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Fri, 30 Sep 2016
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Fire in the Sky


Continued Adventures of Comet Lovejoy

The scorched core of sungrazing Comet Lovejoy is still intact as it recedes from the sun. Even the comet's flamboyant tail, temporarily lost in transit through the solar corona, has regrown. Click here to view the last 24 hours of coronagraph images from the Solar and Heliospheric Observatory (SOHO).

SOHO images show two tails: the ion tail and the dust tail. The ion tail is made of gas and is blown directly away from the sun by the solar wind. The heavier dust tail is curved and more closely traces the comet's orbit.

Now that the comet is more than five degrees from the sun, it is possible (albeit still not easy) for amateur astronomers to photograph it just before sunrise. A team led by Czech astronomer Jan Ebr captured this image at sunrise on Dec. 17th:


Comet Lovejoy Survives

Incredibly, sungrazing Comet Lovejoy appears to have survived its close encounter with the sun. Lovejoy flew only 140,000 km over the stellar surface during the early hours of Dec. 16th. Experts expected the icy sundiver to be destroyed. Instead, NASA's Solar Dynamics Observatory caught the comet emerging from perihelion (closest approach) at least partially intact:

SDO also recorded Comet Lovejoy's entry into the sun's atmosphere: movie.

Comet Lovejoy began the week as a chunk of dusty, rocky ice some 200 meters in diameter. No one can say how much of the comet's core remains intact or how long it will hang together after the searing heat of perihelion.


Comet Lovejoy Has a Friend!

© Sungrazer Blog
Click here to see animation.
This is too cute: Comet Lovejoy has a friend! Look in the upper-half of the animation opposite, starting at center and moving diagonally up and to the left, perfectly in step with Lovejoy... It's another Kreutz-group comet! (if you can't see it, here's a hint)

As nice as this is, I am not in the least surprised. SOHO's Kreutz-group comets are very "clumpy", for want of a better word. We frequently see them arrive in pairs or sometimes trios, and the big bright ones in particular will often have a companion comet. I suspected we would get at least one with Comet Lovejoy and indeed we do. It's much more typical of the size and brightness of Kreutz comets we see, and offers a wonderful comparison to highlight just how special Comet Lovejoy is.

So what is this new comet called? Is it another "Comet Lovejoy"? Sadly not. It looks to me like it was actually spotted in the LASCO C3 images by seasoned comet hunter Zhijian Xu at Dec 14 2011 11:48:48. So will it be Comet Xu?? No again. It will be Comet SOHO, number 2190-something, I think. Oh, and notice how it's orbit is obviously slightly different from Lovejoy's? That's also something we see all the time; the companion comets are frequently in slightly different orbits. They are obviously closely related though and the smaller one must have fragmented from Lovejoy some significant time ago, and with some slight (non-gravitational) force between them to "push" them apart like this. These kinds of break-ups are theorized to happen decades before they reach the Sun in order for them to have this kind of separation in space, though this process is not well-known or well-understood at all. It one reason that studying these Kreutz comets is so important, as this knowledge can be applied to all comets and solar system bodies, and give a broader understanding of their orbital and physical evolution.


Geminid Fireballs

On the night of Dec. 13/14, NASA's All-Sky Meteor Network recorded 35 fireballs streaking over the southern USA. Twenty-two of them had remarkably similar orbits:

The clustered green orbits match the trajectory of near-Earth asteroid 3200 Phaethon, source of the annual Geminid meteor shower. The Geminids have been active this week as Earth passes through the asteroid's mysterious debris stream. The other, non-Geminid orbits correspond to random meteoroids. Not belonging to any organized debris stream, random meteoroids litter the inner solar system and produce a daily drizzle of "sporadic" fireballs.

NASA's fireball network, which connects multiple cameras in New Mexico, Alabama, Georgia and Tennessee, is a "smart" system. It rapidly and autonomously calculates meteoroid orbits from the fireballs it records. Another orbit diagram is just hours away; stay tuned.


Comet Lovejoy update - will it miss the sun?


Canada: Meteorite Alert! Remote Cameras Capture Slow-Moving Fireball near Toronto

© University of Western Ontario
The huge fireball event as seen from a remote camera in Orangeville, Ontario.
In newly released footage from the University of Western Ontario, a bright, slow-moving fireball was captured in the skies near Toronto, Canada on December 12, 2011 by remote cameras watching for meteors. Although this meteor looks huge as it burns up in Earth's atmosphere, astronomers estimate the rock to have been no bigger than a basketball. Footage reveals it entered the atmosphere at a shallow angle of 25 degrees, moving about 14 km per second. It first became visible over Lake Erie then moved toward the north-northeast.

See below for the video.

But in a meteorite-hunter alert, Peter Brown, the Director of Western's Centre for Planetary & Space Exploration said that data garnered from the remote cameras suggest that surviving fragments of the rock are likely, with a mass that may total as much as a few kilograms, likely in the form of many fragments in one gram to hundreds of a gram size range.


Significant Comet Plunges in the Sun

A comet nearly as wide as two football fields (200m) is plunging toward the sun where it will most likely be destroyed in a spectacular light show on Dec. 15/16. Although Comet Lovejoy (C/2011 W3) could become as bright as Jupiter or Venus when it "flames out," the glare of the sun will hide the event from human eyes. Solar observatories in space, however, will have a grand view. Yesterday the brightening comet entered the field of view of NASA's STEREO-B spacecraft.

"You can clearly see the comet heading diagonally through the images," says Karl Battams of the Naval Research Lab who prepared the animation. "During the 16-hour sequence, the comet brightens from magnitude +8 to +6.5, approximately."

It will soon grow much brighter. "This comet is a true sungrazer, and will skim approximately 140,000 km (1.2 solar radii) above the solar surface on Dec. 15/16," notes Battams. At such close range, solar heating will almost certainly destroy the icy interloper,creating a cloud of vapor and comet dust that will reflect lots of sunlight. The Solar and Heliospheric Observatory (SOHO) will have a particularly good view.


US: Mysterious Explosion and Fireballs Seen as Homes Shaken in Rural Kentucky

There are still no answers as to what caused an apparent explosion in Perry County Sunday night.

Crews spent hours searching Sunday night after initial reports of a possible plane crash, but they gave up the search around 1:00 a.m. and said it was probably an explosion at an abandoned mine.

Now officials with the Division of Abandoned Mine Lands are saying there is no evidence at the mine that would support an explosion.

Some say they felt their homes shaking, others say they saw a fireball, but as of now no one can say for sure what happened in Perry County Sunday night.

Preliminary reports of possible plane crash were ruled out after searching for hours and finding no crash scene, that led officials to this explanation.


Earth Hit By Fireball Storm

Ranging in size from microscopic space dust to mountainous asteroids, trillions of meteoroids zing through the inner solar system on a daily basis. What are the odds that five of them would cross the same point in space? Pretty good, actually. In fact, it happened just last night. Regard the following orbit diagram, then read on for an explanation:

© MSFC Meteroid Environment Office
These are the orbits of five objects that hit Earth on the night of Dec. 7/8. NASA's All Sky Fireball Network recorded the meteoroids as they disintegrated in the atmosphere over the United States, each one producing a bright fireball. Note how all the orbits converge on a single point--our planet.

Every night the network's cameras scan the skies over the United States, forming an inventory of what hits the atmosphere. Combining images from multiple cameras, network software rapidly calculates the basic parameters of each interloper: orbit, speed, disintegration height, and more. At the moment, cameras are located in only four states (New Mexico, Alabama, Georgia, Tennessee), but the network is expanding to provide even better coverage. Soon we'll see just how congested our intersection in space really is.


Newfound Comet to Dive Through Sun Next Week

© Unknown
Illustration only
A newly discovered comet is racing toward a mid-December rendezvous with the sun - a rendezvous that it will likely not survive.

The comet is categorized by astronomers as a "sungrazer" and it is destined to do just that; literally graze the surface of the sun (called the photosphere) and pass through the sun's intensely hot corona, where temperatures have been measured at upwards of 3.6-million degrees Fahrenheit (2-million degrees Celsius).

While the comet will not collide with the sun, most astronomers say the odds are rather long that it will remain intact after its closest pass by the sun. The most exciting aspect of the event is that the comet's expected destruction should be visible on your computer monitor.

And there is a very slight chance that, should the comet somehow manage to survive, it might briefly become visible in broad daylight.