At the end of a day devoted to Earth, people can look to the heavens for a beautiful shower of Lyrid meteors.
On April 22nd 2015, millions of people around the world will gather together at festivals and other events to celebrate our beautiful blue planet. It's Earth Day, an occasion to pause, reflect, and talk about how to sustain a clean, healthy environment on Earth.
This year, Earth Day will end with a meteor shower.
On April 22-23 ,2015, Earth will pass through a stream of debris from Comet Thatcher, source of the annual Lyrid meteor shower.
As Earth crosses the debris zone, flakes of comet dust, most no bigger than grains of sand, strike Earth's atmosphere traveling 49 km/s (110,000 mph) and disintegrate as streaks of light. Typical Lyrids are about as bright as the stars of the Big Dipper
As meteor showers go, the Lyrids are relatively mild. Most years in April there are no more than 10 to 20 Lyrid meteors per hour. But sometimes, when Earth glides through an unusually dense clump of debris from Comet Thatcher, the rate increases, resulting in what is known as a meteor outburst. Sky watchers in 1982, for instance, counted 90 Lyrids per hour. An even more impressive outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote:
"Shooting stars [were] observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets..."
Another published report from the 19th century lists an observer as having "counted 167 meteors in
about 15 minutes, and could not then number them all.
No such outburst is predicted for 2015-but then again, no outbursts were predicted on those previous occasions either. If you're up late, take a look.
The best time to catch the shower is between about 11 pm on April 22nd and sunrise on April 23rd, in any timezone in the northern hemisphere.
Observing tips: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up. Meteors can appear in any part of the sky, although their trails will tend to point back toward the constellation Lyra, from which the meteors get their name. The hours before dawn are best, because that is when Lyra is highest in the sky.
Sometimes, bright moonlight can spoil a meteor shower. That will not be the case on April 22nd. The Moon is just a slender crescent, and it sets shortly after sunset, so lunar glare will not interfere with the Lyrids. If you can, get away from city lights for the darkest possible sky and the best possible show.
Enjoy Earth Day. And then enjoy Earth Night even more.
Follow The Sun
The TSIS instrument on the International Space Station is continuing NASA's 40-year record of tracking the Sun's radiant energy
The Sounds Of The InterStellar Space
As Voyager 1 recedes from the solar system, researchers are listening for interstellar music (plasma waves) to learn more about conditions outside the heliosphere.
Scifi movies are sometimes criticized when explosions in the void make noise. As the old saying goes, in space, no one can hear you scream. Without air there is no sound.
But if that's true, the sounds of interstellar space were heard by astronomers?
It turns out that space can make music - if you know how to listen.
Some plasma wave data was played for astronomers and The sounds were solid evidence that Voyager 1 had left the heliosphere.
The heliosphere is a vast bubble of magnetism that surrounds the sun and planets. It is, essentially, the sun's magnetic field inflated to enormous proportions by the solar wind. Inside the heliosphere is home. Outside lies interstellar space, the realm of the stars
For decades, researchers have been on the edge of their seats, waiting for the Voyager probes to leave. Ironically, it took almost a year to realize the breakthrough had occurred. The reason is due to the slow cadence of transmissions from the distant spacecraft. Data stored on old-fashioned tape recorders are played back at three to six month intervals. Then it takes more time to process the readings.
The thrill of discovery when some months-old data from the Plasma Wave Instrument reached his desk in the summer of 2013. The distant tones were conclusive: Voyager 1 had made the crossing.
Strictly speaking, the plasma wave instrument does not detect sound. Instead it senses waves of electrons in the ionized gas or plasma that Voyager travels through. No human ear could hear these plasma waves. Nevertheless, because they occur at audio frequencies, between a few hundred and a few thousand hertz, we can play the data through a loudspeaker and listen. The pitch and frequency tell us about the density of gas surrounding the spacecraft.
When Voyager 1 was inside the heliosphere, the tones were low, around 300 Hz, typical of plasma waves coursing through the rarified solar wind. Outside, the frequency jumped to a higher pitch, between 2 and 3 kHz, corresponding to denser gas in the interstellar medium.
So far, Voyager 1 has recorded two outbursts of interstellar plasma music--one in Oct-Nov. 2012 and a second in April-May 2013. Both were excited by bursts of solar activity.
We need solar events to trigger plasma oscillations.
The key players are CMEs, hot clouds of gas that blast into space when solar magnetic fields erupt. A typical CME takes 2 or 3 days to reach Earth, and a full year or more to reach Voyager. When a CME passes through the plasma, it excites oscillations akin to fingers strumming the strings on a guitar. Voyager's Plasma Wave Instrument listens - and learns.
We're in a totally unexplored region of space and expect some surprises out there.
In particular, plasma waves are not excited by solar storms. Shock fronts from outside the solar system could be rippling through the interstellar medium. If so, they would excite new plasma waves that Voyager 1 will encounter as it plunges ever deeper into the realm of the stars.
The next sounds from out there could be surprising indeed.
The Sun's Magnetic Field is About to Flip
Something big is happening on the sun. The sun's global magnetic field is about to flip, a sign that Solar Max has arrived.
