NASA’s Hubble Traces ‘String of Pearls’ Star Clusters in Galaxy Collisions

FEB 08, 2024

Contrary to what you might think, galaxy collisions do not destroy stars. In fact, the rough-and-tumble dynamics trigger new generations of stars, and presumably accompanying planets.

Now NASA's Hubble Space Telescope has homed in on 12 interacting galaxies that have long, tadpole-like tidal tails of gas, dust, and a plethora of stars. Hubble's exquisite sharpness and sensitivity to ultraviolet light have uncovered 425 clusters of newborn stars along these tails, looking like strings of holiday lights. Each cluster contains as many as 1 million blue, newborn stars.

Clusters in tidal tails have been known about for decades. When galaxies interact, gravitational tidal forces pull out long streamers of gas and dust. Two popular examples are the Antennae and Mice galaxies with their long, narrow, finger-like projections.

A team of astronomers used a combination of new observations and archival data to get ages and masses of tidal tail star clusters. They found that these clusters are very young – only 10 million years old. And they seem to be forming at the same rate along tails stretching for thousands of light-years.

"It's a surprise to see lots of the young objects in the tails. It tells us a lot about cluster formation efficiency," said lead author Michael Rodruck of Randolph-Macon College in Ashland, Virginia. "With tidal tails, you will build up new generations of stars that otherwise might not have existed."

The tails look like they are taking a galaxy's spiral arm and stretching it out into space. The exterior part of the arm gets pulled like taffy from the gravitational tug-of-war between a pair of interacting galaxies.

Before the mergers, the galaxies were rich in dusty clouds of molecular hydrogen that simply may have remained inert. But the clouds got jostled and bumped into each other during the encounters. This compressed the hydrogen to the point where it precipitated a firestorm of star birth.

The fate of these strung-out star clusters is uncertain. They may stay gravitationally intact and evolve into globular star clusters – like those that orbit outside the plane of our Milky Way galaxy. Or they may disperse to form a halo of stars around their host galaxy, or get cast off to become wandering intergalactic stars.

This string-of-pearls star formation may have been more common in the early universe when galaxies collided with each other more frequently. These nearby galaxies observed by Hubble are a proxy for what happened long ago, and therefore are laboratories for looking into the distant past.

https://science.nasa.gov/missions/hubble/nasas-hubble-traces-string-of-pearls-star-clusters-in-galaxy-collisions/

Telescopes Show the Milky Way’s Black Hole is Ready for a Kick

FEB 08, 2024

This artist’s illustration depicts the findings of a new study about the supermassive black hole at the center of our galaxy called Sagittarius A (abbreviated as Sgr A). As reported in our latest press release, this result found that Sgr A* is spinning so quickly that it is warping spacetime — that is, time and the three dimensions of space — so that it can look more like a football.

These results were made with NASA’s Chandra X-ray Observatory and the NSF’s Karl G. Jansky Very Large Array (VLA). A team of researchers applied a new method that uses X-ray and radio data to determine how quickly Sgr A is spinning based on how material is flowing towards and away from the black hole. They found Sgr A is spinning with an angular velocity that is about 60% of the maximum possible value, and with an angular momentum of about 90% of the maximum possible value.

Black holes have two fundamental properties: their mass (how much they weigh) and their spin (how quickly they rotate). Determining either of these two values tells scientists a great deal about any black hole and how it behaves. In the past, astronomers made several other estimates of Sgr A’s rotation speed using different techniques, with results ranging from Sgr A not spinning at all to it spinning at almost the maximum rate.

The new study suggests that Sgr A is, in fact, spinning very rapidly, which causes the spacetime around it to be squashed down. The illustration shows a cross-section of Sgr A and material swirling around it in a disk. The black sphere in the center represents the so-called event horizon of the black hole, the point of no return from which nothing, not even light, can escape.

Looking at the spinning black hole from the side, as depicted in this illustration, the surrounding spacetime is shaped like a football. The faster the spin the flatter the football.

The yellow-orange material to either side represents gas swirling around Sgr A*. This material inevitably plunges towards the black hole and crosses the event horizon once it falls inside the football shape. The area inside the football shape but outside the event horizon is therefore depicted as a cavity. The blue blobs show jets firing away from the poles of the spinning black hole. Looking down on the black hole from the top, along the barrel of the jet, spacetime is a circular shape.

A black hole’s spin can act as an important source of energy. Spinning supermassive black holes produce collimated outflows such as jets when their spin energy is extracted, which requires that there is at least some matter in the vicinity of the black hole. Because of limited fuel around Sgr A, this black hole has been relatively quiet in recent millennia with relatively weak jets. This work, however, shows that this could change if the amount of material in the vicinity of Sgr A increases.

To determine the spin of Sgr A*, the authors used an empirically based technique referred to as the “outflow method” that details the relationship between the spin of the black hole and its mass, the properties of the matter near the black hole, and the outflow properties. The collimated outflow produces the radio waves, while the disk of gas surrounding the black hole is responsible for the X-ray emission. Using this method, the researchers combined data from Chandra and the VLA with an independent estimate of the black hole’s mass from other telescopes to constrain the black hole’s spin.

The paper describing these results led by Ruth Daly (Penn State University) is published in the January 2024 issue of the Monthly Notices of the Royal Astronomical Society and appears online at

https://ui.adsabs.harvard.edu/abs/2024MNRAS.527..428D/abstract

The other authors are Biny Sebastian (University of Manitoba, Canada), Megan Donahue (Michigan State University), Christopher O’Dea (University of Manitoba), Daryl Haggard (McGill University) and Anan Lu (McGill University).

https://www.nasa.gov/image-article/telescopes-show-the-milky-ways-black-hole-is-ready-for-a-kick/

>>20378897

Pepe version

NASA Launches New Climate Mission to Study Ocean, Atmosphere

FEB 08, 2024

NASA’s satellite mission to study ocean health, air quality, and the effects of a changing climate for the benefit of humanity launched successfully into orbit at 1:33 a.m. EST Thursday.

Known as PACE, the Plankton, Aerosol, Climate, ocean Ecosystem satellite, launched aboard a SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida. NASA confirmed signal acquisition from the satellite about five minutes after launch, and the spacecraft is performing as expected.

“Congratulations to the PACE team on a successful launch. With this new addition to NASA’s fleet of Earth-observing satellites, PACE will help us learn, like never before, how particles in our atmosphere and our oceans can identify key factors impacting global warming,” said NASA Administrator Bill Nelson. “Missions like this are supporting the Biden-Harris Administration’s climate agenda and helping us answer urgent questions about our changing climate.”

From hundreds of miles above Earth, the PACE mission will study the impact of tiny, often invisible things: microscopic life in water and microscopic particles in the air.

The satellite’s hyperspectral ocean color instrument will allow researchers to measure oceans and other waterbodies across a spectrum of ultraviolet, visible, and near-infrared light. This will enable scientists to track the distribution of phytoplankton and – for the first time from space – identify which communities of these organisms are present on daily, global scales. Scientists and coastal resource managers can use the data to help forecast the health of fisheries, track harmful algal blooms, and identify changes in the marine environment.

The spacecraft also carries two polarimeter instruments, Hyper-Angular Rainbow Polarimeter #2 and Spectro-polarimeter for Planetary Exploration. These will detect how sunlight interacts with particles in the atmosphere, giving researchers new information on atmospheric aerosols and cloud properties, as well as air quality at local, regional, and global scales.

With the combination of the instrument and the polarimeters, PACE will provide insights into the interactions of the ocean and atmosphere, and how a changing climate affects these interactions.

“Observations and scientific research from PACE will profoundly advance our knowledge of the ocean’s role in the climate cycle,” said Karen St. Germain, director, Earth Science Division, Science Mission Directorate, at NASA Headquarters in Washington. “The value of PACE data skyrockets when we combine it with data and science from our Surface Water and Ocean Topography mission – ushering in a new era of ocean science. As an open-source science mission with early adopters ready to use its research and data, PACE will accelerate our understanding of the Earth system and help NASA deliver actionable science, data, and practical applications to help our coastal communities and industries address rapidly evolving challenges.”

“It’s been an honor to work with the PACE team and witness firsthand their dedication and tenacity in overcoming challenges, including the global pandemic, to make this observatory a reality,” said Marjorie Haskell, PACE program executive at NASA Headquarters. “The passion and teamwork are matched only by the excitement of the science community for the data this new satellite will provide.”

Earth’s oceans are responding in many ways to climate change – from sea level rise to marine heat waves to a loss of biodiversity. With PACE, researchers will be able to study climate change’s effects on phytoplankton, which play a key role in the global carbon cycle by absorbing carbon dioxide from the atmosphere and converting it into their cellular material. These tiny organisms drive larger aquatic and global ecosystems that provide critical resources for food security, recreation, and the economy.

“After 20 years of thinking about this mission, it’s exhilarating to watch it finally realized and to witness its launch. I couldn’t be prouder or more appreciative of our PACE team,” said Jeremy Werdell, PACE project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The opportunities PACE will offer are so exciting, and we’re going to be able to use these incredible technologies in ways we haven’t yet anticipated. It’s truly a mission of discovery.”

https://www.nasa.gov/news-release/nasa-launches-new-climate-mission-to-study-ocean-atmosphere/