Spotless Days Current Stretch: 8 days 2018 total: 95 days (51%) 2017 total: 104 days (28%) 2016 total: 32 days (9%) 2015 total: 0 days (0%) 2014 total: 1 day (<1%) 2013 total: 0 days (0%) 2012 total: 0 days (0%) 2011 total: 2 days (<1%) 2010 total: 51 days (14%) 2009 total: 260 days (71%) Updated 05 Jul 2018
Geomagnetic Storms: Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2018 Jul 05 2200 UTC
Thursday, Jul. 5, 2018
What's up in space
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MORE THAN A WEEK WITHOUT SUNSPOTS: The sun has been without sunspots for 8 consecutive days. Consider this the shape of things to come. The sun is rapidly plunging into a deep solar minimum. By the end of 2018, spotless intervals will be measured in weeks, not days, as the solar cycle continues to weaken. How does this affect us? Ironically, weak solar activity boosts cosmic radiation in Earth's atmosphere--a situation that is expected to worsen in the years ahead. Free:Aurora Alerts.
SPACE PLANE BUZZES ARCTURUS: Did you know that the US Air Force is flying a space plane around Earth? The secretive X-37B spacecraft, which looks like a miniature version of NASA's old space shuttle, has been in orbit since September 2017 when it launched from Cape Canaveral onboard a SpaceX Falcon 9 rocket. Last night, Kevin Fetter of Brockville, Ontario, video recorded the X-37B flying past the bright star Arcturus:
"The space plane was about as bright as a 4th magnitude star--definitely visible to the unaided eye," says Fetter. "Back in April, I watched it pass across the Moon. Very cool to see!"
The X-37B is on a classified mission, and its orbit has not been published by the US government. Nevertheless, we know where it is. Fetter and other satellite observers have spotted the spacecraft many times, allowing its orbit to be calculated. This means you can see it, too. Flyby predictions are published by Heavens Above, where the space plane is listed as "OTV 5 (USA 277)."
APPROACHING GREEN COMET EXPLODES: A comet that could become visible to the naked eye in August has just exploded in brightness. Amateur astronomer Michael Jäger of Austria reports that Comet PANSTARRS (C/2017 S3) brightened 16-fold during the late hours of July 2nd, abruptly increasing in magnitude from +12 to +9. He took this picture of the comet's expanding green atmosphere shortly after the outburst:
"The gas cloud around the comet's nucleus is about 4 arc minutes wide," says Jäger. That means the comet's atmosphere is 260,000 km in diameter, almost twice as wide as the planet Jupiter. These dimensions make it a relatively easy target for backyard telescopes.
Comet PanSTARRS is falling toward the sun from the Oort cloud, a vast reservoir of fresh comets in the distant outer solar system. It has never visited the inner planets before, and, as a result, no one can say what will happen when its fragile ices are exposed to solar heat as it approaches the sun in August. Previous estimates of the comet's brightness max out at magnitude +4--that is, barely visible to the unaided eye from dark-sky sites. Additional outbursts could boost its visibility even more.
The comet was discovered on Sept. 23, 2017, by the PanSTARRS telescope on the summit of the Haleakalā volcano in Maui. PanSTARRS's primary mission is to detect near-Earth asteroids that threaten our planet. In the process,it sweeps up variable stars, supernovas, and comets like this one. With almost a year of data in hand, astronomers have been able to nail down the comet's orbit. Click on the image to launch an interactive 3D visualization from JPL:
Comet PanSTARRS is approaching the sun on a hyperbolic orbit--a narrow open-ended path that will ultimately fling it back to the outer solar system. At perihelion (closest approach to the sun) on August 15-16, the comet will be inside the orbit of Mercury, blasted by solar radiation at point-blank range. What will happen then? Stay tuned.
TRANS-PACIFIC SPACE WEATHER BALLOON LAUNCH: No one has ever done this before. On June 23rd, Spaceweather.com and the students of Earth to Sky Calculus launched two space weather balloons separated by the entire Pacific Ocean. One balloon was released from Kawhia, New Zealand; the other from Bishop, California, more than 10,800 km away. These GPS pushpins show the balloons in flight:
The purpose of the unprecedented double launch was to measure cosmic rays in the atmosphere--specifically, to find out how they differ on opposite sides of the Pacific. We have been traveling around the globe for the past two years, mapping Earth's planetary radiation field with sensors carried aloft by helium balloons. New Zealand is now part of our monitoring network.
Launching balloons around the world runs up a big helium bill. To help pay it, the California team launched this iridescent crystal pyramid to the stratosphere:
You can have it for $149.95. The students are selling this pyramid and several others like it to fund the Earth to Sky ballooning program. Each one comes with a greeting card showing the pyramid in flight and telling the story of its journey to the edge of space. All sales support hands-on STEM research.
Every night, a network of NASA all-sky cameras scans the skies above the United States for meteoritic fireballs. Automated software maintained by NASA's Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth's atmosphere and many other characteristics. Daily results are presented here on Spaceweather.com.
On Jul. 5, 2018, the network reported 24 fireballs. (23 sporadics, 1 July Pegasid)
In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). [Larger image] [movies]
Near Earth Asteroids
Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.
On July 5, 2018 there were 1912 potentially hazardous asteroids.
Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.
Cosmic Rays in the Atmosphere
Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:
This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.
What is this all about? Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly space weather balloons to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 13% since 2015:
Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.
The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
The data points in the graph above correspond to the peak of the Reneger-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Reneger and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.