Looks like our home galaxy, the Milky Way, has gone on the ultimate weight-loss program, according to astronomers. 
 
 According to a new supercomputer simulation, it turns out that the entire mass of our Milky Way galaxy is about half that of the great Andromeda galaxy, our nearest neighboring spiral galaxy some 2.6 million light-years away from us. Astronomers had long thought the galaxies were twins. 
 
 While the two galaxies have similar extents and structures, the difference in weight seems to involve the amount of so-called dark matter that is gravitationally bound to each galaxy. While dark matter remains unseen, astronomers can measure the weight of the stuff (thought to be masses of an exotic class of physics particle) by its gravitational effects on galaxies. 
 
 The study, published in the Monthly Notices of the Royal Astronomical Society, suggests that Andromeda possesses twice as much dark matter as our home galaxy. 
 
 See for Yourself 
 
 Late July and early August tend to be some of the best times to glimpse the ghostly glows of the Milky Way in the late night sky. The best place to observe its faint band of light is from the dark countryside, far from the city lights. 
 
 With the moon currently in its new phase and out of our skies, this week will be a particularly good time to glimpse our own home galaxy. Look for the misty, white powder trail that is our Milky Way galaxy, stretching up from the northeastern horizon, arching high up the eastern sky, and then reaching down to the southern horizon. 
 
 Best seen in dark skies, the splash of Milky Way that we see in the summertime consists mostly of stars from one of its spiral arms and stars from its dense, bright core. The core hangs above the southern horizon when viewed from northern latitudes. 
 
 Sit back comfortably on a reclining lawn chair and cruise this entire swatch of glittering sky with binoculars, and you will notice that the galaxy’s hazy glow is actually a river of countless stars, all of them thousands of light-years distant. 
 
 Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook. 

 Image copyright NASA Image caption The researchers say their work should help them learn more about how the outer regions of galaxies are structured 
 
 The Milky Way is lighter than astronomers previously thought, researchers have concluded. 
 
 A team of scientists led by the University of Edinburgh found it has about half the mass of a neighbouring galaxy, known as Andromeda. 
 
 Their estimates come from working out the mass of invisible matter found in the outer regions of both galaxies. 
 
 They concluded that dark matter accounted for Andromeda's extra weight. 
 
 Dark matter is a little-understood invisible substance which makes up most of the outer regions of galaxies. 
 
 The researchers have estimated that Andromeda contains twice as much dark matter as the Milky Way, causing it to be twice as heavy. 
 
 The Milky Way and Andromeda have similar structures and are the two largest in a region of galaxies which astronomers call the Local Group. 
 
 The researchers say their work should help them learn more about how the outer regions of galaxies are structured. 
 
 Image copyright NASA Image caption The researchers concluded that Andromeda contains twice as much dark matter as the Milky Way 
 
 According to the research group, previous studies were only able to measure the mass enclosed within both galaxies' inner regions. 
 
 Dr Jorge Penarrubia, of the University of Edinburgh's School of Physics and Astronomy, who led the study, said: "We always suspected that Andromeda is more massive than the Milky Way, but weighting both galaxies simultaneously proved to be extremely challenging. 
 
 "Our study combined recent measurements of the relative motion between our galaxy and Andromeda with the largest catalogue of nearby galaxies ever compiled to make this possible." 
 
 The study, published in the journal Monthly Notices of the Royal Astronomical Society, was carried out in collaboration with the University of British Columbia, Carnegie Mellon University and NRC Herzberg Institute of Astrophysics. 
 
 The work was supported by the UK's Science and Technology Facilities Council.
– If our galaxy were a boxer, it would have just slipped down a few weight classes—and would be no match for our neighbor Andromeda. New research has revealed that the Milky Way, while still mind-bogglingly vast, is only around half the weight of the Andromeda galaxy, which is about 2.6 million light years from us, the BBC reports. Scientists who calculated the amount of invisible matter in the outer regions of both galaxies believe invisible "dark matter" explains the huge difference in mass between the two. "We always suspected that Andromeda is more massive than the Milky Way, but weighting both galaxies simultaneously proved to be extremely challenging," the lead researcher says. ''Our study combined recent measurements of the relative motion between our galaxy and Andromeda with the largest catalog of nearby galaxies ever compiled to make this possible.'' This is one of the best times of year to get a good look at our lightweight galaxy in the night sky, especially with the moon in a new phase this week, National Geographic notes. (But you've only got 4 billion years left to see the Milky Way before Andromeda crashes into it, forming a gigantic combined galaxy.)