| Asteroid |
Date(UT) |
Miss Distance |
Velocity (km/s) |
Diameter (m) |
| 2001 XG1 |
2018-Dec-10 |
7.9 LD |
14.2 |
78 |
| 2018 VX6 |
2018-Dec-10 |
16.6 LD |
11.2 |
74 |
| 2018 XA2 |
2018-Dec-10 |
17.9 LD |
6.2 |
16 |
| 2018 XX3 |
2018-Dec-10 |
1.3 LD |
4.6 |
4 |
| 2018 XA4 |
2018-Dec-11 |
1 LD |
12.8 |
5 |
| 2018 XM4 |
2018-Dec-11 |
3.5 LD |
6.7 |
51 |
| 2018 XM2 |
2018-Dec-12 |
14 LD |
12.9 |
31 |
| 2018 XT4 |
2018-Dec-12 |
14.6 LD |
5.1 |
18 |
| 2018 XL1 |
2018-Dec-12 |
2.4 LD |
6.2 |
15 |
| 2018 XJ1 |
2018-Dec-13 |
5.6 LD |
6.3 |
18 |
| 2018 XF4 |
2018-Dec-13 |
7.6 LD |
14.6 |
34 |
| 2015 XX169 |
2018-Dec-13 |
17 LD |
5.8 |
12 |
| 2018 XE2 |
2018-Dec-14 |
10.7 LD |
21.1 |
39 |
| 2018 XG4 |
2018-Dec-15 |
2.7 LD |
7.8 |
11 |
| 2018 VO9 |
2018-Dec-15 |
2.6 LD |
2.9 |
15 |
| 2018 XH1 |
2018-Dec-15 |
11.6 LD |
6.7 |
25 |
| 2018 XS4 |
2018-Dec-16 |
2.8 LD |
8.6 |
32 |
| 2018 XR4 |
2018-Dec-17 |
5.3 LD |
11.4 |
15 |
| 2018 XC4 |
2018-Dec-21 |
1.6 LD |
7.8 |
20 |
| 2017 XQ60 |
2018-Dec-21 |
11.3 LD |
15.6 |
47 |
| 163899 |
2018-Dec-22 |
7.4 LD |
6.2 |
1232 |
| 418849 |
2018-Dec-23 |
16.6 LD |
17.6 |
269 |
| 2018 XE4 |
2018-Dec-26 |
5.4 LD |
9.4 |
18 |
| 2014 AD16 |
2019-Jan-04 |
12.9 LD |
9.4 |
12 |
| 2018 XO4 |
2019-Jan-06 |
7.9 LD |
4 |
30 |
| 2016 AZ8 |
2019-Jan-07 |
11.6 LD |
9.1 |
224 |
| 2013 YM2 |
2019-Jan-09 |
7.3 LD |
4.3 |
20 |
| 2018 XN |
2019-Jan-14 |
11.9 LD |
5.6 |
59 |
| 2013 CW32 |
2019-Jan-29 |
13.9 LD |
16.4 |
148 |
| 2013 RV9 |
2019-Feb-06 |
17.9 LD |
5.9 |
68 |
| 2017 PV25 |
2019-Feb-12 |
7.3 LD |
6.1 |
43 |
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 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.
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.
| |
The
official U.S. government space weather bureau |
| |
The
first place to look for information about sundogs,
pillars, rainbows and related phenomena. |
| |
Researchers
call it a "Hubble for the sun." SDO
is the most advanced solar observatory ever. |
| |
3D
views of the sun from NASA's Solar and Terrestrial
Relations Observatory |
| |
Realtime
and archival images of the Sun from SOHO. |
| |
from
the NOAA Space Environment Center |
| |
fun to read, but should be taken with a grain of salt! Forecasts looking ahead more than a few days are often wrong. |
| |
from the NOAA Space Environment Center |
| |
the
underlying science of space weather |
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