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Cluster Merger: Galaxy Clusters Caught in a First Kiss

For the first time, astronomers have found two giant clusters of galaxies that are just about to collide. This observation can be seen as a missing ‘piece of the puzzle’ in our understanding of the formation of structure in the Universe, since large-scale structures—such as galaxies and clusters of galaxies—are thought to grow by collisions and mergers. The result was published in Nature Astronomy on June 24, 2019 and used data from NASA’s Chandra X-ray Observatory and other X-ray missions.

Clusters of galaxies are the largest known bound objects and consist of hundreds of galaxies that each contain hundreds of billions of stars. Ever since the Big Bang, these objects have been growing by colliding and merging with each other. Due to their large size, with diameters of a few million light years, these collisions can take about a billion years to complete. Eventually the two colliding clusters will have merged into one bigger cluster.

Because the merging process takes much longer than a human lifetime, we only see snapshots of the various stages of these collisions. The challenge is to find colliding clusters that are just at the stage of first touching each other. In theory, this stage has a relatively short duration and is therefore hard to find. It is like finding a raindrop that just touches the water surface in a photograph of a pond during a rain shower. Obviously, such a picture would show a lot of falling droplets and ripples on the water surface, but only few droplets in the process of merging with the pond. Similarly, astronomers found a lot of single clusters and merged clusters with outgoing ripples indicating a past collision, but until now no two clusters that are just about to touch each other.

An international team of astronomers have now announced the discovery of two clusters on the verge of colliding. This enabled astronomers to test their computer simulations, which show that in the first moments a shock wave, analogous to the sonic boom produced by supersonic motion of an airplane, is created in between the clusters and travels out perpendicular to the merging axis. “These clusters show the first clear evidence for this type of merger shock,” says first author Liyi Gu from RIKEN national science institute in Japan and SRON Netherlands Institute for Space Research. “The shock created a hot belt region of 100-million-degree gas between the clusters, which is expected to extend up to, or even go beyond the boundary of the giant clusters. Therefore, the observed shock has a huge impact on the evolution of galaxy clusters and large scale structures.”

Astronomers are planning to collect more ‘snapshots’ to ultimately build up a continuous model describing the evolution of cluster mergers. SRON-researcher Hiroki Akamatsu: “More merger clusters like this one will be found by eROSITA, an X-ray all-sky survey mission that will be launched this year. Two other upcoming X-ray missions, XRISM and Athena, will help us understand the role of these colossal merger shocks in the structure formation history.”

Liyi Gu and his collaborators studied the colliding pair during an observation campaign, carried out with three X-ray satellites (ESA’s XMM-Newton satellite, NASA’s Chandra, and JAXA’s Suzaku satellite) and two radio telescopes (the Low-Frequency Array, a European project led by the Netherlands, and the Giant Metrewave Radio Telescope operated by National Centre for Radio Astrophysics of India).

Source: chandra.harvard.edu

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The Interstellar Research Initiative plans to send people to the exoplanet of Proxima Centauri b

In an attempt to protect humanity from extinction in the event of some kind of global catastrophe of a planetary scale, a group of scientists announced a bold plan for the colonization of a distant exoplanet.

Proxima Centauri b

Scientists from the Initiative for Interstellar Studies said they were considering sending people to a potentially inhabited exoplanet in another stellar system.

The most promising option they consider, Proxima Centauri b, which is 4.24 light years away from Earth, which means the journey will take centuries or even millennia. This suggests that generations will succeed each other during the journey.

Technically, this is possible.

However, the challenges facing the mission are so numerous and complex that it can take decades to prepare.

“From the point of view of physics, there are no fundamental obstacles. There are many nuances, but this is not a violation of the fundamental laws of physics, ”said Andreas Hein, Executive Director of Initiative for Interstellar Studies.

No problem.

The main problem is the lack of experience being far beyond the Earth for such a period of time.

Even a flight to Mars, which will last about 6-8 months, raises a lot of questions.

Proxima Centauri b

There is no reliable protection against merciless radiation yet. Medical problems caused by a prolonged stay in space are still poorly understood. Other than that, there is no guarantee that Proxima Centauri b is indeed liveable.

Can you imagine what a setup would be if people born on a spaceship for one purpose would come to a planet absolutely unsuitable for settlement …

However, the authors of the project do not plan to curtail the program and continue to work actively in this direction.

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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.

Source

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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 Space.com.

“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.

Source 7news.com.au

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