Gaia Finds Ancient Streams of Stars That Formed the Milky Way

ESA’s Gaia space telescope discovered two star streams that helped form the infant Milky Way. Both are so ancient that they likely formed before even the oldest parts of our present-day galaxy’s spiral arms and disc. This image shows the location and distribution of Shakti (yellow) and Shiva (blue) stars throughout the Milky Way. Credit: ESA/Gaia/DPAC/K. Malhan.

Using ESA’s Gaia spacecraft, astronomers have tracked down two streams of stars that likely formed the foundation of the Milky Way. Named “Shakti and Shiva,” the two streams contain about 10 million stars, all of which are 12 to 13 billion years old and likely came together even before the spiral arms and disk were formed. These star streams are all moving in roughly similar orbits and have similar compositions. Astronomers think they were probably separate galaxies that merged into the Milky Way shortly after the Big Bang.,

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Nancy Grace Roman will Map the Far Side of the Milky Way

Spiral galaxy seen in visible and infrared

The Galaxy is a collection of stars, planets, gas clouds and to the dismay of astronomers, dust clouds. The dust blocks starlight from penetrating so it’s very difficult to learn about the far side of the Galaxy. Thankfully the upcoming Nancy Grace Roman telescope has infrared capability so it can see through the dust. A systematic survey of the far side of the Milky Way is planned to see what’s there and could discover billions of objects in just a month. 

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Astronomers Build a 3D Map of Dust Within Thousands of Light-Years

3D Map of Dust in Galaxy

If you explore the night sky it won’t be long before you realise there is a lot of dust and gas up there. The interstellar dust between the stars accounts for 1% of the mass of the interstellar medium but reflects 30% of the starlight in infrared wavelengths. The dust plays a key role in the formation of stars and the evolution of the Galaxy. A team of astronomers have attempted to map the dust out to a distance of 3000 light years and have just released the first 3D map of the dust in our Galaxy. 

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Astronomers Measure the Mass of the Milky Way by Calculating How Hard it is to Escape

Artist view of the Milky Way galaxy. Credit: ESA

If you want to determine your mass, it’s pretty easy. Just step on a scale and look at the number it gives you. That number tells you the gravitational pull of Earth upon you, so if you feel the number is too high, take comfort that Earth just finds you more attractive than others. The same scale could also be used to measure the mass of Earth. If you place a kilogram mass on the scale, the weight it gives is also the weight of Earth in the gravitational field of the kilogram. With a bit of mass, you have the mass of Earth.

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There’s Less Dark Matter at the Core of the Milky Way

A study by MIT physicists suggest the Milky Way’s gravitational core may be lighter in mass, and contain less dark matter, than previously thought. Credits:Credit: ESA/Gaia/DPAC, Edited by MIT News

Science really does keep you on your toes. First there was matter and then there were galaxies. Then those galaxies had more stuff in the middle so stars further out were expected to move slowly, then there was dark matter as they actually seemed to move faster but now they seem to be moving slower in our Galaxy so perhaps there is less dark matter than we thought after all! 

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Astronomers Have Mapped the Milky Way's Magnetic Fields in 3D

Magnetic fields mapped within the Whirlpool Galaxy. Credit: NASA, SOFIA science team, ESA, STScI

Our galaxy is filled with magnetic fields. They come not just from stars and planets, but from dusty stellar nurseries and the diffuse hydrogen gas of interstellar space. We’ve long known of this galactic magnetic field, but mapping it in detail has posed a challenge. Now a new study gives us a detailed 3-dimensional map of these fields, with a few surprises.

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Webb’s Infrared Eye Reveals the Heart of the Milky Way

The full view of the NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera) instrument reveals a 50 light-years-wide portion of the Milky Way’s dense centre. An estimated 500,000 stars shine in this image of the Sagittarius C (Sgr C) region, along with some as-yet unidentified features. Image Credit: NASA, ESA, CSA, STScI, S. Crowe (UVA)

The JWST is taking a break from studying the distant Universe and has trained its infrared eye on the heart of the Milky Way. The world’s most powerful space telescope has uncovered some surprises and generated some stunning images of the Milky Way’s galactic center (GC.) It’s focused on an enormous star-forming region called Sagittarius C (Sgr C).

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Gaze Into the Heart of the Milky Way in This Latest JWST Image

James Webb Space Telescope’s NIRCam (Near-Infrared Camera) instrument reveals a 50 light-years-wide portion of the Milky Way’s dense center. An estimated 500,000 stars shine in this image of the Sagittarius C (Sgr C) region, along with some as-yet unidentified features. Credit: NASA, ESA, CSA, STScI, S. Crowe (UVA).

Thanks to its infrared capabilities, the James Webb Space Telescope (JWST) allows astronomers to peer through the gas and dust clogging the Milky Way’s center, revealing never-before-seen features. One of the biggest mysteries is the star forming region called Sagittarius C, located about 300 light-years from the Milky Way’s supermassive black hole. An estimated 500,000 stars are forming in this region that’s being blasted by radiation from the densely packed stars. How can they form in such an intense environment?

Right now, astronomers can’t explain it.

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Astronomers Want JWST to Study the Milky Way Core for Hundreds of Hours

This overview of the Milky Way's Galactic Center (GC) shows the region of the proposed JWST survey. Image Credit: NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech)

To understand the Universe, we need to understand the extreme processes that shape it and drive its evolution. Things like supermassive black holes (SMBHs,) supernovae, massive reservoirs of dense gas, and crowds of stars both on and off the main sequence. Fortunately there’s a place where these objects dwell in close proximity to one another: the Milky Way’s Galactic Center (GC.)

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Astronomers Release a Cosmic Atlas of 380,000 Galaxies in our Neighborhood

Optical mosaics of 42 galaxies from the SGA-2020 sorted by increasing angular diameter from the top-left to the bottom-right. This figure illustrates the tremendous range of types, sizes, colors and surface brightness profiles, internal structure, and environments of the galaxies in the SGA. Credit: CTIO/NOIRLab/DOE/NSF/AURA/J. Moustakas.

The Milky Way is just one galaxy in a vast cosmic web that makes up the Universe’s large-scale structure. While ESA’s Gaia spacecraft is building a map of our stellar neighborhood, a team of astronomers with the Dark Energy Spectroscopic Instrument (DESI) Legacy Survey have released a comprehensive galactic map that includes all the data from three wide-ranging surveys completed between 2014 and 2017. Called the Siena Galaxy Atlas (SGA), it contains the distance, location, and chemical profile of 380,000 galaxies across half of the night sky.

“Previous galaxy compilations have been plagued by incorrect positions, sizes and shapes of galaxies, and also contained entries which were not galaxies but stars or artifacts,” explained Arjun Dey, an astronomer with NOIRLab, who was involved in the project. “The SGA cleans all this up for a large part of the sky. It also provides the best brightness measurements for galaxies, something we have not reliably had before for a sample of this size.”

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