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All-sky surveys – visualizing our dynamic galaxy

John Healy

Advances in all-sky surveys permit better visualization of the motions and dynamics inside our galaxy. And provide a better understanding of the evolution of the Milky Way.

X-ray all-sky surveys

As noted in this Space.com article, while “optical telescopes are much easier to design than X-ray telescopes … some of the most interesting objects in the Universe don’t emit light at visible wavelengths and therefore remain mostly hidden to optical telescopes.”

• Space.com > “German X-ray space telescope captures most complete map of black holes ever” by Tereza Pultarova (July 27, 2021) – eROSITA can see light from objects which took 7 billion years to reach its detectors.

(quote) The first science from the 2019 eROSITA space observatory [entire sky-survey] is here. … revealing more than 3 million newfound objects in less than two years. … Previous X-ray telescopes … such as ESA’s XMM Newton, or NASA’s Chandra X-ray Observatory, could only observe rather small sections of the sky [but deeply] in one go.

“For the first time, we have an X-ray telescope that can be used in very similar ways as the large field optical telescopes that we use today,” Merloni [mission’s senior scientist] said. “With eROSITA, we cover the entire sky very efficiently and can study large-scale structures, such as the entire Milky Way.”

… the catalogues contain information about 3 million sources of X-ray radiation — black holes, neutron stars and galaxy clusters. About 77% of those sources are distant black holes in other galaxies, 20% are neutron stars, stars and black holes in the Milky Way. The remaining 3% are galaxy clusters, he added.

Caption > The energetic universe as seen with the eROSITA X-ray telescope. The first eROSITA all-sky survey was conducted over a period of six months by letting the telescope rotate continuously, … To generate this image – in which the whole sky is projected onto an ellipse (so-called Aitoff projection) with the centre of the Milky Way in the middle and the body of the Galaxy running horizontally – photons have been colour-coded according to their energy … Piercing through this turbulent, hot diffuse medium, are hundreds of thousands of X-ray sources, which appear mostly white in the image, and uniformly distributed over the sky. Among them, distant active galactic nuclei (including a few emitting at a time when the Universe was less than one tenth of its current age) are visible as point sources, while clusters of galaxies reveal themselves as extended X-ray nebulosities. In total, about one million X-ray sources have been detected in the eROSITA all-sky image, …

Wiki image credits

Johannes Buchner
CC BY-SA 4.0
File:SRG-eROSITA all-sky image.jpg
Created: 19 June 2020

References

• European Space Agency’s Gaia (2013)
• European Southern Observatory’s ground-based Very Large Telescope
• European Space Agency’s XMM Newton X-ray space observatory (1999)
• Chandra X-ray Observatory (1999)

Related posts

• The Milky Way’s shape — a peculiar disk
• Yes, Virginia, there is a black hole in the center of our Milky Way

• Levels of understanding – what are X-rays?
• Celebrating X-Ray Astronomy — Chandra

4 thoughts on “All-sky surveys – visualizing our dynamic galaxy”

  1. Processing of Sloan Digital Sky Survey data revealed that dwarf galaxies likely contain black holes, thereby revising census of these objects. Energetic patterns and “Iron 10” emissions and X-rays.

    • Quanta Magazine > “Tiny Galaxies Reveal Secrets of Supermassive Black Holes” by Charlie Wood, Staff Writer (March 14, 2022) – Dwarf galaxies weren’t supposed to have big black holes. Their surprise discovery has revealed clues about how the universe’s biggest black holes could have formed.

    In 2008, Marta Volonteri helped develop a radical proposal: Astronomers should search the smallest of galaxies for colossal black holes … The only problem was that big black holes weren’t supposed to exist in little galaxies.

    Researchers believe that galaxies like the Milky Way are the patchwork products of more than 10 billion years of mashups, in which galaxies repeatedly smash into their neighbors, growing larger each time. Dwarf galaxies remain small either because they have dodged encounters with other galaxies, or because they formed relatively

  2. Our everyday experience belies the frame of reference for the Earth’s high velocity through the cosmos.

    • NASA > APOD > “CMB Dipole: Speeding Through the Universe” (April 4, 2022)

    Image Credit: DMR, COBE, NASA, Four-Year Sky Map

    Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies.

    But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background radiation (CMBR).

    In the featured all-sky map from the COBE satellite in 1993, microwave light in the Earth’s direction of motion appears blueshifted and hence hotter, while microwave light on the opposite side of the sky is redshifted and colder.

    The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained. Why are we moving so fast? What is out there?

    Earthrise

  3. Another all-sky survey mission for 2024 ff – a near-infrared space observatory will create a 3-D map of the entire sky.

    • The Caltech Weekly 8-18-2022 > Caltech News > “A Test Chamber for NASA’s New Cosmic Mapmaker Makes a Dramatic Entrance” (August 16, 2022) – Unlike any previous map, it will provide images of individual objects as well as a light spectrum for every point in the sky.

    It required three years of design and construction, a monthlong boat ride across the Pacific Ocean, and a 30-ton crane, but the customized test chamber for NASA’s upcoming Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) space telescope has finally reached its destination at Caltech’s Cahill Center for Astronomy and Astrophysics.

    SPHEREx is managed by JPL for NASA’s Astrophysics Division within the Science Mission Directorate in Washington D.C. Bock is the mission’s principal investigator. Ball Aerospace in Boulder, Colorado, will supply the spacecraft. The science analysis of the SPHEREx data will be conducted by a team of scientists located at 10 institutions across the U.S. and in South Korea. Data will be processed and archived at IPAC at Caltech. The SPHEREx dataset will be publicly available.

    all-sky survey mission

  4. Northern Extended Millimeter Array
    Credit: Wiki (Creative Commons)

    Interferometry and multi-wavelength collaborative astronomy in the news – a powerful radio telescope (array) gets even better.

    • Space.com > “Major radio telescope ‘levels up’ to get unprecedented views of the early universe” by Robert Lea (Oct 25, 2022) – The upgraded antenna array allows astronomers to zoom in on cosmic objects and investigate them in finer detail [~detect a cellphone from over 310 miles (500 km) away].

    The Northern Extended Millimeter Array (NOEMA), a powerful radio telescope in the French Alps, has leveled up to full capacity. On Sept. 30, the telescope, which comprises 12 antennas, was inaugurated and became the most powerful millimeter radio telescope in the Northern Hemisphere.

    The first antenna of the NOEMA system was inaugurated in 2014, and the telescope now includes 12 antennas. In addition, the length of the tracks that all 12 antennas can move along has been extended from 2,500 feet (760 meters) to just over a mile (1.7 kilometers), according to a statement from the French National Center for Scientific Research (CNRS).

    The newly powered-up NOEMA telescope is one of the few radio observatories across the globe that can collect data on a vast number of molecular and atomic signatures — the “fingerprints” of molecules and atoms — at the same time, which astronomers call “multiline observations.”

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