Galaxy Is 13 Times the Size of Milky Way

A huge galaxy with swirling gases that appear to undulate has been identified as possibly the largest galaxy in the universe, scientists reported today.

For at least 20 years astronomers thought the galaxy was average in size, probably no bigger than our own Milky Way; but when they examined it recently with a huge radio telescope in New Mexico they learned that it is actually 13 times larger than the Milky Way. Its544434554could not be seen with optical telescopes.

The galaxy was measured at 1.3 million light-years in diameter. A light-year is the distance light travels in a year, or about 6 trillion miles. The Milky Way is only about 100,000 light-years across.

The galaxy, called Markarian 348, is 300 million light-years from Earth in the direction of the constellation Andromeda. It is a member of a class of galaxies known for their high level of energy. The discovery of its actual size, reported in the journal Science, makes it the largest known galaxy in the universe, but the astronomers who made the finding said there may be others at least as large that have not been subjected to the same level of scrutiny.

“We don’t know how many other galaxies are this big,” said Susan M. Simkin, an astronomer at Michigan State University and the lead author of the Science report.

Of perhaps greater importance than the galaxy’s size, however, is that the radio telescope was able to confirm that a great cloud of hydrogen surrounding the galaxy is swirling and undulating because of gravitational forces similar to the tides of the Earth’s oceans, which are caused by the gravitational tug of the moon and sun.

That finding is important because it suggests that the swirling gases pull other intergalactic material into the galaxy as it grows even larger.

Suspicions Confirmed

“People have had a suspicion for a long time that these galaxies are fed by material that’s induced into the nucleus,” Simkin said in a telephone interview.

The gravitational field that seems to be pulling material into Markarian 348 is a smaller galaxy nearby, she said.

That has created a galaxy that appears to have at least one, and possibly two, long, spiraling arms that are wound tightly at the center and branch out at irregular angles.

The discovery is part of a flood of new findings growing out of the multiplicity of instruments available to astronomers today.

Mt. Palomar Telescopes

Simkin and astronomer Hong-Jun Su used the optical telescopes of Mt. Palomar in Southern California and Kitt Peak in Arizona for their observations. At the same time, Jacqueline van Gorkom and John Hibbard studied the galaxy with the Very Large Array, a series of 27 radio telescopes, each measuring 82 feet in diameter, near Socorro, N. M.

Radio telescopes work in much the same way as optical instruments, using the radio wave segment of the electromagnetic spectrum to create images just as optical telescopes use visible light.

But radio telescopes also “see” materials that do not reflect visible light, such as certain gases that emit radio waves. Thus the astronomers were able to measure the hydrogen cloud around the galaxy, and even detect stars concealed by the gas.

The astronomers also used the radio telescope to determine the velocity of the gas--its speed and direction--and thus learned that it was undulating in concert with the movement of the smaller galaxy nearby.