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SIGMA HYDRID METEORS: On the nights of Dec. 3rd and 4th, NASA's network of all-sky meteor cameras recorded 16 fireballs from the sigma Hydrid meteoroid stream. Earth passes through the sigma Hydrid stream every year in early- to mid- December; the source of the debris is unknown. Typically, the shower produces no more than 1 or 2 faint meteors per hour. The detection of 16 bright fireballs in only a couple of nights suggests that sigma Hydrid activity could be higher than usual. Listen for sigma Hydrid echoes in the audio feed from our live meteor radar.
DAWN COMET HAS TWO TAILS: Now that the morning Moon is waning in brightness, amateur astronomers are once again getting a good view of Comet Catalina. Images reveal not one, but two tails. Akihiro Yamazaki sends this picture from Yamanashi, Japan, taken Dec. 4th:
"This is a 36 x 30 second exposure through my 6-inch Astro-Physics telescope," says Yamazaki. "I used a SONY-A7S digital camera set at ISO 2500."
Why does Comet Catalina have two tails? Almost all comets do. The sun-warmed nucleus of a comet spews a mixture of dust and gas into space. Quickly, the mixture separates into two distinct tails: The gaseous "ion tail" is pushed straight away from the sun by solar wind. The weightier dust tail resists solar wind pressure and aligns itself more or less with the comet's orbit. In Yamazaki's picture of Comet Catalina, the ion tail points up; the dust tail points down.
This is Comet Catalina's first visit to the inner solar system--and its last. The comet's close encounter with the sun in mid-November has placed it on a slingshot trajectory toward interstellar space. Although the comet is leaving the solar system, it will become easier to see in the weeks ahead as it approaches Earth. At the moment the comet shines like a 7th magnitude star--invisible to the naked eye. It could brighten by one or two magnitude by mid-January. Sky maps and observing tips may be found in this article from Sky and Telescope.
A date of special interest is Dec. 7th when the comet pairs up with the planet Venus and the waning crescent Moon in the early morning sky. Catalina will be about 4o degrees away from the Venus-Moon combo. Stay tuned for more information about that, and meanwhile browse the realtime comet gallery for sightings. Backyard astronomy alerts: text or voice
Realtime Comet Photo Gallery
SPACECRAFT BUZZES EARTH, PROCEEDS TO ASTEROID: Japan's Hayabusa 2 spacecraft swung past Earth on Dec 3rd at 7:08 p.m. JST, passing over the Pacific Ocean around the Hawaiian islands at an altitude of about 3,090 km. JAXA (the Japanese space agency) has just released these images of our planet taken by the speeding probe:
More images are available here with captions in Japanese.
The flyby was a slingshot maneuver designed to propel Hayabusa 2 toward asteroid Ryugu, the target of an ambitious sample return mission in 2018-2020. JAXA says the spacecraft is in good health following its close encounter with Earth. [press release]
Realtime Space Weather Photo Gallery
Realtime Aurora Photo Gallery
Realtime Noctilucent Cloud Photo Gallery
Realtime Meteor Photo Gallery
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 Dec. 5, 2015, the network reported 41 fireballs.
(32 sporadics, 8 sigma Hydrids, 1 Geminid)
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]
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 December 5, 2015 there were 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 |
These measurements are based on regular space weather balloon flights: learn more.
|Situation Report -- Oct. 30, 2015 ||Stratospheric Radiation (+37o N) |
|Cosmic ray levels are elevated (+6.1% above the Space Age median). The trend is flat. Cosmic ray levels have increased +0% in the past month. |
|Sept. 06: 4.14 uSv/hr (414 uRad/hr) |
|Sept. 12: 4.09 uSv/hr (409 uRad/hr) |
|Sept. 23: 4.12 uSv/hr (412 uRad/hr) |
|Sept. 25: 4.16 uSv/hr (416 uRad/hr) |
|Sept. 27: 4.13 uSv/hr (413 uRad/hr) |
|Oct. 11: 4.02 uSv/hr (402 uRad/hr) |
|Oct. 22: 4.11 uSv/hr (411 uRad/hr) |
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. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. Here is the data from our latest flight, Oct. 22nd:
Radiation levels peak at the entrance to the stratosphere in a broad region called the "Pfotzer Maximum." This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are more than 80x sea level.
Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Oct 22th measurements, a plane flying at 45,000 feet is exposed to 2.79 uSv/hr. At that rate, a passenger would absorb about one dental X-ray's worth of radiation in about 5 hours.
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.
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| ||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 |
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