Posts tagged ESO
Posts tagged ESO
This zoom sequence starts with a broad panorama of the central parts of the Milky Way. We then gradually close in on one of the bright regions of dust and gas where new stars are forming. In the final sequence we see a very detailed new close-up view of Messier 17, sometimes called the Omega or Swan Nebula in a new picture from ESO’s Very Large Telescope (VLT). Credit: ESO/INAF-VST/OmegaCAM/Nick Risinger
By Alan Boyle
A mysterious giant “blob” of glowing hydrogen gas on the edge of the observable universe has to be powered by the galaxies hidden within it, astronomers have concluded.
The detective story surrounding the power source for the Lyman-alpha blob, one of the biggest objects in the known universe, is discussed in this week’s issue of the journal Nature. An international team of astronomers used the European Southern Observatory’s Very Large Telescope in Chile to track down the answer to a decade-old question.
"We have shown for the first time that the glow of this enigmatic object is scattered light from brilliant galaxies hidden within, rather than the gas throughout the cloud itself shining," the University of Toulouse’s Matthew Hayes, lead author of the paper, said in an ESO news release.
The 300,000-light-year-wide blob of gas was spotted in the year 2000, shining at a distance of 11.5 billion light-years in the constellation Aquarius. It’s called a “Lyman-alpha blob,” or LAB-1, because it shines brightly in a characteristic wavelength of ultraviolet light known as the Lyman-alpha radiation.
Just as the Sun rises in the east and sets in the west, so do the stars appear to slowly march across the sky. Their leisurely pace is imperceptible to a casual observer, but you can test the effect for yourself: on the next clear night note the position of a bright star, and then check again a few hours later. The change is not caused by the motion of the stars themselves, but rather the rotation of the Earth.
Long-exposure photography is the ideal way to capture this motion. A camera is set up on a tripod, and the shutter opened to the sky. Normal snapshots gather light for a fraction of a second, but these special images need starlight to pour onto them for much longer, like a bucket collecting rainwater.
To obtain this image, ESO Photo Ambassador Gianluca Lombardi collected light for a total of 25 minutes. This may not seem like a long time, but the streaks of light in the night sky tell a different story. The Earth has rotated so that the pin-pricks of starlight have become star trails. In the top left, the trails form arcs around the southern celestial pole, which is outside the photograph. The ghostly traces of someone walking across the Paranal observing platform can also be seen.
Many familiar and outstanding pictures of astronomical objects are obtained using the same principle of accumulating light over a long period of time to build up an image. It is common for telescopes to gather light for several hours to make a single picture. This brings with it an additional challenge: the Earth rotating means that the telescope must also move to keep track of its target.
The Orion Nebula is one of the best-known star-forming regions in our celestial neighborhood, but astronomers can still find some “hidden treasures” if they just look at the nebula in a different light.
Case in point: this ethereal picture of the Orion Nebula, featured today by the European Southern Observatory in Chile. The image is based on data from the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile, and submitted by Russia’s Igor Chekalin for the ESO’s Hidden Treasures astrophotography competition. This particular image took seventh place. Another one of Chekalin’s entries, showing the M78 reflection nebula in Orion, won first prize (and earned Chekalin a trip to Chile).
The Orion Nebula, also known as M42, is a huge complex of gas and dust where massive stars are constantly being squeezed into existence. It’s about 1,350 light-years away, which is pretty close by astronomical standards. You’ve probably already figured out that the nebula is in the constellation Orion, which is at center stage in the night sky at this time of year.
The hidden treasures that Chekalin found were data sets from roughly 52-minute exposures taken in five different wavelengths. The rays of light that passed through a red filter and through a filter sensitive to glowing hydrogen gas are represented as red in this image. Light in the yellow-green part of the spectrum is shown here as green. The blue-filter image is reproduced as blue, and ultraviolet shows up as purple. The result is a beautiful picture that sheds new light on the nebula’s gauzy structure.
Explanation: Is this what will become of our Milky Way Galaxy? Perhaps if we collide with the Andromeda Galaxy in a few billion years, it might. Pictured above is NGC 7252, a jumble of stars created by a huge collision between two large galaxies. The collision will take hundreds of millions of years and so is effectively caught frozen in time in the above image. The resulting pandemonium has been dubbed the Atoms-for-Peace galaxy because of its similarity to a cartoon of a large atom. The above image was taken recently by the MPG/ESO 2.2 meter telescope in Chile. NGC 7252 spans about 600,000 light years and lies about 220 million light years away toward the constellation of the Water Bearer (Aquarius). Since the sideways velocity of the Andromeda Galaxy (M31) is presently unknown, no one really knows for sure if the Milky Way will ever collide with M31.