Tag Archives: astronomy

Dark Matter Looks WIMPy

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Graphic Credit: The Astronomist.

Data from the ISS-based Alpha Magnetic Spectrometer experiment supports the idea that dark matter consists of the invisible particles called weakly interacting massive particles, or WIMPs.

The universe seems to be full of dark matter, yet no one knows what it’s made of. The best guess is that invisible particles called weakly interacting massive particles, or WIMPs, contribute all this missing mass. And that idea matches the latest data generated by the Alpha Magnetic Spectrometer, or AMS experiment. This instrument lives on the International Space Station, and it may be seeing direct signs of dark matter. The study is in the journal Physical Review Letters. [M. Aguilaret al. (AMS Collaboration), Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station]

The AMS catches charged particles flying through space. Its new results show more positrons than expected. Positrons are the antimatter counterparts to electrons.
Normal astrophysical processes create some positrons, but not as many as AMS registered. One possible explanation is that these excess positrons are a by-product of dark matter interactions. That is, they’re being created by the elusive WIMPs.

When two WIMPs collide, they can annihilate each other, giving rise to other particles—such as positrons. The data from AMS so far match these predictions.

The positrons might also have a more mundane source, such as the spinning stars called pulsars. Time will tell if the space-based AMS has indeed seen the first sign of what makes up dark matter—or if we’re still stuck in the dark.

—Clara Moskowitz for Scientific American

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The Perseid Meteor Shower Due To Shine Tonight!

by DANA FARRINGTON

For the main article, click here

A Perseid meteor streaks across the sky over the Lovell Radio Telescope in Holmes Chapel, U.K., on Aug. 13, 2013.

A Perseid meteor streaks across the sky over the Lovell Radio Telescope in Holmes Chapel, U.K., on Aug. 13, 2013.

Christopher Furlong/Getty Images

 

The annual Perseid meteor shower will streak the sky tonight. The best time to watch is between 3 and 4 a.m., for all time zones across the world, NASA says.

“This year, light from a nearly full moon will make the meteors harder to see, but NASA says you can still expect around 30 to 40 per hour,” reports NPR’s Geoff Brumfiel.

Brumfiel spoke with Rhiannon Blaauw of NASA’s Meteoroid Environment Office for shower-watching tips:

“Just lie on your back, look straight up, give your eyes time to adjust to the dark; it takes longer than people think,” Blaauw said. “And if you can, get away from city lights — it’s not great to be in the middle of Chicago.”

If you manage to stay awake, but would rather stay in bed, NASA will be posting a Ustream view of the skies over Marshall Space Flight Center at 9:30 p.m. ET.

The best places to watch the Perseid meteor shower for 2014.
 

NASA

For those of you interested in brushing up on your meteor knowledge, here’s some background from NASA:

“The Perseids have been observed for at least 2,000 years and are associated with the comet Swift-Tuttle, which orbits the sun once every 133 years. Each year in August, the Earth passes through a cloud of the comet’s debris. These bits of ice and dust — most over 1,000 years old — burn up in the Earth’s atmosphere to create one of the best meteor showers of the year.”

 

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Mars alignment tonight!

Mars will be exactly opposite the sun in the sky in a rare cosmic alignment set to take place Tonight (April 8 2014).

Called an opposition, this happens with Mars from Earth’s perspective every 778 days, or 2 years, 1 month and 18 days. Think of Earth and Mars as two cars racing on circular tracks. Because Earth is closer to the sun, it travels faster, completing a circuit in 365 days. Mars is farther from the sun and takes longer, 687 days. By the time Mars has completed one circuit, Earth has a lot of catching up to do to get to a point between the Red Planet and the sun.

This is complicated by the fact that the two racetracks are not exact circles. As Johannes Kepler discovered in the 16th century, the planets follow slightly elliptical paths around the sun, sometimes closer to the Sun (perihelion), sometimes farther away (aphelion).

Some planets, like Venus and Earth, follow paths that are almost perfect circles. Other planets, like Mercury and Mars, follow more elliptical orbits, which are described as being more eccentric, or differing from a circle.

On the day of opposition, Mars, Earth and the sun fall on a straight line. Six days later, both planets will have moved a little along their orbits, but, because of the eccentricity of its orbit, Mars will be slightly closer to Earth than it was before.

If you look at the complete orbits of the four inner planets, you can see how Venus and Earth follow almost perfect circles centered on the sun. The orbits of Mercury and Mars are slightly askew.

From a practical point of view, Mars appears as a very tiny object in most amateur telescopes, almost always a disappointment to a beginner looking at it. The detailed images you see online are almost always made by combining hundreds of individual frames by a process called stacking, which minimizes the “noise” caused by the turbulence in Earth’s atmosphere.

To see that sort of detail at the eyepiece requires tremendous patience, waiting for the rare instants when the Earth’s atmosphere steadies, allowing the fine detail to pop into view. At those instants of clarity, you will see Mars’ polar cap and traces of its subtle differences in terrain.

From The Weather Channel – If you have a telescope it might pay to go out and see Mars 🙂