Spotless Days Current Stretch: 28 days 2020 total: 184 days (70%) 2019 total: 281 days (77%) 2018 total: 221 days (61%) 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%) 2008 total: 268 days (73%) 2007 total: 152 days (42%) 2006 total: 70 days (19%) Updated 18 Sep 2020
Thermosphere Climate Index today: 3.50x1010W Cold Max: 49.4x1010 W Hot (10/1957) Min: 2.05x1010 W Cold (02/2009) explanation | more data:gfx, txt Updated 18 Sep 2020
Cosmic RaysSolar minimum is underway. The sun's magnetic field is weak, allowing extra cosmic rays into the solar system. Neutron counts from the University of Oulu's Sodankyla Geophysical Observatory show that cosmic rays reaching Earth in 2020 are near a Space Age peak. Oulu Neutron Counts Percentages of the Space Age average: today: +9.9% High 48-hr change: +0.1% Max: +11.7% Very High (12/2009) Min: -32.1% Very Low (06/1991) explanation |more data Updated 18 Sep 2020 @ 1600 UT
Geomagnetic Storms: Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2020 Sep 18 2200 UTC
Friday, Sep. 18, 2020
What's up in space
Safe aurora tours: Thinking of a visit to Norway? Marianne's Heaven on Earth Aurora Tours has a 7-seater minivan for families who don't require social distancing. See the Northern Lights or take a scenic day tour. Book here
THE SUN IS STRANGELY SPOTLESS: If Solar Cycle 25 has begun, then why is the sun so quiet? The solar disk has been blank--zero sunspots--for 28 straight days; and we haven't had a significant solar flare in more than a month. Strange? It only seems that way. The early months of new solar cycles are often interrupted by quiet spells, sometimes long ones. Solar Minimum doesn't give up easily, although, eventually, it will give up. Stay tuned. Aurora alerts:SMS text.
WILDFIRE THREATENS MT. WILSON: Astronomers are worried about Mt. Wilson Observatory, and this photo shows why. Last night, an automated webcam caught flames exploding from a hillside just below the 150-ft tall Solar Tower:
Photo Credit: High Performance Wireless Research and Education Network
The Bobcat Fire, which erupted on Sept. 6th in the Angeles National Forest, is out of control and threatening the historic observatory. On Tuesday afternoon, the blaze was within 500 feet of the facility. Firefighters saved it using a variety of tactics, including carving out lines by hand and with bulldozers, setting strategic backfires (indeed, the photo above might be a backfire), and dropping water from airplanes. After two harrowing nights of firefighting, the observatory still stands.
The impact of Mt. Wilson on astronomy can hardly be overstated. Edwin Hubble used the 100-in telescope, the largest telescope in the world from 1917 to 1949, to discover that the Universe is expanding. Fritz Zwicky found evidence for dark matter. And, working with the observatory's solar towers, George Ellery Hale showed that sunspots were giant islands of magnetism floating on the surface of the sun.
The observatory is still in peril. Best wishes to the firefighters who are working so hard to save it.
SPACE PLANE GLIDES BY VENUS: Did you know, there's a space plane orbiting Earth? It's the US Air Force's Boeing X-37 mini-shuttle. Kevin Fetter of Brockville, Ontario, video-recorded it last night passing by the planet Venus:
"The other satellite in the video is SAOCOM 1-B which passed above Venus," says Fetter.
The X-37 is a semi-secret robotic spacecraft with resembles NASA's old space shuttle. In fact, it started as a NASA project in 1999 before being transferred to the United States Department of Defense in 2004. The X-37 has been orbiting Earth off and on since April 2010, with some flights lasting as long as 780 days in orbit. The latest mission, the sixth, launched on an Atlas V rocket on May 17, 2020.
Earlier this month, China launched its own space plane, apparently to keep up with the X-37. The Chinese version also resembles NASA's retired space shuttle. It completed its first test flight, a 2-day trip into low-Earth orbit, on Sept. 6th when it landed somewhere in China.
INFINITY BLACK PEARL: It came from Tahiti--and now it's been to the edge of space. On April 15, 2020, this genuine Black Tahitian South Sea Cultured Pearl flew to the stratosphere onboard an Earth to Sky Calculus cosmic ray balloon, soaring 107,611 feet above the Sierra Nevada mountains of central California:
You can have it for $249.95. The students of Earth to Sky Calculus are selling these exotic space pearls to fund their cosmic ray monitoring program.
Measuring 8 mm in diameter, the pearl is mounted on a 925 sterling silver infinity twist and suspended on a matching 17 inch long sterling silver chain. Each pearl comes with a greeting card showing the pendant in flight and telling the story of its journey to the edge of space.
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 Sept. 18, 2020, the network reported 34 fireballs. (34 sporadics)
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 September 18, 2020 there were 2037 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
SOMETHING NEW! We have developed a new predictive model of aviation radiation. It's called E-RAD--short for Empirical RADiation model. We are constantly flying radiation sensors onboard airplanes over the US and and around the world, so far collecting more than 22,000 gps-tagged radiation measurements. Using this unique dataset, we can predict the dosage on any flight over the USA with an error no worse than 15%.
E-RAD lets us do something new: Every day we monitor approximately 1400 flights criss-crossing the 10 busiest routes in the continental USA. Typically, this includes more than 80,000 passengers per day. E-RAD calculates the radiation exposure for every single flight.
The Hot Flights Table is a daily summary of these calculations. It shows the 5 charter flights with the highest dose rates; the 5 commercial flights with the highest dose rates; 5 commercial flights with near-average dose rates; and the 5 commercial flights with the lowest dose rates. Passengers typically experience dose rates that are 20 to 70 times higher than natural radiation at sea level.
To measure radiation on airplanes, we use the same sensors we fly to the stratosphere onboard Earth to Sky Calculus cosmic ray balloons: neutron bubble chambers and X-ray/gamma-ray Geiger tubes sensitive to energies between 10 keV and 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
Column definitions: (1) The flight number; (2) The maximum dose rate during the flight, expressed in units of natural radiation at sea level; (3) The maximum altitude of the plane in feet above sea level; (4) Departure city; (5) Arrival city; (6) Duration of the flight.
SPACE WEATHER BALLOON DATA: 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 18% since 2015:
The data points in the graph above correspond to the peak of the Regener-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.
En route to the stratosphere, our sensors also pass through aviation altitudes:
In this plot, 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.
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.
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.