Tag Archive: Milky Way


Our galaxy, the Milky Way, is a large spiral galaxy surrounded by dozens of smaller satellite galaxies. Scientists have long theorized that occasionally these satellites will pass through the disk of the Milky Way, perturbing both the satellite and the disk. A team of astronomers from Canada and the United States have discovered what may well be the smoking gun of such an encounter, one that occurred close to our position in the galaxy and relatively recently, at least in the cosmological sense.

“We have found evidence that our Milky Way had an encounter with a small galaxy or massive dark matter structure perhaps as recently as 100 million years ago,” said Larry Widrow, professor at Queen’s University in Canada. “We clearly observe unexpected differences in the Milky Way’s stellar distribution above and below the Galaxy’s midplane that have the appearance of a vertical wave — something that nobody has seen before.”

The discovery is based on observations of some 300,000 nearby Milky Way stars by the Sloan Digital Sky Survey. Stars in the disk of the Milky Way move up and down at a speed of about 20-30 kilometers per second while orbiting the center of the galaxy at a brisk 220 kilometers per second. Widrow and his four collaborators from the University of Kentucky, the University of Chicago and Fermi National Accelerator Laboratory have found that the positions and motions of these nearby stars weren’t quite as regular as previously thought.

“Our part of the Milky Way is ringing like a bell,” said Brian Yanny, of the Department of Energy’s Fermilab. “But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo.”

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Unfortunately, stars don’t have birth certificates. So, astronomers have a tough time figuring out their ages. Knowing a star’s age is critical for understanding how our Milky Way galaxy built itself up over billions of years from smaller galaxies.

White dwarfs

Jason Kalirai of the Space Telescope Science Institute and The Johns Hopkins University’s Center for Astrophysical Sciences, both in Baltimore, Md., has found the next best thing to a star’s birth certificate. Using a new technique, Kalirai probed the burned-out relics of Sun-like stars, called white dwarfs, in the inner region of our Milky Way galaxy’s halo. The halo is a spherical cloud of stars surrounding our galaxy’s disk.

Those stars, his study reveals, are 11.5 billion years old, younger than the first generation of Milky Way stars. They formed more than 2 billion years after the birth of the universe 13.7 billion years ago. Previous age estimates, based on analysing normal stars in the inner halo, ranged from 10 billion to 14 billion years.

Kalirai’s study reinforces the emerging view that our galaxy’s halo is composed of a layer-cake structure that formed in stages over billions of years.

This illustration shows the Milky Way galaxy's inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. Astronomers have proposed that the Milky Way's halo is composed of two populations of stars. The age of the stars in the inner halo, according to measurements by the Paranal Observatory, is 11.5 billion years old. The measurements suggest the inner-halo stars are younger than the outer-halo population, some of which could be 13.5 billion years old. Credit: NASA, ESA, and A. Feild (STScI)

One of the biggest questions in astronomy is, when did the different parts of the Milky Way form?” Kalirai said. “Sun-like stars live for billions of years and are bright, so they are excellent tracers, offering clues to how our galaxy evolved over time. However, the biggest hindrance we have in inferring galactic formation processes in the Milky Way is our inability to measure accurate ages of Sun-like stars. In this study, I chose a different path: I studied stars at the end of their lives to determine their masses and then connected those masses to the ages of their progenitors. Given the nature of these dead stars, their masses are easier to measure than Sun-like stars.”

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Whatta view!

The antennas of the European Southern Observatory’s Atacama Large Millimeter/Submillimeter Array, also known as ALMA, are set against the splendor of the Milky Way.

Watch the Milky Way spin

The International Space Station’s crew has been sending down tons of stunning imagery of the planet below, but the main appeal of this video goes in a different direction — toward the gorgeous galaxy right above our heads.

The time-lapse video is based on pictures taken on Dec. 29 while the space station sailed high above Africa, crossing over to the South Indian Ocean. You can make out the flashes of lightning storms, and if you look very closely you can see the long streak of Comet Lovejoy against the backdrop of the Milky Way. The best frame for seeing the comet comes around the 12-second mark in the 23-second clip.

A statistical analysis based on a survey of millions of stars suggests that there’s at least one planet for every star in the sky, and probably more. That would add up to 160 billion planets or so in the Milky Way.

“We conclude that stars are orbited by planets as a rule, rather than the exception,” an international research team reports today in the journal Nature.

The estimate may sound amazing: Just a year ago, the world was wowed by the claim that at least half of the 100 billion or more stars in the Milky Way possessed planets, yielding a figure of 50 billion planets. The latest survey now suggests that there’s an average of 1.6 planets per star system, which would work out to 160 billion. But perhaps the most amazing thing about the findings is … astronomers don’t find them amazing at all.

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Trust Us: Tempest Milky Way

A meteor, the Milky Way and the Northern Lights. Capturing just one of these natural beauties in a photo is a feat many photographers would be proud of.

Amateur photographer Tommy Eliassen struck photo gold in this beautifully composed image he shot in Ifjord, Finnmark, Norway.

Eliassen made the photo on Sept. 25 using a Nikon D700 with a wide angle lens and long exposures between 25-30 seconds.

In an interview with Caters News, The 33-year-old, who capitalized on a narrow window of clear skies, talked about the experience.

I quickly went and took some pictures in a regular spot of mine, and thought to myself that I had got some good aurora shots and also some separate good milky way shots. But just as the clouds started to come in over the mountains I noticed this faint aurora lining up perfectly beside the milky way. Normally the lights from the aurora is much, much stronger than the lights from the stars, so getting the right exposure on both is difficult. But it was ideal conditions – almost once in a lifetime.

He was able to snap seven images of the scene before clouds moved back in.

“I was so focused on getting it right that I didn’t think about it at the time. But afterwards I realised that this was something special and that it might be years before I get an opportunity like it again,” he said. More here.

Astronomers at The Australian National University have found evidence for the textile that forms the fabric of the Universe.

In findings published in the October Astrophysical Journal, the researchers discovered proof of a vast filament of material that connects our Milky Way galaxy to nearby clusters of galaxies, which are similarly interconnected to the rest of the Universe.

The team included Dr. Stefan Keller, Dr. Dougal Mackey and Professor Gary Da Costa from the Research School of Astronomy and Astrophysics at ANU.

“By examining the positions of ancient groupings of stars, called globular clusters, we found that the clusters form a narrow plane around the Milky Way rather than being scattered across the sky,” Dr. Keller said.

“Furthermore, the Milky Way’s entourage of small satellites are seen to inhabit the same plane.

“What we have discovered is evidence for the cosmic thread that connects us to the vast expanse of the Universe.

“The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth.” More here.

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