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Tiny Neptune Moon Spotted by Hubble May Have Broken from Larger Moon
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By European Space Agency
Week in images: 28 April - 02 May 2025
Discover our week through the lens
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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
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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
Skywatching Skywatching Home What’s Up What to See Tonight Meteor Showers Eclipses Moon Guide More Tips & Guides Skywatching FAQ Night Sky Network Eta Aquarids & Waiting for a Nova!
The first week of May brings the annual Eta Aquarid meteors, peaking on the 6th. And sometime in the next few months, astronomers predict a “new star” or nova explosion will become visible to the unaided eye.
Skywatching Highlights
All Month – Planet Visibility:
Venus: Appears very bright and low in the east in the hour before sunrise all month. Mars: Easy to find in the west in the first few hours of the night, all month long. Sets around midnight to 1 a.m. local time. Jupiter: Shines brightly in the west following sunset all month. Early in the month it sets about two hours after the Sun, but by late May it’s setting only an hour after sunset. Saturn: Begins the month next to Venus, low in the eastern sky before sunrise. Quickly separates from Saturn and rises higher in the sky each day before dawn. Daily Highlights
May 6 – Eta Aquarid Meteors – The peak of this annual shower is early on the morning of May 6th. The two or three nights before that are also decent opportunities to spy a few shooting stars. On the peak night this year, the Moon sets by around 3 a.m., leaving dark skies until dawn, for ideal viewing conditions. Seeing 10-20 meteors per hour is common for the Northern Hemisphere, while south of the equator, observers tend to see substantially more.
May 3 – Mars & Moon: The first quarter Moon appears right next to the Red Planet on the 3rd. Find them in the west during the first half of the night that evening.
All month – Venus & Saturn: Low in the eastern sky each morning you’ll find bright Venus paired with much fainter Saturn. They start the month close together, but Saturn pulls away and rises higher over the course of the month.
All month – Mars & Jupiter: The planets to look for on May evenings are Mars and Jupiter. They’re visible for a couple of hours after sunset in the western sky.
All month – Corona Borealis: Practice finding this constellation in the eastern part of the sky during the first half of the night, so you have a point of comparison when the T CrB nova appears there, likely in the next few months.
Transcript
What’s Up for May? Four bright planets, morning and night, a chance of meteor showers, and waiting for a nova.
May Planet Viewing
For planet watching this month, you’ll find Mars and Jupiter in the west following sunset. Mars sticks around for several hours after it gets dark out, but Jupiter is setting by 9:30 or 10 p.m., and getting lower in the sky each day. The first quarter Moon appears right next to the Red Planet on the 3rd. Find them in the west during the first half of the night that evening.
Sky chart showing Venus and Saturn with the crescent Moon in the predawn sky on May 23., 2025. NASA/JPL-Caltech In the morning sky, Venus and Saturn are the planets to look for in May. They begin the month appearing close together on the sky, and progressively pull farther apart as the month goes on. For several days in late May, early risers will enjoy a gathering of the Moon with Saturn and Venus in the eastern sky before dawn. Watch as the Moon passes the two planets while becoming an increasingly slimmer crescent. You’ll find the Moon hanging between Venus and Saturn on the 23rd.
Eta Aquarid Meteor Shower
Early May brings the annual Eta Aquarid meteor shower. These are meteors that originate from Comet Halley. Earth passes through the comet’s dust stream each May, and again in October. Eta Aquarids are fast moving, and a lot of them produce persistent dust trains that linger for seconds after the meteor’s initial streak.
This is one of the best annual showers in the Southern Hemisphere, but tends to be more subdued North of the Equator, where we typically see 10-20 meteors per hour. On the peak night this year, the Moon sets by around 3 a.m., leaving dark skies until dawn, for ideal viewing conditions. While the peak is early on the morning of May 6th, the two or three nights before that are also decent opportunities to spy a few shooting stars.
Waiting for a Nova
Sky chart showing constellation Corona Borealis with the location where nova “T CrB” is predicted to appear. The view depicts the constellation with the nova occurring, indicated by an arrow. NASA/JPL-Caltech Astronomers have been waiting expectantly for light from a distant explosion to reach us here on Earth. An event called a nova is anticipated to occur sometime in the coming months. Some 3,000 light years away is a binary star system called T Coronae Borealis, or “T CrB.” It consists of a red giant star with a smaller white dwarf star orbiting closely around it. Now the giant’s outer atmosphere is all puffed up, and the dwarf star is close enough that its gravity continually captures some of the giant’s hydrogen. About every 80 years, the white dwarf has accumulated so much of the other star’s hydrogen, that it ignites a thermonuclear explosion. And that’s the nova.
T Coronae Borealis is located in the constellation Corona Borealis, or the “Northern Crown,” and it’s normally far too faint to see with the unaided eye. But it’s predicted the nova will be as bright as the constellation’s brightest star, which is about as bright as the North Star, Polaris. You’ll find Corona Borealis right in between the two bright stars Arcturus and Vega, and you can use the Big Dipper’s handle to point you to the right part of the sky. Try having a look for it on clear, dark nights before the nova, so you’ll have a comparison when a new star suddenly becomes visible there.
A sky chart indicating how to locate the constellation Corona Borealis between the bright stars Arcturus and Vega. The Big Dipper’s handle points in the direction of Corona Borealis. NASA/JPL-Caltech Now, you may have heard about this months ago, as astronomers started keeping watch for the nova midway through 2024, but it hasn’t happened yet. Predicting exactly when novas or any sort of stellar outburst will happen is tricky, but excitement began growing when astronomers observed the star to dim suddenly, much as it did right before its previous nova in 1946. When the nova finally does occur, it won’t stay bright for long, likely flaring in peak brightness for only a few days. And since it’s not predicted again for another 80 years, you might just want to join the watch for this super rare, naked eye stellar explosion in the sky!
Here are the phases of the Moon for May.
The phases of the Moon for May 2025. NASA/JPL-Caltech You can stay up to date on all of NASA’s missions exploring the solar system and beyond at NASA Science.
I’m Preston Dyches from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.
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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
Did you know some of the brightest sources of light in the sky come from the regions around black holes in the centers of galaxies? It sounds a little contradictory, but it’s true! They may not look bright to our eyes, but satellites have spotted oodles of them across the universe.
One of those satellites is NASA’s Fermi Gamma-ray Space Telescope. Fermi has found thousands of these kinds of galaxies since it launched in 2008, and there are many more out there!
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Watch a cosmic gamma-ray fireworks show in this animation using just a year of data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope. Each object’s magenta circle grows as it brightens and shrinks as it dims. The yellow circle represents the Sun following its apparent annual path across the sky. The animation shows a subset of the LAT gamma-ray records available for more than 1,500 objects in a continually updated repository. Over 90% of these sources are a type of galaxy called a blazar, powered by the activity of a supermassive black hole. NASA’s Marshall Space Flight Center/Daniel Kocevski Black holes are regions of space that have so much gravity that nothing — not light, not particles, nada — can escape. Most galaxies have supermassive black holes at their centers, and these black holes are hundreds of thousands to billions of times the mass of our Sun. In active galactic nuclei (also called “AGN” for short, or just “active galaxies”) the central region is stuffed with gas and dust that’s constantly falling toward the black hole. As the gas and dust fall, they start to spin and form a disk. Because of the friction and other forces at work, the spinning disk starts to heat up.
This composite view of the active galaxy Markarian 573 combines X-ray data (blue) from NASA’s Chandra X-ray Observatory and radio observations (purple) from the Karl G. Jansky Very Large Array in New Mexico with a visible light image (gold) from the Hubble Space Telescope. Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center. X-ray: NASA/CXC/SAO/A.Paggi et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA The disk’s heat gets emitted as light, but not just wavelengths of it that we can see with our eyes. We detect light from AGN across the entire electromagnetic spectrum, from the more familiar radio and optical waves through to the more exotic X-rays and gamma rays, which we need special telescopes to spot.
In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light as shown in this artist’s concept. NASA/Goddard Space Flight Center Conceptual Image Lab About one in 10 AGN beam out jets of energetic particles, which are traveling almost as fast as light. Scientists are studying these jets to try to understand how black holes — which pull everything in with their huge amounts of gravity — somehow provide the energy needed to propel the particles in these jets.
This artist’s concept shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy’s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA’s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees. NASA’s Goddard Space Flight Center Many of the ways we tell one type of AGN from another depend on how they’re oriented from our point of view. With radio galaxies, for example, we see the jets from the side as they’re beaming vast amounts of energy into space. Then there’s blazars, which are a type of AGN that have a jet that is pointed almost directly at Earth, which makes the AGN particularly bright.
Blazar 3C 279’s historic gamma-ray flare in 2015 can be seen in this image from the Large Area Telescope on NASA’s Fermi satellite. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky. NASA/DOE/Fermi LAT Collaboration Fermi has been searching the sky for gamma ray sources since 2008. More than half of the sources it has found have been blazars. Gamma rays are useful because they can tell us a lot about how particles accelerate and how they interact with their environment.
So why do we care about AGN? We know that some AGN formed early in the history of the universe. With their enormous power, they almost certainly affected how the universe changed over time. By discovering how AGN work, we can understand better how the universe came to be the way it is now.
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Last Updated Apr 30, 2025 Related Terms
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