Showing posts with label Space News. Show all posts
Showing posts with label Space News. Show all posts

Thursday, September 23, 2021

Peering into the Moon's shadows

The 17 newly studied craters and depressions are located near the South Pole. While the smallest of these regions (region 11) has a size of only 0.18 square kilometers, the largest (region 9) measures 54 square kilometers. Region 9 is not located in the section of the south polar region shown here, but a bit further to the North, in Schrödinger Basin. The representations of the lunar surface shown here are based on altimeter data from the Lunar Reconnaissance Orbiter. 
Credit: MPS/University of Oxford/NASA Ames Research Center/FDL/SETI Institute

The Moon’s polar regions are home to craters and other depressions that never receive sunlight. Today, a group of researchers led by the Max Planck Institute for Solar System Research (MPS) in Germany present the highest-resolution images to date covering 17 such craters in the journal Nature Communications. Craters of this type could contain frozen water, making them attractive targets for future lunar missions, and the researchers focused further on relatively small and accessible craters surrounded by gentle slopes. In fact, three of the craters have turned out to lie within the just-announced mission area of NASA's Volatiles Investigating Polar Exploration Rover (VIPER), which is scheduled to touch down on the Moon in 2023. Imaging the interior of permanently shadowed craters is difficult, and efforts so far have relied on long exposure times resulting in smearing and lower resolution. By taking advantage of reflected sunlight from nearby hills and a novel image processing method, the researchers have now produced images at 1-2 meters per pixel, which is at or very close to the best capability of the cameras.

The Moon is a cold, dry desert. Unlike the Earth, it is not surrounded by a protective atmosphere and water which existed during the Moon’s formation has long since evaporated under the influence of solar radiation and escaped into space. Nevertheless, craters and depressions in the polar regions give some reason to hope for limited water resources. Scientists from MPS, the University of Oxford and the NASA Ames Research Center have now taken a closer look at some of these regions.

Friday, September 17, 2021

Black Hole Snacks on a Star


This illustration shows a glowing stream of material from a star, torn to shreds as it was being devoured by a supermassive black hole. The feeding black hole is surrounded by a ring of dust, not unlike the plate of a toddler is surrounded by crumbs after a meal. NASA/JPL-Caltech

While black holes and toddlers don't seem to have much in common, they are remarkably similar in one aspect: Both are messy eaters, generating ample evidence that a meal has taken place.

But whereas one might leave behind droppings of pasta or splatters of yogurt, the other creates an aftermath of mind-boggling proportions. When a black hole gobbles up a star, it produces what astronomers call a "tidal disruption event." The shredding of the hapless star is accompanied by an outburst of radiation that can outshine the combined light of every star in the black hole's host galaxy for months, even years. 

In a paper published in The Astrophysical Journal, a team of astronomers led by Sixiang Wen, a postdoctoral research associate at the University of Arizona Steward Observatory, use the X-rays emitted by a tidal disruption event known as J2150 to make the first measurements of both the black hole's mass and spin. This black hole is of a particular type – an intermediate-mass black hole – which has long eluded observation.

"The fact that we were able to catch this black hole while it was devouring a star offers a remarkable opportunity to observe what otherwise would be invisible," said Ann Zabludoff, UArizona professor of astronomy and co-author on the paper. "Not only that, by analyzing the flare we were able to better understand this elusive category of black holes, which may well account for the majority of black holes in the centers of galaxies."

Wednesday, September 15, 2021

New ALMA study reveals the many molecular faces of protoplanetary disks

Pictured is a collage showing about 50% of the complete data from the MAPS collaboration. Image credit: Charles Law, Molecules with ALMA at Planet-forming Scales

An international group of scientists, including University of Michigan astronomers, has mapped the chemical composition of protoplanetary disks surrounding five nearby young stars—an effort that will allow the astronomers to search the disks for planet formation in real time.

The survey provides the most detailed pictures of planet-forming gases to date, which will help scientists understand how planets form, ranging from gas giants called hot Jupiters to our own life-sustaining planet.

“The goal of this program was to survey the chemistry of planet formation with the highest resolution possible in a limited amount of time—just 130 hours. We wanted to know how planets are born and what sets their composition at birth,” said Edwin Bergin, U-M professor of astronomy, co-principal investigator of the survey and co-author on the papers.

“This can then be compared to the composition of exoplanetary atmospheres and in solar system planets to understand how common Jupiters are and, eventually, life-bearing worlds like the Earth.”

The collaboration used the Atacama Large Millimeter/submillimeter Array, or ALMA, to complete the most extensive chemical composition mapping of the protoplanetary disks at high resolution that allows scientists to probe the makeup of their planet- and comet-forming regions.

The new study unlocks clues about the role of molecules in planetary system formation, and whether these young planetary systems in-the-making have what it takes to host life. The results of the program, called MAPS, or Molecules with ALMA at Planet-forming Scales, will appear in an upcoming 20-paper special edition of The Astrophysical Journal Supplement Series.

Planets form in the disks of dust and gas, called protoplanetary disks, surrounding young stars. The chemical makeup of these disks may have an impact on the planets themselves, including how and where planetary formation occurs, the chemical composition of the planets, and whether those planets have the organic composition necessary to support life.

“A planet’s composition is a record of the location in the disk in which it was formed,” said U-M astronomer Arthur Bosman, lead author of many of the studies. “Connecting planet and disk composition enables us to peer into the history of a planet and helps us to understand the forces that formed it.”
This composite image of ALMA data from the young star HD 163296 shows hydrogen cyanide emission laid over a starfield. The MAPS project zoomed in on hydrogen cyanide and other organic and inorganic compounds in planet-forming disks to gain a better understanding of the compositions of young planets and how the compositions link to where planets form in a protoplanetary disk. Image credit: ALMA (ESO/NAOJ/NRAO)/D. Berry (NRAO), K. Öberg et al (MAPS)

MAPS specifically looked at the protoplanetary disks surrounding the young stars IM Lup, GM Aur, AS 209, HD 163296 and MW480, where evidence of ongoing planet formation has already been detected. The project led to multiple discoveries, including a link between dust and chemical substructures and the presence of large reservoirs of organic molecules in the inner disk regions of the stars.

“With ALMA, we were able to see how molecules are distributed where exoplanets are currently assembling, and what we saw is that most planets likely form in a chemical environment that looks rather similar to the solar nebula, the birthplace of our solar system,” said MAPS principal investigator Karin Öberg, an astronomer at the Harvard Smithsonian Center for Astrophysics.

“Most importantly, we saw that the planet-forming disks around these five young stars are factories of a special class of organic molecules, so-called nitriles, which are implicated in the origins of life here on Earth.”

Bosman led Maps VII, which examined the elemental composition of the gas at locations in three of the five disks targeted by MAPS where Jupiter-like planets may be forming. In his study, Bosman and co-authors found the gas surrounding these potentially nascent planets to be poor in carbon, oxygen and heavier elements, while rich in hydrocarbons, such as methane.

“The chemistry that is seen in protoplanetary disks should be inherited by forming planets,” Bosman said. “A carbon- and oxygen-poor environment suggests the existence of a subset of giant planets that have low water abundances in general. This is the opposite of current planet composition studies, and we are finding that the building blocks of many giant planets out there are very different from what we think formed our own solar system giants, Jupiter and Saturn.”

Bosman and Bergin pushed ALMA’s techniques to its limits in order to observe the velocities of gas very close to a disk’s star, within three astronomical units—an astronomical unit is the distance between the Earth and the sun. Gas swirls at higher velocity the closer it is to the star, and based on these velocities, Bosman and Bergin were able to observe one object that appears to be on the verge of planet formation. These results are published in the study MAPS XV.

“This allows us to look for signatures of these hidden forming planets in the gas structure—sort of a planet calling card: ‘I’m here,'” Bergin said.

U-M postdoctoral fellows and graduate students also led papers published in the supplement series. In MAPS XIX, postdoctoral fellow Jane Huang and co-authors showed that one disk (GM Aur) is still accreting material from its parent cloud while actively forming planets, providing a fresh supply of material to these young worlds.

In MAPS XVII, graduate student Jenny Calahan and co-authors measured the gas temperature and its structure using sophisticated models around HD 163296. In MAPS VIII, graduate student Felipe Alarcón and co-authors explored how the observed chemical composition comes to be with a detailed chemical model of the AS209 planet-forming disk.

Altogether, MAPS is providing exactly that: a map for scientists to follow, connecting the dots between the gas and dust in a protoplanetary disk and the planets that eventually form from them to create a planetary system.


Source/Credit: University of Michigan


Thursday, September 9, 2021

ESO captures best images yet of peculiar “dog-bone” asteroid

These eleven images are of the asteroid Kleopatra, viewed at different angles as it rotates. The images were taken at different times between 2017 and 2019 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s VLT.   Kleopatra orbits the Sun in the Asteroid Belt between Mars and Jupiter. Astronomers have called it a “dog-bone asteroid” ever since radar observations around 20 years ago revealed it has two lobes connected by a thick “neck”. 
Credit / Source: ESO/Vernazza, Marchis et al./MISTRAL algorithm (ONERA/CNRS)

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), a team of astronomers have obtained the sharpest and most detailed images yet of the asteroid Kleopatra. The observations have allowed the team to constrain the 3D shape and mass of this peculiar asteroid, which resembles a dog bone, to a higher accuracy than ever before. Their research provides clues as to how this asteroid and the two moons that orbit it formed.

“Kleopatra is truly a unique body in our Solar System,” says Franck Marchis, an astronomer at the SETI Institute in Mountain View, USA and at the Laboratoire d'Astrophysique de Marseille, France, who led a study on the asteroid — which has moons and an unusual shape — published today in Astronomy & Astrophysics. “Science makes a lot of progress thanks to the study of weird outliers. I think Kleopatra is one of those and understanding this complex, multiple asteroid system can help us learn more about our Solar System.”

Kleopatra orbits the Sun in the Asteroid Belt between Mars and Jupiter. Astronomers have called it a “dog-bone asteroid” ever since radar observations around 20 years ago revealed it has two lobes connected by a thick “neck”. In 2008, Marchis and his colleagues discovered that Kleopatra is orbited by two moons, named AlexHelios and CleoSelene, after the Egyptian queen’s children.

To find out more about Kleopatra, Marchis and his team used snapshots of the asteroid taken at different times between 2017 and 2019 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s VLT. As the asteroid was rotating, they were able to view it from different angles and to create the most accurate 3D models of its shape to date. They constrained the asteroid’s dog-bone shape and its volume, finding one of the lobes to be larger than the other, and determined the length of the asteroid to be about 270 kilometers or about half the length of the English Channel.

This image provides a size comparison of the asteroid Kleopatra with northern Italy.   The top half of the image shows a computer model of Kleopatra, a “dog-bone” shaped asteroid which orbits the Sun in the Asteroid Belt between Mars and Jupiter. End to end, Kleopatra is 270 kilometers long.   The bottom half of the image gives an aerial view of northern Italy, with the footprint Kleopatra would have if it were hovering above it.   
Credit / Sou: ESO/M. Kornmesser/Marchis et al.
In a second study, also published in Astronomy & Astrophysics and led by Miroslav Brož of Charles University in Prague, Czech Republic, the team reported how they used the SPHERE observations to find the correct orbits of Kleopatra’s two moons. Previous studies had estimated the orbits, but the new observations with ESO’s VLT showed that the moons were not where the older data predicted them to be.

“This had to be resolved,” says Brož. “Because if the moons’ orbits were wrong, everything was wrong, including the mass of Kleopatra.” Thanks to the new observations and sophisticated modelling, the team managed to precisely describe how Kleopatra’s gravity influences the moons’ movements and to determine the complex orbits of AlexHelios and CleoSelene. This allowed them to calculate the asteroid’s mass, finding it to be 35% lower than previous estimates.

Combining the new estimates for volume and mass, astronomers were able to calculate a new value for the density of the asteroid, which, at less than half the density of iron, turned out to be lower than previously thought. The low density of Kleopatra, which is believed to have a metallic composition, suggests that it has a porous structure and could be little more than a “pile of rubble”. This means it likely formed when material reaccumulated following a giant impact.

Kleopatra’s rubble-pile structure and the way it rotates also give indications as to how its two moons could have formed. The asteroid rotates almost at a critical speed, the speed above which it would start to fall apart, and even small impacts may lift pebbles off its surface. Marchis and his team believe that those pebbles could subsequently have formed AlexHelios and CleoSelene, meaning that Kleopatra has truly birthed its own moons.

The new images of Kleopatra and the insights they provide are only possible thanks to one of the advanced adaptive optics systems in use on ESO’s VLT, which is located in the Atacama Desert in Chile. Adaptive optics help to correct for distortions caused by the Earth’s atmosphere which cause objects to appear blurred — the same effect that causes stars viewed from Earth to twinkle. Thanks to such corrections, SPHERE was able to image Kleopatra — located 200 million kilometers away from Earth at its closest — even though its apparent size on the sky is equivalent to that of a golf ball about 40 kilometers away.

ESO’s upcoming Extremely Large Telescope (ELT), with its advanced adaptive optics systems, will be ideal for imaging distant asteroids such as Kleopatra. “I can’t wait to point the ELT at Kleopatra, to see if there are more moons and refine their orbits to detect small changes,” adds Marchis.

Source/Credit: ESO

09-09-21 12:00UTC

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