The next big discovery in astronomy? Scientists probably found it years ago – but they don’t know it yet

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An artist’s illustration of a black hole “eating” a star.
NASA/JPL-Caltech

By Eileen Meyer, University of Maryland, Baltimore County

Earlier this year, astronomers stumbled upon a fascinating finding: Thousands of black holes likely exist near the center of our galaxy.

The X-ray images that enabled this discovery weren’t from some state-of-the-art new telescope. Nor were they even recently taken – some of the data was collected nearly 20 years ago.

No, the researchers discovered the black holes by digging through old, long-archived data.

Discoveries like this will only become more common, as the era of “big data” changes how science is done. Astronomers are gathering an exponentially greater amount of data every day – so much that it will take years to uncover all the hidden signals buried in the archives.

The evolution of astronomy

Sixty years ago, the typical astronomer worked largely alone or in a small team. They likely had access to a respectably large ground-based optical telescope at their home institution.

Their observations were largely confined to optical wavelengths – more or less what the eye can see. That meant they missed signals from a host of astrophysical sources, which can emit non-visible radiation from very low-frequency radio all the way up to high-energy gamma rays. For the most part, if you wanted to do astronomy, you had to be an academic or eccentric rich person with access to a good telescope.

Old data was stored in the form of photographic plates or published catalogs. But accessing archives from other observatories could be difficult – and it was virtually impossible for amateur astronomers.

Today, there are observatories that cover the entire electromagnetic spectrum. No longer operated by single institutions, these state-of-the-art observatories are usually launched by space agencies and are often joint efforts involving many countries.

With the coming of the digital age, almost all data are publicly available shortly after they are obtained. This makes astronomy very democratic – anyone who wants to can reanalyze almost any data set that makes the news. (You too can look at the Chandra data that led to the discovery of thousands of black holes!)

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Colossal cosmic collision alters understanding of early universe

Reuters reports:

Astronomers have detected the early stages of a colossal cosmic collision, observing a pile-up of 14 galaxies 90 percent of the way across the observable universe in a discovery that upends assumptions about the early history of the cosmos.

Researchers said on Wednesday the galactic mega-merger observed 12.4 billion light-years away from Earth occurred 1.4 billion years after the Big Bang that gave rise to the universe. Astronomers call the object a galactic protocluster, a precursor to the type of enormous galaxy clusters that are the largest-known objects in today’s universe.

It marked the first time scientists observed the birth of a galaxy cluster, with at least 14 galaxies crammed into an area only about four times the size of our average-sized Milky Way galaxy.

A protocluster as massive as the one observed here, designated as SPT2349-56, should not have existed at that time, according to current notions of the early universe. Scientists had figured this could not happen until several billion of years later. [Continue reading…]

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Gaia mission releases map of more than a billion stars – here’s what it can teach us

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Gaia’s view of our Milky Way and neighbouring galaxies.
ESA/Gaia/DPAC, CC BY-SA

By George Seabroke, UCL

Most of us have looked up at the night sky and wondered how far away the stars are or in what direction they are moving. The truth is, scientists don’t know the exact positions or velocities of the vast majority of the stars in the Milky Way. But now a new tranche of data from the European Space Agency’s Gaia satellite, aiming to map stars in our galaxy in unprecedented detail, has come in to shed light on the issue.

The Gaia Archive opened on April 25, making public Gaia’s second data release to everyone. To quote the character Dave Bowman in the sci-fi classic 2001: A Space Odyssey: “It’s full of stars”. In fact, it contains data on the distances to more than 1.3 billion stars.

The Gaia satellite was launched in 2013 and has been scanning the sky with its two telescopes continuously ever since, with the aim of deciphering how our Milky Way galaxy formed and evolved. To do this, it is measuring something called parallax. If you hold a finger at arms length and look at it with one eye and then the other, your finger appears to shift position compared to the background. The angular change is called parallax.

Being in space allows Gaia to see similar tiny shifts in star positions. Observations at different locations six months apart (half way of its orbit around the Earth) are akin to looking at your finger with one eye and then the other. When you know the parallax as well as the distance from Gaia to the sun (or the distance from your nose to your eye), you can use simple trigonometry to work out the distance to each star (or your finger).

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Stephen Hawking, in his own words

In memory of Stephen Hawking, who died on Wednesday at 76, the New York Times has gathered a selection of his quotes:

“Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at.”

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First glimpses of the cosmic dawn

Marina Koren reports:

Near the beginning, not long after the Big Bang, the universe was a cold and dark place swirling with invisible gas, mostly hydrogen and helium. Over millions of years, gravity pulled some of this primordial gas into pockets. The pockets eventually became so dense they collapsed under their own weight and ignited, flooding the darkness with ultraviolet radiation. These were the very first stars in the universe, flashing into existence like popcorn kernels unfurling in the hot oil of an empty pan.

Everything flowed from this cosmic dawn. The first stars illuminated the universe, collapsed into the black holes that keep galaxies together, and produced the heavy elements that would make planets and moons and the human beings that evolved to gaze upon it all.

This epoch in our cosmic history has long fascinated scientists. They hoped that someday, using technology that was calibrated just right, they could detect faint signals from that moment. Now, they think they’ve done it.

Astronomers said Wednesday they have found, for the first time, evidence of the earliest stars. Using a table-sized radio instrument in the desert in Western Australia, the researchers detected radio emissions from the cold hydrogen that interacted with brand-new stars in that stage of the early universe.

Astronomers from Arizona State University, MIT, and the University of Colorado at Boulder, funded by the National Science Foundation, spent more than a decade trying to find this signal, calibrating and recalibrating the technology. Their results were published in Nature. [Continue reading…]

 

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