(page 1 of 2)
|Astronomers in Brazil have discovered a cluster of stars forming at the edge of the Milky Way, according to a press release from the Royal Astronomical Society.| Excerpt from news.discovery.com This is unusual because it was believed that stars generally take form closer to the center of our spiral-shaped galaxy, rather than from its swirling, spiral arms, which are thousands of light-years away. These two clusters of stars — named Camargo 438 and 439 — were seen in a cloud at the galaxy’s outskirts.Denilso Camargo, an astronomer at the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, led a team that analyzed data from NASA’s orbiting Wide-Field Infrared Survey Explorer (WISE) observatory. They zeroed in on dense clumps of gas in so-called giant molecular clouds(GMCs) that are known to generate stars. GMCs are mainly located in the inner part of the galactic disc.The new star clusters lie about 16,000 light-years away from the main disk of the Milky Way galaxy. How did they form there? The scientists aren’t yet sure but Camargo theorizes that one of two scenarios could have led to the stars’ formation.In the first scenario, called the “chimney model,” supernovas could have flung the gas and dust that formed the cloud out of the Milky Way. Another explanation is the material could have drifted in from outside the galaxy.“Our work shows that the space around the Galaxy is a lot less empty that we thought,” said Camargo. “The new clusters of stars are truly exotic.”Camargo’s team published their results in the journal Monthly
Excerpt from slate.comWE CALL Earth a water world, and that’s pretty fair: Our planet’s surface is 70 per cent covered in it, it makes up a percentage of our air, and there’s even a substantial amount of it mixed in to the planet’s mantle, deep underground. But where the heck did it come from?This is no idle question. We have a lot of water here, and it must have come from somewhere. There are two obvious source — it formed here along with the Earth, or it was brought to Earth from space. Which is the dominant source has been a topic of long and heated debate among astronomers.The first big science results have just been announced by the European science team working with the Rosetta probe, and, in my opinion, they throw more gasoline on the fire. Measurements made by the probe show that comets like 67P/Churyumov — Gerasimenko — the one Rosetta is orbiting — couldn’t have been the source of our water.But that hardly helps answer the underlying question! Why not? Ah, the details …When the Earth formed 4.55 billion years ago (give or take), there was a lot of water in the disk of material swirling around the Sun. Close in to the Sun, where it was warm, that water was a gas, and farther out it formed ice. We see that latter part echoed down through time now in the form of icy moons around the outer planets.You’d expect water collected on Earth along with everything else (metals, silicates, and so on). When the Earth cooled, a lot of that water bubbled up from the interior or was outgassed by volcanism.
But we have another big source, too: comets. These are dirty snowballs, rock and dust held together by water frozen as ice. They formed farther out in the solar system, where ice was more plentiful. Long ago, just a few hundred million years after Earth formed and started to cool, there was a tremendous flood of comets sent down into the inner solar system, disturbed by the gravitational dance of the outer planets as they slowly settled down into their orbits. This Late Heavy Bombardment, as it’s called, could have supplied all of Earth’s water.How to tell? Well, it turns out that in this one case, hipsters are right: Locally sourced is measurably different than stuff trucked in.Water is made up of one oxygen atom and two hydrogen atoms. Hydrogen atoms, it so happens, come in two flavours: The normal kind that has single proton in its nucleus, and a heavier kind called deuterium that has a proton and a neutron (there’s also tritium, with two neutrons, but that’s exceedingly rare). Deuterium is far more rare than the normal kind of hydrogen, but how rare depends on what you look at. The ratio of deuterium to hydrogen in Earth’s water can be different than, say, water in comets, or on Mars.Note I said, “can be”. We know the ratio differs across the solar system. But suppose we find the same ratio in comets as we do on Earth. That would be powerful evidence that water here began out there. Astronomers have looked at a lot of comets trying to pin down the ratio, and what they’ve found is maddening: Some comets have a ratio very different from Earth’s, and only one (103P/Hartley 2) has a ratio similar to ours.
Where does water come from? Source: Getty Images
Now that’s interesting: 103/P is a Jupiter-family comet, meaning it used to orbit the Sun far out, but dropped into the inner solar system, got its orbit modified by Jupiter, and now has a much shorter path that keeps it in the inner solar system.Rosetta’s comet, 67/P, is also a Jupiter-family comet. You’d expect them to have roughly similar deuterium/hydrogen ratios.They don’t. 67/P, according to Rosetta, has three times the deuterium per hydrogen atom as Earth (and 103/P).What does that mean? It’s not clear, which is why this is maddening. It could be simply that not all Jupiter-family comets have the same ratio; they may all have different origins (born scattered across the solar system, so with different D/H ratios), but now belong to the same family. Or it could mean that 67/P is an oddball, with a much higher ratio than most other comets like it. That would seem unlikely, though, since we’ve studied so few you wouldn’t expect an oddball to be found so easily.Making things more complicated, some asteroids in the main belt between Mars and Jupiter have water on them, and it appears to have an Earth-like D/H ratio. But we think they have so little water that it would take a lot more of them impacting the early Earth to give us our water than it would comets. That’s possible, but we know lots of comets hit us back then, so it’s still weird that the D/H ratios don’t seem to work out. Still, it’s nice that there could be another potential source to study, and this new Rosetta result does lend credence to the idea that asteroids did the wet work.
Jets of material — including water — emanate from comet 67P/Churyumov — Gerasimenko. Source: AP
So if you ask where Earth’s water come from, the answer is: We still don’t know...
So what do comets have to do with it? Source: Getty Images
The image shows NGC 7793’s spiral arms and small central bulge.Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful micro-quasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. A micro-quasar is an object that has some of the properties of quasars in miniature. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disk rather than at its center.Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disk around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1,000 light-years across.
|Hubble Finds Jets and Explosions in NGC 7793. Image credit: ESA/Hubble & NASA|
This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.