Tag Archive: Galaxies


OUR home galaxy has been weighed, and it is surprisingly lean. The latest gauge of the dark matter mass of the Milky Way suggests it weighs only a quarter to a third of the amount previously estimated.

This could explain the dearth of smaller galaxies buzzing around the Milky Way. But it also means we may live in a cosmic anomaly.

It is thought the first galaxies were born as normal matter coalesced around globs of dark matter, the invisible stuff thought to make up about 80 per cent of the matter in the universe. We can’t see dark matter itself, but we can trace its effects in the motions of stars in modern galaxies.

Stars on the edges of large spirals like the Milky Way are orbiting so fast that they should fly off, so something must be holding on to them. That thing is thought to be a halo of dark matter encircling the visible disc.

Knowing our galaxy’s total mass will tell us a lot about it. “Is our Milky Way typical, or is it actually quite weird?” asks Alis Deason of the University of California, Santa Cruz.

A smattering of stars live in the Milky Way’s dark matter halo, and previous studies have used their motion to figure out the halo’s mass. But we are embedded in a spiral arm, which means dust and gas blocks much of our view of our relatively flat galaxy, so those models had to make assumptions about the parts we can’t see.

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Scientists have observed in unprecedented detail the birth of a massive star within a dark cloud core about 10,000 light years from Earth.

The team used the new ALMA (Atacama Large Millimetre/submillimetre Array) telescope in Chile – the most powerful radio telescope in the world – to view the stellar womb which, at 500 times the mass of the Sun and many times more luminous, is the largest ever seen in our galaxy.

The researchers say their observations – to be published in the journal Astronomy and Astrophysics – reveal how matter is being dragged into the centre of the huge gaseous cloud by the gravitational pull of the forming star – or stars – along a number of dense threads or filaments.

“The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” said lead author Dr Nicolas Peretto, from Cardiff University. “We wanted to see how monster stars form and grow, and we certainly achieved our aim. One of the sources we have found is an absolute giant — the largest protostellar core ever spotted in the Milky Way!

“Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its centre. This cloud is expected to form at least one star 100 times more massive than the Sun and up to a million times brighter. Only about one in 10,000 of all the stars in the Milky Way reach that kind of mass.”

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Dark Matter Milky Way

Are there dark doings near the center of the Milky Way? That may be so when it comes to the collision of dark matter particles. Although such particles are invisible, we could still theoretically see the mess they make when they collide. It’s this idea that leads physicists to scour the galaxy for some glimmer of dark matter collisions. Spot a line produced by a pair of gamma-rays emanating from just the right spot and you may have found coveted clues to the dark matter mystery.

Now a collaboration of scientists using the Fermi Gamma-Ray Spacecraft’s Large Area Telescope instrument (Fermi–LAT) has confirmed seeing an unusual gamma-ray line near the galactic center. If the finding stands up to further scrutiny, it’s possible this line comes from the annihilation of dark matter.

In April theoretical physicist Christoph Weniger, now at the GRAPPA Institute in Amsterdam, analyzed Fermi–LAT’s publicly available data and spotted a strange gamma-ray line near the galactic center. There’s no known astrophysical event that can tidily explain this line—but the collision of dark matter particles might. If that were the case, it would be a major discovery: Once physicists spot the products of such an annihilation, they could begin to understand the particles that collided.

But there was a catch: Weniger is not a member of the Fermi-LAT collaboration and therefore cannot be able to account for the quirks of their instrument. What was needed was a weigh-in from Fermi-LAT collaboration physicists; they know the data best and would be able to confirm any hint of dark matter.

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100,000 Stars is a new experiment for Chrome web browsers (or any other WebGL browser like Firefox or Safari) that lets you interactively explore the Milky Way galaxy with your mouse and scroll wheel. MIND = BLOWN

100,000 Stars: An Interactive Exploration of the Milky Way Galaxy website space science interactive

100,000 Stars: An Interactive Exploration of the Milky Way Galaxy website space science interactive

NASA Galaxy Formation Simulation

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If we want to find intelligent life elsewhere in the universe, it might be wise to look for stars with asteroid belts similar the one in our own Solar System.

According to the theory of punctuated equilibrium, evolution goes faster and further when life has to make rapid changes to survive new environments — and few things have as dramatic an effect on the environment as an asteroid impact. If humans evolved thanks to asteroid impacts, intelligent life might need an asteroid belt like our own to provide just the right number of periodic hits to spur evolution on. Only a fraction of current exoplanet systems have these characteristics, meaning places like our own Solar System — and intelligent aliens — might be less common than we previously thought.

Astronomers Rebecca Martin of the University of Colorado in Boulder and Mario Livio of the Space Telescope Institute in Baltimore have hypothesised that the location of the Solar System’s asteroid belt — between Jupiter and Mars — is not an accident, and actually necessary for life. As the Solar System formed, the gravitational forces between Jupiter and the Sun would have pulled and stretched clumps of dust and planetoids in the inner Solar System. The asteroid belt lies on the so-called “snow line” — fragile materials like ice will stay frozen further out, but closer in they will melt and fall apart.

During the formation of the Solar System, cold rock and ice coalesced into the planets as we know them. However, as Jupiter formed, it shifted in its orbit closer to the Sun just a little bit before stopping. The tidal forces at work between Jupiter and the Sun would have torn apart the material on the snow line, preventing a planet forming and leaving behind an asteroid belt — which today has a total mass only one percent of that which would have been there originally.

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Hubble Space Telescope image - dubbed eXtreme Deep Field - of the universe. In the image are 5,000 galaxies. The image took 2,000 exposures lasting a total of 500 hours.

The Hubble Space Telescope (HST) has produced one of its most extraordinary views of the Universe to date.

Called the eXtreme Deep Field, the picture captures a mass of galaxies stretching back almost to the time when the first stars began to shine.

But this was no simple point and snap – some of the objects in this image are too distant and too faint for that.

Rather, this view required Hubble to stare at a tiny patch of sky for more than 500 hours to detect all the light.

“It’s a really spectacular image,” said Dr Michele Trenti, a science team member from the University of Cambridge, UK.

“We stared at this patch of sky for about 22 days, and have obtained a very deep view of the distant Universe, and therefore we see how galaxies were looking in its infancy.”

The XDF will become a tool for astronomy. The objects embedded in it can be followed up by other telescopes. It should keep scientists busy for years, enabling them to study the full history of galaxy formation and evolution.

The new vista is actually an updating of a previous HST product – the Hubble Ultra Deep Field.

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Hubble has spotted an ancient galaxy that shouldn't exist

This galaxy is so large, so fully-formed, astronomers say it shouldn’t exist at all. It’s called a “grand-design” spiral galaxy, and unlike most galaxies of its kind, this one is old. Like, really, really old. According to a new study conducted by researchers using NASA’s Hubble Telescope, it dates back roughly 10.7-billion years — and that makes it the most ancient spiral galaxy we’ve ever discovered.

“The vast majority of old galaxies look like train wrecks,” said UCLA astrophysicist Alice Shapley in a press release. “Our first thought was, why is this one so different, and so beautiful?”

Shapley is co-author of the paper describing the discovery, which is published in the latest issue of Nature. She and her colleagues had been using Hubble to investigate some of our Universe’s most distant cosmic entities, but the discovery of BX442 — which is what they’ve dubbed the newfound galaxy — came as a huge surprise.

“The fact that this galaxy exists is astounding,” said University of Toronto’s David Law, lead author of the study. “Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe.”

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What Earth looked like from between 13 billion years ago to how it will likely look 250 million years in the future.

Harvard scientists use 1,024-core supercomputer to produce a partial simulation of the life of the universe, modelling thousands of individual stars and galaxies with a Arepo, new software for cosmological simulations of galaxy formation across billions of years.

The largest ever three dimensional map of galaxies and black holes was released by astronomers today.  It will help explain the mysterious dark matter and dark energy that they know makes up 96 percent of the universe.

The map is the creation of the Sloan Digital Sky Survey III (SDSS-III) an international project mapping the Milky Way in which a team from the University of Portsmouth is the only UK institution.  Early last year, the SDSS-III released the largest-ever image of the sky and astronomers have used new data to expand this image into a full three-dimensional map.

Data Release 9 (DR9) includes images of 200 million galaxies and spectra of 1.35 million galaxies, including 540,000 spectra of new galaxies from when the universe was half its present age. Spectra show how much light a galaxy gives off at different wavelengths. Because this light is shifted to longer redder wavelengths as the Universe expands, spectra allow scientists to work out how much the Universe has expanded since the light left each galaxy.

It will allow better estimates of how much of the universe is made up of dark matter – matter that can’t be seen directly see because it doesn’t emit or absorb light – and dark energy, the even more mysterious force that drives the accelerating expansion of the universe.

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No-one is really sure exactly how many there are. Many millions probably. One thing that might be useful in answering this is a 2 year survey (the 2dF Galaxy Survey) which has just finished.

So far they have surveyed 100, 000 galaxies to make a 3-D map of the universe, but their goal is 250,000! And that’s certainly not all of them that are out there. Look at the 2dF website for more on this. There are 4 million names in the NASA Extragalactic database! (NED) Although this is probably not everything either.

It is estimated that there are as many as 200 billion galaxies in the observable universe, but we aren’t able to see all of them yet as our telescopes are not big enough. This number is interesting because it is similar in magnitude to the number of stars estimated to be in our Galaxy.

We have the Hexagon on Saturn, the Red Rectangle nebula — and now there’s a squarish galaxy for astronomers to deal with.

“It’s one of those things that just makes you smile because it shouldn’t exist, or rather, you don’t expect it to exist,” Alister Graham, a professor at Australia’s Swinburne University of Technology, said this week in a news release. “It’s a little like the precarious Leaning Tower of Pisa, or the discovery of some exotic new species which at first glance appears to defy the laws of nature.”

And yet, there it is: LEDA 074886, a rectangular-looking dwarf galaxy that’s part of the NGC 1407 Group of more than 250 galaxies in the constellation Eridanus, 70 million light-years away. The “emerald-cut galaxy” was spotted in a wide-field image taken using Japan’s Subaru Telescope, and discussed in a research paperto be published in The Astrophysical Journal.

Most galaxies are either spheroidal, disk-shaped or irregular and lumpy, Graham noted. LEDA 074886 seems to have four rounded corners. Graham and his colleagues suspect that the galaxy is actually shaped like a shallow cylinder or an inflated disk, seen somewhat side-on. That would fit with observations from the Keck Telescope, which picked up the signs of a rapidly spinning, thin disk embedded in the galaxy’s center.

“One possibility is that the galaxy may have formed out of the collision of two spiral galaxies,” said Swinburne Professor Duncan Forbes, one of the study’s co-authors. “While the pre-existing stars from the initial galaxies were strewn to large orbits, creating the emerald-cut shape, the gas sank to the midplane, where it condensed to form new stars and the disk that we have observed.”

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Scientists have discovered the largest black holes yet, and they’re far bigger than researchers expected based on the galaxies in which they were found.

The discovery suggests we have much to learn about how monster black holes grow, scientists said.

All large galaxies are thought to harbor super-massive black holes at their hearts that contain millions to billions of times the mass of our sun. Until now, the largest black hole known was a mammoth dwelling in the giant elliptical galaxy Messier 87. This black hole has a mass 6.3 billion times that of the sun.

Now research suggests black holes in two nearby galaxies are even bigger.

The scientists used the Gemini and Keck observatories in Hawaii and the McDonald Observatory in Texas to monitor the velocities of stars orbiting around the centers of a pair of galaxies. These velocities reveal the strength of the gravitational pull on those stars, which in turn is linked with the masses of the black holes lurking there.

The new findings suggest that one galaxy, known as NGC 3842, the brightest galaxy in the Leo cluster of galaxies nearly 320 million light years distant, has a central black hole 9.7 billion solar masses large. The other, named NGC 4889, the brightest galaxy in the Coma cluster more than 335 million light years away, has a black hole of comparable or larger mass. Both encompass regions or “event horizons” about five times the distance from the sun to Pluto.

Image of the center of our Galaxy from laser-guide-star adaptive optics on the Keck Telescope. This is an HKL-band color mosaic, where H(1.8 microns) = blue, K(2.2 microns) = green, and L(3.8 microns) = red. More massive black holes have larger event horizons, the region within which even light cannot escape. If a 10 billion solar mass black hole resided at the Galactic center, its immense event horizon would be visible (illustrated by the central black disk). The actual black hole at the Galactic center is 2,500 times smaller.

“For comparison, these black holes are 2,500 times as massive as the black hole at the center of the Milky Way galaxy, whose event horizon is one-fifth the orbit of Mercury,” said study lead author Nicholas McConnell at the University of California, Berkeley.

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Kepler 21b

The National Optical Astronomy Observatory announced on Wednesday the discovery of Kepler-21b, a new planet that’s close to the size of earth and is only about 352 light years away.

“By astronomical standards, that’s right next door,” Katy Garmany, the Deputy Press Officer at the National Optical Astronomy Observatory.

Astronomers frequently discover new planets (according to Time magazine, we’re up to over 2,000), but Garmany said that what’s exciting about Kepler 21-b is that the planet is relatively Earth-sized. While its mass is about 10 times the size of our planet, its radius is only 1.6 times the size of Earth’s.

“Until a few years ago, the smallest extra-solar planet that we had discovered was the size of Jupiter or Saturn, which are about ten times bigger than the Earth,” Garmany said. “Now we’re getting down to something almost the size of the Earth, showing that we have the technology to find the earth-size planets.”

The new planet has a star that’s just a bit bigger and hotter than Earth’s sun, although it’s substantially younger. But because the planet is so close to its star, it’s far too hot to have liquid water, the base for life as we know it. At only 6 million kilometers (about 3.7 million miles) away from the star, Kepler-21b’s temperature is a blistering 2,960 degrees Fahrenheit, according to scientists’ estimates.

By contrast, Earth is about 150,000,000 km (93 million miles) from its own sun.

The discovery of Kepler-21b was a collaboration of both sky (the Kepler observatory) and ground-based telescopes at the Kitt Peak National Observatory in Arizona.

Phil Plait, the Bad Astronomer, writes in Discover Magazine that researchers examined the planet for 15 months. The results of the study will be published in Astrophysical Journal.

Astronomers have used radio interferometry to obtain a radio astronomical photograph of a cosmic explosion, the youngest supernova SN2011dh, just 14 days after a star exploded in the Galàxia del Remolí (M51) galaxy last June. The international astronomer team coordinated telescopes around Europe to achieve this feat.

The Galaxy and the supernova SN2001dh through a telescope. In the extension, image of SN2001dh captured by a European network of radio telescopes on 14 June, two weeks after its explosion.

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The Visible Universe, Then and Now

Before the telescope was invented in 1608, our picture of the universe consisted of six planets, our moon, the sun and any stars we could see in the Milky Way galaxy. But as our light-gathering capabilities have grown, so too have the boundaries of the visible universe. Our interactive map shows how the known universe has grown from 1950 to 2011.

In the late 1700s, William Herschel, an English astronomer using a telescope with an 18.7-inch aperture, made the first systematic surveys of the skies, revealing more than 2,000 distant galaxies, nebulae and other objects invisible to the naked eye. Since then, increasingly powerful optical and radio telescopes have greatly expanded our store of knowledge.

In 1948, astronomers erected the 200-inch Hale Telescope at Palomar Observatory in California, and now, large-scale projects such as the Sloan Digital Sky Survey and NASA’s Kepler mission use sensitive digital imaging and computational power to collect and analyze hundreds of terabytes of data on millions of galaxies billions of light-years from Earth. With each additional bit of data, the universe itself grows larger.

One of the most cherished principles in science – the constancy of physics – may not be true, according to research carried out at the University of New South Wales (UNSW), Swinburne University of Technology and the University ofCambridge.

The study found that one of the four known fundamental forces, electromagnetism – measured by the so-called fine-structure constant and denoted by the symbol ‘alpha’ – seems to vary across the Universe.

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“I work around the clock (1043 Planck times per second) providing the gravitational attraction to hold this galaxy cluster together. And some baryonic cosmologist wants to explain me away as a modification of Newtonian gravity?

“I have been silent for 13.7 billion years, but no more.

“I AM THE 96%”

The first direct image of a planet in the process of forming around its star has been captured by astronomers who combined the power of the 10-meter Keck telescopes with a bit of optical sleight of hand.

What astronomers are calling LkCa 15 b, looks like a hot “protoplanet” surrounded by a swath of cooler dust and gas, which is falling into the still-forming planet. Images have revealed that the forming planet sits inside a wide gap between the young parent star and an outer disk of dust.

“LkCa 15 b is the youngest planet ever found, about 5 times younger than the previous record holder,” said astronomer Adam Kraus of the University of Hawaii’s Institute for Astronomy. “This young gas giant is being built out of the dust and gas. In the past, you couldn’t measure this kind of phenomenon because it’s happening so close to the star. But, for the first time, we’ve been able to directly measure the planet itself as well as the dusty matter around it.”

Youngest planet seen as it's forming

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Around the world, a new generation of astronomers are hunting for the most mysterious objects in the universe. Young stars, black holes, even other forms of life. They have created a dazzling new set of super-telescopes that promise to rewrite the story of the heavens.

This film follows the men and women who are pushing the limits of science and engineering in some of the most extreme environments on earth. But most strikingly of all, no-one really knows what they will find out there.

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