Galaxies Collide

Canada and the World

Current Events with a Canadian Perspective

Last update

15 February 2011

Site map

Galaxies Collide

A vast cloud of gas, perhaps big enough to be a galaxy,

is colliding with the outer edges of the Milky Way

Smith’s Cloud contains enough hydrogen to create millions of stars similar to the Sun and it’s thought to be just one of many so-called dark galaxies that may be out there.

Smith’s Cloud Named after its Discoverer

In 1963, Gail Smith (now Gail Bieger) was an astronomy student at Leiden University in the Netherlands, when she spotted a massive cloud of hydrogen gas.

The cloud is 11,000 light years long and 2,500 light years wide. Space.com says if the cloud could be seen from Earth “it would span 30 times the width of the moon.”

At the time of its discovery it was thought to have a mass about a million times larger than the mass of the Sun.

Jay Lockman, of the National Radio Astronomy Observatory in Green Bank, West Virginia is quoted by space.com as saying: “My guess is that this [gas cloud] is a remnant of the original formation of the Milky Way (below) in the way that comets and meteors are remnants of the formation of the solar system.”

NASA Images

Cloud is Bumping into the Milky Way

According to an article in The New Scientist (November 22, 2009), Smith’s Cloud “appears to be crashing into our own [galaxy].”

The magazine is reporting on the work of Matthew Nichols and Joss Bland-Hawthorn of the University of Sydney, Australia, whose calculations suggest the cloud has a mass some 100 times greater than the original estimate. The New Scientist writes that the cloud “has managed to avoid disintegrating during its smash-up with our own, much bigger galaxy.”

Earlier Collision Appears to have Occurred

On January 12, 2008, BBC News Science reporter Paul Rincon wrote that: “The monster cosmic ‘fog bank’ is careering towards our galaxy at more than 240km/s (150 miles/s) and is set to strike the Milky Way at an angle of 45 degrees.” The cloud is already brushing the outer edge of the Milky Way.

Meanwhile, Nichols and Bland-Hawthorn say that the trajectory of Smith’s Cloud suggests it may have passed through the Milky Way something like 70 million years ago.

Galactic Collision Creates Stars

Interviewed by sciencedaily.com (January 13, 2008) Jay Lockman said that when the full force of the collision takes place, and this may be as much as 40 million years away, it could trigger a “tremendous burst of star formation. Many of those stars will be very massive, rushing through their lives quickly and exploding as supernovae. Over a few million years, it’ll look like a celestial New Year’s celebration, with huge firecrackers going off in that region of the galaxy.”

There may be more Dark Galaxies

The discovery of the first dark galaxy was confirmed by the National Astronomy and Ionosphere Center on June 13, 2007.

Citing evidence from the Hubble Space Telescope and other observations, the center says all but one of the hypotheses had been ruled out to explain “the existence of VIRGOHI 21, an intergalactic gas cloud 50 million light-years from the Earth. An international team of astronomers found that it was rotating like an ordinary galaxy but without any starlight shining out, making it a coveted dark galaxy.”

In The New Scientist, Leo Blitz of the University of California, Berkeley says that Smith’s Cloud is not alone: “Many more such dark galaxies may be out there.”

Sources

“Space Cloud to Collide With Our Galaxy.” Jeanna Bryner, Space.com, January 11, 2008.

“Dark Galaxy Crashing into the Milky Way.” New Scientist, Issue 2735, November 22, 2009.

“Massive Gas Cloud Speeding Toward Collision with Milky Way.” ScienceDaily, January 13, 2008.