Astronomy

We can judge the value of any scientific endeavour based on how much of our knowledge it overturns or transforms. By that metric, the ESA’s Gaia mission is a resounding success. The spacecraft gave us a precise, 3D map of our Milky Way galaxy and has forced us to abandon old ideas and replace them with compelling new ones.

Currently, we’re marking the end of the Gaia mission, our best effort to understand the Milky Way. Gaia is an astrometry mission that’s built an impressive map of the Milky Way by taking three trillion observations of two billion individual objects in the galaxy, most of them stars, over an 11-year period. Measuring the same objects repeatedly means Gaia’s map is 3D and shows the proper motion of stars throughout the galaxy. Rather than a static map, it reveals the galaxy’s kinetic history and some of the changes it’s gone through.

Gaia showed us our galaxy’s turbulent history, including the streams of stars stemming from past disruptive events. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

We’ve waited a long time for such a detailed look at our galaxy.

Radio astronomy, which gained momentum in the 1950s, helped us understand the structure of the Milky Way. Radio telescopes could see through intervening dust clouds and detect the distribution of hydrogen in the galaxy. In 1952, astronomers began the first major radio survey of the Milky Way. Astronomers theorized that the galaxy had a spiral structure, and finally, they detected the spiral arms, revealing the Milky Way’s basic structure.

In a 1958 paper, the authors wrote that “The distribution of the hydrogen evidently shows great irregularities. Nevertheless, several arms can be followed over considerable lengths.”

This figure shows the hydrogen distribution in the plane of the Milky Way’s disk. Though it appears outdated to our modern eyes and isn’t visually intuitive, it was exciting at the time. Image Credit: From “The galactic system as a spiral nebula” by Oort et al. 1958.

Astronomers also used RR Lyrae and Cepheids, two types of variable stars with known intrinsic brightnesses (standard candles), to calculate their distances. This allowed them to trace the Milky Way’s structure. Globular clusters also helped astronomers map the Milky Way.

In the 1980s, infrared telescopes like NASA’s IRAS peered through cosmic dust to help find features like the Milky Way’s central bar. Then, in 1989, the ESA’s Hipparcos mission was launched. Hipparcos was an astrometry mission and was Gaia’s predecessor. Though not nearly as precise, and though it only measured 100,000 stars, it was finally able to measure their proper motions. It revealed more details of the Milky Way and helped confirm its barred spiral form. It also provided some insights into our galaxy’s history and evolution.

But astronomers craved more detailed knowledge. Gaia was launched in 2013 to meet this need, and it’s been a total success.

Gaia is a tribute to ingenuity. We’re effectively trapped inside the Milky Way, and no spacecraft can get beyond it to capture an external view of the galaxy. Gaia has given us that view without ever leaving L2.

While many prior efforts to trace the Milky Way’s structure depended on sampling select stellar populations, Gaia precisely measured the position and motion of almost two billion stars throughout the galaxy.

Gaia’s map of the Milky Way has become iconic. This image is constructed from Gaia data that’s mapping two billion of the galaxy’s stars. It also mapped stars in the Large and Small Magellanic clouds. Image Credit: ESA/Gaia/DPAC

Gaia’s work has culminated in artist impressions of the Milky Way based on its voluminous data. These impressions show that the Milky Way has multiple arms and that they’re not as prominent as we thought.

Gaia’s observations have given us a much more detailed and precise look at the Milky Way’s spiral arms. It has identified previously unknown structures in the arms, including fossil arms in the outer disk. These could be remnants of past tidal arms or distortions in the disk, or remnants of ancient interactions with other galaxies. Gaia has also found many previously unknown filamentary structures at the disk’s edge.

The Gaia mission has also allowed us to finally see our galaxy from the side. We’ve learned that the galactic disk has a slight wave to it. Astronomers think this was caused by a smaller galaxy interacting with the Milky Way. The Sagittarius Dwarf Spheroidal galaxy could be responsible for it.

The Sagittarius Dwarf Spheroidal Galaxy has been orbiting the Milky Way for billions of years. According to astronomers, the three known collisions between this dwarf galaxy and the Milky Way have triggered major episodes of star formation, one of which may have given rise to our Solar System. Image Credit: ESA/Gaia

Alongside the compelling science, artists have created illustrations based on Gaia data that really hit home. The stunning side view of our galaxy is one of the most accurate views of the Milky Way we’ve ever seen.

This artist’s reconstruction of Gaia data shows the Milky Way’s central bulge, galactic disk, and outer reaches. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Gaia has updated our understanding of the galaxy we live in and brought its history to life. Even if it had no more to offer beyond today, it would still be an outstanding, successful mission. But even though its mission is over, we still don’t have all of its data.

Its final data release, DR5, will be available by the end of 2030.

Who knows what else the mission will show us about our home, the Milky Way galaxy.

The post The Most Accurate View of the Milky Way appeared first on Universe Today.

As apparent acts of sabotage cut undersea data cables around the world, NATO held its first demonstration of a project to quickly reroute crucial communications to satellite internet

As apparent acts of sabotage cut undersea data cables around the world, NATO held its first demonstration of a project to quickly reroute crucial communications to satellite internet

One of the most exciting developments in modern astronomy is how astronomers can now observe and study the earliest galaxies in the Universe. This is due to next-generation observatories like the James Webb Space Telescope (JWST), with its sophisticated suite of infrared instruments and spectrometers, and advances in interferometry – a technique that combines multiple sources of light to get a clearer picture of astronomical objects. Thanks to these observations, astronomers can learn more about how the earliest galaxies in the Universe evolved to become what we see today.

Using Webb and the Atacama Large Millimeter/submillimeter Array (ALMA), an international team led by researchers from the National Astronomical Observatory of Japan (NAOJ) successfully detected atomic transitions coming from galaxy GHZ2 (aka. GLASS-z12), located 13.4 billion light-years away. Their study not only set a new record for the farthest detection of these elements This is the first time such emissions have been detected in galaxies more than 13 billion light-years away and offers the first direct insights into the properties of the earliest galaxies in the Universe.

The galaxy was first identified in July 2022 by the Grism Lens-Amplified Survey from Space (GLASS) observing program using the JWST’s Near-Infrared Camera (NIRCam). A month later, follow-up observations by ALMA confirmed that the galaxy had a spectrographic redshift of more than z = 12, making it one of the earliest and most distant galaxies ever observed. The exquisite observations by both observatories have allowed astronomers to gain fresh insights into the nature of the earliest galaxies in the Universe.

The Atacama Large Millimeter/submillimeter Array (ALMA). Credit: C. Padilla, NRAO/AUI/NSF

Jorge Zavala, an astronomer at the East Asian ALMA Regional Center at the NAOJ, was the lead author of this study. As he explained in an ALMA-NAOJ press release:

“We pointed the more than forty 12-m antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) and the 6.5-m James Webb Space Telescope (JWST) for several hours at a sky position that would appear totally empty to the naked human eye, aiming to catch a signal from one of the most distant astronomical objects known to date. And [we] successfully detected the emission from excited atoms of different elements such as Hydrogen and Oxygen from an epoch never reached before.”

Confirming and characterizing the physical properties of distant galaxies is vital to testing our current theories of galaxy formation and evolution. However, insight into their internal physics requires detailed and sensitive astronomical observations and spectroscopy – the absorption and emission of light by matter- allowing scientists to detect specific chemical elements and compounds. Naturally, these observations were challenging for the earliest galaxies, given that they are the most distant astronomical objects ever studied.

Nevertheless, the ALMA observations detected the emission line associated with doubly ionized oxygen (O III), confirming that the galaxy existed about 367 million years after the Big Bang. Combined with data obtained by Webb’s Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) instruments, the team was able to characterize this object effectively. Based on their observations, the team discovered that GHZ2 was experiencing extreme bursts of star formation 13.4 billion years ago under conditions that differ considerably from what astronomers have seen in star-forming galaxies over the past few decades.

For instance, the relative abundance of heavier elements in this galaxy (metallicity) is significantly lower than that of most galaxies studied. This was expected given the dearth of heavier elements during the early Universe when Population III stars existed, which were overwhelmingly composed of hydrogen and helium. These stars were massive, hot, and short-lived, lasting only a few million years before they went supernova. Similarly, the team attributed GHZ2’s high luminosity to its Population III stars, which are absent from more evolved galaxies.

The scattered stars of the globular cluster NGC 6355 are strewn across this image from the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, E. Noyola, R. Cohen

This luminosity is amplified by the fact that GHZ2, which is a few hundred million times the mass of the Sun, occupies a region of around 100 parsecs (~325 light-years). This indicates that the galaxy has a high stellar density similar to that of Globular Clusters observed in the Milky Way and neighboring galaxies. Other similarities include low metallicity, the anomalous abundances of certain chemicals, high star formation rates, high stellar mass surface density, and more. As such, studying galaxies like GHZ2 could help astronomers explain the origin of globular clusters, which remains a mystery.

Said Tom Bakx, a researcher at Chalmers University, these observations could pave the way for future studies of ancient galaxies that reveal the earliest phases of galaxy formation:

“This study is a crown on the multi-year endeavor to understand galaxies in the early Universe. The analysis of multiple emission lines enabled several key tests of galaxy properties, and demonstrates the excellent capabilities of ALMA through an exciting, powerful synergy with other telescopes like the JWST.”

Further Reading: ALMA, AJL

The post Webb and ALMA Team Up to Study Primeval Galaxy appeared first on Universe Today.

The James Webb Space Telescope (JWST) has captured the first exquisite images of an interstellar patch of sky, about 11,000 light-years away in the constellation Cassiopeia.

India successfully docked its two SpaDex satellites in Earth orbit yesterday (Jan. 15), becoming just the fourth country to pull off such a satellite meetup.

NASA astronauts Nick Hague and Suni Williams completed a six-hour spacewalk to repair and upgrade equipment outside the International Space Station on Thursday (Jan. 16).

The largest photomosaic of the Andromeda galaxy, assembled from NASA/ESA Hubble Space Telescope observations, unveils hundreds of millions of stars. It took more than 10 years to collect data for this colorful portrait of our neighbouring galaxy and was created from more than 600 snapshots. This stunning, colourful mosaic captures the glow of 200 million stars, and is spread across roughly 2.5 billion pixels.

By using MRI brain scans to identify regions linked to hand movements and sensations, researchers were able to restore a sense of touch to two people with paralysis – and one was able to control and feel a robot arm using his thoughts

By using MRI brain scans to identify regions linked to hand movements and sensations, researchers were able to restore a sense of touch to two people with paralysis – and one was able to control and feel a robot arm using his thoughts

Droughts lasting multiple years are becoming more common and extreme around the globe, expanding by about 50,000 square kilometres annually

Droughts lasting multiple years are becoming more common and extreme around the globe, expanding by about 50,000 square kilometres annually

2024 was the warmest year on record, according to NASA data. The global average temperature was 2.3 degrees Fahrenheit above the mid-20th-century baseline.

In his farewell address, President Biden warned that a powerful “oligarchy” could undo four years of progress on climate policy

Young Stars, Dark Nebulae

The head of the European Space Agency says that ESA is ready for any changes in NASA's direction that U.S. President-elect Donald Trump may make.

Photographer Josh Dury captured rare Comet C/2024 G3 (Atlas) in a dramatic 'once-in-a-lifetime' image after a challenging chase across UK skies at dusk.

Triple star systems are more common than might be imagined – about one in ten of every Sun-like star is part of a system with two other stars. However, the dynamics of such a system are complex, and understanding the history of how they came to be even more so. Science took a step towards doing so with a recent paper by Emily Leiner from the Illinois Institute of Technology and her team.

They examined a star called WOCS 14020 in the star cluster M67, which is about 2,800 light years away from Earth. It is currently orbiting a massive white dwarf star with a mass of about .76 times that of the Sun (about 50% heavier than a typical white dwarf). That pairing hints at a much more interesting past.

Dr. Leiner and her team believe that WOCS 14020 was originally part of a triple star system—specifically, that it orbited a binary pair of much larger stars. Around 500 million years ago, the two stars in the binary merged, briefly creating a much more massive star that pushed some of its material onto its third companion star.

Fraser talks about stellar collisions, which caused WOCS 14020’s current state.

Absorbing that material caused WOCS 14020 to start speeding up its spin. It now rotates once every four days, rather than typically once every thirty days, which is common to other Sun-like stars. This faster rotation feature is key to Dr. Leiner and her team’s classification of the star – a “blue lurker.”

To understand what that classification means, we must first understand another type of star, the blue straggler. Blue stragglers are stars that also have gained mass from another star and appear hotter, brighter, and “bluer” than they would be expected to be given their age. In this case, all three features are directly tied together, as a hotter star is more likely to be brighter and would give off more light in the blue part of the visible spectrum, though it would still appear almost exactly like the Sun to the naked eye.

Blue lurkers are a sub-set of blue stragglers – they also gained mass from a star, but they spin faster instead of being hotter and brighter. This makes this difficult to distinguish in a cluster like M67, as they blend in better with the other surrounding stars, hence the name “lurker.” However, they are relatively rare – out of the 400 main sequence stars in M67, only around 11 are estimated to be “blue lurkers.” That puts the total, even in a space as congested as M67, at only around 3% of stars. Blue lurkers likely make up less than 1% of the general population.

A video explaining blue straggler stars.
Credit – Cosmos:elementary YouTube Channel

Since their evolutionary histories are likely to advance our understanding of the dynamics of the systems that created them, astronomers will spend more time analyzing these blue lurkers when they find them. Unique cases like WOCS 14020, where astronomers have a pretty good idea of the system’s evolutionary history, are instrumental in that regard, and the paper, which was presented at the ongoing 245th American Astronomical Society meeting, was a step towards that greater understanding.

Learn More:
STScI – NASA’s Hubble Tracks Down a ‘Blue Lurker’ Among Stars
Leiner et al – The Blue Lurker WOCS 14020 : A Long-Period Post-Common-Envelope Binary in M67 Originating from a Mergerina Triple System
UT – Blue Straggler Stars are Weird
UT – A Rare Opportunity to Watch a Blue Straggler Forming

The post Colliding Stars, Stellar Siphoning, and a now a “Blue Lurker.” This Star System has Seen it All appeared first on Universe Today.

Wildfires like the Los Angeles blazes destroy so much, but they often spare some evidence of the cause of their ignition

For stargazers and wildlife watchers, monoculars can be an effective alternative to telescopes or binoculars. Here's how they work.