EarthSky

March 17 CME strikes Earth’s magnetic field The video starts...

Tue, 26 Mar 2013 12:57:57 -0400

March 17 CME strikes Earth’s magnetic field

The video starts slowly … but then becomes very beautiful as auroras ripple across the sky. Plus … what causes an aurora.

Göran Strand from Östersund, Sweden captured this time-lapse video showing what happened on March 17, 2013 when a coronal mass ejection (CME) from the sun hit Earth’s magnetic field. It starts slowly … but then becomes very beautiful as auroras ripple across the sky. The entire 3-minute video actually took place over about 4 hours.

What causes an aurora? The March 17 aurora originated from sunspot AR1692, which erupted on March 15, 2013 at about 0600 UTC. This explosion on the sun took hours to unfold, and produced an M1-class solar flare and a bright coronal mass ejection, or CME. The CME consists of charged solar particles hurtling across space. As often happens, the March 15 CME was aimed so that Earth was in the path of the particle stream.

When the charged solar particles struck Earth’s magnetic field, a geomagnetic storm resulted. In other words, when the charged particles from the sun struck atoms and molecules in Earth’s atmosphere, they excited those atoms, causing them to light up.

What does it mean for an atom to be excited? Atoms consist of a central nucleus and a surrounding cloud of electrons encircling the nucleus in an orbit. When charged particles from the sun strike atoms in Earth’s atmosphere, electrons move to higher-energy orbits, further away from the nucleus. Then when an electron moves back to a lower-energy orbit, it releases a particle of light or photon.

What happens in an aurora is similar to what happens in the neon lights we see on many business signs. Electricity is used to excite the atoms in the neon gas within the glass tubes of a neon sign. That’s why these signs give off their brilliant colors. The aurora works on the same principle – but at a far more vast scale.

Bottom line: Beautiful video by Göran Strand in Sweden of auroras seen on March 17, 2013.

NASA’s 3-minute solar cycle primer

What are coronal mass ejections?

Does the sun have a proper name? Earth and other planets in our...

Mon, 25 Mar 2013 18:57:50 -0400

Does the sun have a proper name?

Earth and other planets in our solar system have their own names. Does the sun have a name?

You’ve no doubt heard some star names such as Polaris the North Star – or Betelgeuse in the constellation Orion. But, although it’s also a star, our sun doesn’t have a generally accepted and unique proper name. It’s just the sun.

You sometimes hear people use the name Sol for our sun. Sol is the Roman equivalent of the Greek sun god Helios. And maybe in earlier times people did actually use these names.According to straightdope.com, the first cited use of Sol as a proper name for the sun is the 1450 Ashmole Manuscript Treatise on Astrology, which stated:

Sol is hote & dry but not as mars is.

So much for ancient knowledge.

And meanwhile neither Sol nor Helios is an official name for the sun, according to the International Astronomical Union (IAU), the international body of astronomers which since 1922 has charged itself with the responsibility for naming all things celestial. By the way, the IAU is virtually alone in the world in suggesting we all use Sun and Moon, rather than the lower-case sun and moon. Most astronomers do capitalize these words (frequently along with other non-standard capitalizations such as Galaxy, Solar System and Universe), but most media organizations (which tend to use media stylebooks such as the AP Stylebook) don’t.

So the sun doesn’t have its own name. But it does have a symbol that’s exclusively its own. The sun’s symbol is a circle with a dot in the center – used in mathematical formulas.

In being nameless, our sun has company. There are several thousand stars visible to the eye, and only a few hundred of them have actual names, as opposed to designations. Astronomers use the Greek alphabet to order visible stars in each constellation, according to their brightness. To identify stars invisible to the eye, astronomers turn to star catalogs, which assign a number to each star according to its position in the sky.

Plus, nowadays, there are thoughts to be planets orbiting many if not most stars. Those extrasolar planets haven’t yet been given proper names either, and the IAU has gone back and forth on its decision to name or not to name extrasolar planets.

Meanwhile, if you ask in a public forum, you’ll find many who swear the sun’s proper name is Sol. When all is said and done, I guess, it all comes down to who has the authority to give names to objects in space. Most astronomers tend to go with the International Astronomical Union, but some – like the astronomers affiliated with Uwingu – are trying to change that.

Bottom line: Our sun doesn’t have an official proper name, according to the International Astronomical Union. In antiquity, the names Sol and Helios referred to ancient sun gods and perhaps the sun itself.

What exploded over Russia?

Wed, 27 Feb 2013 18:17:20 -0500

What exploded over Russia?

The wisdom of astronauts This video, called Overview Effect,...

Tue, 26 Feb 2013 19:35:33 -0500

The wisdom of astronauts

This video, called Overview Effect, shows beautiful imagery of Earth as seen from space, and features testimonials from several astronauts on how the experience of looking down on Earth from space changed their lives. The video commemorates the 40th anniversary of the first image of the Earth taken from space, and was put out by Planetary Collective in January 2013.

“I fully understood that the molecules in my body, and the molecules in my partner’s bodies in the spacecraft had been prototyped in some ancient generation of stars…we are stardust.”

-Edgar Mitchell, Apollo Astronaut

OVERVIEW from Planetary Collective on Vimeo.

“We have to start acting as one species with one destiny. We are not going to survive if we don’t do that.”

- Frank White, Author of Overview Effect

This is definitely one of the best things I’ve seen recently.

Cool discovery about the sun’s next-door twin A cool layer in...

Wed, 20 Feb 2013 17:13:10 -0500

Cool discovery about the sun’s next-door twin

A cool layer in the atmosphere of Alpha Centauri A has been detected, the first time this has been seen in a star beyond our own Sun.

Above Image: One of the great curiosities in solar science is that our Sun’s outer atmosphere – the corona – is heated to millions of degrees when its visible surface is ‘only’ about 6000 degrees. Even stranger is a curious temperature minimum of 4000 degrees lying between the two layers, in the chromosphere. Now, using ESA’s Herschel space observatory, scientists have made the first discovery of an equivalent cool layer in the atmosphere of the Sun-like star, Alpha Centauri A. Credit: ESA

The finding is not only important for understanding the Sun’s activity, but could also help in the quest to discover proto-planetary systems around other stars.

The Sun’s nearest neighbours are the three stars of the Alpha Centauri system. The faint red dwarf, Proxima Centauri, is nearest at just 4.24 light-years, with the tight double star, Alpha Centauri AB, slightly further away at 4.37 light-years.

Alpha Centauri B has recently been in the news after the discovery of an Earth-mass planet in orbit around it. But Alpha Centauri A is also very important to astronomers: almost a twin to the Sun in mass, temperature, chemical composition and age, it provides an ideal natural laboratory to compare other characteristics of the two stars.

One of the great curiosities in solar science is that the Sun’s wispy outer atmosphere – the corona – is heated to millions of degrees while the visible surface of the Sun is ‘only’ about 6000ºC. Even stranger, there is a temperature minimum of about 4000ºC between the two layers, just a few hundred kilometres above the visible surface in the part of Sun’s atmosphere called the chromosphere.

Both layers can be seen during a total solar eclipse, when the Moon briefly blocks the bright face of the Sun: the chromosphere is a pink-red ring around the Sun, while the ghostly white plasma streamers of the corona extend out millions of kilometres.

The heating of the Sun’s atmosphere has been a conundrum for many years, but is likely to be related to the twisting and snapping of magnetic field lines sending energy rippling through the atmosphere and out into space – possibly in the direction of Earth – as solar storms. Why there is a temperature minimum has also long been of interest to solar scientists.

Now, by observing Alpha Centauri A in far-infrared light with Herschel and comparing the results with computer models of stellar atmospheres, scientists have made the first discovery of an equivalent cool layer in the atmosphere of another star.

“The study of these structures has been limited to the Sun until now, but we clearly see the signature of a similar temperature inversion layer at Alpha Centauri A,” says René Liseau of the Onsala Space Observatory, Sweden, and lead author of the paper presenting the results.

“Detailed observations of this kind for a variety of stars might help us decipher the origin of such layers and the overall atmospheric heating puzzle.”

Zoom into the constellation Scorpius In this video from the...

Wed, 20 Feb 2013 17:09:58 -0500

Zoom into the constellation Scorpius

In this video from the European Southern Observatory (ESO), zoom into a region of active star formation in the constellation Scorpius. The final frames of this video shows VISTA telescope’s infrared view of NGC 6357 – also known as the Lobster Nebula – about 8000light-years away. NGC 6357 is a region filled with vast clouds of gas and tendrils of dark dust. These clouds are forming stars, including massive hot stars which glow a brilliant blue-white in visible light.

These images were taken as part of a VISTA survey that is currently scanning the Milky Way in a bid to map our galaxy’s structure and explain how it formed

The science of love Cool video that breaks down the science...

Thu, 14 Feb 2013 23:51:11 -0500

The science of love

Cool video that breaks down the science behind the feeling of love. Simply put … love drives the motor of the mind.

On this Valentine’s Day 2013, a wonderful video about what love is, from the super popular YouTube Page AsapSCIENCE. Go, you guys! We ♥ this stuff.

For you, Valentine: Top 10 reasons we fall in love On this...

Thu, 14 Feb 2013 23:25:40 -0500

For you, Valentine: Top 10 reasons we fall in love

On this Valentine’s Day 2013, what the world of science suggests about the mystery we call love.

Science explains love in many ways. From various scientists and scientific studies, here are some reasons why we love.

1. Because we all want to “expand beyond ourselves.” Pyschologist Arthur Aron at Stoney Brook University has conducted studies suggesting that a primary motive for us as humans is to “expand the self and to increase our abilities and our effectiveness.” He toldhowstuffworks.com:

2. Good eye contact. Arthur Aron again (see #1). He conducted a study that encouraged strangers of the opposite sex to discuss intimate details about themselves for 90 minutes. At the end of that time, each coupled stared into each other’s eyes for four minutes in silence. The results? Many of the couples said they felt a deep attraction to each other, even though they’d never met before. Two of the couples ended up married.

3. Because of inner and outer synchronicity. We fall in love, says psychologist Mark B. Kristal in the University at Buffalo College of Arts and Sciences, when processes in our bodies align with appropriate triggers from the outside world. He speaks of “visual, regular olfactory, auditory and tactile cues” happening in “the proper time, order and place.” He toldsoftpedia.com:

4. Because we like the way they smell. Many studies have shown that smell plays a role in love. Plus we’re not just talking about the ordinary smell of your lover’s dirty T-shirts (dirty T-shirts, by the way, have been the stock-in-trade of smell studies), but also those other, perhaps odorless, signals that enter the brain through the olfactory system. That’s right, pheromones. Volumes have been written on the subject of smell and pheromones in attraction, love and marriage, and don’t we all know it’s true?

5. Because we like the way they kiss. Kissing has an element of smell to it, obviously, but kissing all by itself can determine if the relationship holds promise. Sheril Kirshenbaum, author of the book The Science of Kissing, told EarthSky a year ago that a kiss, and especially a first kiss, plays a big role in determining the future of a relationship, according to scientific studies. She said:

6. Because of our hormones. You know how your heart pounds and your mouth goes dry when your new lover rings the doorbell? It’s basically a stress response. Romantic, eh? Adrenaline, dopamine and serotonin all come into play in love’s early stages. Love-struck couples also have high levels of the neurotransmitter dopamine, which stimulates an intense rush of pleasure, essentially the same effect on the brain as taking cocaine (see #9, below). Want to learn more about hormones in love? Try this post from Scientific American: Your brain in love.

7. Because sex is good for us. Sex relieves stress, boosts immunity, burns calories, boosts heart health, improves intimacy … and so much more. You can read more about the health benefits of sex in this post from WebMD.

8. To make and raise babies, together. Martie Haselton, a psychologist at UCLA, believes love is a “commitment device,” a mechanism that encourages two humans to form a lasting bond to ensure the “long-term health of children.” Haselton and her colleagues conducted experiments, asking people to think about how much they love their partners while suppressing thoughts of other attractive people. They then have the same people think about how much they sexually desire their partners while suppressing thoughts about others. It turns out that love does a much better job of pushing out potential rivals than sex does. This is what you’d expect, Haselton says, if love was a drive to form a long-term commitment. She said:

9. Because love is a drug. Neuroscientist Thomas Insel and colleagues at Emory University in Atlanta conducted studies showing that that monogamous pair bonding among prairie voles (small rodents that mate for life) affects the same brain reward circuits that are responsible for addiction to cocaine and heroin. They say their conclusions are probably true for humans, too. If not … viva le vole!

10. Because we are created for love. Who said that? I did.

Okay, so now we know some of what the world of science has to offer on the subject of falling in love. Meanwhile, what’s the best way to stay in love? Psychologist Arthur Aron says the best predictor for lasting longterm relationships is kindness.

And lest you take any of this too seriously, remember …

Although I speak in tongues
Of men and angels
I’m just sounding brass
And tinkling cymbals without love.
- 1 Corinthians 13:1 (translation from Joni Mitchell)

In other words, despite all that science has to offer, there is something about love, falling in love, being in love, showing love, maintaining lifelong love – whether that’s between romantic partners, parents and children, friends or people in the world at large – that transcends all our definitions and attempts to understand. True, scientific studies have shown neurochemical, psychological, olfactory, evolutionary and psychological reasons for love. But, in the end, we love who we love, and the act of loving makes us who we are. Happy Valentine’s Day 2013!

When is the next meteor shower? The next meteor shower is the...

Mon, 11 Feb 2013 18:18:39 -0500

When is the next meteor shower?

The next meteor shower is the Lyrid shower, peaking on the morning of April 22, 2013.

The 2013 Quadrantids were good fun in early January, but now we’re in that yearly lull in major meteor activity. The next major shower won’t happen until April. It’s the Lyrid meteor shower – April’s “shooting stars.” These meteors tend to be bright and often leave trails. About 10-20 meteors per hour at peak can be expected. Plus, the Lyrids are known for uncommon surges that can sometimes bring the rate up to 100 per hour. Those rare outbursts are not easy to predict, but they’re one of the reasons the tantalizing Lyrids will be worth checking out. The radiant for this shower is in the constellation Lyra, which, as seen from mid-latitudes in the Northern Hemisphere, rises in the northeast at about 10 p.m. in April. In 2013, thewaxing gibbous moon lights up the nighttime from sunset until the wee hours of the morning. However, the greatest number of Lyrid meteors commonly fall in the dark hours just before dawn. Best time to watch is the morning of April 22, 2013 between moonset and dawn. To find out when the moon sets in your sky, check out these recommended almanacs.

The fireballs of February. Will they produce again?

EarthSky’s meteor guide for 2013

Tell us if you see a meteor! EarthSky’s Facebook page

By the way, in 2012, at the peak of the Lyrid meteor shower on April 22, people in California and Nevada saw a large fireball streak across the sky and heard a sonic boom. The boom rattled windows, and the fireball was so bright that some people were said to see “spots” afterwards. Later, the incoming object was said to be the size of a mini-van. Was this object related to the Lyrid meteor shower? Probably not. Meteors in annual showers are the result of rice-grain-sized, icy debris left behind in the orbits of comets. They rarely survive the fiery trip through Earth’s atmosphere and make their way to the ground.

The April 22, 2012 fireball, on the other hand, was clearly rocky. In fact, two days after the fireball – thanks to tracking of the meteor by Doppler weather radar – a small rocky fragment was picked up in the Henningsen Lotus Park just west of Coloma, California. It turned out to be the meteorite from the April 22 fireball. NASA scientists later said they struck scientific gold with this object, whose rapid recovery let them study for the first time a primitive meteorite with little exposure to the elements.

What’s the youngest moon you can see? Above Photo Credit:...

Mon, 11 Feb 2013 18:11:48 -0500

What’s the youngest moon you can see?

Above Photo Credit: Extremely young moon seen by EarthSky Facebook friend Susan Gies Jensen on February 10, 2013 in Odessa, Washington. Beautiful job, Susan! Thank you.In general, it’s really tough to spot a moon less than about 20 hours old – 20 hours after the moon passed more or less between the Earth and sun.

In general, it’s really tough to spot a moon less than about 20 hours old – 20 hours after the moon passed more or less between the Earth and sun.

It has become a sport for amateur astronomers to spot the youngest moon. That is a very slim crescent moon, seen low in the western sky for a short time after sunset. A longstanding, though somewhat doubtful record was held by two British housemaids, said to have seen the moon 14 and three-quarter hours after new moon – in the year 1916.

A more reliable record belongs to Stephen James O’Meara who saw the young crescent with the unaided eye 15 hours and 32 minutes after new moon in May 1990. The record with an optical aid presently belongs to Mohsen Mirsaeed, who saw the moon 11 hours and 40 minutes after new moon in 2002.

Young moon. Image Credit: Dan Bush

The moon passes more or less between the Earth and sun once each month at new moon. Then you can’t see the moon – it crosses the sky with the sun during the day. But about a day after new moon, you’ll see a very thin waxing crescent moon setting shortly after the sun. And that’s a young moon – a lighted crescent in the twilight sky.

How young a moon can be seen depends on the time of year and on sky conditions. It’s possible to see the youngest moons – the thinnest crescents, nearest the sunset – around the spring equinox. That would be March for the Northern Hemisphere or September for the Southern Hemisphere.

Bottom line: What’s the youngest moon you can see? In general, it’s really tough to spot a moon less than about 20 hours old – 20 hours after the moon passed more or less between the Earth and sun. But try for your own personal best when the opportunity arises. Remember, you must have absolutely perfect sky conditions!

Astronomers ask public to help name Pluto’s new moons The...

Mon, 11 Feb 2013 16:59:02 -0500

Astronomers ask public to help name Pluto’s new moons

The discoverers of Pluto’s two tiniest moons are inviting the public to help select names for the new moons.

The artist’s concept above shows the Pluto system from the surface of one of the candidate moons. The other members of the Pluto system are just above the moon’s surface. Pluto is the large disk at center, right. Charon, the system’s only confirmed moon, is the smaller disk to the right of Pluto. The other candidate moon is the bright dot on Pluto’s far left. Image credit: NASA, ESA and G. Bacon (STScI)

By tradition, the moons of Pluto have names associated with Hades and the underworld. Beginning today, people can vote by visiting: http://plutorocks.seti.org

“The Greeks were great storytellers and they have given us a colorful cast of characters to work with,” said Mark Showalter, Senior Research Scientist at the Carl Sagan Center of the SETI Institute in Mountain View, California. He and the teams of astronomers who made the discoveries will select two names based on the outcome of the voting.

Until now, these small moons have been referred to as, simply, “P4″ and “P5″. Like Pluto’s three other moons, Charon, Nix and Hydra, they need to be assigned names derived from Greek or Roman mythology.

Visitors to the web site will also be able to submit write-in suggestions. These will be reviewed by the team and could be added to the ballot. Voting will end Feb. 25, 2013. The final names will be announced after their formal approval by the International Astronomical Union.

P4 was discovered in 2011 in images taken by the Hubble Space Telescope. P5 was discovered a year later during a more intensive search for previously unseen objects orbiting the distant, dwarf planet. The moons are only 20 to 30 km (15 to 20 miles) across. Currently, Pluto is receiving special scrutiny by astronomers, because NASA’s New Horizons spacecraft is slated to arrive there in July 2015.

A Google+ Hangout is scheduled on February 11 at 11 am PT with two of the scientists involved in the discovery. Mark Showalter is from the SETI Institute, and Hal Weaver is a researcher at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. Questions from the viewers will be taken during the event using Twitter (hashtag #PlutoRocks), the SETI Institute Facebook page and the Google hangout.

The mission of the SETI Institute is to explore, understand and explain the origin, nature and prevalence of life in the universe. We believe we are conducting the most profound search in human history – to know our beginnings and our place among the stars.

Via SETI Institute

Image Credit: Jeffery Yarger. Female Nephila clavipes on her...

Tue, 29 Jan 2013 12:23:36 -0500

Image Credit: Jeffery Yarger. Female Nephila clavipes on her web. The web was characterized using Brillouin spectroscopy to directly and non-invasively determine the mechanical properties.

Scientists unravel the mysteries of spider silk

Scientists have found a way to obtain a wide variety of elastic properties of the silk of several intact spiders’ webs using a sophisticated but non-invasive laser light scattering technique.

Scientists at ASU are celebrating their recent success on the path to understanding what makes the fiber that spiders spin – weight for weight – at least five times as strong as piano wire. They have found a way to obtain a wide variety of elastic properties of the silk of several intact spiders’ webs using a sophisticated but non-invasive laser light scattering technique.

“Spider silk has a unique combination of mechanical strength and elasticity that make it one of the toughest materials we know,” said Jeffery Yarger, a professor in ASU’s Department of Chemistry and Biochemistry and lead researcher of the study. “This work represents the most complete understanding we have of the underlying mechanical properties of spider silks.”

Spider silk is an exceptional biological polymer, related to collagen (the stuff of skin and bones) but much more complex in its structure. The ASU team of chemists is studying its molecular structure in an effort to produce materials ranging from bulletproof vests to artificial tendons.

The extensive array of elastic and mechanical properties of spider silks in situ, obtained by the ASU team, is the first of its kind and will greatly facilitate future modeling efforts aimed at understanding the interplay of the mechanical properties and the molecular structure of silk used to produce spider webs.

The team published their results in today’s advanced online issue of Nature materials and their paper is titled “Non-invasive determination of the complete elastic moduli of spider silks.”

“This information should help provide a blueprint for structural engineering of an abundant array of bio-inspired materials, such as precise materials engineering of synthetic fibers to create stronger, stretchier and more elastic materials,” explained Yarger.

Other members of Yarger’s team, in ASU’s College of Liberal Arts and Sciences, included Kristie Koski, at the time a postdoctoral researcher and currently a postdoctoral fellow at Stanford University, and ASU undergraduate students Paul Akhenblit and Keri McKiernan.

The Brillouin light scattering technique used an extremely low power laser, less than 3.5 milliwatts, which is significantly less than the average laser pointer. Recording what happened to this laser beam as it passed through the intact spider webs enabled the researchers to spatially map the elastic stiffnesses of each web without deforming or disrupting it. This non-invasive, non-contact measurement produced findings showing variations among discrete fibers, junctions and glue spots.

Four different types of spider webs were studied. They included Nephila clavipes (pictured), A. aurantia (“gilded silver face”-common to the contiguous United States), L. Hesperus, the western black widow and P. viridans, the green lynx spider, the only spider included that does not build a web for catching prey but has major silk elastic properties similar to those of the other species studied.

The group also investigated one of the most studied aspects of orb-weaving dragline spider silk, namely supercontraction, a property unique to silk. Spider silk takes up water when exposed to high humidity. Absorbed water leads to shrinkage in an unrestrained fiber up to 50 percent shrinkage with 100 percent humidity in N. clavipes silk.

Their results are consistent with the hypothesis that supercontraction helps the spider tailor the properties of the silk during spinning. This type of behavior, specifically adjusting mechanical properties by simply adjusting water content, is inspirational from a bio-inspired mechanical structure perspective.

“This study is unique in that we can extract all the elastic properties of spider silk that cannot and have not been measured with conventional testing,” concluded Yarger.

Via ASU

Image Credit: A daytime moon on January 28, 2013 as seen...

Tue, 29 Jan 2013 12:21:00 -0500

Image Credit: A daytime moon on January 28, 2013 as seen by EarthSky Facebook friend Denise Johnson in Ridgecrest, California, in the Mojave Desert. Notice that this moon in this photo is closer to the (western) horizon at sunrise than the moon one day later (photo below). Full moon was January 27. Afterwards, the moon is waning again and inching closer to the sun on the sky’s dome

When can you see a daytime moon?

I saw the moon in a blue sky. Why? How can this happen? I thought the moon was visible only at night!

We get many comments from those who see the moon in the daytime. The comments tend to have an air of disbelief about them, typically going something like this:

I saw the moon in a blue sky. Why? How can this happen? I thought the moon was visible only at night!

In fact, the moon is up in the daytime as often as at night. It’s only the full moon that that rises in the east as the sun is setting in the west and reigns in the sky all night long. That means the moon is up all night long only one night each month. Otherwise, the moon rises and sets on its own schedule, having nothing to do with sunrise or sunset, and varying in a systematic way throughout each month as the moon pursues its monthly orbit around Earth. If you want to understand more about the moon’s rising and setting times, and subsequent phases, check out this post: Understanding moon phases

So when can you see the moon in the daytime? Basically, you need three things to see the daytime moon:

Look within a week or so of the date of full moon.
Before full moon, look for the daytime moon in the afternoon.
After full moon, look for the daytime moon in the morning.
Look up! The daytime moon is often up there, but it’s pale against the blue sky.

Record-setting asteroid flyby in February, 2013 2012 DA14 is...

Tue, 29 Jan 2013 12:17:43 -0500

Record-setting asteroid flyby in February, 2013

2012 DA14 is about half the size of an American football field. It’ll fly closer to Earth than some artificial satellites on February 15, 2013.

There’s no danger of a collision. But asteroid 2012 DA14 will sweep very close to Earth on February 15, 2013. The video below, from NASA’s ScienceCast, explains more.

This asteroid – discovered just last year – is about half the size of an American football field. It’ll fly closer to Earth than geosynchronous satellites, which orbit about 42,000 kilometers (26,000 miles) up. This asteroid flyby is record-setting in the sense that – since astronomers began regular searches for near-Earth asteroids in the 1990s – they have not seen an object so big come so close to Earth.

Yet astronomers estimate that an asteroid the size of 2012 DA14 flies past Earth, on average, every 40 years. Near-Earth asteroids are thought to strike our planet only once in about 1,200 years or so. When did it happen last? An object of about this size exploded in the atmosphere above Siberia in 1908, killing reindeer and leveling hundreds of kilometers of forest. Researchers are still studying this Tunguska event for clues to the impacting object.

By the way, the impact of an asteroid the size of 2012 DA14 – about 50 meters wide – would not destroy Earth. But it would create a large crater, about the size of Meteor Crater in Arizona.

Bottom line: 2012 DA14 will not collide with Earth, but it will sweep close in mid-February 2013.

Bright waxing moon lights up Gemini the Twins on January 24 As...

Fri, 25 Jan 2013 00:14:36 -0500

Bright waxing moon lights up Gemini the Twins on January 24

As seen from around the world on January 24, 2013, the brilliant waxing gibbous moon shines in front of – or near – the constellation Gemini the Twins. At nightfall tomorrow, onJanuary 25, everyone around the world will see a larger waxing gibbous moon in front of Gemini and closer to the stars Castor and Pollux.

Gemini? Here’s your constellation

Castor and Pollux will probably be bright enough to withstand the drenching moonlight for the next several nights. You might even see these Gemini stars on night of the full moon this coming January 26. However, to view the constellation Gemini in all its starlit majesty, you absolutely need a moonless night.

January full moon mimics path of July sun

If you’re familiar with the constellation Orion the Hunter, try star-hopping to Castor and Pollux from Orion’s two brightest stars – Betelgeuse and Rigel – tonight. By the time early February comes rolling around, the moon will be out of the evening sky. In February, use Orion’s two brightest stars to locate Castor and Pollux, and to appreciate Gemini’s presence in a dark, moonless sky.

What is Lunar X? Alien visitation? No. Lunar X is an example of...

Sun, 20 Jan 2013 20:04:00 -0500

What is Lunar X?

Alien visitation? No. Lunar X is an example of how lighting and topography can combine to produce a pattern that seems familiar to the human eye.

Lunar X is a famous optical feature on the moon, visible through telescopes. When the terminator – or line between light and dark on the moon – is located in just the right place, it appears as the letter X on the moon’s surface. A sign of an alien visitation? No. Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye. In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Blanchinus, and Purbach.

In the case of Lunar X, the pattern repeats at each cycle of the moon, but only for a short time. The X is observable for about 4 hours around the first quarter moon phase.

Bottom line: Lunar X is an optical feature on the moon, an apparent X on the moon’s surface, visible through telescopes. It’s caused by sunlight falling on the rims/ridges between the craters La Caille, Blanchinus, and Purbach.

Waxing moon closer to Jupiter on January 20 That dazzling...

Sun, 20 Jan 2013 19:58:00 -0500

Waxing moon closer to Jupiter on January 20

That dazzling starlike object close to the moon on January 20, 2013 is the giant planet Jupiter. You can’t miss this pair in clear skies this evening, no matter where you are on Earth. And they are still getting closer. Tomorrow’s conjunction of Jupiter and the moon will be visible from around the globe, and particularly dazzling for the Americas, where it’ll be the closest these two will appear in our sky until the year 2026.

The image at the top of this post is from EarthSky Facebook friend Janet Furlong in Culpeper, Virginia. She took this photo last night (January 19, 2013). The two brightest objects are the moon and Jupiter. View larger. Janet wrote:

Step outside and lift your head up and view the sky. Totally gorgeous … so much to see tonight.

What motions of the moon and Jupiter cause them to come together this way in our sky? Their most noticeable motion, in course of a single night, is that the moon and Jupiter go westward across the sky. They do so for the same reason that the sun goes westward during the day. It’s because the Earth rotates from west-to-east on its axis, causing the sun, moon, planets and stars to appear to move from east to west on a daily basis.

Get ready for January 21 moon-Jupiter conjunction with these awesome photos

Meanwhile, from tonight to tomorrow night, you will see the moon move closer to Jupiter on the sky’s dome. That change will be caused by a true motion of the moon itself, its motion through space in orbit around Earth. Due to its orbital motion, the moon travels about 13^oeastward in front of the backdrop stars every day. For reference, the moon’s diameter equals one-half degree.

Jupiter changes its position in front of the background stars, too. Yet, in contrast to the moon, it does so at a snail’s pace and sometimes erratically. Jupiter’s true motion is more difficult to make out than that of the moon because Jupiter orbits the sun, not the Earth. Because we view Jupiter from the moving platform of Earth, Jupiter appears to move backwards in its orbit for about four months. Really, this motion is an illusion, called retrograde motion. Jupiter has been moving in a retrograde fashion – westward in front of the stars – for some months now. It will end its retrograde motion, becoming temporarily stationary in front of the stars, on January 30.

Believe it or not, Jupiter’s orbital speed (13 kilometers/second) is much faster than the moon’s (1 km/second). Keep in mind, though, that far-distant Jupiter takes nearly 12 years to circle the sun in its great big orbit. On the other hand, our moon circles the Earth in its tiny orbit in less than four weeks. That’s why, as seen from Earth, the nearby moon appears to travel more swiftly than the distant planet Jupiter.

By the way, unlike the stars, the moon and Jupiter don’t shine by their own light. They shine by reflecting the light of the sun.

Bottom line: Look for these two brilliant beauties – the moon and the planet Jupiter – close together for several nights around January 21, 2013. As seen from the U.S. and Canada, this is the closest the waxing gibbous moon and the giant planet Jupiter will appear until the year 2026. Their close proximity on the sky’s dome wil be visible throughout the world, but particularly dazzling for the Americas.

January 2013 guide to the five visible planets

Space images of the week A compilation of the best space photos...

Sun, 20 Jan 2013 19:55:00 -0500

Space images of the week

A compilation of the best space photos and images from earthsky.org for the week of January 14-18.

This image, taken with NASA’s Spitzer infrared space telescope, shows the mysterious galactic cloud, seen as the black object on the left. The galactic center is the bright spot on the right. Credit: NASA/Spitzer/Benjamin et al., Churchwell et al.

This evocative image shows a dark cloud where new stars are forming along with a cluster of brilliant stars that have already emerged from their dusty stellar nursery. Credit: Credit: ESO/F. Comeron

This wide-field view shows a dark cloud where new stars are forming along with cluster of brilliant stars that have already burst out of their dusty stellar nursery. Credit:ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

Nearly 200 000 light-years from Earth, the Large Magellanic Cloud, a satellite galaxy of the Milky Way, floats in space, in a long and slow dance around our galaxy. As the Milky Way’s gravity gently tugs on its neighbour’s gas clouds, they collapse to form new stars. In turn, these light up the gas clouds in a kaleidoscope of colours, visible in this image from the NASA/ESA Hubble Space Telescope. Credit: NASA, ESA. Acknowledgement: Josh Lake

Neon lights up exploding stars Artistic view of a nova explosion...

Wed, 16 Jan 2013 19:51:27 -0500

Neon lights up exploding stars

Artistic view of a nova explosion depicting the binary stellar system. Image Credit: David A Hardy and STFC.

These dramatic explosions are driven by nuclear processes and make previously unseen stars visible for a short time. The team of scientists measured the nuclear structure of the radioactive neon produced through this process in unprecedented detail.

Their findings, reported in the US journal Physical Review Letters, show there is much less uncertainty in how quickly one of the key nuclear reactions will occur as well as in the final abundance of radioactive isotopes than has previously been suggested.

Led by the University of York, UK, and Universitat Politècnica de Catalunya and the Institut d’Estudis Espacials de Catalunya, Spain, the findings will help with the interpretation of future data from gamma ray observing satellites.

GK Persei 1901 – view of the ejecta a century after the nova explosion. Image Credit: Adam Block/NOAO/AURA/NSF.

While large stars end their lives with spectacular explosions called supernovae, smaller stars, known as white dwarf stars, sometimes experience smaller, but still dramatic explosions called novae. The brightest nova explosions are visible to the naked eye.

A nova occurs when a white dwarf is close enough to a companion star to drag matter – mostly hydrogen and helium – from the outer layers of that star onto itself, building up an envelope. When enough material has accumulated on the surface, a burst of nuclear fusion occurs, causing the white dwarf to brighten and expel the remaining material. Within a few days to months, the glow subsides. The phenomenon is expected to recur after typically 10,000 to 100,000 years.

Traditionally novae are observed in the visible and nearby wavelengths, but this emission only shows up about a week after the explosion and therefore only gives partial information on the event.

Dr Alison Laird, from the University of York’s Department of Physics, said: “The explosion is fundamentally driven by nuclear processes. The radiation related to the decay of isotopes – in particular that from an isotope of fluorine – is actively being sought by current and future gamma ray observing satellite missions as it provides direct insight into the explosion.

“However, to be interpreted correctly, the nuclear reaction rates involved in the production of the fluorine isotope must be known. We have demonstrated that previous assumptions about key nuclear properties are incorrect and have improved our knowledge of the nuclear reaction pathway.”

The experimental work was carried out at the Maier-Leibnitz Laboratory in Garching, Germany, and scientists from the University of Edinburgh played a key role in the interpretation of the data. The study also involved scientists from Canada and the United States.

Dr Anuj Parikh, from the Departament de Fisica i Enginyeria Nuclear at the Universitat Politècnica de Catalunya, said: “The observation of gamma-rays from novae would help to better determine exactly what chemical elements are synthesized in these astrophysical explosions. In this work, details required to calculate the production of the key radioactive fluorine isotope have been measured precisely. This will allow more detailed investigation of the processes and reactions behind the nova.”

This work is part of an ongoing programme of research studying how the elements are synthesised in stars and stellar explosions.

Via University of York

Moon and Uranus pair up in Pisces the Fishes on January 16 As...

Wed, 16 Jan 2013 19:47:56 -0500

Moon and Uranus pair up in Pisces the Fishes on January 16

As seen on our sky’s dome, tonight’s waxing crescent moon shines fairly close Uranus, the seventh planet outward from the sun. In other words, when you gaze at the moon tonight, you’ll be looking toward Uranus, too. Although we show Uranus on our sky chart (top of post), and although Uranus is theoretically visible to the eye, this distant world isn’t at all easy to spot – especially in the light of the moon. But, for the fun of it, we use the moon to help you envision the location of Uranus and the ecliptic on the dome of night tonight.

Most people need a detailed sky chart and an optical aid to see Uranus, which, at best, appears as a faint starlike object to the eye. In 2013, the optimal time for watching Uranus will come October.

Notice Uranus’ location on the chart at the top of this post. On sky charts, the eclipticrepresents the Earth’s orbital plane projected onto the constellations of the Zodiac. Since all the solar system planets revolve around the sun on nearly the same plane, you’ll always find the planets on or near the ecliptic.

Both the moon and Uranus reside in front of the constellation Pisces the Fishes this evening. After a few more days, the moon will move out of the constellation Pisces and into the constellation Aries. For the most part, Uranus will remain within the constellation Pisces for the rest of this year.

portion of the solar disk crosses Cetus in late March

Look at the feature sky chart at top and you’ll see the ecliptic just misses the constellation Cetus the Sea-monster. Because Uranus lies south of the ecliptic this year, it’ll actually pass through the extreme northwest corner of Cetus in March of 2013. Annually, in late March, even a fraction of the solar disk clips Cetus before fully returning into Pisces.

This year, Uranus retrogrades – goes westward – in front of backdrop stars for a total of five months (July 18 to December 18). We explain why a planet goes in retrograde on our January 30 program on Jupiter.

On the evening of January 16, the waxing crescent moon pairs up with Uranus and lights up the constellation Pisces the Fishes