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NASA’s Webb Telescope Reveals Links Between Galaxies Near and Far
Jan 9, 2023
A new analysis of distant galaxies imaged by NASA’s James Webb Space Telescope shows that they are extremely young and share some remarkable similarities to “green peas,” a rare class of small galaxies in our cosmic backyard.
“With detailed chemical fingerprints of these early galaxies, we see that they include what might be the most primitive galaxy identified so far. At the same time, we can connect these galaxies from the dawn of the universe to similar ones nearby, which we can study in much greater detail,” said James Rhoads, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings at the 241st meeting of the American Astronomical Society in Seattle.
A paper describing the results, led by Rhoads, was published Jan. 3 in The Astrophysical Journal Letters.
Green pea galaxies were discovered and named in 2009 by volunteers taking part in Galaxy Zoo, a project where citizen scientists help classify galaxies in images, starting with those from the Sloan Digital Sky Survey. Peas stood out as small, round, unresolved dots with a distinctly green shade, a consequence of both the colors assigned to different filters in the survey’s composite images and a property of the galaxies themselves.
Green pea galaxy colors are unusual because a sizable fraction of their light comes from brightly glowing gas clouds. The gases emit light at specific wavelengths – unlike stars, which produce a rainbow-like spectrum of continuous color. Peas are also quite compact, typically only about 5,000 light-years across or about 5% the size of our Milky Way galaxy.
“Peas may be small, but their star-formation activity is unusually intense for their size, so they produce bright ultraviolet light,” said Keunho Kim, a postdoctoral researcher at the University of Cincinnati and a member of the analysis team. “Thanks to ultraviolet images of green peas from Hubble and ground-based research on early star-forming galaxies, it’s clear that they both share this property.”
In July 2022, NASA and its partners in the Webb mission released the deepest and sharpest infrared image of the distant universe yet seen, capturing thousands of galaxies in and behind a cluster known as SMACS 0723. The cluster’s mass makes it a gravitational lens, which both magnifies and distorts the appearance of background galaxies. Among the faintest galaxies behind the cluster were a trio of compact infrared objects that looked like they could be distant relatives of green peas. The most distant of these three galaxies was magnified by about 10 times, providing a significant assist from nature on top of the telescope’s unprecedented capabilities.
Webb did more than image the cluster – its Near-Infrared Spectrograph (NIRSpec) instrument also captured the spectra of selected galaxies in the scene. When Rhoads and his colleagues examined these measurements and corrected them for the wavelength stretch resulting from the expansion of space, they saw characteristic features emitted by oxygen, hydrogen, and neon line up in a stunning resemblance to those seen from nearby green peas.
Additionally, the Webb spectra made it possible to measure the amount of oxygen in these cosmic dawn galaxies for the first time.
As stars produce energy, they transmute lighter elements like hydrogen and helium into heavier ones. When stars explode or lose their outer layers at the ends of their lives, these heavier elements become incorporated into the gas that forms the next stellar generations, and the process continues. Over cosmic history, stars have steadily enriched the universe.
Two of the Webb galaxies contain oxygen at about 20% of the level in our Milky Way. They resemble typical green peas, which nevertheless make up less than 0.1% of the nearby galaxies observed by the Sloan survey. The third galaxy studied is even more unusual.
“We’re seeing these objects as they existed up to 13.1 billion years ago, when the universe was about 5% its current age,” said Goddard researcher Sangeeta Malhotra. “And we see that they are young galaxies in every sense – full of young stars and glowing gas that contains few chemical products recycled from earlier stars. Indeed, one of them contains just 2% the oxygen of a galaxy like our own and might be the most chemically primitive galaxy yet identified.”
https://www.nasa.gov/feature/goddard/2023/nasa-s-webb-telescope-reveals-links-between-galaxies-near-and-far
https://iopscience.iop.org/article/10.3847/2041-8213/acaaaf
This is a month old but I didn't see it until today.
First Images Released From NOAA-21 VIIRS Instrument
Dec 16, 2022
Bright blue water in the Caribbean Sea and smog in Northern India appear in the first global image produced with data from NOAA-21’s VIIRS instrument.
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on NOAA-21 began collecting Earth science data on Dec. 5 as the satellite passed over the East Coast of the United States. Data for the global image was collected over a period of 24 hours between Dec. 5 and 6. This came three weeks after NASA launched the NOAA-21 satellite from Vandenberg Space Force Base in California on Nov. 10, 2022.
The VIIRS instrument — which also flies on the NOAA-20 and the NASA/NOAA Suomi-NPP satellites — provides global measurements of the atmosphere, land, and oceans. It was built by Raytheon Intelligence & Space in El Segundo, California.
"VIIRS serves so many disciplines, it’s an absolutely critical set of measurements,” said Dr. James Gleason, NASA project scientist for the JPSS Flight Project. “VIIRS provides many different data products that are used by scientists in unrelated fields, from agricultural economists trying to do crop forecasts, to air quality scientists forecasting where wildfire smoke will be, to disaster support teams who count night lights to understand the impact of a disaster.”
Over the oceans, VIIRS measures sea surface temperature, a metric that’s important for monitoring hurricane formation. It also measures ocean color, which helps scientists monitor phytoplankton activity, a key indicator of ocean ecology and marine health.
“The turquoise color that's visible around Cuba and the Bahamas in the bottom-left image above comes from sediment in the shallow waters around the continental shelf,” said NOAA's Dr. Satya Kalluri, Joint Polar Satellite System program scientist.
Over land, VIIRS can detect and measure wildfires, droughts and floods, and its data can be used to track the thickness and movement of wildfire smoke. The bottom-right image above shows haze and smog over Northern India that is likely due to agricultural burning. The snow-capped Himalayas and the Tibetan plateau are also visible to the north.
One of the unique features of VIIRS is its Day-Night Band, which captures images of lights at night, including city lights, lightning, auroras and lights from ships and fires. And one of its most important uses is imagery over Alaska, Dr. Kalluri said. This is because these satellites, which orbit the Earth from the North pole to the South pole, fly directly over the Arctic several times a day.
The instrument also generates critical environmental products on snow and ice cover, clouds, fog, aerosols and dust, and the health of the world’s crops.
This “first light” image comes two weeks after the first image from the satellite’s Advanced Technology Microwave Sounder (ATMS) was released. The satellite, known as JPSS-2 during the build and launch, was officially renamed NOAA-21 after launch, following NOAA’s naming conventions for polar orbiting satellites.
“We had two VIIRS on orbit, and now we’ve got three,” Dr. Gleason said. “We launch multiple weather satellites to make doubly and now triply sure we always have one going. Space is a dangerous environment. Stuff happens and you can lose an instrument or a satellite, but we cannot lose the data. It’s too important, to too many people.”
https://www.nasa.gov/image-feature/first-images-released-from-noaa-21-viirs-instrument