You may have never noticed it, but our solar system is moving around quite a clip. Stars in the outer reaches of the Milky Way including our Sun, orbit at an average speed of 130 miles per second. But this is nothing compared to the most massive spiral galaxies. The super spirals, which are larger, brighter and more massive than the Milky Way, spin even faster than expected at their mass, at speeds of up to 350 miles per second.
Their rapid rotation is the result of sitting within an extremely massive cloud or halo of dark matter – invisible matter, detectable only by its gravity. The largest "super helix" studied here is located in a halo of dark matter weighing at least 40 trillion times the mass of our Sun. The existence of super helices gives more evidence that an alternative theory of gravity, known as Modified Newtonian Dynamics, or MOND, is incorrect.
When it comes to galaxies, how fast is fast? The Milky Way, an average spiral galaxy, spins at 130 miles per second (210 km / sec) in the neighborhood of our Sun. A new study finds that the most massive spiral galaxies spin faster than expected. These "super spirals," the largest of which weigh about 20 times our Milky Way, spin at speeds of up to 350 miles per second (570 km / sec).
Super spirals are exceptional in almost every way. Besides being much more massive than the Milky Way, they are also brighter and larger in physical size. The largest span is 450,000 light-years compared to the diameter of 100,000 light-years in the Milky Way. To date, only about 100 super spirals are known. Super spirals were discovered as an important new class of galaxies during the study of Sloan Digital Sky Survey (SDSS) data as well as the NASA / IPAC Extragalactic Database (NED).
"Super spirals are very much by many measures," says Patrick Ogle of the Space Telescope Science Institute in Baltimore, Maryland. "They Break the Speed Records."
Ogle was the first author of an article published on October 10, 2019 in the Astrophysical Journal Letters . The document presents new data on the super helix rotational speed collected with the South African Large Telescope (SALT), the largest single optical telescope in the Southern Hemisphere. Additional data were obtained using a 5-meter Hale telescope at the Palomar Observatory, operated by the California Institute of Technology. NASA WISE data were critical to measuring galactic masses in stars and the rate of star formation.
Referring to the new study, Tom Jarrett of the University of Cape Town, South Africa says: This work perfectly illustrates the powerful synergy between optical and infrared galaxy observations, revealing stellar motion by SDSS and SALT spectroscopy and other special star properties. the stellar mass or backbone of receiving galaxies – via WISE mid-infrared imaging.
The theory suggests that super spirals rotate rapidly because they are located in incredibly large clouds or halos of dark matter. Dark matter has been associated with the rotation of the galaxy for decades. Astronomer Vera Rubin pioneered the speed of galaxy rotation, showing that spiral galaxies rotate faster than if their gravity were due solely to constituent stars and gas. Additionally, an invisible substance known as dark matter should affect the rotation of the galaxy. A spiral galaxy with a mass in stars is expected to rotate at a certain speed. The Ogle team finds that the super spirals significantly exceed the expected rotation speed.
Super spirals are also found in larger than average dark matter halos. The largest halo that Ogle measures contains dark enough matter to weigh at least 40 trillion times our Sun. This amount of dark matter usually contains a group of galaxies, not a single galaxy.
"It seems that the rotation of a galaxy is determined by the mass of the halo of its dark matter," explains Ogle.
The fact that super spirals disrupt the usual relationship between the galactic mass in the stars and the speed of rotation is new evidence against an alternative theory of gravity, known as Modified Newtonian Dynamics or MOND. MOND proposes that on larger rocks such as galaxies and galactic clusters, gravity be slightly higher than would be predicted by Newton or Einstein. This would cause, for example, the outer regions of a spiral galaxy to spin faster than expected based on its mass in stars. MOND is designed to reproduce the standard link in the rotation speed of the spiral, therefore cannot explain hermits as super spirals. Supercoiled observations suggest that non-Newtonian dynamics are not required.
Despite being the most massive spiral galaxies in the universe, super spirals are actually low in star weight compared to what would be expected for the amount of dark matter they contain. This suggests that a large amount of dark matter inhibits star formation. There are two possible reasons: 1) Any additional gas that is drawn into the galaxy collapses and warms up, preventing its cooling and star formation, or 2) the rapid rotation of the galaxy makes it difficult for gas clouds to collapse against the effects of centrifugal force. .
"This is the first time we find spiral galaxies that are as large as they can ever be," Ogle says.
Despite these destructive effects, super spirals can still form stars. Although the largest elliptical galaxies formed all or most of their stars more than 10 billion years ago, the super spirals still form stars to this day. They convert about 30 times the mass of the Sun into stars each year, which is normal for a galaxy of this size. By comparison, our Milky Way forms about one solar mass of stars a year.
Ogle and his team have offered additional observations to help answer key questions about super helices, including observations designed to better investigate the movement of gas and stars within disks. After its launch in 2021, NASA's James Web Web Space Telescope can study super spirals over longer distances and, respectively, younger ages to learn how they evolve over time. And NASA's WFIRST mission can help find more super spirals that are extremely rare, thanks to its large field of view.
The Space Telescope Science Institute Extends the Space of Astronomy to Host the Hubble Space Telescope Center The Hubble Space Telescope The James Webb Space Science and Operations Center and the Broadcasting Center for Scientific Operations infrared observation telescope (WFIRST). STScI also maintains the Miculsky Space Telescope (MAST) archive, which is a NASA-funded project for maintaining and providing the astronomical community with various astronomical data archives and is a data repository for Hubble, Webb, Kepler, K2, TESS missions and more.