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Galaxy that resembles Milky Way

It was recently discovered that a neighbouring galaxy resembles our home galaxy, the Milky Way. In the latest photograph, the galaxy can be seen edge-on, so it’s really difficult to tell precisely what size it has. Astronomers, however, know from previous studies that it also has spiral arms, and a bar-like structure at its centre, which makes it remarkably similar to our own corner of the Universe. The recent image was collected with the Wide Field Imager (WFI) instrument, which is located on the 2.2-meter MPG telescope, at the La Silla Observatory, in Chile. The entire ensemble is operated by the European Southern Observatory, which also has a number of other outposts in the country. The detailed photo revealed the fact that the distant galaxy was also similar to the Milky Way as far as its general structure was concerned.

The New General Catalogue (NGC) is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects. The NGC is one of the largest comprehensive catalogues, as it includes all types of deep space objects and is not confined to, for example, galaxies. The catalogue was compiled in the 1880s by John Louis Emil Dreyer using observations mostly from William Herschel and his son John, for a total of 7,840 objects. Dreyer had already published an update to the Herschel’s Catalogue of Nebulae, but a new update was turned down by the Royal Astronomical Society, who asked Dreyer to compile a New General Catalogue.
Observations of the galaxy, NGC 4945, suggest that this hive of stars is a spiral galaxy much like our own, with swirling, luminous arms and a bar-shaped central region. It appears cigar-shaped from our perspective on Earth, but the galaxy is actually a disc many times wider than it is thick, with bands of stars and glowing gas spiralling around its centre.

 X-ray observations show that NGC 4945 has an unusual, energetic, Seyfert 2 nucleus that might house a large black hole. It was discovered by James Dunlop in 1826. Scientific investigations also revealed that the nucleus of NGC 4945 was highly active, which means that it produces and spreads a lot more energy and radiation than galaxies such as the Milky Way, which, in spite of its size, is considered to be relatively calm. 

S A Mohan Krishna (The author is an amateur astronomer)


Algae may have made speedy rebound

The asteroid that struck the planet 65 million years ago was very bad for the dinosaurs, as everyone knows, but it wasn’t too good for smaller things, either. Even algae and other primary producers in the ocean were affected, probably because atmospheric debris from the impact reduced the sunlight available for photosynthesis. But there is new evidence, reported in Science, that primary productivity in the oceans was not down for long. An analysis of sediments along a bluff in Denmark suggests that algae recovered in less than a century. Julio Sepulveda, a geochemist at the Massachusetts Institute of Technology and formerly at the University of Bremen in Germany, and colleagues studied a 15-inch layer of clay at Kulstirenden on the island of Zealand.

The layer was deposited in the first 10,000 years after the asteroid impact and is far thicker than most other so-called boundary layers found around the world. That thickness is important, Sepulveda said, because it allows for more precise determination of the time scale of changes.  The researchers analysed the sediments for chemical markers for the presence of algae and other organisms. “We are basically looking at fossil molecules,” Sepulveda said. “A huge fraction of the primary production is coming from these micro-organisms, and some of them leave no fossil record. What can get preserved are the remains of their bodies as organic material.” Algae leave certain signatures of organic compounds and isotopes of carbon and nitrogen; bacteria leave different signatures. In the earliest sublayers, the researchers found much evidence for bacteria but little for algae, suggesting that right after the impact, algae production was greatly reduced.

Henry Fountain, NYT News Service

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