Tag Archives: ALMA

Ancient galaxies from the study are visible to ALMA (right) but not to Hubble (left). Credit: © 2019 Wang et al.

‘Hidden’ ancient galaxies discovery may redefine our understanding of the Universe

The discovery of 39 ‘hidden’ ancient galaxies urges scientists to rethink their theories of fundamental aspects of the Universe — including supermassive black holes, star formation rates, and the ever-elusive, dark matter.

Ancient galaxies from the study are visible to ALMA (right) but not to Hubble (left). Credit: © 2019 Wang et al.

In an unprecedented discovery of astronomers, researchers have utilised the combined power of a multitude of observatories across the globe to discover a vast array of 39 previously hidden galaxies.

The finding — described by the researchers from the University of Tokyo as a ‘treasure trove’ — is the first multiple discoveries of this kind. But the finding is significant for more than its size alone.

In addition to containing a wealth of newly discovered ancient galaxies, an abundance of this particular type of galaxy suggests that scientists may have to refine current models of the universe.

This is because our current understanding of the universe and how it formed is built upon observations of galaxies in ultraviolet light. But observations in these wavelengths under-represent the most massive galaxies — those with high dust content and crucially, the most ancient.

This means that a discovery of such galaxies — such as the one just made — must force us to reconsider the rates of star formation in the early universe. The study explains that the population of stars discovered may mean that star formation rates were actually ten times greater in early epochs than previous estimates held.

There are also particular ramifications for our understanding of both supermassive black holes and their distribution, and for the concept of dark matter — the elusive substance which makes up 80% of the matter in the universe.

Despite the wealth of astronomical data that has become available to scientists since the launch of the Hubble Space Telescope, researchers at the Institute of Astronomy in Toyko were aware there were things that Hubble simply couldn’t show us. It was these things — fundamental pieces of the cosmic puzzle — that they wanted to investigate.

They achieved this by unifying different observatories, using them to look more deeply in the Universe than Hubble alone could do. This is what led them to this huge collection of galaxies.

Researcher Tao Wang describes the uniqueness and magnitude of the team’s discovery: “This is the first time that such a large population of massive galaxies was confirmed during the first two billion years of the 13.7-billion-year life of the universe.

“These were previously invisible to us.”

Wang continues: “This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now.”

A different view of the universe

Wang explains that if we could see these galaxies and the light they shed, our view from the Milky way would be significantly different: “For one thing, the night sky would appear far more majestic. The greater density of stars means there would be many more stars close by appearing larger and brighter.

“But conversely, the large amount of dust means farther-away stars would be far less visible, so the background to these bright close stars might be a vast dark void.”

The galaxies have been difficult to see from Earth due to how faint they are. Were we able to see these stars, their density would make the night sky majestic, Wang says.

The light from these galaxies also has to battle extinction — the absorption of light) by intervening interstellar dust clouds. The light from the galaxies also has to travel great distances meaning the wavelength is redshifted by the expansion of the universe making it even less visible.

Professor Kotaro Kohno. Credit: © 2019 Rohan Mehra — Division of Strategic Public Relations

Professor Kotaro Kohno explains that this phenomenon is how the galaxies escaped Hubble’s gaze: “The light from these galaxies is very faint with long wavelengths invisible to our eyes and undetectable by Hubble.

“So we turned to the Atacama Large Millimeter/submillimeter Array (ALMA), which is ideal for viewing these kinds of things. I have a long history with that facility and so knew it would deliver good results.”

This redshift due to cosmic expansion does have its advantages, however. It allows astronomers to estimate not just the distances to the galaxies in question, but it also allows them to calculate just how long ago the light was emitted.

The hidden implications of these hidden galaxies

The team’s finding is so controversial and poses such a radical rethink that they found their fellow astronomers were initially reluctant to believe they had found what they claimed.

A few of the 66 radio telescope antennas that make up ALMA. Credit: © 2019 Kohno et al.

Wang explains: “It was tough to convince our peers these galaxies were as old as we suspected them to be. Our initial suspicions about their existence came from the Spitzer Space Telescope’s infrared data.

“But ALMA has sharp eyes and revealed details at submillimeter wavelengths, the best wavelength to peer through dust present in the early universe. Even so, it took further data from the imaginatively named Very Large Telescope in Chile to really prove we were seeing ancient massive galaxies where none had been seen before.”

The discovery has the potential to reshape our ideas of the supermassive black holes that scientists currently believe nestle at the centre of most galaxies.

Kohno elaborates: “The more massive a galaxy, the more massive the supermassive black hole at its heart.

“So the study of these galaxies and their evolution will tell us more about the evolution of supermassive black holes, too.”

Kohno also explains that some ideas regarding dark matter may have to be revised, too: “Massive galaxies are also intimately connected with the distribution of invisible dark matter. This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now.”

In addition to the potential shake up the team believes that their findings may already present, they expect more surprises to come.

Wang concludes: These gargantuan galaxies are invisible in optical wavelengths so it’s extremely hard to do spectroscopy, a way to investigate stellar populations and chemical composition of galaxies. ALMA is not good at this and we need something more.

“I’m eager for upcoming observatories like the space-based James Webb Space Telescope to show us what these primordial beasts are really made of.”


Original research: T. Wang, C. Schreiber, D. Elbaz, Y. Yoshimura, K. Kohno, X. Shu, Y. Yamaguchi, M. Pannella, M. Franco, J. Huang, C.F. Lim & W.H. Wang. A dominant population of optically invisible massive galaxies in the early Universe. Nature. DOI: 10.1038/s41586–019–1452–4

How to “Weigh” Baby Planets

Similar to how stars are formed, the most popular theory among today’s scientists regarding the creation of planets is that they are a result of a nebula breaking down. During the long evolution of the deteriorating gaseous cloud, the nebula transforms into a structure called a protoplanetary disk, with a newly-formed star at its center. Such a disk provides a place of incubation for developing planets.

Just recently, for the first time on record, young planets-to-be (also referred to as protoplanets) developing in one of these protoplanetary disks were actually “weighed”. Several scientific papers published earlier this month as inclusions in the Astrophysical Journal Letters discuss a new mode of operation which can be employed to calculate various physical attributes of these protoplanets. It’s also rather accurate and dependable.

One group of astronomers headed by Richard Teague was responsible for the discovery of two young planets having a mass close to the size of the mass of Jupiter, the largest planet in our solar system. The two bodies orbit a star which has been labeled HD 163296. This four-million-year-old ball of burning gas is still a youngster as a star the size of our Sun would have a normal life expectancy of about 10 billion years and beyond.

A Developing Star System. Source: SciTechDaily.

But a separate party of scientists, this one based in Australia and headed by Christophe Pinte, was also spending time examining the same system. They noticed a third protoplanet in a revolution around the very same star. However, the finding attributed to Pinte’s team was a young planet nearly twice as massive as the gas giant Jupiter.

Both of the teams employed data from the Atacama Large Millimeter/submillimeter Array (ALMA). This is a system of radio telescopes located in Chile, South America. The two teams of astronomers closely examined the motion of the nebulous gas. Both managed to develop a process of measuring the gas’s velocity by observing the change in the wavelength of light emitted by carbon monoxide molecules.

The gravitational pull of a planet would best explain the gaseous movements. Richard Teague thinks this method of measurement could be used effectively in observing many other stars and protoplanets. In this way, he hopes scientists will be able to discover what types of protoplanets are most common in the cosmos.

Giant Radio telescope spots colliding galaxies

A new radio telescope array built in the world’s highest and driest desert in the world has just photographed two colliding galaxies for its first public test shots.

The Atacama Large Millimeter/submillimeter Array, a joint project between Canada, Chile, the European Union, Japan, Taiwan and the United States was officially opened for business after a decade of planning and building. The world’s largest astronomy project, ALMA is described as the most powerful millimeter/submillimeter-wavelength telescope ever and the most complex ground-based observatory, and these first images are a perfect description of what it has to give.

“Today marks the recognition of the successful coalition of thousands of people from all over the world all working with the same goal: to build the world’s most advanced radio telescope to see into the universe’s coldest, darkest places, where galaxies and stars and perhaps the building blocks of life are created,” said ALMA director Thijs de Graauw.

What ALMA photographed isn’t visible in normal light, because the murky material that leads to star birth blocks visible wavelengths of light.

“In the past we couldn’t study them because they were behind the dust. The thing that’s been missing is the youngest stars, which are the most interesting,” said astronomer Brad Whitmore of the Space Telescope Science Institute in a webcast. “This is a beautiful example where we’ll be able to see the full life histories of star clusters.”

What happens is that gas and dust absorb the light of stars and then re-emit the energy, but in different wavelengths of light. However, like black out curtains the thickest molecular dust clouds trap almost all wavelengths, making them extremely hard to spot.

Radio waves are an exception; in the same way that radio frequencies pass even through the thickest of walls, so do they pass through these dust clouds; and ALMA is capable of not only noticing the presence of hot young stars, but also determine rich chemical information about them.

 

“For the last 25 years, we have really only relied on being able to see carbon monoxide or hydrogen cyanide,” said astronomer Kartik Sheth of the National Radio Astronomy Observatory in the webcast. “For the first time, we can see the entire chemical spectrum.”

“We will use ALMA to image the ‘birth ring’ of planetesimals that we believe orbits this young star,” he said. “We hope to discover clumps in these dusty asteroid belts, which can be the markers of unseen planets.”

Via Wired

[AMAZING VIDEO] Chilean sky light up by heavens

A regular starry night at the ALMA site.

I just stumbled onto this spectacular time-lapse video of the Chilean ALMA site skyline, where an entire night from the observatory’s high ground is fast forwarded. A regular starry night at the ALMA site. The Atacama Large Millimeter/submillimeter Array (ALMA) is an international partnership between Europe, North America, East Asia and the Republic of Chile to build the largest astronomical project in existence, and sits on top of the Chajnantor plateau at 5000 meters altitude in the Atacama desert of northern Chile. Oh, and it’s no surprise or wonder to anyone anymore why they chose this exact site to invest more than $1 billion in the most ambitious ground-based telescope currently under construction.

Be sure to play the video at 720pp (HD) and watch it in full screen. Enjoy!

Many thanks to SciGuy for sharing this.