Astronomy

It seems like we've found a moon orbiting an extrasolar planet. The moon is approximately Neptune-sized and the planet is approximately Jupiter-sized (which could cover a large range of masses, because once things get about as massive as Saturn they mostly get denser rather than bigger when you add more mass, until they hit star size.)

Large Exomoon Likely Orbits a Faraway World

Teachey and Kipping found that two aspects of the transit data from Hubble were consistent with their exomoon hypothesis. First, the planet transited the star 1.25 hours earlier than expected on the basis of the orbital period measured by Kepler. “That is indicative of something gravitationally tugging on the planet” during this particular transit, Kipping explained.
[...]
Second, the Hubble observations of the host star’s brightness showed two dips in brightness instead of just the one from the planet. “The location, shape, and depth of this event appear consistent with a Neptune-sized moon [also] transiting in front of the star,” Kipping said. The team also saw this secondary dip in the star’s light in some of the Kepler transits.

I wonder if they'll be able to infer enough information about the exomoon's orbit to work out anything about the masses of the planet and moon. I'm guessing likely not, but it is impressive how much information astronomers are able to squeeze out of seemingly tiny amounts of data, so maybe.

Back in October I wrote about Alpha Centauri B's first known planet, and associated discoveries about Alpha Centauri B. I talked about all the work that went into filtering out noise (redshift and blueshift from other sources) to find the signal from the planet.

Well, that was a very complex process, and some work since then has followed up and suggests that it may have gone awry, and there may not be a planet after all. Here's an article with more info:
No Planet of Alpha Centauri B?

It doesn't conclude for sure that there is no planet, but it casts doubt on the idea that there is; ultimately, more data will be needed to resolve the issue, and we might have to wait a while for that data, since the orbits of Alpha Centauri A and B are bringing them closer together in the sky from our point of view, which will make it impossible to study just the light of Alpha Centauri B without some light from Alpha Centauri A getting mixed in.

The smallest solar system yet discovered, including the smallest known extrasolar planets, has recently been announced.

Here is a news release from NASA.

And here is a longer one from Caltech.

The three planets are all smaller than earth in diameter; the smallest is about the size of Mars. They orbit a red dwarf star whose diameter not even twice as big as Jupiter's, although it'll be a lot more massive. (Neither of the articles gives an estimate of the mass of the red dwarf star that I can see.) And the distances of the planets from their star are similar to those of Jupiter's moons from Jupiter, making it seem almost more comparable to Jupiter + moons than to Sun + planets.

Again, first more information presented by people who know more than I do:

Emily Lakdawalla's post on Day 2 includes:
- a bit about recent flyby data from the comets Hartley 2 and Tempel 1.
- size data on Makemake based on an occultation; also, results from infrared data indicate that Makemake has a surface with mixed really really bright and really really dark patches
- weird results from an occultation about Quaoar's size - it 'looked like someone had taken a bite out of it'
- a few things about Titan

Three official press releases of the day:
One on a discovery made using the Kepler spacecraft on the discovery of a star with three identified planets. The smallest has a mass of 6.9 times that of Earth, while the larger two have mass of 16-17 times that of Earth (i.e., about Neptune's mass). All three are much closer to their star than Mercury is to the sun.

A second on oddities of comet Hartley 2, including that it may be two former comets that got stuck together.

Third, and most exciting to me, is one about a global false-colour map of Titan using data from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). This is really hard to do because of Titan's atmosphere, which is opaque to most wavelengths of light, and even with the wavelengths that can penetrate it, there are still atmospheric effects, e.g. from clouds and mist.

And now for what I've managed to extract from Twitter. As with last time, I could have introduced all kinds of distortions, so take all this with a good dose of grains of salt. There was also plenty more interesting stuff that I saw but couldn't understand/contextualize well enough to put it into a post. (Lots of that was about Titan.)

Vesta
Vesta's pole star is Deneb.

Titan
Titan seems to have seasonal rain in normally dry equatorial deserts.
There's a case made for Titan having dust storms.
Does Titan have ice volcanoes? Maybe, maybe not. Lots of things that looked like volcanoes at first seem not to be on closer inspection, but there's one good candidate: Sotra Facula.

Kuiper Belt Objects
Results from Eris occulting a star were presented, but couldn't be reported on Twitter due to an embargo :-( . They'll be published in Nature on Oct. 26th.

Makemake occulted a star with of magnitude V=18.2 on April 23, 2011. They observed the occultation with 7 telescopes in 5 locations, and found a drop in magnitude of 0.4. They were able to calculate Makemake's albedo as about 0.71, which is greater than Pluto's, and is consistent with the value of 0.81 derived from measurements the infrared telescopes Spitzer and Herschel. They calculate Makemake's size based on the occultation as about 1610 +22/-180 km x 1444+/-9 km. Whether or not the occultation data indicates an atmosphere is still being worked out.

Quaoar occulted a star too, and they observed it from at least 5 sites. Quaoar has is less reflective than was previously thought; this means that it's also larger and less dense. Its diameter is now estimated as 1045-1095 km, and density at 1.95-2.75 grams per cubic centimeter. It might have a methane atmosphere with a pressure of 0.1 ubar [I think ubar is an alternate abbreviation for µbar = microbar, but I'm not certain] at a temperature of 45K.

Extrasolar planets
The Kepler spacecraft's major measurements come from planets transiting their stars, but the measurements are also affected by how the planet and star distort each other tidally. Using these tidal distortions, it's possible figure out the mass ratio between the planet and the star just from observing transits. (Neat! It always amazes me how much information astronomers can squeeze out of a seemingly tiny bit of data.)

Upcoming missions
The European Space Agency's Solar Orbiter mission has been approved. It will orbit the sun in a highly inclined orbit inward of Mercury's orbit, and is expected to launch in 2017.

Other stuff
WISE shows 4 things that might potentially be very low mass brown dwarfs orbiting the sun. But they might also be extragalactic sources of radiation. (That's a big difference!)

Sources of tweets that I've used to compile this (again, I hope I haven't left anyone out):
DrFunkySpoon
GovertTweets
AllPlanets
elakdawalla
PlanetDr
spacemandave