Bizarre Galaxy Is Result Of Pair Of Spiral Galaxies Smashing Together

A recent NASA/ESA Hubble Space Telescope image captures what appears to be one very bright and bizarre galaxy, but is actually the result of a pair of spiral galaxies that resemble our own Milky Way smashing together at breakneck speeds. The product of this dramatic collision, called NGC 2623, or Arp 243, is about 250 million light-years away in the constellation of Cancer (the Crab).

Not surprisingly, interacting galaxies have a dramatic effect on each other. Studies have revealed that as galaxies approach one another massive amounts of gas are pulled from each galaxy towards the centre of the other, until ultimately, the two merge into one massive galaxy. The object in the image, NGC 2623, is in the late stages of the merging process with the centres of the original galaxy pair now merged into one nucleus. However, stretching out from the centre are two tidal tails of young stars showing that a merger has taken place. During such a collision, the dramatic exchange of mass and gases initiates star formation, seen here in both the tails.

The prominent lower tail is richly populated with bright star clusters — 100 of them have been found in these observations. The large star clusters that the team have observed in the merged galaxy are brighter than the brightest clusters we see in our own vicinity. These star clusters may have formed as part of a loop of stretched material associated with the northern tail, or they may have formed from debris falling back onto the nucleus. In addition to this active star-forming region, both galactic arms harbour very young stars in the early stages of their evolutionary journey.

Some mergers (including NGC 2623) can result in an active galactic nucleus, where one of the supermassive black holes found at the centres of the two original galaxies is stirred into action. Matter is pulled toward the black hole, forming an accretion disc. The energy released by the frenzied motion heats up the disc, causing it to emit across a wide swath of the electromagnetic spectrum.

NGC 2623 is so bright in the infrared that it belongs to the group of very luminous infrared galaxies (LIRG) and has been extensively studied as the part of the Great Observatories All-sky LIRG Survey (GOALS) project that combines data from some of the most advanced space-based telescopes, including Hubble. Additional data from infrared and X-ray telescopes can further characterise objects like active galactic nuclei and nuclear star formation by revealing what is unseen at visible wavelengths.

The GOALS project includes data from NASA/ESA's Hubble Space Telescope, NASA's Spitzer Space Telescope, NASA's Chandra X-ray Observatory and NASA's Galaxy Evolution Explorer (GALEX). The joint efforts of these powerful observing facilities have provided a clearer picture of our local Universe.

This data used for this colour composite were taken in 2007 by the Advanced Camera for Surveys (ACS) aboard Hubble. The observations were led by astronomer Aaron S. Evans. A team of over 30 astronomers, including Evans, recently published an important overview paper, detailing the first results of the GOALS project. Observations from ESA's X-ray Multi-Mirror Mission (XMM-Newton) telescope contributed to the astronomers' understanding of NGC 2623.

Let There Be Blobs: Mystery Object Spotted in the Early Universe

Looking deep into the sky—and, by extension, far back in time—astronomers have spotted a curious space blob that existed when the universe was only 800 million years old, about 6 percent of its present age.

Masami Ouchi, a fellow at The Observatories of the Carnegie Institution in Pasadena, Calif., who led the research reported in the May 10 issue of the Astrophysical Journal, says that the luminous gas cloud, which spans some 55,000 light-years (about half the diameter of the Milky Way), is unique for its time. "There are no extended objects found at such an early epoch," he says. Other known objects in its class, called Lyman-alpha blobs, are from somewhat more recent history, Ouchi says—at least two billion to three billion years after the big bang.

Lyman-alpha blobs are an astronomical mystery that may be primordial galaxies. "The consensus is that these are enormous protogalaxies, which over the course of time will yield very massive old galaxies such as we see in the local universe," says Dan Smith, a postdoctoral researcher at Liverpool John Moores University in England. Smith, who was not involved in the study, calls the detection of such an early Lyman-alpha blob "a very exciting result."

But as of now, it is not known what Lyman-alpha blobs are or what causes them to glow. Resolving the proposed explanations for these early objects could shed light on how galaxies such as the Milky Way take shape. Some theories hold that Lyman-alpha blobs are formed by inflows of cold streams of gas, a mechanism that Smith points out has recently been suggested by some researchers as the dominant mode of galaxy growth. Other explanations posit that the blobs' gas emits radiation due to heating by an active galactic nucleus harboring a churning object such as a supermassive black hole or by an accelerated phase of star formation known as a starburst.

The Lyman-alpha blob has been dubbed Himiko, after a queen in ancient Japan. "I found the name of Himiko is very suitable," Ouchi says, "given the fact that this object was discovered in an ancient universe [by] the Subaru Telescope," which is operated by the National Astronomical Observatory of Japan.

100 Years Ago: Punch Cards and the Census

SEPTEMBER 1959
RADIATION— “What should the citizen conclude about ionizing radiation? Ionizing radiation has always been with us and will be for all foreseeable time. Our genetic system is probably well adjusted by natural selection to normal background radiation. Added radiation will increase the frequency of mutations; most of these will be harmful. Exposure to radiation in large amounts will increase malignant disease; small amounts may possibly do the same. In view of these potentially harmful effects every reasonable effort should be made to reduce the levels of ionizing radiation to which man is exposed to the lowest levels that can reasonably be attained. As to fallout from nuclear-weapons tests, the citizen will conclude that it contributes in a small way to world-wide levels of radiation. For this reason alone the tests should be discontinued. —George W. Beadle”

SEPTEMBER 1909
CENSUS— “The counting at the end of each decade of every man, woman, and child in the United States is one of the biggest undertakings the government is called upon to assume. To facilitate counting, machines will be used invented by Mr. James Powers, a mechanical expert of the Census Bureau, for use in the thirteenth census, which were successfully tried in the recent Cuban Census and now in use in the Division of Vital Statistics. The mechanical method for counting the census requires two types of machines. The keynote of the system, however, is a punched card, which contains the data collected by the enumerators, who travel from house to house in every nook and corner of the land. The data include the nature and extent of our industries, and the amount of our wealth.”

HENRY HUDSON’S 300TH— “The  ship ‘Half Moon’ set sail from Amsterdam April 4th, 1609, with a crew of eighteen Dutch and English sailors. On September 3rd, the ‘Half Moon’ let go her anchor inside of Sandy Hook (New Jersey). The week was spent exploring the bay with a small boat, and ‘they found a good entrance between two headlands’ (The Narrows) and thus entered on the 12th of September ‘as fine a river as can be found.’ When the replica of Henry Hudson’s ‘Half Moon’ was lifted by the floating crane at the Brooklyn navy yard from the deck of the ‘Soestdyk,’ on which she was brought over from Holland, and lowered into the water, there was a general expression of surprise at her diminutive appearance; for she was no larger than a small harbor tug.”

SEPTEMBER 1859
WORMS— “The common earthworm, though apt to be despised and trodden on, is really a useful creature. According to Mr. [Charles] Darwin, they give a kind of under tillage to the land, performing the same below ground that the spade does above for the garden, and the plow for arable soil. Fields which have been overspread with lime, burnt marl, or cinder, become, in time, covered by finely-divided soil. This result, usually attributed by farmers to the ‘working down’ of these materials, is really due to the action of earthworms. Mr. Darwin says, ‘A field manured with marl has been covered, in the course of 80 years, with a bed of earth averaging 13 inches in thickness.’”

COTTON MARKET— “The ‘crop year’ for cotton has just closed, and it has been somewhat eventful. The previous year of the financial panic had passed with a very small consumption, leaving large stocks of goods in the hands of merchants and considerable supplies of raw materials with the manufacturers. Returning ease in the money market has been accompanied by abundant crops, cheap food, low rates for transportation, and a large consumption of goods, promising to absorb the whole of the crop. Up to January, purchases at home and abroad were very large, at improving prices.”

EVIL BROADCLOTH— “Professor Hamilton says: ‘Gentlemen have adopted as a national costume a thin, tight-fitting black suit of broadcloth. To foreigners, we seem always in mourning: we travel in black, we write in black, we work in black. Even the day-laborer chooses always the same unvarying, monotonous black broadcloth. It is too thin to be warm in the winter, and too black to be cool in the summer.’”