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Vue d’artiste d’un multi-vers selon le modèle de l’inflation chaotique éternelle.
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Vue d’artiste d’univers multiples. Univers donnant naissance a d’autres univers grâce a leurs trous noirs.
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Vue d’artiste d’un multi-vers. En physique quantique, le vide est effervescent, ses bulles peuvent croitre au point de devenir des univers. La théorie de corde produit un mécanisme qui assure a ces univers d’être différents les uns des autres.
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Star clusters are collections of hundreds to millions of stars that were born at the same time from the same cloud of gas. This shared origin makes star clusters unique tools for understanding how stars form and evolve. Additionally, they are useful for studying the major chapters in the history of galaxies. But before Andromeda’s star clusters can unlock these secrets, we need the help of Citizen Scientists to find the clusters. Not just the big bright ones, but the small faint ones as well. This is the goal of the Andromeda Project.
Star clusters vary greatly in terms of mass, size, age, and local environment. As a result, star clusters can appear quite different from one another depending on the properties of the clusters and where they are located in the galaxy. This makes the process of identifying clusters tricky and difficult to automate. From the first year of PHAT data, a team of eight astronomers searched through each image, manually identifying star clusters by eye. Using less than 1/5th the total PHAT survey area, we cataloged about 600 star clusters (Johnson+ 2012). With the Andromeda Project, we hope that you will help us find the thousands of star clusters hiding in the rest of the survey!
Because the appearances of star clusters vary so much, it is important for us to learn what kinds of clusters we can actually see. For this reason, we have inserted realistic synthetic clusters with known ages, masses, and sizes into some of the PHAT images. By identifying both real and synthetic clusters, we will learn what types of clusters are undetectable in Andromeda. This information is critical for understanding the age and mass distributions of the clusters by allowing us to determine whether certain populations of clusters do not exist or if they are simply avoiding detection.
After you help us to find these star clusters, we will use several techniques to determine the age and mass of these objects. In some clusters, we can resolve individual stars that allow us to determine the age, mass, and other aspects of the object. In other clusters, where individual stars are too faint or too close together, we can use the summed light from a cluster to determine its properties (Fouesneau+ 2012, in prep.). With these ages and masses in hand, we can use these clusters to study a host of interesting topics: rapid and rare stages of stellar evolution, the structure and scale of star formation, the evolution of cluster populations, and how Andromeda has changed over billions of years.
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For the first time a clever new technique has allowed astronomers to study the atmosphere of an exoplanet in detail — even though it does not pass in front of its parent star. An international team has used ESO’s Very Large Telescope to directly catch the faint glow from the planet Tau Boötis b. They have studied the planet’s atmosphere and measured its orbit and mass precisely for the first time — in the process solving a 15-year old problem. Surprisingly, the team also finds that the planet’s atmosphere seems to be cooler higher up, the opposite of what was expected. The results will be published in the 28 June 2012 issue of the journal Nature.
The planet Tau Boötis b  was one of the first exoplanets to be discovered back in 1996, and it is still one of the closest exoplanets known. Although its parent star is easily visible with the naked eye, the planet itself certainly is not, and up to now it could only be detected by its gravitational effects on the star. Tau Boötis b is a large “hot Jupiter” planet orbiting very close to its parent star.
Like most exoplanets, this planet does not transit the disc of its star (like the recent transit of Venus). Up to now such transits were essential to allow the study of hot Jupiter atmospheres: when a planet passes in front of its star it imprints the properties of the atmosphere onto the starlight. As no starlight shines through Tau Boötis b’s atmosphere towards us, this means the planet’s atmosphere could not be studied before.
But now, after 15 years of attempting to study the faint glow that is emitted from hot Jupiter exoplanets, astronomers have finally succeeded in reliably probing the structure of the atmosphere of Tau Boötis b and deducing its mass accurately for the first time. The team used the CRIRES  instrument on the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile. They combined high quality infrared observations (at wavelengths around 2.3 microns)  with a clever new trick to tease out the weak signal of the planet from the much stronger one from the parent star .
Lead author of the study Matteo Brogi (Leiden Observatory, the Netherlands) explains: “Thanks to the high quality observations provided by the VLT and CRIRES we were able to study the spectrum of the system in much more detail than has been possible before. Only about 0.01% of the light we see comes from the planet, and the rest from the star, so this was not easy”.
The majority of planets around other stars were discovered by their gravitational effects on their parent stars, which limits the information that can be gleaned about their mass: they only allow a lower limit to be calculated for a planet’s mass . The new technique pioneered here is much more powerful. Seeing the planet’s light directly has allowed the astronomers to measure the angle of the planet’s orbit and hence work out its mass precisely. By tracing the changes in the planet’s motion as it orbits its star, the team has determined reliably for the first time that Tau Boötis b orbits its host star at an angle of 44 degrees and has a mass six times that of the planet Jupiter in our own Solar System.
“The new VLT observations solve the 15-year old problem of the mass of Tau Boötis b. And the new technique also means that we can now study the atmospheres of exoplanets that don’t transit their stars, as well as measuring their masses accurately, which was impossible before”, says Ignas Snellen (Leiden Observatory, the Netherlands), co-author of the paper.“This is a big step forward.”
As well as detecting the glow of the atmosphere and measuring Tau Boötis b’s mass, the team has probed its atmosphere and measured the amount of carbon monoxide present, as well as the temperature at different altitudes by means of a comparison between the observations and theoretical models. A surprising result from this work was that the new observations indicated an atmosphere with a temperature that falls higher up. This result is the exact opposite of the temperature inversion — an increase in temperature with height — found for other hot Jupiter exoplanets  .
The VLT observations show that high resolution spectroscopy from ground-based telescopes is a valuable tool for a detailed analysis of non-transiting exoplanets’ atmospheres. The detection of different molecules in future will allow astronomers to learn more about the planet’s atmospheric conditions. By making measurements along the planet’s orbit, astronomers may even be able to track atmospheric changes between the planet’s morning and evening.
"This study shows the enormous potential of current and future ground-based telescopes, such as the E-ELT. Maybe one day we may even find evidence for biological activity on Earth-like planets in this way”, concludes Ignas Snellen.
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This galaxy is so large, so fully-formed, astronomers say it shouldn’t exist at all. It’s called a “grand-design” spiral galaxy, and unlike most galaxies of its kind, this one is old. Like, really, really old. According to a new study conducted by researchers using NASA’s Hubble Telescope, it dates back roughly 10.7-billion years — and that makes it the most ancient spiral galaxy we’ve ever discovered.
"The vast majority of old galaxies look like train wrecks," said UCLA astrophysicist Alice Shapley in a press release. "Our first thought was, why is this one so different, and so beautiful?"
Shapley is co-author of the paper describing the discovery, which is published in the latest issue of Nature. She and her colleagues had been using Hubble to investigate some of our Universe’s most distant cosmic entities, but the discovery of BX442 — which is what they’ve dubbed the newfound galaxy — came as a huge surprise.
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One thing that amazes me about astronomy is that even after, what, 30 years of doing it (I was really young when I started) I still get surprised at some basic facts.
That picture above is the spiral galaxy M101, a staple of amateur observing. It’s a big, bright, face-on spiral, and since it’s in Ursa Major (near the Big Dipper) it’s up most of the year. I’ve seen it a few times myself, though usually when I’m looking in books. Actually, in a lot of those books, it’s claimed that our own Galaxy would look like M101 if you could get outside of it.
But boy, is that ever wrong! M101 is a lot bigger than the Milky Way. A lot. It’s 170,000 light years across, compared to 100,000 for us. We have an impressive 100 billion stars in the Milky Way, but M101 is bursting with something like a trillion stars,ten times the number in the Milky Way! That’s staggering. I had no clue M101 was so huge.
The picture above is a stunning new release from Hubble (click it for a higher-res version). It’s almost as awesome as the galaxy itself: the original image is 12,000 x 16,000 pixels in size, making it one of the largest images of a spiral galaxy ever produced. The images span nearly a decade and were originally taken for several different projects (it was nice to see the name of my old friend Kip Kuntz as the head of one of those projects; he assisted me way back when on my very first trip to Baltimore to work on Hubble data for my PhD). It took 54 separate Hubble pointing to span the face of this galaxy.
If you have the stomach (and the broadband) for it, you can download the 455 megabyte full-resolution version, but you’d have to be insane. On my monitor, it would be ten screens in width and 20 in height!
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