Category: Astronomy

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Sky watchers observing from high latitude areas may be in for a treat tonight. Forecasters from the National Oceanic and Atmospheric Administration have predicted a 30-35% chance of geo-magnetic storm activity during the late hours of February 14-15. Activity could reach as far south as Michigan, Minnesota, and Wisconsin. The source of this potential light show is a solar wind stream flowing energetically from a coronal hole on the Sun. If you’re lucky, the night sky where you live could look like this for Valentine’s Day night.

Coronal holes are darker, colder areas of the Sun’s corona that have lower-density plasma than elsewhere in the Sun’s outer atmosphere. Coronal holes are areas where the fast-moving component of the solar wind is known to pass through as it escapes into space.

When energy from the Sun interacts with the Earth’s outer atmosphere, it excites oxygen and nitrogen molecules some 100 and 400km above the surface, respectively, emitting a green (oxygen) or red (nitrogen) glow. This in turn excites observers on the ground, who may see the auroral dance take on any of several characteristic forms.

There may just be a glow to the north (or south if you live in the southern hemisphere), just over the horizon; or you may see arcs or bands of light, sometimes with vertical rays spiking high into the night sky. During strong events you may witness the famous curtain effect, or the coronal effect where all the rays appear to converge almost directly overhead.

So if the sky is clear tonight, take your Valentine outside, find a place to snuggle up and you may be rewarded with a light show you can share and remember for years to come.

Here are some cool desert pictures, taken from space.

This is an image of the Gobi Desert taken from space. The top part of the image looks pockmarked, but that’s because the wind generated an enormous dust storm that obscured a large part of the region.

This is the Thar Desert, also known as the Great Indian Desert, on the border between India and Pakistan. Not much grows here, so farmers mostly raise grazing animals, moving to different pastures depending on the season. You can see how the Himalayas rise up at the top of the image.

This is a view of the Sahara Desert in Africa, seen from space. Large clouds of dust obscure parts of the desert. There’s so little rainfall that farming is impossible.

Here’s a photo of the Simpson Desert in Queensland, Australia. Normally this region is very dry, but this photo was taken after a period of heavy rainfall and flooding, where huge flooded areas are seen from space.

This is a photo of the Taklimakan Desert in China. This is a depression that sits between two mountain ranges, preventing rain clouds from reaching the desert. At the top of the image are the Tien Shan Mountains, and the Kunlun Mountains are at the bottom of the image.

We’ve written many articles about deserts for Universe Today. Here’s an article about the largest desert on Earth, and here’s an article about the Atacama Desert.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Here are some amazing deep space pictures.

This is an image of the Bullet Cluster taken by Hubble. It’s a beautiful photograph, but it’s also evidence for dark matter. This cluster was formed through the collision of two clusters of galaxies. The strange thing is that the dark matter was separated away from the gas and dust in the cluster.

This is a picture of the active galaxy M82 taken by the three Great Observatories: Hubble, Chandra and Spitzer. This picture was released to celebrate 16 years of activity for Hubble.

This is a picture of a massive star forming region called the Papillon Nebula. This is just a smaller region in the much larger nebula N159.

Here’s a classic picture of the Sombrero Galaxy, located about 28 million light-years from Earth. This galaxy measures 50,000 light-years across.

This is an image of a strange disk of gas at the core of galaxy NGC 4261. Astronomers think that this is the result of a supermassive black hole feeding on gas and dust.

We’ve written many articles about deep space for Universe Today. Here’s an article about new deep space photos taken by Hubble, and here’s an article about alcohol in deep space.

If you’d like more amazing photographs, the best place to look is NASA’s Astronomy Picture of the Day. I also recommend you check out the website for the Hubble Space Telescope.

We’ve recorded many episodes of Astronomy Cast, including one about Hubble. Check it out, Episode 88: The Hubble Space Telescope.

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The southern lights, or aurora australis, is the southern hemisphere counterpart to the northern lights, or aurora borealis. They are one of nature’s most spectacular light shows, a sorta reward to the people who live that far south, in return for all the cold weather.

Because the southern lights most often occur in a band, or ring, more-or-less centered on the south magnetic pole (the auroral zone, radius approx 2,500 km), and because there is hardly any land in this band (and what little there is, no one lives there!), far fewer people have seen the southern lights than their northern siblings. However, they are sometimes seen in New Zealand (especially the South Island), Tasmania, in the far south of Chile and Argentina, etc. Most often they appear as sheets of color (mostly green, but sometimes other colors too, like red, or purple), on the southern horizon.

The southern lights are caused, ultimately, by energetic particles – mostly electrons – in the solar wind interacting with atoms and molecules in the Earth’s upper atmosphere, mediated by the Earth’s magnetic field. The energetic electrons excite and ionize oxygen and nitrogen in the tenuous air 100 to 300 km up, and these ions give off light as their electrons cascade back to their ground levels. Southern lights occur most often in an oval-shaped ring because the Earth’s magnetic field forces the energetic particles to dance a complicated dance, in which they touch down (come closest to the Earth) in this band.

Southern lights are seen more often during the peak years of the 11-year solar cycle, because the solar wind blows in violent gusts more often then (sunspots and flares play a key role in producing such gusts).

More to explore: Northern & Southern Lights (International Solar-Terrestrial Physics Program and NASA), The Aurora Australis – the Southern Lights (Antarctic Connection), and Auroras: the Northern and Southern Lights (part of a series of astronomy lectures) is a good selection to get you started.

Such a colorful phenomenon in the sky, there must be plenty of Universe Today stories on the southern lights, right? Right! Here are a few for you to check out: Saturn’s Eerie Southern Lights, Northern & Southern Aurorae are Siblings, But Not Twins, and New Finding Shows Super-Huge Tornados Power the Auroras.

Astronomy Cast episodes in which the southern lights dance? Sure! Auroras, and Magnetism Everywhere.

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There are actually three, Kepler’s laws that is, of planetary motion: 1) every planet’s orbit is an ellipse with the Sun at a focus; 2) a line joining the Sun and a planet sweeps out equal areas in equal times; and 3) the square of a planet’s orbital period is proportional to the cube of the semi-major axis of its orbit. As it’s the third which is most often used, Kepler’s law usually means Kepler’s third law (of planetary motion).

Tycho Brahe’s decades-long, meticulous observations of the stars and planets provided Kepler with what today we’d call a robust, well-controlled dataset to test his hypotheses concerning planetary motion (this way of describing it is, dear reader, a deliberate anachronism). In particular, Tycho’s observations of the position of Mars in the Uraniborg night sky were the primary source of hard data Kepler used to derive, and test, his three laws.

Kepler’s laws have an important place in the history of astronomy, cosmology, and science in general. They marked a key step in the revolution which moved the center of the universe from the Earth (geocentric cosmology) to the Sun (heliocentric), and they laid the foundation for the unification of heaven and earth, by Newton, a century later (before Newton the rules, or laws, which governed celestial phenomena were widely believed to be disconnected with those controlling things which happened on Earth; Newton showed – with his universal law of gravitation – that the same law rules both heaven and earth).

Although Kepler’s laws are only an approximation – they are exact, in classical physics, only for a planetary system of just one planet (and then the focus is the baricenter, not the Sun) – for systems in which one object dominates, mass-wise, they are a good approximation.

Further Reading: Kepler’s Three Laws of Planetary Motion, and Understanding Solar System Dynamics: Orbits and Kepler’s Laws (both from NASA) are good, and this University of Virginia webpage is fun!

Several Universe Today articles cover one aspect of Kepler’s Law or another, among them Let’s Study Law: Kepler Would Be So Proud!, and Happy Birthday Johannes Kepler

Astronomy Cast has three episode relevant to Kepler’s law: Gravity, and two Questions Shows Jan 27th, 2009, and May 19th, 2009; check them out!