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We’re Living Next Door To A Cannibal Galaxy Whose Violent Past Has Been Revealed

A study of the small galaxies swallowed by our nearest large galactic neighbor has revealed something of how galaxies grow. In the process, it has hinted at something that, if true, would change the way we see the universe in profound ways.

All galaxies, including our own Milky Way, grow by consuming smaller ones. Inevitably, the nearest large galaxy to our own, M31, also known as Andromeda, has eaten many small neighbors. Our first insight into the nature of these events is useful because Andromeda and the Milky Way are on course to meet. That’s 4 billion years away, but it’s good to be prepared.

Dr Dougal Mackey of the Australian National University and Professor Geraint Lewis from the University of Sydney analyzed streams of stars within Andromeda’s halo and identified some as the remnants of galaxies, even gaining approximations of when this occurred. Rather than a steady process, they identified two bursts separated by billions of years. The galaxies in the two rounds arrived at right angles to each other and maintained that motion even after being pulled apart.

“We are cosmic archaeologists, except we are digging through the fossils of long-dead galaxies rather than human history,” Lewis said in a statement.

Mackey told IFLScience the consumed galaxies contained globular clusters, groups of stars bound so closely together that only the most powerful gravitational disruptions pull them apart.

Individual stars in Andromeda’s halo are usually too distant and faint for us to track their movements, but the clusters are a different matter, allowing the pair to identify in Nature the streams whose shared movements pin them as past galaxies.

“Once you get below a certain mass, galaxies don’t contain globular clusters,” Mackey said, so the smallest are currently untraceable. However, he added that the contribution of these to Andromeda’s growth was minor.

One day, Andromeda will swallow the Milky Way as well. However, Mackey acknowledged to IFLScience this will be a very different process. The galaxies Andromeda has eaten up until now have masses a tenth of its total at most, usually much smaller. The Milky Way, on the other hand, is at least half Andromeda’s size.

The merger of the two will destroy the spiral structure of each, creating an egg-like elliptical galaxy. By then, the Sun will have burned the Earth beyond recognition, but if humanity somehow survives elsewhere, consequences will be limited. Our view of the night sky will change utterly, but the space between the stars is so great that even when stars from Andromeda become mixed among our nearest neighbors, it is unlikely any will pass close enough to disrupt orbits within the inner solar system.

One feature of the pair’s work is still tentative but could turn out to be awe-inspiring. Around a decade ago astronomers noticed a curious pattern in the dwarf galaxies that surround Andromeda. Around half these galaxies orbit in a specific plane, something astronomers had not expected and struggled to explain. We now know this pattern is unstable, and can neither have been in place for a long time (astronomically speaking) or have lasted that far into the future.

This study found that some of the swallowed galaxy remnants conform to the same pattern, but surprisingly, it is the much older set that do this, rather than the more recent arrival. This suggests these long-lost galaxies also once lay in a similar plane, indicating an abiding underlying structure to the local area of the universe. The most likely explanation is the universe is made up of a web of dark matter filaments and Andromeda lies on one of these, with gravity so powerful it aligns the movement of clusters of small galaxies.




European Space Agency to launch space waste collector

A four-armed robotic junk collector will be launched into space by the European Space Agency in what it says will be the first mission to remove an item of debris from orbit.

European Space Agency to launch space waste collector

The ClearSpace-1 mission, scheduled for launch in 2025, will cost €120m and will grab a single piece of junk. But the agency hopes the mission will pave the way for a wide-reaching clear-up operation, with Esa’s director general calling for new rules that would compel those who launch satellites to take responsibility for removing them from orbit once they are retired from use.

Jan Wörner, CEO of ESA, said:

Imagine how dangerous sailing the high seas would be if all the ships ever lost in history were still drifting on top of the water. That is the current situation in orbit, and it cannot be allowed to continue.

In the past 60 years, thousands of tonnes of junk has accumulated around the Earth, including old rocket parts, about 3,500 defunct satellites and an estimated 750,000 smaller fragments, some from collisions between larger bits of junk. The fragments are typically circulating with a velocity of 20,000km/h (12,500mph).

Unless a clear-up operation is mounted, the chances of collisions will escalate as thousands more satellites are put into orbit.

Funding for the mission was agreed at Space19+, ESA’s misterial council, which took place in Seville, Spain, at the end of November. The mission will be run by a consortium led by a Swiss startup called Clearspace.

The target for ClearSpace-1 is a piece of junk called Vespa, which was left in an orbit around 800km above the Earth by ESA’s Vega launcher in 2013. Vespa weighs 100kg – around the size of a small satellite – and was selected because it has a simple shape and sturdy construction, which make it unlikely to fragment when it is grabbed.

The “chaser” ClearSpace space probe will be launched into the target orbit where it will track down Vespa, grab it using a quartet of robotic arms and drag it out of orbit, with Vespa and the chaser both burning up in the atmosphere on the way down to Earth.

A future ambition is to create a clear-up robot that could eject junk into the atmosphere, before continuing to capture and de-orbit other pieces of junk.


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Asteroid as big as the pyramids on its way and could zoom past Earth on Friday

An asteroid as big as the Egyptian pyramids is zooming towards Earth and will squeeze past us on Friday – if it doesn’t smash on to our home planet’s surface.

Named 2019 WR3, NASA expects the space rock to make a “close approach” to Earth later this week.

The space agency has classified the asteroid as a “near-Earth object (NEO)” which means its orbit brings it very close – in cosmic terms – to Earth.

The asteroid was first spotted late last week.

NASA has now observed the asteroid some 74 times to better get a sense of its size and trajectory.

WR3 is believed to have a diameter of between 76m to 170m.

It is expected that on December 6, the asteroid will pass within 5.44 million km of Earth at speeds of 27,036 km/hr.

The warning comes as the European Space Agency approves a $471 million mission called Hera to examine whether a rogue asteroid on its way to Earth could be deflected out of the way.

Working with NASA, the ESA will send a pair of spacecraft to a double-asteroid system called Didymos to examine the asteroids and send valuable data back home.

The larger asteroid Didymoon is about 800m across, orbited by a moon about 160m wide.

If an asteroid the size of Didymoon were to hammer into Earth, it would be devastating.

Patrick Michel, ESA’s lead scientist for Hera, said it was vital to keep an eye on it so we can take action if needed.

“The probability is low but the consequences are high,” Michel told

“This is why it’s relevant to take care of it. Moreover, we have the tools … We can’t lose more time.”

The Hera spacecraft will launch in 2024.

Meanwhile, Queens University Belfast professor Alan Fitzsimmons has called for amateur astronomers to assist the Hera mission’s broader goal of protecting Earth against asteroids by nominating asteroids to watch.

“We will get a serious asteroid impact sometime,” he told the BBC.

“It may not be in our lifetime, but mother nature controls when that will happen.

‘We will get a serious asteroid impact sometime.’

“We will need to do something about it. We’ll need to move that asteroid so it misses us and doesn’t hit us.

“Asteroid research is one area of astronomy where amateur observes continue to make an essential contribution,” he said.


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An ultralight source of x-rays detected, coming from the Draco constellation

ESA / Hubble

Intriguing ultralight source of X-rays, one of the brightest ever seen. It comes from a galaxy of the Draco constellation.

The ultraluminous X sources were discovered in 1980 with the Einstein space detector. The X-rays currently detected come from a galaxy located 14.8 million light years from Earth. This type of radiation has been quite mysterious to astronomers because it is extremely bright.

These astronomical systems ULEX, for its acronym in English, UltraLuminous X-ray source, have a brightness level of more than 10 raised to 39 erg per second (Ergis are units of measure of energy). The galaxy is called UGC 6456, and, interestingly, it is found in the constellation Draco (Dragon), a constellation object of legends and mythology.

X-ray source, UGC 6456 ULX

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Ultra-light X-ray sources. Credit: NASA

The study was conducted by Russian astronomers. These electromagnetic emissions are less luminous than a galactic core, but shine more than any process of formation or evolution of stars.

The group of astronomers is led by Alexander Vinokurov, from the Special Astrophysical Observatory, located in Nizhnij Arkhyz, Russia. The study presented says:

We present preliminary results of a study of the ultra-bright X-ray source UGC 6456 ULX. (…) To identify an optical counterpart of UGC 6456 ULX, we use archive images of the Chandra X-Ray Observatory and HST.

Note: HST stands for the Hubble Space Telescope.

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Overlay of images B, V and Rc of the UGC 6456 galaxy. The box shows the HST WFPC2 / F555W image of the region around the UGC 6456 ULX source, marked by the square; the circle indicates the 0.8 inch error box, derived from the Chandra Observatory data. Credit: Vinokurov et al.

The UGC 6456 galaxy is listed as a compact blue dwarf galaxy and is one of the closest to our Milky Way. Its UGC 6456 ULX source, or ultralight X-ray source, has mysterious properties, which they had not been studied in detail.

Among the brightest ever observed

The emissions of UGC 6456 ULX have brightness changes of more than two orders of magnitude with a maximum value of 17 erg duodecillions per second in the energy range of 0.3–8 keV (electron volts).

A duodecillón is a very long numerical scale equivalent to a 10 followed by 72 zeros! An electron volt is a unit of measurement that represents the energy per motion that an electron experiences.

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Map of the constellation Draco. Credit: Torsten Bronger / Wikimedia commons.

The magnitude of this source in its bright state is exceeded by an amount of -7.6. That makes her one of the ultraluminous sources of X-rays brightest ever discovered in the optical range.

The study presents a correlation between X-ray flows and optical (observable) flows in UGC 6456 ULX. This could indicate that the emission of optical light is produced by the X-ray re-processing in the outer parts of the so-called «Optically thick wind».

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Illustration of the phenomenon. Credit: NASA

The detection of many hydrogen and helium emission lines could relate to the wind that emerges from the powerful and dynamic accretion disk. This disk is a structure full of powder and cosmic gas that forms around a central object.

More details are expected with the following observations of this ultra-light source of X-rays. The light and energy changes of this system are similar to that of another known source, the so-called NGC 7793 P13, which has a neutron star.

The scientific study has been published on the pre-print website


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