Using the sharp-eyed NASA Hubble Space Telescope, astronomers have for the first time precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.
According to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years. Coincidentally, it takes our Sun the same amount of time to complete a rotation around the center of our Milky Way galaxy. The arrows in this photo illustration represent the highest-quality Hubble measurements of the motion of the LMC’s stars to show how the galaxy rotates.
The Hubble team, composed of Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Md., and Nitya Kallivayalil of the University of Virginia in Charlottesville, Va., used Hubble to measure the average motion of hundreds of individual stars in the LMC, located 170,000 light-years away. Hubble recorded the stars’ slight movements over a seven-year period.
In a report published today, new research suggests the enigmatic “ribbon” of energetic particles discovered at the edge of our solar system by NASA’s Interstellar Boundary Explorer (IBEX) may be only a small sign of the vast influence of the galactic magnetic field.
IBEX researchers have sought answers about the ribbon since its discovery in 2009. Comprising primarily space physicists, the IBEX team realized that the galactic magnetic field wrapped around our heliosphere — the giant “bubble” that envelops and protects our solar system — appears to determine the orientation of the ribbon and the placement of energetic particles measured in it.
An unlikely teaming of IBEX researchers with ultra-high-energy cosmic ray physicists, however, has produced complementary insights that dovetail with IBEX’s studies to produce a more complete picture of the interactions at the solar system boundary and how they reach much farther out into the space between the stars.
Students and staff at UCL’s teaching observatory, the University of London Observatory, have spotted one of the closest supernova to Earth in recent decades. At 19:20 GMT on 21 January, a team of students – Ben Cooke, Tom Wright, Matthew Wilde and Guy Pollack – assisted by Dr Steve Fossey, spotted the exploding star in nearby galaxy Messier 82 (the Cigar Galaxy).
The discovery was a fluke – a 10 minute telescope workshop for undergraduate students that led to a global scramble to acquire confirming images and spectra of a supernova in one of the most unusual and interesting of our near-neighbour galaxies.
“The weather was closing in, with increasing cloud,” Fossey says, “so instead of the planned practical astronomy class, I gave the students an introductory demonstration of how to use the CCD camera on one of the observatory’s automated 0.35–metre telescopes.”
Using the new, high-frequency capabilities of the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT), astronomers have captured never-before-seen details of the nearby starburst galaxy M82. These new data highlight streamers of material fleeing the disk of the galaxy as well as concentrations of dense molecular gas surrounding pockets of intense star formation.
M82, which is located approximately 12 million light-years away in the constellation Ursa Major, is a classic example of a starburst galaxy — one that is producing new stars tens- to hundreds-of-times faster than our own Milky Way. Its relatively nearby location made it an ideal target for the GBT’s newly equipped “W-Band” receiver, which is capable of detecting the millimeter wavelength light that is emitted by molecular gas. This new capability makes the GBT the world’s largest single-dish, millimeter-wave telescope.
“With this new vision, we were able to look at M82 to explore how the distribution of molecular gas in the galaxy corresponded to areas of intense star formation,” said Amanda Kepley, a post-doctoral fellow at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, and lead author on a paper accepted for publication in the Astrophysical Journal Letters. “Having this new capability may help us understand why stars form where they do.”
According to new Hubble Space Telescope observations of our Milky Way’s siblings, which existed long ago, the night sky must have looked much emptier in the distant past, when our galaxy was still under construction. The vast majority of our Milky Way’s stars had not yet been born. Yet the heavens were ablaze with a firestorm of new star formation.
By tracing the Milky Way’s siblings, astronomers find that our galaxy built up most of its stars between 11 billion and 7 billion years ago. The Hubble telescope’s superb resolving power allowed the researchers to study how the structure of Milky Way-like galaxies changed over time. The observations suggest that our galaxy’s flat disk and central bulge grew simultaneously into the majestic spiral galaxy of today.
Doom may be averted for the Smith Cloud, a gigantic streamer of hydrogen gas that is on a collision course with the Milky Way Galaxy. Astronomers using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and Robert C. Byrd Green Bank Telescope (GBT) have discovered a magnetic field deep in the cloud’s interior, which may protect it during its meteoric plunge into the disk of our Galaxy.
This discovery could help explain how so-called high velocity clouds (HVCs) remain mostly intact during their mergers with the disks of galaxies, where they would provide fresh fuel for a new generation of stars.
Currently, the Smith Cloud is hurtling toward the Milky Way at more than 150 miles per second and is predicted to impact in approximately 30 million years. When it does, astronomers believe, it will set off a spectacular burst of star formation. But first, it has to survive careening through the halo, or atmosphere, of hot ionized gas surrounding the Milky Way.
It is common knowledge that our Galaxy is permanently in motion. Being a barred spiral galaxy it rotates around the Galactic centre. It has now been discovered that our Galaxy, the Milky Way, also makes small wobbling or squishing movements. It acts like a Galactic mosh pit or a huge flag fluttering in the wind, north to south, from the Galactic plane with forces coming from multiple directions, creating a chaotic wave pattern. The source of the forces is still not understood however: possible causes include spiral arms stirring things up or ripples caused by the passage of a smaller galaxy through our own.
In this study, RAVE stars were used to examine the kinematics (velocities) of stars in a large, 3D region around the Sun – the region surveys 6500 light years above and below the Sun’s position as well as inwards and outwards from the Galactic centre, reaching a quarter of the way to the centre. Using a special class of stars, red clump stars, which all have about the same brightness, mean distances to the stars could be determined. This was important as then the velocities measured with RAVE, combined with other survey data, could be used to determine the full 3D velocities (up-down, in-out and rotational). The RAVE red clump giants gave an unprecedented number of stars with which it is possible to study 3D velocities in a large region around the Sun.
ESA’s billion-star surveyor Gaia will be launched from Europe’s spaceport in Kourou on 20 November to begin a five-year mission to map the stars with unprecedented precision.
Gaia’s main goal is to create a highly accurate 3D map of our Milky Way Galaxy by repeatedly observing a billion stars to determine their positions in space and their movement through it.
Other measurements will assess the vital physical properties of each star, including temperature, luminosity and composition. The resulting census will allow astronomers to determine the origin and the evolution of our Galaxy.
Gaia will map the stars from an orbit around the Sun, near a location some 1.5 million km beyond Earth’s orbit known as the L2 Lagrangian point.
The spacecraft will spin slowly, sweeping its two telescopes across the entire sky and focusing their light simultaneously onto a single digital camera, the largest ever flown in space – it has nearly a billion pixels.
PGC 6240 is an elliptical galaxy that resembles a pale rose in the sky, with hazy shells of stars encircling a very bright centre. Some of these shells are packed close to the centre of the galaxy, while others are flung further out into space. Several wisps of material have been thrown so far that they appear to be almost detached from the galaxy altogether.
Astronomers have studied PGC 6240 in detail due to this structure, and also because of its surrounding globular clusters — dense, tightly packed groups of gravitationally bound stars that orbit galaxies. Over 150 of these clusters orbit our own galaxy, the Milky Way, all composed of old stars.
All the globular clusters around a certain galaxy form at approximately the same time, giving them all the same age. This is echoed within the clusters — all the stars within a single cluster form at around the same time, too. Because of this, most galaxies have cluster populations of pretty similar ages, both in terms of overall cluster, and individual stars. However, PGC 6240 is unusual in that its clusters are varied — while some do contain old stars, as expected, others contain younger stars which formed more recently.
Astronomers have detected cold streams of primordial hydrogen, vestigial matter left over from the Big Bang, fueling a distant star-forming galaxy in the early Universe. Profuse flows of gas onto galaxies are believed to be crucial for explaining an era 10 billion years ago, when galaxies were copiously forming stars. To make this discovery, the astronomers – led by Neil Crighton of the Max Planck Institute for Astronomy and Swinburne University – made use of a cosmic coincidence: a bright, distant quasar acting as a “cosmic lighthouse” illuminates the gas flow from behind. The results were published October 2 in the Astrophysical Journal Letters.
The systematic survey of absorption systems comprises observations with the Large Binocular Telescope and from data taken with the W. M. Keck Observatory’s HIRES echelle spectrograph installed on the 10 meter Keck I telescope on the summit of Mauna Kea, Hawaii. The foreground galaxy was discovered by Charles Steidel, Gwen Rudie (California Institute of Technology) and collaborators using the Keck Observatory’s LRIS spectrograph on the same telescope.