New Moon of Pluto

http://www.cbat.eps.harvard.edu/cbet/cbet002769.txt

Pluto is bigger than Eris

A rare occultation of a star by the Kuiper Belt Object known as Eris was recorded in several stations in Chile and at first glance the data suggest Eris is in fact smaller than Pluto--the albedo of Eris must be higher than predicted.

Sky & Telescope has a good write-up.

Here's a report from one of the observers.

And here's Mike Brown's take on the observation (An observation of the observation).

Kepler starts releasing smaller planet data: 1.5 Earth Mass transit exoplanet found

http://www.nytimes.com/2010/08/27/science/space/27planet.html?hp

Fly-by of Lutetia is a success

Another successful asteroid fly-by!
http://www.planetary.org/blog/article/00002577/

Jupiter's SEB has gone pale

Jupiter's South Equatorial Belt, normally a brown-red, has gone as pale as the cream white zones surrounding it. Check out the report with images at the Planetary Society Blog: http://networkedblogs.com/3Jnoh. This is one of those things that happens every 5-10 years or so.

An asteroid collision

Color me surprised: I did not believe, when this object was first reported, and further debate on the Minor Planet Mailing List, that this was in fact a collision.

Martian swirly art

I am sure you've already seen this image from Mars of the swirly traces of dust devils removing the light dust from the darker surface. But here it is.


Click to enlarge to a 2560x1920 version
This is a dune field in a crater just off of Syrtis Major.

Links to other sizes.

Happy Pluto Day

Happy Pluto Day to all my fellow Illinois residents. The Legislature solved all the other Illinois woes and is now solving the vital issue of the day.

Astronomers like Mike Brown continue discovering large Kuiper Belt Objects, like 2007 OR10.


http://blogs.discovermagazine.com/badastronomy/2009/03/13/ten-things-you-dont-know-about-pluto/

Giant's Causeway on Mars

Much like the original Giant's Causeway, the universality of basalt lava exists elsewhere in the inner solar system--including Mars. Here is a very reasonable interpretation of a basalt flow on Mars.
.

I still need to scan my Iceland crazy basalt cooling images.

Avalanches in Mars Polar Regions

This is neat: real processes captured by MRO.

Seen via the Bad Astronomer.

More Mercury science releases

The Messenger science team produced some great press release images and the Planetary Society Blog has a great analysis. Make sure you take a gander at the Mercury departure movie.

Messenger reaches Mercury

The Messenger spacecraft is now 17 hours away from closest approach to Mercury, the first spacecraft to visit the tiny, dense, and baked interior planet in 30 years. Only about half of Mercury is currently mapped. It only passes by this time; it will flyby twice again, then finally enter orbit in 2011. See an orbital movie here. You might also remember this Earth flyby movie, mentioned almost two years ago here.

Latest Mars Asteroid update

The latest observations nearly exclude the possibility of 2007 WD5 colliding with Mars, dropping the probability to 0.01%.

http://neo.jpl.nasa.gov/news/news156.html

This unfolding story and the present results have been made possible by the tracking efforts of many astronomers at several observatories around the world:

* 2007 WD5 was discovered using the Mt. Lemmon 1.5-meter telescope by Andrea Boattini of the University of Arizona's Catalina Sky Survey, which is led by Steve Larson.
* Follow-up from archival images taken by the 1.8-meter telescope on Kitt Peak in Arizona were provided by Terrence H. Brezzi of the University of Arizona's Spacewatch Project, which is led by Robert McMillan.
* Andy Puckett of the Univ. of Alaska obtained pre-discovery measurements from archival images of the Sloan Digital Sky Survey’s 2.5-meter telescope on Apache Point, NM.
* Bill Ryan of New Mexico Tech's Magdalena Ridge Observatory observed 2007 WD5 on several crucial nights, with critical support from university and observatory staff.
* Observations from the 6.5-meter Multi-Mirror Telescope (MMT) Observatory in Arizona were provided by a team consisting of Holger Israel (Univ. Bonn), Matt Holman (Harvard/CfA), Steve Larson (Univ. Ariz.), Faith Vilas (MMTO), Cesar Fuentes (Harvard/CfA), David Trilling (Univ. Ariz.) and Maureen Conroy (Harvard/CfA).
* The 3.5-meter telescope at the Calar Alto Observatory in Spain provided follow-up through a team consisting of Adriano Campo Bagatin (Univ. Alicante), Gilles Bergond (Calar Alto Obs.), Rene Duffard (Inst. de Astrofisica de Andalucia), Jose Luis Ortiz (Inst. de Astrofisica de Andalucia), Reiner Stoss (Obs. Astronomico de Mallorca and Astronomisches Rechen-Institut) and Javier Licandro (Inst. de Astrofisica de Canarias).
* Fabrizio Bernardi, Marco Micheli and Dave Tholen of the Univ. of Hawaii Institute for Astronomy observed the asteroid at its faintest using the 2.2-meter UH telescope on Mauna Kea in Hawaii.

Saturn's extra-weird moons

Meet the craziest of the wacky, the weird moons of Saturn's panoply: Atlas and Pan.
In the December 7th 2007 issue of Science Sébastien Charnoz, André Brahic, Peter C. Thomas, and Carolyn C. Porco argue the equatorial ridges on these moons are a result of post-formation dumping. Pan sits in the Encke Gap in the A ring. Atlas is just outside the A ring. And it makes sense, too. They are in the outer regions of the ring system, the ridges are aligned with the Saturn ring plane, and that the kinematics would allow particles to preferentially land on the equators of these moons, plus the fact that they don't rapidly rotate (to dismiss a "frozen" rapid rotator), you can easily see this is an easy case.

Indeed, if you look at the Atlas image you can see how the central sphere is a rocky body, and the equatorial ridge is smooth, as if made of dusty particles.

One question not addressed in the paper is if Iapetus' equatorial ridge is similar in origin--others have attempted to use rapid rotation to explain that one, and it doesn't sit well when other satellites in the same system have ring-based ridges.

All of these images break my brain from the multiple viewing geometries.

Probable Future APOD from Cassini

NASA/JPL/Space Science Institute -- click to enlarge
Mimas is an old and quite battered moon. You know, the one that's 'That's No Moon', right? What's neat is that it's surface is ancient: you can date how old a surface is in the solar system by measuring the crater density. Such an old icy surface has been darkened to an albedo of 0.50 (50% reflectivity). And it compares so dramatically against the next moon out, Encedalus, which has fewer craters and is the brightest surface in the solar system: an albedo of 0.99 (99% of light reflects back from it).

The Cassini spacecraft peers through the fine, smoke-sized ice particles of Saturn's F ring toward the cratered face of Mimas. The F ring's core, which contains significantly larger particles, is dense enough to completely block the light from Mimas.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 18, 2007. The view was acquired at a distance of approximately 772,000 kilometers from Mimas

This one is nice.
But this one is in color!

Via Planetary Society Blog, a Cassini image that will likely be a future Astronomy Picture of the Day.

End of the year non-review #2: More Hayabusa data

I played with the first of the Hayabusa data a few days ago (by that I mean in July)--and Emily Lakdawalla at the Planetary Society is too--see their post and the great rotation animation. I've been playing with a single image of the surface. If you just add the colors together, you get a relatively neutral surface:

A relatively colorless image

If you boost the saturation of the image you can begin to see significant differences in the rocks on the surface and the underlying regolith.

(movement of the satellite is the source of the color fringes)

Near-infrared Spectral Results of Asteroid Itokawa..." talks about the rich pyroxene and olivine (olivine being a very simple Fe and Mg silicate) results--suggesting the origin of the asteroid was from the inner asteroid belt, with any variations in spectra due to clast size. (see this graph for an example) (both links may require a subscription).

P.S. See additional Itokawa talk here. And see my synthesis of a color image of Earth from Hayabusa.

P.P.S. Look at that crazy huge boulder sitting on the surface: here and here!

New major exoplanet announcement from Corot?

The Corot satellite is a French astroseismology/transit/photometry project.
Steinn Sigurðsson over at Dynamics of Cats is pushing rumors of an announcement regarding a whole new bundle of exoplanet discoveries soon, possibly today.

For a sample of Corot data, see this 120-day graph of a star:

Image from CNES
showing various stellar oscillations as well as a periodic transit of something across the face of the star.

More rumors here too, for today.

Stellar Oscillations
Convection cells at the surface of a star create a large acoustic noise. The noise has multiple ways of traveling through the stellar interior, and can interfere constructively on the surface as the star 'rings'. It can also be used to probe the interior of the star just like earthquakes on Earth showed us the existence of the solid inner core and the liquid outer core. And it can be used to see the farside of the Sun! The ringing can have many, many modes--over a thousand. See the cute animated gif of a l=2, m=2 oscillation of a star here.


Transmission of acoustic waves through a stellar interior

Incoming asteroid--errr, satellite

Astronomers at the Catalina Sky Survey near Tucson discovered an object on November 7th and when the orbit was calculated it was a Near Earth Object (or NEO) and would barely pass by Earth in only five days time. By barely, it was calculated at only a Earth's diameter away--a little under 8,000 miles.

Photometric measurements suggested the object was 20m in diameter, which is pretty big as things go--the Meteor Crater parent body was estimated at 30-50m.

But as Russian astronomer Denis Denisenko noted on the MPML, the object had a peculiar orbit: it passed quite close by Mars at nearly the same time as an ESA orbiter called Rosetta. See a view at Mars here. And, Rosetta happens to have the largest solar panels short of the ISS, two 14 meter long panels that make 64 square meters in total, matching the expected brightness of the object. Sure enough, Rosetta is due at Earth for a orbit changing interaction with Earth in five days so it can rendezvous with a comet in 2014. The people in charge of maintaining minor planet orbits decried the lack of coordination between the artificial satellite organizations and the minor planet community--as satellites are launched it's easy to watch them go away, but the NEO watchers are rightfully concerned about inbound objects, and the data about spacecraft outside of near-Earth space is skimpy.

Comet Holmes from Chicago

We had a great clear Monday after the RAS meeting so we got everyone to come up to the observatory to see the great outburst of Comet Holmes. Photometrically it seems the same brightness, but in binoculars or in the telescope it's much bigger and fainter than a few days ago.


Comet Holmes at Ryerson Observatory. 36x5s exposures, 0.25m f/6.

We imaged it through our 10-inch reflector while looking at it through the six-inch refractor. I processed the images to match the visual look. This comet is so bright I was able to take reasonable images with my digital camera just pointed at the eyepiece, with a few seconds of exposure, but I can't find my memory card reader, so those will have to wait.

So--it's still naked-eye, and now obviously not a star, so get out and take a look--the lower right "star" of an isoceles triangle containing Mirfak, above the bright star Capella in the northeast. (See a finder chart here).

A lot of people were asking details about why exactly the comet increased in brightness a millionfold. Without reading further, I vaguely heard a suggestion that the heat from perihelion takes a while to move deeper into the comet to where there is still volatile ices to blow out. Right now, the comet is moving out between Mars and Jupiter.

A fantastic historical read is Fred Whipple's paper in Icarus, volume 60, issue 3: "Comet P/Holmes, 1892III: A case of duplicity?" (link may need a subscription). I quote:

It may be added that the comet was discovered as a bright object nearly 5 months earlier than its perihelion passage, although the observing geometry was favorable all the time (at perihelion, the comet should have been only 1.5 mag fainter than near opposition 5 months later). It was also the first short period comet of q > 2 ever discovered.
Barnard's 1913) description on November 9.2 at Lick Observatory is revealing:
"'Its appearance was absolutely, different from any comet 1 have ever seen--a perfectly circular and clean cut disk of dense light, almost planetary in outline with a faint, hazy nucleus and a slight condensation some 5 seconds south following the nucleus (brightness -- Andromeda Nebula, diameter 260" at 8h0 '" P.S.T. and 286" at 9h40"').'" He observed the comet to brighten perceptibly by the next night at which time he saw an outer faint diffused envelope some 12' (800,000 km) in diameter.
Barnard's description carries great weight because he was a superb and experienced observer, having already discovered 15 comets and observed many more. His comments were generally confirmed by many other observers over thc world. Interest in the comet flared as the comet burst again to nearly naked eye brilliance on January
16, 1893, after having laded some 5-6 mag by late December and early January.
On subsequent returns P/Holmes hits remained extremely faint and inactive.

• Circular -- check


• Sudden nearly naked-eye burst -- check


• Andromeda galaxy reference -- looked at Andromeda tonight right afterwards -- check


• About 10 arcminutes in diameter -- check

Don't read anything into his comet satellite hypothesis though.

Reading further back, Bobrovnikoff wrote in 1943:

The comet was not well observed in December, 1892, and in the first part of January, 1893. On January 16, Palisa, in Vienna, found with the 27-inch refractor, instead of a diffuse comet of 10th or 12th magnitude as expected, a yellow star of 8th magnitude with an envelope of 20" in diameter. The comet increased in brightness the next day and could be seen with the naked eye. After January 18 it began to decline in brightness, and by the beginning of April it became very faint.

Go see Comet Holmes.

If it's clear where you are, go outside right now and see Comet Holmes with your eyeballs, even with a nearly full moon nearby and even if you live in a horribly light polluted city. Binoculars will help, but you can see the comet with just your eyes right now, although it looks just like a star.

Look to the Northeast. Capella is the bright white star. Look up further towards the zenith to a compact triangle of stars, with the brightest star on the top apex. That star is Mirfak. Comet Holmes is the one on the lower left, the one closest to the line between Mirfak and Capella. Tonight, Capella and the moon form the bottom two points of a skinny-ish trapezoid, with Mirfak and Algol the top two.

Binoculars will reveal the star as a glowing blob, much bigger than the nearly stellar yellow object I saw on Wednesday. A telescope will reveal a stellar nucleus and a glowing blob surrounding it, getting bigger every day.

Finding charts (albeit poor in magnitude distinction are here). Sky and Telescope has one too--just move Capella up higher in the sky the later in the evening. A report here