Universe Today

January 19, 2024January 19, 2024 by Mark Thompson

Early Galaxies Looked Nothing Like What We See Today

Though an estimated 100 million black holes roam among the stars in our Milky Way galaxy, astronomers have never identified an isolated black hole – until now. Following six years of meticulous observations, NASA’s Hubble Space Telescope has provided, for the first time ever, strong evidence for a lone black hole plying interstellar space. The black hole that was detected lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. However, its discovery allows astronomers to estimate, statistically, that the nearest isolated black hole to Earth might be as close as 80 light-years. Black holes are born from rare, monstrous stars (less than one-thousandth of the galaxy’s stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball. Hubble can’t photograph the wayward black hole because it doesn’t emit any light, but instead swallows all radiation due to its intense gravitational pull. Instead, Hubble measurements capture the ghostly gravitational footprint of how the stealthy black hole warps space, which then deflects starlight from anything that momentarily lines up exactly behind it. Ground-based telescopes, which monitor the brightness of millions of stars in the rich star fields in the direction of the central bulge of our Milky Way, look for the tell-tale sudden brightening of one of them when a massive object passes between us and the star. Then Hubble follows up on the most interesting such events. Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, along with his team, made the discovery in a survey designed to find just such isolated black holes. The warping of space due to the gravity of a foreground object passing in front of a star located far behind it will momentarily bend and amplify the light of the background star as it passes in front of it. The phenomenon, called gravitational microlensing, is used to study stars and exoplanets in the approximately 20,000 events seen so far inside our galaxy. The signature of a foreground black hole stands out as unique among other microlensing events. The very intense gravity of the black hole will stretch out the duration of the lensing event for over 200 days. Also, If the intervening object was instead a foreground star, it would cause a transient color change in the starlight as measured because the light from the foreground and background stars would momentarily be blended together. But no color change was seen in the black hole event. Next, Hubble was used to measure the amount of deflection of the background star’s image by the black hole. Hubble is capable of the extraordinary precision needed for such measurements. The star’s image was offset from where it normally would be by two milliarcseconds. That’s equivalent to measuring the diameter of a 25-cent coin in Los Angeles as seen from New York City. This astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole. The amount of deflection by the black hole’s intense warping of space allowed Sahu’s team to estimate it weighs seven solar masses. The isolated black hole is traveling across the galaxy at 90,000 miles per hour (fast enough to travel from Earth to the moon in less than three hours). That’s faster than most of the other neighboring stars in that region of our galaxy. “Astrometric microlensing in conceptually simple but observationally very tough,” said Sahu. “It is the only technique for identifying isolated black holes.” When the black hole passed in front of a background star located 28,000 light-years away in the galactic bulge, the starlight coming toward Earth was amplified for a duration of 265 days as the black hole passed by. However, it took several years of Hubble observations to follow how the background star’s position appeared to be deflected by the bending of light by the foreground black hole. The existence of stellar-mass black holes has been known since the early 1970’s, but all of them—until now—are found in binary star systems. Gas from the companion star falls into the black hole, and is heated to such high temperatures that it emits X rays. About two dozen black holes have had their masses measured in X-ray binaries through their gravitational effect on their companions. Black hole masses in X-ray binaries inside our galaxy range from 5 to 20 solar masses. Black holes detected in other galaxies by gravitational waves from mergers between black holes and companion objects have been as high as 90 solar masses. “Detections of isolated black holes will provide new insights into the population of these objects in our Milky Way,” said Sahu. He expects that his program will uncover more free-roaming black holes inside our galaxy. But it is a needle-in-a-haystack search. The prediction is that only one in 1500 microlensing events are caused by isolated black holes. NASA’s upcoming Nancy Grace Roman Space Telescope will discover several thousand microlensing events out of which many are expected to be black holes, and the deflections will be measured with very high accuracy. In a 1916 paper on general relativity, Albert Einstein predicted that his theory could be tested by observing the sun’s gravity offsetting the apparent position of a background star. This was tested by astronomer Arthur Eddington during a solar eclipse on May 29, 1919. Eddington measured a background star being offset by 2 arc seconds, validating Einstein’s theories. Both scientists could hardly have imagined that over a century later this same technique would be used – with unimaginable precision of a thousandfold better — to look for black holes across the galaxy.

Talk to anyone about galaxies and it often conjurs up images of spiral or elliptical galaxie. Thanks to a survey by the James Webb Space Telescope it seems the early Universe was full of galaxies of different shapes. In the first 6 billion years up to 80% of the galaxies were flat, surfboard like. But that’s not it, there were others like pool noodles too, yet why they looked so different back then is a mystery.

January 19, 2024January 19, 2024 by Brian Koberlein

M87*'s Event Horizon Image. One Year Later

The elliptical galaxy M87 seen by various telescopes. Credit: NASA's Scientific Visualization Studio/M.SubbaRao & NASA/CXC/SAO/A.Jubett

Fifty-five million light years from Earth there is a massive elliptical galaxy known as Messier 87, or M87 for short. It was cataloged by Charles Messier in the 1700s, along with 102 other fuzzy objects in the sky that were definitely not comets. It was confirmed to be a galaxy in the early 1900s, and by the mid-twentieth century, it was known to be a powerful radio source. But these days it is most widely known for the supermassive black hole deep in its core. Called M87*, it is the first black hole directly observed by astronomers. The first image of M87* was released in 2019, and was based on observations taken by the Event Horizon Telescope (EHT) in 2017. Now a new image based on 2018 data has been released. The similarities and differences between the two images tell us a great deal about M87* and black holes in general.

January 19, 2024January 19, 2024 by Nancy Atkinson

This Strange-Looking Galaxy is Actually Two. And They're Merging

This NASA/ESA Hubble Space Telescope image features Arp 122, a peculiar galaxy that in fact comprises two galaxies – NGC 6040, the tilted, warped spiral galaxy and LEDA 59642, the round, face-on spiral – that are in the midst of a collision. ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Acknowledgement: L. Shatz

This strange-looking galaxy seems to be a spiral with a long tidal tail stretching away. It’s known as Arp 122, and it’s actually not just one galaxy, but two separate galaxies. NGC 6040 is the warped spiral galaxy seen edge-on, while LEDA 59642 is the round, face-on spiral. The two are colliding about 540 million light-years from Earth, and it gives us a preview of the Milky Way’s future collision with Andromeda.

This image was taken by the venerable Hubble Space Telescope

What will Arp 122 look like when the merger is complete? We’ll try to keep you posted, but this ongoing merger will take hundreds of millions of years, so be patient.

January 19, 2024January 19, 2024 by Nancy Atkinson

The Ice Sheet on Mars is Even Thicker Than Previously Believed

Map of potential ice thickness in Mars’s Medusae Fossae Formation (MFF). Credit: ESA.

Maybe Mars isn’t as dry as we thought. ESA’s Mars Express has revealed new details about a region near Mars’ equator that could contain a massive deposit of water ice several kilometers deep. If it is indeed ice, there is enough of it in this one deposit that if melted, water would cover the entire planet up to 2.7 meters (almost 9 feet) deep.

But ice is just one explanation for the unusual features detected by the orbital spacecraft. Another is that this is a giant pile of dust several kilometers deep — although the dust would still need to have some ice mixed in.

January 18, 2024January 18, 2024 by Matt Williams

A Biocatalytic Reactor for Detoxifying Water on Mars!

Artist's impression of water under the Martian surface. Credit: ESA/Medialab

Mars is the next frontier of human space exploration, with NASA, China, and SpaceX all planning to send crewed missions there in the coming decades. In each case, the plans consist of establishing habitats on the surface that will enable return missions, cutting-edge research, and maybe even permanent settlements someday. While the idea of putting boots on Martian soil is exciting, a slew of challenges need to be addressed well in advance. Not the least of which is the need to locate sources of water, which consist largely of subsurface deposits of water ice.

Herein lies another major challenge: Martian ice deposits are contaminated by toxic perchlorates, potent oxidizers that cause equipment corrosion and are hazardous to human health (even at low concentrations). To this end, crewed missions must bring special equipment to remove perchlorates from water on Mars if they intend to use it for drinking, irrigation, and manufacturing propellant. This is the purpose of Detoxifying Mars, a proposed concept selected by the NASA Innovative Advanced Concepts (NIAC) program for Phase I development.

January 18, 2024January 18, 2024 by Evan Gough

The JWST Solves the Mystery of Ancient Light

This image shows the galaxy EGSY8p7, a bright galaxy in the early Universe where light emission is seen from, among other things, excited hydrogen atoms — Lyman-alpha emission. The galaxy was identified in a field of young galaxies studied by Webb in the CEERS survey. In the bottom two panels, Webb’s high sensitivity picks out this distant galaxy along with its two companion galaxies, where previous observations saw only one larger galaxy in its place. This discovery of a cluster of interacting galaxies sheds light on the mystery of why the hydrogen emission from EGSY8p7, shrouded in neutral gas formed after the Big Bang, should be visible at all. Image Credit: ESA/Webb, NASA & CSA, S. Finkelstein (UT Austin), M. Bagley (UT Austin), R. Larson (UT Austin), A. Pagan (STScI), C. Witten, M. Zamani (ESA/Webb)

The very early Universe was a dark place. It was packed with light-blocking hydrogen and not much else. Only when the first stars switched on and began illuminating their surroundings with UV radiation did light begin its reign. That occurred during the Epoch of Reionization.

But before the Universe became well-lit, a specific and mysterious type of light pierced the darkness: Lyman-alpha emissions.

January 18, 2024January 18, 2024 by Laurence Tognetti

Planetary Surfaces: Why study them? Can they help us find life elsewhere?

Universe Today recently explored the importance of studying impact craters and what they can teach us about finding life beyond Earth. Impact craters are considered one of the many surface processes—others include volcanism, weathering, erosion, and plate tectonics—that shape surfaces on numerous planetary bodies, with all of them simultaneously occurring on Earth. Here, we will explore how and why planetary scientists study planetary surfaces, the challenges faced when studying other planetary surfaces, what planetary surfaces can teach us about finding life, and how upcoming students can pursue studying planetary surfaces, as well. So, why is it so important to study planetary surfaces throughout the solar system?

January 17, 2024January 17, 2024 by Evan Gough

Early Mars Climate was Complex, with Streams Flowing Intermittently for Millions of Years

This figure from new research shows an unnamed river valley network on Mars. By dating the craters in the image, a researcher at the Planetary Science Institute was able to determine when the river channels were formed. Image Credit: MOLA MEGDR, NASA/USGS; THEMIS mosaic, ASU/NASA/USGS; CTX, NASA/MSSS.

There’s overwhelming evidence that Mars was once wet and warm. Rivers flowed across its surface and carved intricate channel systems revealed by our orbiters. Expansive oceans even larger than Earth’s may have covered a third of its surface. Then something happened: Mars lost its atmosphere, cooled down, and surface water disappeared.

January 17, 2024January 17, 2024 by Matt Williams

NASA Selects a Sample Return Mission to Venus

Graphic depiction of Sample Return from the Surface of Venus. Credit: Geoffrey Landis

In Dante Alighieri’s epic poem The Divine Comedy, the famous words “Abandon all hope, ye who enter here” adorn the gates of hell. Interestingly enough, Dante’s vision of hell is an apt description of what conditions are like on Venus. With an average temperature of 450 °C (842 °F), atmospheric pressures 92 times that of Earth, and clouds of sulfuric acid rain to boot, Venus is the most hostile environment in the Solar System. It is little wonder why space agencies, going all the way back to the beginning of the Space Age, have had such a hard time exploring Venus’ atmosphere.

Despite that, there are many proposals for missions that could survive Venus’ hellish environment long enough to accomplish a sample return mission. One such proposal, the Sample Return from the Surface of Venus, comes from aerospace engineer and author Geoffrey Landis and his colleagues at the NASA Glenn Research Center. Their proposed concept was selected for this year’s NASA Innovative Advanced Concepts (NIAC) program. It consists of a solar-powered aircraft that would fashion propellant directly from Venus’ atmosphere and deploy a sample-return rover to the surface.

January 17, 2024January 17, 2024 by Brian Koberlein

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.