High Velocity Smith Molecular Gas Cloud to Collide With Milky Way Galaxy

Summary: The high velocity Smith molecular gas cloud will collide with the Milky Way’s outer disk, 55,000 light years from Earth, about 27 million years from now.

Diagram of Smith Cloud's 100-million-year-long trajectory: According to Hubble Space Telescope measurements, Smith Cloud came from region near edge of Milky Way galaxy's disk of stars 70 million years ago; the cloud now is stretched into cometary shape by gravity and gas pressure; following a ballistic path, Smith Cloud will fall back into disk and trigger new star formation 30 million years from now: NASA/ESA/Ann Feild (Space Telescope Science Institute), Public Domain, via NASA

Astronomers are forecasting the collision of the high velocity Smith molecular gas cloud with the Milky Way Galaxy, according to a paper published online Dec. 30, 2016, in Astrophysical Journal Letters.

The co-researchers and co-writers base their predictions upon atypical certainty in constructing and projecting the distance and speed of the high velocity Smith molecular gas cloud. They calculate per second and per hour movements of the high velocity Smith molecular gas cloud at 193 miles (310.6 kilometers) and 700,000 miles (1,126,540.8 kilometers). They describe an orbit 100 million years long bringing the high velocity Smith molecular gas cloud to the Milky Way Galaxy in about 27 million years.

The 10 researchers expect the high density Smith molecular gas cloud to collide with the galaxy’s outer disk.

Calculations furnish distances from the galactic center to the galaxy’s outer disk of 40,000 light years and to the solar system’s Sun of 15,000 light years.

The composition of the high velocity Smith molecular gas cloud gets astronomers’ attention, more so than collisions that are not unusual in galactic or interstellar space. Calculations head the Andromeda Galaxy, 2.53 million light years from Earth, on a collision course with the Milky Way Galaxy in three or four billion years. Nirmala Nataraj, author of Earth and Space: Photographs from the Archives of NASA, indicates that such collisions “often leave many of their respective star systems intact.”

The collisions of clouds and galaxies jumpstart the formation of stars, of which the Milky Way already has 400 billion.

NASA @NASA via Twitter Jan. 28, 2016

Astronomers know of the high velocity Smith molecular gas cloud’s hydrogen-emitting radio waves detected in 1963 by Gail Bieger-Smith, Leiden University astronomy student in the Netherlands.

Fifty-two years later, the Hubble Space Telescope’s Cosmic Origins Spectrograph leads to the discovery of the high velocity Smith molecular gas cloud’s chemical composition and origins. The Green Bank Telescope’s 21-centimeter (8.27-inch) spectra, the Hubble ultraviolet spectra and the Voigt-profile fitting the S II 1250, 1253 and 1259 triplet measure absorption lines. The 10 researchers note that the weighted average of the Green Bank, Hubble and Voigt measurements is [S/H] = -0.28 +/- 014, or 0.53+0.21-0.15 solar metallicity.

Andrew Fox of Space Telescope Science Institute observes that "the Smith cloud is enriched in sulfur to Milky Way-like levels.”

The 10-member research team profiles the high velocity Smith molecular gas cloud as 2,500 light years across, 11,000 light years wide and 70 million years old.

The co-researchers question the great speeds and the large mass of the high velocity Smith molecular gas cloud, whose collision will produce 2 million new stars. Higher present than original launch masses possibly result from accumulations of “cooling gas from the corona during its formation trajectory” through the Milky Way’s galactic disk. Nicolas Lehner of Indiana’s University of Notre Dame, suggests velocity from “the death of many massive stars” or a “100 million solar masses dark matter clump.”

Gail Bieger-Smith tells radio astronomer regarding discoveries with Leiden’s 25-meter (82.02-foot) Dwingeloo radio dish: “I’d love to witness the collision!”

Hubble's Cosmic Origins Spectrograph measures how light from distant background objects is affected during passage through the Smith Cloud, yielding clues to the cloud's chemical composition. Astronomers trace Smith Cloud's origin to the disk of our Milky Way. Combined ultraviolet and radio observations correlate to cloud's infall velocities, solid evidence that spectral features link to Smith Cloud's dynamics: NASA/ESA/Ann Feild (Space Telescope Science Institute), Public Domain, via NASA

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Smith Cloud's journey there and back again: NASA/ESA/Ann Feild (Space Telescope Science Institute), Public Domain, via NASA @ http://www.nasa.gov/feature/goddard/2016/hubble-sees-monstrous-cloud-boomerang-back-to-our-galaxy

"Monstrous cloud launched from our galaxy is like a boomerang, returning in 30 million years.": NASA @NASA via Twitter Jan. 28, 2016, @ https://twitter.com/NASA/status/692848384202248192

Smith Cloud characterization by Hubble: NASA/ESA/Ann Feild (Space Telescope Science Institute), Public Domain, via NASA @ http://www.nasa.gov/feature/goddard/2016/hubble-sees-monstrous-cloud-boomerang-back-to-our-galaxy

For further information:

Fox, Andrew J.; Lehner, Nicolas; Lockman, Felix J.; Wakker, Bart P.; Hill, Alex S.; Heitsch, Fabian; Stark, David V.; Barger, Kathleen A.; Sembach, Kenneth R.; and Rahman, Mudbi. 30 Dec. 2015. “On the Metallicity and Origin of the Smith High-Velocity Cloud.” Astrophysical Journal Letters 816(1). DOI: 10.3847/2041-8205/816/1/L11.
Available @ http://arxiv.org/abs/1512.04957

GeoBeats News. 30 January 2016. "NASA: A Monstrous Cloud Is Headed Back To Our Galaxy." YouTube.
Available @ http://www.youtube.com/watch?v=RhJbcF68YSM

Marriner, Derdriu. 20 January 2016. “Earth and Space: Photographs from the Archives of NASA Book Review.” Wizzley.
Available @ https://wizzley.com/earth-and-space-photographs-from-the-archives-of-nasa-book-review/

“Monstrous ‘Smith Cloud’ Boomerangs Bank to the Milky Way.” Astronomy Now > 28 Jan. 2016.
Available @ http://astronomynow.com/2016/01/28/monstrous-smith-cloud-boomerangs-back-to-the-milkyway/

NASA @NASA. 28 January 2016. "Monstrous cloud launched from our galaxy is like a boomerang, returning in 30 million years." Twitter.
Available @ https://twitter.com/NASA/status/692848384202248192

Nataraj, Nirmala. 2015. Earth and Space: Photographs from the Archives of NASA. Preface by Bill Nye. San Francisco, CA: Chronicle Books LLC.

Siegel, Ethan. 28 January 2016. “Monstrous Cosmic Gas Cloud Set to Ignite the Milky Way.” Forbes > Science.
Available @ http://www.forbes.com/sites/startswithabang/2016/01/28/monstrous-cosmic-gas-cloud-set-to-ignite-the-milky-way/#5d62896e60b7

Sky and Telescope. 1 May 2008. “The Mystery of the Million-Mass Cloud.” Allesoversterrenkunde > Actueel.
Available @ http://allesoversterrenkunde.nl/!/actueel/artikelen/_detail/gli/the-mystery-of-the-million-mass-cloud/

Thomson, Jason. 29 January 2016. “Monstrous Gas Cloud Is Careening toward the Milky Way: When Will It Hit?” The Christian Science Monitor > Science > First Look.
Available @ http://www.csmonitor.com/Science/2016/0129/Humongous-gas-cloud-is-careening-toward-the-Milky-Way-When-will-it-hit