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Astronomers Find Elusive Planets in Decade-Old Hubble Data
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By NASA
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.
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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
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Hubble’s Galaxies
Tracing the Growth of Galaxies
Reshaping Our Cosmic View: Hubble Science Highlights
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By NASA
4 min read
May’s Night Sky Notes: How Do We Find Exoplanets?
Astronomers have been trying to discover evidence that worlds exist around stars other than our Sun since the 19th century. By the mid-1990s, technology finally caught up with the desire for discovery and led to the first discovery of a planet orbiting another sun-like star, Pegasi 51b. Why did it take so long to discover these distant worlds, and what techniques do astronomers use to find them?
The Transit Method
A planet passing in front of its parent star creates a drop in the star’s apparent brightness, called a transit. Exoplanet Watch participants can look for transits in data from ground-based telescopes, helping scientists refine measurements of the length of a planet’s orbit around its star. Credit: NASA’s Ames Research Center One of the most famous exoplanet detection methods is the transit method, used by Kepler and other observatories. When a planet crosses in front of its host star, the light from the star dips slightly in brightness. Scientists can confirm a planet orbits its host star by repeatedly detecting these incredibly tiny dips in brightness using sensitive instruments. If you can imagine trying to detect the dip in light from a massive searchlight when an ant crosses in front of it, at a distance of tens of miles away, you can begin to see how difficult it can be to spot a planet from light-years away! Another drawback to the transit method is that the distant solar system must be at a favorable angle to our point of view here on Earth – if the distant system’s angle is just slightly askew, there will be no transits. Even in our solar system, a transit is very rare. For example, there were two transits of Venus visible across our Sun from Earth in this century. But the next time Venus transits the Sun as seen from Earth will be in the year 2117 – more than a century from the 2012 transit, even though Venus will have completed nearly 150 orbits around the Sun by then!
The Wobble Method
As a planet orbits a star, the star wobbles. This causes a change in the appearance of the star’s spectrum called Doppler shift. Because the change in wavelength is directly related to relative speed, astronomers can use Doppler shift to calculate exactly how fast an object is moving toward or away from us. Astronomers can also track the Doppler shift of a star over time to estimate the mass of the planet orbiting it. NASA, ESA, CSA, Leah Hustak (STScI) Spotting the Doppler shift of a star’s spectra was used to find Pegasi 51b, the first planet detected around a Sun-like star. This technique is called the radial velocity or “wobble” method. Astronomers split up the visible light emitted by a star into a rainbow. These spectra, and gaps between the normally smooth bands of light, help determine the elements that make up the star. However, if there is a planet orbiting the star, it causes the star to wobble ever so slightly back and forth. This will, in turn, cause the lines within the spectra to shift ever so slightly towards the blue and red ends of the spectrum as the star wobbles slightly away and towards us. This is caused by the blue and red shifts of the star’s light. By carefully measuring the amount of shift in the star’s spectra, astronomers can determine the size of the object pulling on the host star and if the companion is indeed a planet. By tracking the variation in this periodic shift of the spectra, they can also determine the time it takes the planet to orbit its parent star.
Direct Imaging
Finally, exoplanets can be revealed by directly imaging them, such as this image of four planets found orbiting the star HR 8799! Space telescopes use instruments called coronagraphs to block the bright light from the host star and capture the dim light from planets. The Hubble Space Telescope has captured images of giant planets orbiting a few nearby systems, and the James Webb Space Telescope has only improved on these observations by uncovering more details, such as the colors and spectra of exoplanet atmospheres, temperatures, detecting potential exomoons, and even scanning atmospheres for potential biosignatures!
NASA’s James Webb Space Telescope has provided the clearest look in the infrared yet at the iconic multi-planet system HR 8799. The closest planet to the star, HR 8799 e, orbits 1.5 billion miles from its star, which in our solar system would be located between the orbit of Saturn and Neptune. The furthest, HR 8799 b, orbits around 6.3 billion miles from the star, more than twice Neptune’s orbital distance. Colors are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by the coronagraph. In this image, the color blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI) You can find more information and activities on NASA’s Exoplanets page, such as the Eyes on Exoplanets browser-based program, The Exoplaneteers, and some of the latest exoplanet news. Lastly, you can find more resources in our News & Resources section, including a clever demo on how astronomers use the wobble method to detect planets!
The future of exoplanet discovery is only just beginning, promising rich rewards in humanity’s understanding of our place in the Universe, where we are from, and if there is life elsewhere in our cosmos.
Originally posted by Dave Prosper: July 2015
Last Updated by Kat Troche: April 2025
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By NASA
ESA/Hubble & NASA, L. C. Ho, D. Thilker Today’s rather aquatic-themed NASA/ESA Hubble Space Telescope image features the spiral galaxy Messier 77, also known as the Squid Galaxy, which sits 45 million light-years away in the constellation Cetus (The Whale).
The designation Messier 77 comes from the galaxy’s place in the famous catalog compiled by the French astronomer Charles Messier. Another French astronomer, Pierre Méchain, discovered the galaxy in 1780. Both Messier and Méchain were comet hunters who cataloged nebulous objects that could be mistaken for comets.
Messier, Méchain, and other astronomers of their time mistook the Squid Galaxy for either a spiral nebula or a star cluster. This mischaracterization isn’t surprising. More than a century would pass between the discovery of the Squid Galaxy and the realization that the ‘spiral nebulae’ scattered across the sky were not part of our galaxy but were in fact separate galaxies millions of light-years away. The Squid Galaxy’s appearance through a small telescope — an intensely bright center surrounded by a fuzzy cloud — closely resembles one or more stars wreathed in a nebula.
The name ‘Squid Galaxy’ is recent, and stems from the extended, filamentary structure that curls around the galaxy’s disk like the tentacles of a squid. The Squid Galaxy is a great example of how advances in technology and scientific understanding can completely change our perception of an astronomical object — and even what we call it!
Hubble previously released an image of M77 in 2013. This new image incorporates recent observations made with different filters and updated image processing techniques which allow astronomers to see the galaxy in more detail.
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By NASA
This artist’s concept depicts a magnetar – a type of neutron star with a strong magnetic field – losing material into space. Shown as thin green lines, the magnetic field lines influence the movement of charged material around the magnetar. NASA/JPL-Caltech Since the big bang, the early universe had hydrogen, helium, and a scant amount of lithium. Later, some heavier elements, including iron, were forged in stars. But one of the biggest mysteries in astrophysics is: How did the first elements heavier than iron, such as gold, get created and distributed throughout the universe?
“It’s a pretty fundamental question in terms of the origin of complex matter in the universe,” said Anirudh Patel, a doctoral student at Columbia University in New York. “It’s a fun puzzle that hasn’t actually been solved.”
Patel led a study using 20-year-old archival data from NASA and ESA telescopes that finds evidence for a surprising source of a large amount of these heavy elements: flares from highly magnetized neutron stars, called magnetars. The study is published in The Astrophysical Journal Letters.
Study authors estimate that magnetar giant flares could contribute up to 10% of the total abundance of elements heavier than iron in the galaxy. Since magnetars existed relatively early in the history of the universe, the first gold could have been made this way.
“It’s answering one of the questions of the century and solving a mystery using archival data that had been nearly forgotten,” said Eric Burns, study co-author and astrophysicist at Louisiana State University in Baton Rouge.
How could gold be made at a magnetar?
Neutron stars are the collapsed cores of stars that have exploded. They are so dense that one teaspoon of neutron star material, on Earth, would weigh as much as a billion tons. A magnetar is a neutron star with an extremely powerful magnetic field.
On rare occasions, magnetars release an enormous amount of high-energy radiation when they undergo “starquakes,” which, like earthquakes, fracture the neutron star’s crust. Starquakes may also be associated with powerful bursts of radiation called magnetar giant flares, which can even affect Earth’s atmosphere. Only three magnetar giant flares have been observed in the Milky Way and the nearby Large Magellanic Cloud, and seven outside.
Patel and colleagues, including his advisor Brian Metzger, professor at Columbia University and senior research scientist at the Flatiron Institute in New York, have been thinking about how radiation from giant flares could correspond to heavy elements forming there. This would happen through a “rapid process” of neutrons forging lighter atomic nuclei into heavier ones.
Protons define the element’s identity on the periodic table: hydrogen has one proton, helium has two, lithium has three, and so on. Atoms also have neutrons which do not affect identity, but do add mass. Sometimes when an atom captures an extra neutron the atom becomes unstable and a nuclear decay process happens that converts a neutron into a proton, moving the atom forward on the periodic table. This is how, for example, a gold atom could take on an extra neutron and then transform into mercury.
In the unique environment of a disrupted neutron star, in which the density of neutrons is extremely high, something even stranger happens: single atoms can rapidly capture so many neutrons that they undergo multiple decays, leading to the creation of a much heavier element like uranium.
When astronomers observed the collision of two neutron stars in 2017 using NASA telescopes and the Laser Interferomete Gravitational wave Observatory (LIGO), and numerous telescopes on the ground and in space that followed up the initial discovery, they confirmed that this event could have created gold, platinum, and other heavy elements. But neutron star mergers happen too late in the universe’s history to explain the earliest gold and other heavy elements. Recent research by co-authors of the new study — Jakub Cehula of Charles University in Prague, Todd Thompson of The Ohio State University, and Metzger — has found that magnetar flares can heat and eject neutron star crustal material at high speeds, making them a potential source.
A rupture in the crust of a highly magnetized neutron star, shown here in an artist’s rendering, can trigger high-energy eruptions. Credit: NASA’s Goddard Space Flight Center/S. Wiessinger New clues in old data
At first, Metzger and colleagues thought that the signature from the creation and distribution of heavy elements at a magnetar would appear in the visible and ultraviolet light, and published their predictions. But Burns in Louisiana wondered if there could be a gamma-ray signal bright enough to be detected, too. He asked Metzger and Patel to check, and they found that there could be such a signature.
“At some point, we said, ‘OK, we should ask the observers if they had seen any,’” Metzger said.
Burns looked up the gamma ray data from the last giant flare that has been observed, which was in December 2004. He realized that while scientists had explained the beginning of the outburst, they had also identified a smaller signal from the magnetar, in data from ESA (European Space Agency)’s INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), a recently retired mission with NASA contributions. “It was noted at the time, but nobody had any conception of what it could be,” Burns said.
Metzger remembers that Burns thought he and Patel were “pulling his leg” because the prediction from their team’s model so closely matched the mystery signal in the 2004 data. In other words, the gamma ray signal detected over 20 years ago corresponded to what it should look like when heavy elements are created and then distributed in a magnetar giant flare.
Patel was so excited, “I wasn’t thinking about anything else for the next week or two. It was the only thing on my mind,” he said.
Researchers supported their conclusion using data from two NASA heliophysics missions: the retired RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) and the ongoing NASA’s Wind satellite, which had also observed the magnetar giant flare. Other collaborators on the new study included Jared Goldberg at the Flatiron Institute.
Next steps in the magnetar gold rush
NASA’s forthcoming COSI (Compton Spectrometer and Imager) mission can follow up on these results. A wide-field gamma ray telescope, COSI is expected to launch in 2027 and will study energetic phenomena in the cosmos, such as magnetar giant flares. COSI will be able to identify individual elements created in these events, providing a new advancement in understanding the origin of the elements. It is one of many telescopes that can work together to look for “transient” changes across the universe.
Researchers will also follow up on other archival data to see if other secrets are hiding in observations of other magnetar giant flares.
“It very cool to think about how some of the stuff in my phone or my laptop was forged in this extreme explosion of the course of our galaxy’s history,” Patel said.
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elandau@nasa.gov
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By NASA
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 Visits Glittering Cluster, Capturing Its Ultraviolet Light
This NASA/ESA Hubble Space Telescope image features the globular cluster Messier 72 (M72). ESA/Hubble & NASA, A. Sarajedini, G. Piotto, M. Libralato As part of ESA/Hubble’s 35th anniversary celebrations, the European Space Agency (ESA) shared new images that revisited stunning, previously released Hubble targets with the addition of the latest Hubble data and new processing techniques.
ESA/Hubble released new images of NGC 346, the Sombrero Galaxy, and the Eagle Nebula earlier in the month. Now they are revisiting the star cluster Messier 72 (M72).
M72 is a collection of stars, formally known as a globular cluster, located in the constellation Aquarius roughly 50,000 light-years from Earth. The intense gravitational attraction between the closely packed stars gives globular clusters their regular, spherical shape. There are roughly 150 known globular clusters associated with the Milky Way galaxy.
The striking variety in the color of the stars in this image of M72, particularly compared to the original image, results from the addition of ultraviolet observations to the previous visible-light data. The colors indicate groups of different types of stars. Here, blue stars are those that were originally more massive and have reached hotter temperatures after burning through much of their hydrogen fuel; the bright red objects are lower-mass stars that have become red giants. Studying these different groups help astronomers understand how globular clusters, and the galaxies they were born in, initially formed.
Pierre Méchain, a French astronomer and colleague of Charles Messier, discovered M72 in 1780. It was the first of five star clusters that Méchain would discover while assisting Messier. They recorded the cluster as the 72nd entry in Messier’s famous collection of astronomical objects. It is also one of the most remote clusters in the catalog.
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 Apr 25, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Globular Clusters Goddard Space Flight Center Star Clusters Stars The Universe Keep Exploring Discover More Topics From Hubble
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Hubble’s Star Clusters
Hubble’s 35th Anniversary
Hubble’s Night Sky Challenge
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