot gas, but no galaxies. For some reason, the galaxies were stripped away from the densest part of the dark matter. Here’s what Dr. Hendrik Hoekstra, from the University of Victoria had to say:

“It blew us away that it looks like the galaxies are removed from the densest core of dark matter. This would be the first time we’ve seen such a thing and could be a huge test of our knowledge of how dark matter behaves.”

In addition to this core, they also found a corresponding “light region”, which had galaxies, but little or no dark matter. Somehow this collision separated the dark matter from the regular matter.

So what could have stripped these two apart? One possibility is that the galaxies and dark matter were torn apart by a series of gravitational slingshots. Unfortunately, the researchers weren’t able to come up with a realistic computer simulation that had gravitational interactions powerful enough to do this.

Here’s the stranger possibility: we know that dark matter is affected by gravity, but maybe there’s also some kind of unknown interaction between particles of dark matter. This would be extremely difficult to detect since we can’t even see the stuff.

The astronomers have secured time with the Hubble Space Telescope, and will come back and take another look with its powerful gaze. This should help answer some of the mysteries they’ve unearthed.

Original Source: Chandra News Release