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Hubble Provides Multiple Views of How to Feed a Black Hole
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By NASA
5 min read
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The blazar BL Lacertae, a supermassive black hole surrounded by a bright disk and jets oriented toward Earth, provided scientists with a unique opportunity to answer a longstanding question: How are X-rays generated in extreme environments like this?
NASA’s IXPE (Imaging X-ray Polarimetry Explorer) collaborated with radio and optical telescopes to find answers. The results (preprint available here), to be published in the journal Astrophysical Journal Letters, show that interactions between fast-moving electrons and particles of light, called photons, must lead to this X-ray emission.
This artist’s concept depicts the central region of the blazar BL Lacertae, a supermassive black hole surrounded by a bright disk and a jet oriented toward Earth. The galaxy’s central black hole is surrounded by swirls of orange in various shades representing the accretion disk of material falling toward the black hole. While black holes are known for pulling in material, this accretion process can result in the ejection of jets of electrons at nearly the speed of light. The jet of matter is represented by the cone of light that starts at the center of the black hole and widens out as it reaches the bottom of the image. It is streaked with lines of white, pink and purple which represent helix-shaped magnetic fields. We can observe these jets in many wavelengths of light including radio, optical, and X-ray. NASA’s Imaging X-ray Polarimetry Explorer (IXPE) recently collaborated with radio and optical telescopes to observe this jet and determine how the X-rays are generated in these types of celestial environments.NASA/Pablo Garcia Scientists had two competing possible explanations for the X-rays, one involving protons and one involving electrons. Each of these mechanisms would have a different signature in the polarization of X-ray light. Polarization is a property of light that describes the average direction of the electromagnetic waves that make up light.
If the X-rays in a black hole’s jets are highly polarized, that would mean that the X-rays are produced by protons gyrating in the magnetic field of the jet or protons interacting with jet’s photons. If the X-rays have a lower polarization degree, it would suggest that electron-photons interactions lead to X-ray production.
IXPE, which launched Dec. 9, 2021, is the only satellite flying today that can make such a polarization measurement.
“This was one of the biggest mysteries about supermassive black hole jets” said Iván Agudo, lead author of the study and astronomer at the Instituto de Astrofísica de Andalucía – CSIC in Spain. “And IXPE, with the help of a number of supporting ground-based telescopes, finally provided us with the tools to solve it.”
Astronomers found that electrons must be the culprits through a process called Compton Scattering. Compton scattering (or the Compton effect) happens when a photon loses or gains energy after interacting with a charged particle, usually an electron. Within jets from supermassive black holes, electrons move near the speed of light. IXPE helped scientists learn that, in the case of a blazar jet, the electrons have enough energy to scatter photons of infrared light up to X-ray wavelengths.
BL Lacertae (BL Lac for short) is one of the first blazars ever discovered, originally thought to be a variable star in the Lacerta constellation. IXPE observed BL Lac at the end of November 2023 for seven days along with several ground-based telescopes measuring optical and radio polarization at the same time. While IXPE observed BL Lac in the past, this observation was special. Coincidentally, during the X-ray polarization observations, the optical polarization of BL Lac reached a high number: 47.5%.
“This was not only the most polarized BL Lac has been in the past 30 years, this is the most polarized any blazar has ever been observed!” said Ioannis Liodakis, one of the primary authors of the study and astrophysicist at the Institute of Astrophysics – FORTH in Greece.
IXPE found the X-rays were far less polarized than the optical light. The team was not able to measure a strong polarization signal and determined that the X-rays cannot be more polarized than 7.6%. This proved that electrons interacting with photons, via the Compton effect, must explain the X-rays.
The fact that optical polarization was so much higher than in the X-rays can only be explained by Compton scattering.
Steven Ehlert
Project Scientist for IXPE at Marshall Space Flight Center
“The fact that optical polarization was so much higher than in the X-rays can only be explained by Compton scattering”, said Steven Ehlert, project scientist for IXPE and astronomer at the Marshall Space Flight Center.
“IXPE has managed to solve another black hole mystery” said Enrico Costa, astrophysicist in Rome at the Istituto di Astrofísica e Planetologia Spaziali of the Istituto Nazionale di Astrofísica. Costa is one of the scientists who conceived this experiment and proposed it to NASA 10 years ago, under the leadership of Martin Weisskopf, IXPE’s first principal investigator. “IXPE’s polarized X-ray vision has solved several long lasting mysteries, and this is one of the most important. In some other cases, IXPE results have challenged consolidated opinions and opened new enigmas, but this is how science works and, for sure, IXPE is doing very good science.”
What’s next for the blazar research?
“One thing we’ll want to do is try to find as many of these as possible,” Ehlert said. “Blazars change quite a bit with time and are full of surprises.”
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845
Lane Figueroa
Marshall Space Flight Center, Huntsville, Ala.
lane.e.figueroa@nasa.gov
256.544.0034
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Last Updated May 06, 2025 EditorBeth RidgewayContactElizabeth R. Landauelizabeth.r.landau@nasa.govLocationMarshall Space Flight Center Related Terms
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Black Holes
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By NASA
6 min read
NASA Data Helps Map Tiny Plankton That Feed Giant Right Whales
This North Atlantic right whale, named “Bowtie,” was spotted feeding in southern Maine waters in January 2025. A new technique aims to use NASA satellite data to see the plankton these whales depend on from space. Credit: New England Aquarium, taken under NMFS permit # 25739 In the waters off New England, one of Earth’s rarest mammals swims slowly, mouth agape. The North Atlantic right whale filters clouds of tiny reddish zooplankton — called Calanus finmarchicus — from the sea. These zooplankton, no bigger than grains of rice, are the whale’s lifeline. Only about 370 of these massive creatures remain.
For decades, tracking the tiny plankton meant sending research vessels out in the ocean, towing nets and counting samples by hand. Now, scientists are looking from above instead.
Using NASA satellite data, researchers found a way to detect Calanus swarms at the ocean surface in the Gulf of Maine, picking up on the animals’ natural red pigment. This early-stage approach, described in a new study, may help researchers better estimate where the copepods gather, and where whales might follow.
Tracking the zooplankton from space could aid both the whales and maritime industries. By predicting where these mammals are likely to feed, researchers and marine resource managers hope to reduce deadly vessel strikes and fishing gear entanglements — two major threats to the species. Knowing the feeding patterns could also help shipping and fishing industries operate more efficiently.
Calanus finmarchicus, a tiny zooplankton powering North Atlantic food webs, fuels right whale populations with its energy-rich lipid reserves. Credit: Cameron Thompson “NASA invests in this kind of research because it connects space-based observation with real-world challenges,” said Cynthia Hall, a support scientist at NASA headquarters in Washington. She works with the Early Career Research Program, which partly funded the work. “It’s yet another a way to put NASA satellite data to work for science, communities, and ecosystems.”
Revealing the Ocean’s Hidden Patterns
The new approach uses data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. The MODIS instrument doesn’t directly see the copepods themselves. Instead, it reads how the spectrum of sunlight reflected from the ocean surface changes in response to what’s in the water.
When large numbers of the zooplankton rise to the surface, their reddish pigment — astaxanthin, the same compound that gives salmon its pink color — subtly alters how photons, or particles of light, from the sun are absorbed or scattered in the water. The fate of these photons in the ocean depends on the mix of living and non-living matter in seawater, creating a slight shift in color that MODIS can detect.
“We didn’t know to look for Calanus before in this way,” said Catherine Mitchell, a satellite oceanographer at Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine. “Remote sensing has typically focused on smaller things like phytoplankton. But recent research suggested that larger, millimeter-sized organisms like zooplankton can also influence ocean color.”
A few years ago, researchers piloted a satellite method for detecting copepods in Norwegian waters. Now, some of those same scientists — along with Mitchell’s team — have refined the approach and applied it to the Gulf of Maine, a crucial feeding ground for right whales during their northern migration. By combining satellite data, a model, and field measurements, they produced enhanced images that revealed Calanus swarms at the sea surface, and were able to estimate numbers of the tiny animals.
“We know the right whales are using habitats we don’t fully understand,” said Rebekah Shunmugapandi, also a satellite oceanographer at Bigelow and the study’s lead author. “This satellite-based Calanus information could eventually help identify unknown feeding grounds or better anticipate where whales might travel.”
Tracking Elusive Giants
Despite decades of study, North Atlantic right whales remain remarkably enigmatic to scientists. Once fairly predictable in their movements along the Eastern Seaboard of North America, these massive mammals began abandoning some traditional feeding grounds in 2010-2011. Their sudden shift to unexpected areas like the Gulf of Saint Lawrence caught people off guard, with deadly consequences.
“We’ve had whales getting hit by ships and whales getting stuck in fishing gear,” said Laura Ganley, a research scientist in the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston, which conducts aerial and boat surveys of the whales.
In 2017, the National Oceanic and Atmospheric Administration designated the situation as an “unusual mortality event” in an effort to address the whales’ decline. Since then, 80 North Atlantic right whales have been killed or sustained serious injuries, according to NOAA.
NASA satellite imagery from June 2009 was used to test a new method for detecting the copepod Calanus finmarchicus in the Gulf of Maine and estimating their numbers from space. Credit: NASA Earth Observatory image by Wanmei Liang, using data from Shunmugapandi, R., et al. (2025) In the Gulf of Maine, there’s less shipping activity, but there can be a complex patchwork of lobster fishing gear, said Sarah Leiter, a scientist with the Maine Department of Marine Resources. “Each fisherman has 800 traps or so,” Leiter explained. “If a larger number of whales shows up suddenly, like they just did in January 2025, it is challenging. Fishermen need time and good weather to adjust that gear.”
What excites Leiter the most about the satellite data is the potential to use it in a forecasting tool to help predict where the whales could go. “That would be incredibly useful in giving us that crucial lead time,” she said.
PACE: The Next Generation of Ocean Observer
For now, the Calanus-tracking method has limitations. Because MODIS detects the copepods’ red pigment, not the animals themselves, that means other small, reddish organisms can be mistaken for the zooplankton. And cloud cover, rough seas, or deeper swarms all limit what satellites can spot.
MODIS is also nearing the end of its operational life. But NASA’s next-generation PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite — launched in 2024 — is poised to make dramatic improvements in the detection of zooplankton and phytoplankton.
NASA’s Ocean Color Instrument on the PACE satellite captured these swirling green phytoplankton blooms in the Gulf of Maine in April 2024. Such blooms fuel zooplankton like Calanus finmarchicus. Credit: NASA “The PACE satellite will definitely be able to do this, and maybe even something better,” said Bridget Seegers, an oceanographer and mission scientist with the PACE team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The PACE mission includes the Ocean Color Instrument, which detects more than 280 wavelengths of light. That’s a big jump from the 10 wavelengths seen by MODIS. More wavelengths mean finer detail and better insights into ocean color and the type of plankton that the satellite can spot.
Local knowledge of seasonal plankton patterns will still be essential to interpret the data correctly. But the goal isn’t perfect detection, the scientists say, but rather to provide another tool to inform decision-making, especially when time or resources are limited.
By Emily DeMarco
NASA Headquarters
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Last Updated May 05, 2025 Editor Emily DeMarco Related Terms
Earth Moderate Resolution Imaging Spectroradiometer (MODIS) Oceans PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) Explore More
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By NASA
This NASA/ESA Hubble Space Telescope image features a peculiar spiral galaxy called Arp 184 or NGC 1961.ESA/Hubble & NASA, J. Dalcanton, R. J. Foley (UC Santa Cruz), C. Kilpatrick A beautiful but skewed spiral galaxy dazzles in this NASA/ESA Hubble Space Telescope image. The galaxy, called Arp 184 or NGC 1961, sits about 190 million light-years away from Earth in the constellation Camelopardalis (The Giraffe).
The name Arp 184 comes from the Atlas of Peculiar Galaxies compiled by astronomer Halton Arp in 1966. It holds 338 galaxies that are oddly shaped and tend to be neither entirely elliptical nor entirely spiral-shaped. Many of the galaxies are in the process of interacting with other galaxies, while others are dwarf galaxies without well-defined structures. Arp 184 earned its spot in the catalog thanks to its single broad, star-speckled spiral arm that appears to stretch toward us. The galaxy’s far side sports a few wisps of gas and stars, but it lacks a similarly impressive spiral arm.
This Hubble image combines data from three Snapshot observing programs, which are short observations that slotted into time gaps between other proposals. One of the three programs targeted Arp 184 for its peculiar appearance. This program surveyed galaxies listed in the Atlas of Peculiar Galaxies as well as A Catalogue of Southern Peculiar Galaxies and Associations, a similar catalog compiled by Halton Arp and Barry Madore.
The remaining two Snapshot programs looked at the aftermath of fleeting astronomical events like supernovae and tidal disruption events — like when a supermassive black hole rips a star apart after it wanders too closely. Since Arp 184 hosted four known supernovae in the past three decades, it is a rich target for a supernova hunt.
Image credit: ESA/Hubble & NASA, J. Dalcanton, R. J. Foley (UC Santa Cruz), C. Kilpatrick
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Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Posters Hubble on the NASA App Glossary More 35th Anniversary Online Activities 2 min read
Hubble Images a Peculiar Spiral
This NASA/ESA Hubble Space Telescope image features a peculiar spiral galaxy called Arp 184 or NGC 1961. ESA/Hubble & NASA, J. Dalcanton, R. J. Foley (UC Santa Cruz), C. Kilpatrick A beautiful but skewed spiral galaxy dazzles in this NASA/ESA Hubble Space Telescope image. The galaxy, called Arp 184 or NGC 1961, sits about 190 million light-years away from Earth in the constellation Camelopardalis (The Giraffe).
The name Arp 184 comes from the Atlas of Peculiar Galaxies compiled by astronomer Halton Arp in 1966. It holds 338 galaxies that are oddly shaped and tend to be neither entirely elliptical nor entirely spiral-shaped. Many of the galaxies are in the process of interacting with other galaxies, while others are dwarf galaxies without well-defined structures. Arp 184 earned its spot in the catalog thanks to its single broad, star-speckled spiral arm that appears to stretch toward us. The galaxy’s far side sports a few wisps of gas and stars, but it lacks a similarly impressive spiral arm.
This Hubble image combines data from three Snapshot observing programs, which are short observations that slotted into time gaps between other proposals. One of the three programs targeted Arp 184 for its peculiar appearance. This program surveyed galaxies listed in the Atlas of Peculiar Galaxies as well as A Catalogue of Southern Peculiar Galaxies and Associations, a similar catalog compiled by Halton Arp and Barry Madore.
The remaining two Snapshot programs looked at the aftermath of fleeting astronomical events like supernovae and tidal disruption events — like when a supermassive black hole rips a star apart after it wanders too closely. Since Arp 184 hosted four known supernovae in the past three decades, it is a rich target for a supernova hunt.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated May 01, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Spiral Galaxies The Universe Keep Exploring Discover More Topics From Hubble
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