GEOMAGNETIC STORM IN PROGRESS: A G1-class geomagnetic storm is underway on Jan 14th as Earth enters a stream of fast-moving solar wind. G1-class storms are relatively minor and have little effect on satellites or global power grids. However, they can confuse migratory animals that navigate using magnetism at high latitudes and, moreover, may spark bright auroras around the Arctic Circle. Visit Spaceweather.com for more information and updates.
BLUE COMET PANSTARRS: Beyond the orbit of Mars, an unusual blue comet is approaching the sun. Every time astronomers look at Comet PanSTARRS (C/2016 R2), it has a different appearance. Daily images show gaseous jets waving wildly around the comet’s core and dusty clouds billowing down the comet’s tail. This hyperactivity comes despite the fact that the comet is located in a region of space where deep cold and feeble sunlight usually discourage such volatility. What’s happening? The comet’s blue color is a crucial clue. Read more in today’s edition of Spaceweather.com.
The only interesting January event for viewers in Montreal will be the so-called Blue Moon on the 31st. There will be another in March.
For eclipses, lunar or solar, this is a good year to move to Asia, Africa, or Greenland.
The two best meteor showers of 2018 are predicted to be the Perseids in August and the Geminids in December.
The Perseids are usually a good show–esp if there is no moon in the sky which will be the case in 2018 as the crescent moon sets early. The best night will be that of the 12-13, but the days before and after that also offer good viewing. The best nights are over a weekend, so with all this going for it, rest assured it will rain all week.
I have braved the cold for the Geminids — and it was darn cold that night!– but it was not all that exciting. There were fewer meteors than an average Perseid shower, but OTOH, they were very bright. And some years are better than others, so you never know!
Researchers identify new and previously overlooked mechanism for air penetration that helps explain why meteoroids explode.
By Jake Parks | Published: Monday, December 11, 2017
On February 15, 2013, a near-Earth asteroid with a diameter of 66 feet (20 meters) entered Earth’s atmosphere traveling at around 40,000 miles per hour (60,0000 km/h). Within a few seconds, the cosmic projectile detonated 12 miles above the Chelyabinsk region of Russia, releasing as much energy as about 30 Hiroshima atomic bombs. This created a gigantic fireball — known as a superbolide — that caused shock waves to propagate outward for dozens of miles, damaging several thousand buildings and injuring 1,500 people.
Though the progenitor of the explosion had an initial mass of over 10,000 metric tons, only about 0.1 percent of that mass is believed to have reached the ground, indicating that something in the upper atmosphere not only caused the rock to explode, but also caused it to disintegrate much more than expected.
A relatively small meteor streaked through the sky and eventually exploded over the Chelyabinsk region of Russia on February 15, 2013. With a blast energy equivalent to roughly 500,000 tons of TNT, the explosion created shock waves that caused damage to thousands of buildings and injured nearly 1,500 people.
Today, a team of researchers published a study in Meteoritics & Planetary Science that proposes a new and previously overlooked mechanism for air penetration in meteoroids, which could help explain the powerful breakup of the Chelyabinsk meteoroid.
According to the paper, as a meteoroid hurtles through Earth’s atmosphere, high-pressure air in the front of the object infiltrates cracks and pores in the rock, which generates a great deal of internal pressure. This pressure is so great that it causes the object to effectively blow up from the inside out, even if the material in the meteoroid is strong enough to resist the intense external atmospheric pressures.
“There’s a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it,” said the study’s co-author Jay Melosh, a professor of Earth, Atmospheric, and Planetary Sciences at Purdue University, in a press release. “If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces.
According to the paper, “This process of pressure internalization, new to meteoritic studies, would not have been recognized without a two-material fluid dynamics code.” This unique computer code allowed researchers to generate models that let both air and solid material coexist in any part of the calculation.
“I’ve been looking for something like this for a while,” Melosh said. “Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together. Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation.”
Though this process of air penetration is a very effective way for our atmosphere to shield us from smaller meteoroids, larger and denser ones will likely not be as affected by it. However, the more we can learn about how different meteoritic materials explode, the more prepared we can be for the next Chelyabinsk.
THE SUN IS DIMMING: Today at the Cape Canaveral Air Force Station in Florida, SpaceX launched a new sensor to the International Space Station named “TSIS-1.” Its mission: to measure the dimming of the sun. As the sunspot cycle plunges toward its 11-year minimum, NASA satellites are tracking a slight but significant decline in total solar irradiance (TSI). TSIS-1 will monitor this dimming with better precision than previous satellites as Solar Minimum approaches in the years ahead. Visit today’s edition of Spaceweather.com to learn more about TSIS-1 and natural variations in the sun’s electromagnetic output.
Remember, SpaceWeather.com is on Facebook! Above: This plot shows the total solar irradiance (TSI) since 1978 as observed by NASA and European satellites. The sun’s electromagnetic output (top frame) waxes and wanes with the sunspot cycle (bottom frame).
Why is Earth Magnetized and Venus Not?
A new analysis reveals that the gigantic impact that led to the Moon’s formation might have also switched on Earth’s magnetic field. Read more…
Infant Stars Huddle near Black Hole
A team of astronomers has found signs of small stars forming within a few light-years of the Milky Way’s central black hole. Read more…
3. Astronomers have discovered a supermassive black hole scarfing down gas just 690 million years after the Big Bang.
Astronomers are like historians on steroids. They doggedly push back the curtain of cosmic time, peering back to ever-earlier eras in the universe. The latest discovery in this quest, announced today in the journal Nature, is the quasar J1342+0928. This black-hole-powered beacon blazes at us from a redshift of 7.54, or a mere 690 million years after the Big Bang. Read more…
And in the chance we ever see a clear sky again:
4. Wednesday, December 13 The Geminid meteor shower should be at its peak late tonight, and there’s no Moon to interfere. Bundle up warmly. Bring a reclining lawn chair to a dark spot with no glary lights and an open view of the sky. Lie back, gaze into the stars, and be patient. Under a dark sky you might see a meteor at least once a minute on average. Light pollution cuts down on the numbers. See our article Fantastic Year for Geminid Meteor Shower.
You’ll see the most meteors from about 10 p.m. until dawn local time, when your side of Earth turns to face most directly into the oncoming meteoroid stream. But any that you may see early in the evening, when the shower’s radiant in Gemini is still low, will be long, dramatic “Earth-grazers” skimming into the upper atmosphere at a shallow angle.
5. This Week’s Sky at a Glance, December 8 – 16
See what’s in the sky this week. The asteroid 3200 Phaethon, source of the Geminid meteoroid stream, should reach about 11th magnitude from December 12th through 17th as it passes several million miles from Earth. Read more…
6. A “ROCK COMET” IS APPROACHING EARTH: You’ve heard of comets. But have you ever heard of a rock comet? They exist, and a big one is approaching Earth this week. 3200 Phaethon will fly past our planet on Dec. 16th only 10 million km away. Measuring some 5 km in diameter, it is large enough for amateur astronomers to photograph through backyard telescopes. Moreover, this strange object is the parent of the annual Geminid meteor shower, which is also coming this week. Sky watchers can see dozens of Geminids per hour on Dec. 13th and 14th as gravelly bits of the rock comet disintegrate in Earth’s upper atmosphere. Visit today’s edition of Spaceweather.com to find out how to observe the Geminids and their progenitor in the nights ahead.
If you tried to start a car that’s been sitting in a garage for decades, you might not expect the engine to respond. But a set of thrusters aboard the Voyager 1 spacecraft successfully fired up Wednesday after 37 years without use.
WATCH OUT FOR THE SUPERMOON: This weekend’s full Moon is the biggest and brightest full Moon of 2017, almost 8% wider and 16% brighter than average. The extra dose of luminosity, which peaks on Sunday night, Dec. 3rd, is going to cast unusually sharp midnight shadows as this “supermoon” lights up the wintry landscape of the northern hemisphere. Visit today’s edition of Spaceweather.com to find out why the Moon is so big, and when is the best time to look.
Remember, SpaceWeather.com is on Facebook! Above: On Nov. 29th, the waxing supermoon created a luminous halo in the sky as it shined through icy clouds over Tuscon, Arizona. Supermoons also make super halos. Look for them this weekend! Photo credit: Eliot Herman
GEOMAGNETIC STORM PREDICTED (G1-CLASS): NOAA forecasters estimate a 55% chance of G1-class geomagnetic storms on Nov. 29th when Earth’s magnetic field is expected to receive a glancing blow from a CME, hurled toward us days ago by a magnetic explosion on the sun. There’s more: A fissure in the sun’s atmosphere is spewing solar wind into space, and the gaseous material could reach Earth on Nov. 29th as well. G1-class storms have little effect on power grids and satellites. However, they can affect migratory animals that navigate using magnetism. Such storms can also cause spectacular auroras around the Arctic Circle. Visit Spaceweather.com for more information and updates.