420 Years Ago: Astronomer Johannes Kepler Observes a Supernova

In October 1604, a new star appeared in the sky, puzzling astronomers of the day. First observed on Oct. 9, German astronomer Johannes Kepler (1571-1630) began his observations on Oct. 17 and tracked the new star for over a year. During that time, it brightened to magnitude -2.5, outshining Jupiter, and for several weeks remained visible in the daytime. Publication of his detailed observations in 1606 led astronomers to call the star Kepler’s Supernova, today formally designated as supernova SN 1604. Astronomers of the day did not know what caused the star’s sudden appearance and eventual disappearance, but the phenomenon helped shape European cosmology toward the heliocentric model proposed by Polish astronomer Nicolaus Copernicus half a century earlier. Today, astronomers designate SN 1604 as a Type Ia supernova, resulting from the explosion of a white dwarf star, and use ground-based and space-based telescopes to study its remnants.

Left: Portrait of Johannes Kepler by August Köhler. Middle: Kepler’s book about his observations of the 1604 supernova open to the page depicting the location of the new star. Right: Closeup of Kepler’s illustration of the location of the new star, designated N, in the constellation Ophiuchus near the right foot of the serpent-bearer.

Italian astronomer Lodovico delle Colombo first observed the supernova in the constellation Ophiuchus on Oct. 9. Kepler, then working in Prague, heard rumors of the new star but did not observe it until Oct. 17. He continued to monitor the star for over a year, inspired by the earlier work of Danish astronomer Tycho Brahe’s observations of a similar phenomenon, the 1572 supernova. The new star quickly brightened to magnitude -2.5, outshining Jupiter, and for three weeks could be seen in the daytime before finally fading into obscurity in March 1606. Kepler could only make naked eye observations, since Italian astronomer Galileo Galilei didn’t turn his newly invented telescope to the skies for another four years after SN 1604 faded from view.

Later in 1606, Kepler summarized his observations in his book De Stella nova in pede Serpentarii (On the New Star in Ophiuchus’ Foot), published in Prague. SN 1604 is believed to be about 20,000 light years away, near the edge of a dark nebula complex. Kepler and his contemporaries observed not only the last known supernova to occur in the Milky Way Galaxy but also the last supernova visible to the naked eye until 1987. That one, Supernova 1987A, appeared in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way.

A Type Ia supernova results from a white dwarf drawing in material from a nearby red giant star, the additional mass leading to a runaway thermonuclear explosion.

Astronomers today understand that what Kepler and others believed as the birth of a new star actually represented the violent death of a star. Astronomers today classify supernovas according to their characteristics, and SN 1604 belongs to the group known as Type Ia supernovas, typically found in binary star systems composed of a white dwarf and a red giant. The gravitation force of the white dwarf draws in material from its larger less dense companion until it reaches a critical mass, around 1.4 times the mass of our Sun. At that point, a runaway thermonuclear chain reaction begins, causing a release of tremendous amounts of energy, including light, that we see as a sudden brightening of an otherwise dim star.

Images of Kepler’s supernova remnants in different portions of the electromagnetic spectrum. Left: X-ray image from the Chandra X-ray Observatory. Middle: Visible image from the Hubble Space Telescope. Right: Infrared image from the Spitzer Space Telescope.

Supernova explosions leave remnants behind and those of SN 1604 remain visible today. Ground-based and space-based instruments using different parts of the electromagnetic spectrum study these remnants to gain a better understanding of their origins. The remnants of SN 1604 emit energy most strongly in the radio and X-ray parts of the electromagnetic spectrum. In recent years, astronomers have used Type Ia supernovas to determine the rate of expansion of the universe. Because Type Ia supernovas all occur in stars of about 1.4 solar masses, they give out about the same amount of light. This makes them useful as distance indicators – if one Type Ia supernova is dimmer than another one, it is further away by an amount that astronomers can calculate. Based on this information, astronomers believe that the expansion of the universe is accelerating, possibly caused by the presence of a mysterious substance called dark energy.

Events in world history in 1604:

January 1 – First performance of William Shakespeare’s play A Midsummer’s Night’s Dream.

March 22 – Karl IX begins his rule as King of Sweden.

August 5 – Sokolluzade Mehmed Pasha becomes the new Ottoman Grand Vizier in Constantinople.

August 18 – England and Spain sign the Treaty of London, ending their 20-year war.

September 1 – Sri Guru Granth Sahib, Sikhism’s religious text, is installed at Hamandir Sahib in Amritsar, India.

October 4 – Emperor of Ethiopia Za Dengel is killed in battle with the forces of Za Sellase, who restores his cousin Yaqob to the throne.

November 1 – First performance of William Shakespeare’s tragedy Othello.

December 29 – A magnitude 8.1 earthquake shakes the Taiwan Strait causing significant damage.

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NASA’s Hubble, New Horizons Team Up for a Simultaneous Look at Uranus

NASA’s Hubble Space Telescope and New Horizons spacecraft simultaneously set their sights on Uranus recently, allowing scientists to make a direct comparison of the planet from two very different viewpoints. The results inform future plans to study like types of planets around other stars.

Astronomers used Uranus as a proxy for similar planets beyond our solar system, known as exoplanets, comparing high-resolution images from Hubble to the more-distant view from New Horizons. This combined perspective will help scientists learn more about what to expect while imaging planets around other stars with future telescopes.

“While we expected Uranus to appear differently in each filter of the observations, we found that Uranus was actually dimmer than predicted in the New Horizons data taken from a different viewpoint,” said lead author Samantha Hasler of the Massachusetts Institute of Technology in Cambridge and New Horizons science team collaborator.

Direct imaging of exoplanets is a key technique for learning about their potential habitability, and offers new clues to the origin and formation of our own solar system. Astronomers use both direct imaging and spectroscopy to collect light from the observed planet and compare its brightness at different wavelengths. However, imaging exoplanets is a notoriously difficult process because they’re so far away. Their images are mere pinpoints and so are not as detailed as the close-up views that we have of worlds orbiting our Sun. Researchers can also only directly image exoplanets at “partial phases,” when only a portion of the planet is illuminated by their star as seen from Earth.

Uranus was an ideal target as a test for understanding future distant observations of exoplanets by other telescopes for a few reasons. First, many known exoplanets are also gas giants similar in nature. Also, at the time of the observations, New Horizons was on the far side of Uranus, 6.5 billion miles away, allowing its twilight crescent to be studied—something that cannot be done from Earth. At that distance, the New Horizons view of the planet was just several pixels in its color camera, called the Multispectral Visible Imaging Camera.

On the other hand, Hubble, with its high resolution, and in its low-Earth orbit 1.7 billion miles away from Uranus, was able to see atmospheric features such as clouds and storms on the day side of the gaseous world.

“Uranus appears as just a small dot on the New Horizons observations, similar to the dots seen of directly-imaged exoplanets from observatories like Webb or ground-based observatories,” added Hasler. “Hubble provides context for what the atmosphere is doing when it was observed with New Horizons.”

The gas giant planets in our solar system have dynamic and variable atmospheres with changing cloud cover. How common is this among exoplanets? By knowing the details of what the clouds on Uranus looked like from Hubble, researchers are able to verify what is interpreted from the New Horizons data. In the case of Uranus, both Hubble and New Horizons saw that the brightness did not vary as the planet rotated, which indicates that the cloud features were not changing with the planet’s rotation.

However, the importance of the detection by New Horizons has to do with how the planet reflects light at a different phase than what Hubble, or other observatories on or near Earth, can see. New Horizons showed that exoplanets may be dimmer than predicted at partial and high phase angles, and that the atmosphere reflects light differently at partial phase.

NASA has two major upcoming observatories in the works to advance studies of exoplanet atmospheres and potential habitability.

“These landmark New Horizons studies of Uranus from a vantage point unobservable by any other means add to the mission’s treasure trove of new scientific knowledge, and have, like many other datasets obtained in the mission, yielded surprising new insights into the worlds of our solar system,” added New Horizons principal investigator Alan Stern of the Southwest Research Institute.

NASA’s upcoming Nancy Grace Roman Space Telescope, set to launch by 2027, will use a coronagraph to block out a star’s light to directly see gas giant exoplanets. NASA’s Habitable Worlds Observatory, in an early planning phase, will be the first telescope designed specifically to search for atmospheric biosignatures on Earth-sized, rocky planets orbiting other stars.

“Studying how known benchmarks like Uranus appear in distant imaging can help us have more robust expectations when preparing for these future missions,” concluded Hasler. “And that will be critical to our success.”

Launched in January 2006, New Horizons made the historic flyby of Pluto and its moons in July 2015, before giving humankind its first close-up look at one of these planetary building block and Kuiper Belt object, Arrokoth, in January 2019. New Horizons is now in its second extended mission, studying distant Kuiper Belt objects, characterizing the outer heliosphere of the Sun, and making important astrophysical observations from its unmatched vantage point in distant regions of the solar system.

The Uranus results are being presented this week at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences, in Boise, Idaho.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

The Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, built and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. Southwest Research Institute, based in San Antonio and Boulder, Colorado, directs the mission via Principal Investigator Alan Stern and leads the science team, payload operations and encounter science planning. New Horizons is part of NASA’s New Frontiers program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.

Media Contacts:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

Hannah Braun, Ray Villard
Space Telescope Science Institute, Baltimore, MD

Science Contacts:

Samantha Hasler
Massachusetts Institute of Technology, Cambridge, MA

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Artemis I Radiation Measurements Validate Orion Safety for Astronauts

NASA’s Orion spacecraft is designed to keep astronauts safe in deep space, protecting them from the unforgiving environment far from Earth. During the uncrewed Artemis I mission, researchers from NASA, along with several collaborators, flew payloads onboard Orion to measure potential radiation exposure to astronauts.

Radiation measurements were taken inside Orion by 5,600 passive sensors and 34 active radiation detectors during its 25.5-day mission around the Moon and back, which provided important data on exposure within the Earth’s Van Allen radiation belt. These detailed findings were published in a recent scientific article through a collaborative effort by NASA’s Space Radiation Analysis Group, the DLR (German Space Center), and ESA (European Space Agency). The measurements show that while radiation exposure can vary depending on location within Orion, the spacecraft can protect its crew from potentially hazardous radiation levels during lunar missions.

Space radiation could pose major risks to long-duration human space flights, and the findings from the Artemis I mission represent a crucial step toward future human exploration beyond low Earth orbit, to the Moon, and eventually to Mars.

NASA’s HERA (Hybrid Electronic Radiation Assessor) and Crew Active Dosimeter, which were tested previously on the International Space Station, and ESA’s Active Dosimeter, were among the instruments used to measure radiation inside Orion. HERA’s radiation sensor can warn crew members need to take shelter in the case of a radiation event, such as a solar flare. The Crew Active Dosimeter can collect real-time radiation dose data for astronauts and transmit it back to Earth for monitoring. Radiation measurements were conducted in various areas of the spacecraft, each offering different levels of shielding.

In addition, the Matroshka AstroRad Radiation Experiment, a collaboration between NASA and DLR, involved radiation sensors placed on and inside two life-sized manikin torsos to simulate the impact of radiation on human tissue. These manikins enabled measurements of radiation doses on various body parts, providing valuable insight into how radiation may affect astronauts traveling to deep space.

Researchers found that Orion’s design can protect its crew from potentially hazardous radiation levels during lunar missions. Though the spacecraft’s radiation shielding is effective, the range of exposure can greatly vary based on spacecraft orientation in specific environments. When Orion altered its orientation during an engine burn of the Interim Cryogenic Propulsion Stage, radiation levels dropped nearly in half due to the highly directional nature of the radiation in the Van Allen belt.

“These radiation measurements show that we have an effective strategy for managing radiation risks in the Orion spacecraft. However, key challenges remain, especially for long-duration spaceflights and the protection of astronauts on spacewalks,” said Stuart George, NASA’s lead author on the paper.

NASA’s long-term efforts and research in mitigating space radiation risks are ongoing, as radiation measurements on future missions will depend heavily on spacecraft shielding, trajectory, and solar activity. The same radiation measurement hardware flown on Artemis I will support the first crewed Artemis mission around the Moon, Artemis II, to better understand the radiation exposure seen inside Orion and ensure astronaut safety to the Moon and beyond.

For more information on NASA’s Artemis campaign, visit:

https://www.nasa.gov/artemis

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Laura Sorto

NASA’s Hubble Watches Jupiter’s Great Red Spot Behave Like a Stress Ball

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NASA’s Hubble Watches Jupiter’s Great Red Spot Behave Like a Stress Ball

Astronomers have observed Jupiter’s legendary Great Red Spot (GRS), an anticyclone large enough to swallow Earth, for at least 150 years. But there are always new surprises – especially when NASA’s Hubble Space Telescope takes a close-up look at it.

Hubble’s new observations of the famous red storm, collected 90 days between December 2023 to March 2024, reveal that the GRS is not as stable as it might look. The recent data show the GRS jiggling like a bowl of gelatin. The combined Hubble images allowed astronomers to assemble a time-lapse movie of the squiggly behavior of the GRS.

“While we knew its motion varies slightly in its longitude, we didn’t expect to see the size oscillate. As far as we know, it’s not been identified before,” said Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of the science paper published in The Planetary Science Journal. “This is really the first time we’ve had the proper imaging cadence of the GRS. With Hubble’s high resolution we can say that the GRS is definitively squeezing in and out at the same time as it moves faster and slower. That was very unexpected, and at present there are no hydrodynamic explanations.”

Hubble monitors Jupiter and the other outer solar system planets every year through the Outer Planet Atmospheres Legacy program (OPAL) led by Simon, but these observations were from a program dedicated to the GRS. Understanding the mechanisms of the largest storms in the solar system puts the theory of hurricanes on Earth into a broader cosmic context, which might be applied to better understanding the meteorology on planets around other stars.

Simon’s team used Hubble to zoom in on the GRS for a detailed look at its size, shape, and any subtle color changes. “When we look closely, we see a lot of things are changing from day to day,” said Simon. This includes ultraviolet-light observations showing that the distinct core of the storm gets brightest when the GRS is at its largest size in its oscillation cycle. This indicates less haze absorption in the upper atmosphere.

“As it accelerates and decelerates, the GRS is pushing against the windy jet streams to the north and south of it,” said co-investigator Mike Wong of the University of California at Berkeley. “It’s similar to a sandwich where the slices of bread are forced to bulge out when there’s too much filling in the middle.” Wong contrasted this to Neptune, where dark spots can drift wildly in latitude without strong jet streams to hold them in place. Jupiter’s Great Red Spot has been held at a southern latitude, trapped between the jet streams, for the extent of Earth-bound telescopic observations.

The team has continued watching the GRS shrink since the OPAL program began 10 years ago. They predict it will keep shrinking before taking on a stable, less-elongated, shape. “Right now it’s over-filling its latitude band relative to the wind field. Once it shrinks inside that band the winds will really be holding it in place,” said Simon. The team predicts that the GRS will probably stabilize in size, but for now Hubble only observed it for one oscillation cycle.

The researchers hope that in the future other high-resolution images from Hubble might identify other Jovian parameters that indicate the underlying cause of the oscillation.

The results are being presented at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences, in Boise, Idaho.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

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Media Contacts:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

Ray Villard
Space Telescope Science Institute, Baltimore, MD

Science Contacts:
Amy Simon
NASA Goddard Space Flight Center, Greenbelt, MD

Michael H. Wong
University of California, Berkeley, Berkeley, CA

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NASA Terminal Transmits First Laser Communications Uplink to Space 

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NASA Terminal Transmits First Laser Communications Uplink to Space 

NASA’s LCOT (Low-Cost Optical Terminal), a ground station made of modified commercial hardware, transmitted its first laser communications uplink to the TBIRD (TeraByte Infrared Delivery), a tissue box-sized payload formerly in low Earth orbit.

During the first live sky test, NASA’s LCOT produced enough uplink intensity for the TBIRD payload to identify the laser beacon, connect, and maintain a connection to the ground station for over three minutes. This successful test marks an important achievement for laser communications: connecting LCOT’s laser beacon from Earth to TBIRD required one milliradian of pointing accuracy, the equivalent of hitting a three-foot target from over eight American football fields away.

The test was one of many laser communications achievements TBIRD made possible during its successful, two-year mission. Prior to its mission completion on Sept. 15, 2024, the payload transmitted at a record-breaking 200 gigabits per second. In an actual use case, TBIRD’s three-minute connection time with LCOT would be sufficient to return over five terabytes of critical science data, the equivalent of over 2,500 hours of high-definition video in a single pass. As the LCOT sky test demonstrates, the ultra-high-speed capabilities of laser communications will allow science missions to maintain their connection to Earth as they travel farther than ever before.

NASA’s SCaN (Space Communications and Navigation) program office is implementing laser communications technology in various orbits, including the upcoming Artemis II mission, to demonstrate its potential impact in the agency’s mission to explore, innovate, and inspire discovery.

“Optical, or laser, communications can transfer 10 to 100 times more data than radio frequency waves,” said Kevin Coggins, deputy associate administrator and SCaN program manager. “Literally, it’s the wave of the future, as it’ll enable scientists to realize an ever-increasing amount of data from their missions and will serve as our critical lifeline for astronauts traveling to and from Mars.” 

Historically, space missions have used radio frequencies to send data to and from space, but with science instruments capturing more data, communications assets must meet increasing demand. The infrared light used for laser communications transmits the data at a shorter wavelength than radio, meaning ground stations on Earth can send and receive more data per second. 

The LCOT team continues to refine pointing capabilities through additional tests with NASA’s LCRD (Laser Communications Relay Demonstration). As LCOT and the agency’s other laser communications missions continue to reach new milestones in connectivity and accessibility, they demonstrate laser communications’ potential to revolutionize scientists’ access to new data about Earth, our solar system, and beyond. 

“It’s a testament to the hard work and skill of the entire team,” said Dr. Haleh Safavi, project lead for LCOT. “We work with very complicated and sensitive transmission equipment that must be installed with incredible precision. These results required expeditious planning and execution at every level.” 

Experiments like TBIRD and LCRD are only two of SCaN’s multiple in-space demonstrations of laser communications, but a robust laser communications network relies on easily reconfigurable ground stations on Earth. The LCOT ground station showcases how the government and aerospace industry can build and deploy flexible laser communications ground stations to meet the needs of a wide variety of NASA and commercial missions, and how these ground stations open new doors for communications technology and extremely high data volume transmission. 

NASA’s LCOT is developed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. TBIRD was developed in partnership with the Massachusetts Institute of Technology Lincoln Laboratory (MIT-LL) in Lexington. TBIRD was flown and operated as a collaborative effort among NASA Goddard; NASA’s Ames Research Center in California’s Silicon Valley; NASA’s Jet Propulsion Laboratory in Southern California; MIT-LL; and Terran Orbital Corporation in Irvine, California. Funding and oversight for LCOT and other laser communications demonstrations comes from the (SCaN) Space Communications and Navigation  program office within the Space Operations Mission Directorate at NASA Headquarters in Washington. 

About the Author

Korine Powers

Senior Writer and Education Lead

Korine Powers, Ph.D. is a writer for NASA’s Space Communications and Navigation (SCaN) program office and covers emerging technologies, commercialization efforts, education and outreach, exploration activities, and more.

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Korine Powers