steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
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.
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
A piece of big astronomy news came out yesterday: An earth-sized planet has been discovered orbiting Alpha Centauri B, a relatively sun-like star (a bit smaller and fainter than the Sun) in the nearest star system to the Sun. The planet is not particularly earth-like, though, since it orbits the star in only about 3.2 days, and thus would be extremely hot.

I started to write a long entry talking about Alpha Centauri system the system and the discovery, but I think instead I'm going to link a few articles - there are many more that could easily be found - and talk a bit about some things I noticed in reading the original paper.

News stories )

Links to the original paper )

I gave the paper a quick reading, and while some of it was too technical for me to understand, I was able to follow the basics of it. And I was once again amazed by the amounts of information that astronomers are able to squeeze out of apparently tiny amounts of data - in this case, the spectrum of a star observed repeatedly over time.

Details )

Here's an article that talks about some of the noise sources in non-academic terms.
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
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.
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
Youngest Planet Seen as it's Forming
Using the Keck telescope and some sophisticated techniques, astronomers have been able to see not only a very young gas giant around another star, but also dust and gas around it that it hasn't integrated into itself yet.
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
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's pole star is Deneb.

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):
[ profile] DrFunkySpoon
[ profile] GovertTweets
[ profile] AllPlanets
[ profile] elakdawalla
[ profile] PlanetDr
[ profile] spacemandave
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
Kepler spacecraft discovers 'invisible world'

Kepler normally discovers planets orbiting other stars by observing a star's light dim as a planet passes in front of it. Now it's discovered another one by an interesting indirect method. A star has (at least) two planets. Kepler can detect the first planet in the normal way, by observing changes in the star's light when the planet transits it. The second planet has a gravitational influence on the first planet, and changes the timing of its transits by a few minutes. This change in timing shows us that the second planet is there, even though Kepler can't see it transiting.
kajivar: (Astronomy // Milky Way)
[personal profile] kajivar
Astronomers are announcing a newly discovered exoplanet in the habitable zone of its star, and another one — in the same system — that's just twice the size of Earth.

The Gliese 581 planetary system now has four known planets, with masses of about 1.9, 16 (nearest to the star), 5, and 7 Earth-masses.

Michel Mayor, a well-known exoplanet researcher from the Geneva Observatory, announced the find today. The planet, "e," in the famous system Gliese 581, is only about twice the mass of our Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist. Both planets were discovered by the so-called "wobble method," using the HARPS spectrograph attached to the 3.6-meter (11.8-foot) ESO telescope at La Silla, Chile.

The gentle pull of an exoplanet as it orbits the host star introduces a tiny wobble in the star's motion that can just be detected on Earth with today's most sophisticated technology. Low-mass red dwarf stars such as Gliese 581 are potentially fruitful hunting grounds for low-mass exoplanets in the habitable zone. Such cool stars are relatively faint and their habitable zones lie close in, where the gravitational tug of any orbiting planet found there would be stronger, making the telltale wobble more pronounced.

Many more exoplanets have been discovered using the transit method being employed by NASA's Kepler mission: as planets pass between their host stars and Earth, they cause an observable, periodic dimming.

Planet Gliese 581 e orbits its host star – located only 20.5 light-years away in the constellation Libra ("the Scales") — in just 3.15 days.

"With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet," says co-author Xavier Bonfils from Grenoble Observatory. Being so close to its host star, the planet e is not in the habitable zone. But another planet in this system appears to be.

"Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star," added team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. "'d' could even be covered by a large and deep ocean — it is the first serious 'water world' candidate," he said.

Mayor said it's "amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 — the one around 51 Pegasi. The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b. This is tremendous progress in just 14 years."

But the astronomers aren't finished yet. "With similar observing conditions an Earth-like planet located in the middle of the habitable zone of a red dwarf star could be detectable," says Bonfils. "The hunt continues."

Source: Universe Today
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