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Comets


Comet 2

Comet Finlay surprise outburst, visible in binoculars ... again!

Comet Finlay
© Michael Mattiazzo
Comet Finlay’s up to its old shenanigans again. Here we see it in outburst with a bright, compact head and a half-degree-long tail pointing northeast on Friday, January 16th.
Lost sleep at night, fingers tapping on the keyboard by day. Darn comets are keeping me busy! But of course that's a good problem. Comet 15P/Finlay, which had been languishing in the western sky at dusk at magnitude +10, has suddenly come to life ... for a second time.

Two nights ago, Australian comet observer Michael Mattiazzo took a routine picture of Finlay and discovered it at magnitude +8. Today it's a magnitude brighter and now joins Comet Lovejoy as the second binocular comet of 2015. Comet-wise, we've gone from zero to 60 and the new year's fewer than 3 weeks old!
Fireball

Incoming! Mars pockmarked by over 400 recent meteor impact craters

Impact crater on Mars
© NASA/JPL/UA
Impact crater on Mars.
The surface of Mars is a well worn place in the Solar System, heavily pounded by countless meteor impacts. And some of these craters are hundreds of millions of years old. So it's unusual for there to be a completely fresh impact on the surface of Mars: but that's just what NASA scientists discovered looking through a recent batch of images returned from NASA's Mars Reconnaissance Orbiter.

You're looking at an image taken by the Mars Context Camera, an instrument on board the Mars Reconnaissance Orbiter. In an older photograph taken of the region in February 2012, there was just a bunch of old craters. And then, in the newer image, taken June 2014, this fresh scar on the surface of Mars is clearly visible.

Comment: The only reason we haven't seen over 400 recent impact craters on Earth too is because our planet's dense atmosphere, which Mars doesn't have, is decimating the space rocks currently pelting our planet. At least, it is for now:

A Puzzling Collapse of Earth's Cooling Upper Atmosphere

Earth's magnetic field is weakening 10 times faster now

Comet 2

Green comet 'Lovejoy' lights up the New Year sky

Comet Lovejoy
© The Independent, UK
The comet Lovejoy is set to light up the skies and excite many a stargazer over the first week of the New Year as it reaches its closest point to Earth.

The comet, formerly known as C/2014 Q2, is named after amateur Australian astronomer Terry Lovejoy and was discovered in August.

The comet has been growing more visible in recent weeks to those living in the Southern Hempishere and Nasa's Jet Propulsion Laboratory says the comet will reach its nearest position to Earth on January 7, a distance of about 70.2 million kilometres away. Thus, the green-glowing comet will be visible to those in the Northern Hemisphere.
Comet

Comet Finlay in bright outburst, visible in small telescopes

Comet Finlay
© J. Cerny, M. Masek, K. Honkova, J. Jurysek, J. Ebr, P. Kubanek, M. Prouza, M. Jelinek
Comet Finlay on December 16th shows a bright coma and short tail. Its sudden rise to 9th magnitude was confirmed on December 18th by Australian comet observer Paul Camilleri. The moderately condensed object is about 3 arc minutes in diameter.
Short-period comet 15P/Finlay, which had been plunking along at a dim magnitude +11, has suddenly brightened in the past couple days to +8.7, bright enough to see in 10×50 or larger binoculars. Czech comet observer Jakub Cerny and his team photographed the comet on December 16th and discovered the sudden surge. Wonderful news!

While comets generally brighten as they approach the Sun and fade as they depart, any one of them can undergo a sudden outburst in brightness. You can find Finlay right now low in the southwestern sky at nightfall near the planet Mars. While outbursts are common, astronomers still aren't certain what causes them. It's thought that sub-surface ices, warmed by the comet's approach to the Sun, expand until the pressure becomes so great they shatter the ice above, sending large fragments flying and exposing fresh new ice. Sunlight gets to work vaporizing both the newly exposed vents and aerial shrapnel. Large quantities of dust trapped in the ice are released and glow brightly in the Sun's light, causing the comet to quickly brighten.

Some comets flare up dramatically. Take 29P/Schwassmann-Wachmann. Normally a dim bulb at 17th magnitude, once or twice a year it flares to magnitude 12 and occasionally 10!
Comet 2

New Comet: P/2014 X1 (ELENIN)

CBET nr. 4034, issued on 2014, December 14, announces the discovery of a comet (magnitude ~18) by Leonid Elenin on three CCD images taken on 2014, December 12 with a 0.4-m f/3 astrograph at the ISON-NM Observatory near Mayhill, NM, USA. The new comet has been designated P/2014 X1 (ELENIN).

We performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 120-sec each, obtained remotely on 2014, December 12.4 from H06 (iTelescope network - Mayhill) through a 0.43-m f/6.8 astrograph + CCD + f/4.5 focal reducer, under bad seeing conditions, shows that this object is slightly diffuse with FWHM about 20% - 30% wider than that of nearby field stars of similar brightness.

Our confirmation image (click on it for a bigger version)
Comet P/2014 X1 Elenin
© Remanzacco Observatory
M.P.E.C. 2014-X66 (including pre-discovery Pan-STARRS1 and Mount Lemmon observations, found by G. V. Williams in the MPC archive from September and October) assigns the following elliptical orbital elements to comet P/2014 X1: T 2015 Jan. 7.74; e= 0.71; Peri. = 34.36; q = 1.81; Incl.= 25.97

Congrats to Leonid for the discovery of his third comet!
Comet 2

Comet Lovejoy heading our way

Comet Lovejoy
© Gerald Rhemann
The new Comet Lovejoy, C/2014 Q2, as imaged on November 27th by Gerald Rhemann in Austria using a remotely operated 12-inch f/3.6 astrograph in Namibia.
A new Comet Lovejoy, designated C/2014 Q2, is heading our way out of deep space and out of the deep southern sky. It may brighten to 5th magnitude from late December through much of January as it climbs into excellent viewing position for the Northern Hemisphere, high in the dark winter night.

This is Australian amateur Terry Lovejoy's fifth comet discovery. He turned it up at 15th magnitude in Puppis last August, in search images that he took with a wide-field 8-inch scope. It hasn't moved very much since then - it's still in Puppis as of December 11th - but it's hundreds of times brighter now at visual magnitude 6.8, reports David Seargent in Australia. On the 9th "I saw it easily using a pair of 6x35 binoculars," he writes. Using a 4-inch binocular telescope at 25×, he says it was a good 8 arcminutes wide with a strong central condensation and no visible tail.

And it's picking up speed across the sky for a long northward dash.
Comet 2

New Comet: C/2014 W2 (PANSTARRS)

CBET nr. 4019, issued on 2014, November 21, announces the discovery of a comet (magnitude ~18.7) by PANSTARRS survey in four w-band CCD exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on Nov. 17. The new comet has been designated C/2014 W2 (PANSTARRS).

We performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 120-sec each, obtained remotely on 2014, November 18.9 from I89 (iTelescope network - Nerpio) through a 0.43-m f/6.8 reflector + CCD, shows that this object is a comet: diffuse coma about 6" in diameter.

Our confirmation image (click on it for a bigger version)
Comet C/2014 W2
© Remanzacco Observatory
M.P.E.C. 2014-W55 (including pre-discovery Catalina Sky Survey observations, identified by T. Spahr, on Oct. 26.3, when the comet was at mag 17.7-18.0, and on Nov. 16.3 at mag 17.3-17.5) assigns the following elliptical orbital elements to comet C/2014 W2: T 2016 Mar. 19.554; e= 0.95; Peri. = 85.90; q = 2.67; Incl.= 81.04
Fireball

NASA map downplays sharp rise in meteor fireball impacts over last 20 years

© NASA/JPL
NASA's Near Earth Object (NEO) Program published a diagram a few days ago, showing 556 mapped comet/asteroid fragment impacts on Earth over the last 20 years (see above). NASA says it's based on data gathered from 1994-2013 on small asteroids impacting Earth's atmosphere to create 'fireballs', adding that "the sizes of yellow dots (daytime impacts) and blue dots (nighttime impacts) are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy, and show the location of impacts from objects about 1 meter (3 feet) to almost 20 meters (60 feet) in size."

Note the random distribution of impacts around the globe. But note also what the map and accompanying NASA report do not indicate: the year-on-year distribution of those impact events over that 20-year period. This omission enables them to give the following misleading subheading to their report:
It happens all the time: small asteroids impact Earth's atmosphere
By not providing a year-on-year breakdown of the impacts, and by including their rather banal headline, NASA leaves us to assume that these events were more or less evenly distributed over those 20 years - on average, 27 fireball events of note in 2013 (556 total events/20 years). But we have serious doubts about this.

We know from the American Meteor Society that there were nearly 3,500 observed events in 2013 alone - and just in the US. Check out the data for yourself: browse through the AMS Events database. Select for events in 2013 with both 'sound' and 'fragmentation' reported. Note how many of last year's 184 US fireball events, that were large enough to be both seen breaking up and heard exploding, were witnessed from multiple US states. Now go back to the NASA world fireball map from 1994-2013. Assuming its random global distribution is accurate, we can try a little exercise in extrapolation to get a figure for significant fireball events globally in 2013.
Comet 2

Eight billion asteroids in the Oort cloud?

1996 PW
© JPL/Horizons
When discovered, the object 1996 PW looked like an asteroid but had the elongated, 5,900-year-long orbit of an Oort Cloud comet.
When a telescope atop Hawaii's Haleakala swept up a fast-moving object in August 1996, astronomers didn't know what to make of it. Designated 1996 PW, the little interloper had the highly elongated orbit of a comet that had ventured inward from the Oort Cloud, at the solar system's outermost fringe.

But it had no tail or coma - visually and spectroscopically, it looked like an asteroid.

At the time, dynamicists Paul Weissman (Jet Propulsion Laboratory) and Hal Levison (Southwest Research Institute) proposed that 1996 PW might actually be a rare hybrid: an asteroid from the Oort Cloud. Their suggestion ran completely counter to the consensus notion that only comets existed in that vast, distant reservoir. But Weissman and Levison had run the numbers: they calculated that, along with a trillion or so comets, roughly 8 billion asteroids could have been flung out into the Oort Cloud by close planetary encounters early in solar-system history.

When other researchers suggested that 1996 PW was probably just an "extinct" comet, having depleted the volatile ices that create a coma or tail, the notion of asteroids in the Oort Cloud got shelved - but not completely forgotten.

Comment:

Electric Universe: Tail discovered on long-known asteroid

Icy asteroids: Resident asteroids sprout comet-like dust tails

Comet

Rosetta's comet sings a mysterious 'song'

Comet 67P
© ESA/Rosetta/NavCam
Through some kind of interaction in the comet's environment, 67P's weak magnetic field seems to be oscillating at low frequencies.
The Rosetta mission has detected a mysterious signal coming from Comet 67P/Churyumov-Gerasimenko.

The mission has five instruments in the Rosetta Plasma Consortium (RPC) that measure the plasma environment surrounding the comet.

Plasma is a charged gas and the RPC is tasked with understanding variations in the comet's activity, how 67P's jets of vapour and dust interacts with the solar wind and the dynamic structure of the comet's nucleus and coma.

But when recording signals in the 40-50 millihertz frequency range, the RPC scientists stumbled on a surprise - the comet was singing, they report.

Through some kind of interaction in the comet's environment, 67P's weak magnetic field seems to be oscillating at low frequencies. In an effort to better understand this unique 'song', mission scientists have increased the frequency 10,000 times to make it audible to the human ear.
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