Katie Bouman is known for her work in compiling the first images of an event horizon—the “surface” of a black hole.
Credit: © Caltech

March is Women’s History Month, an annual observance of women’s achievements and contributions to society. This month, Behind the Headlines will feature woman pioneers in a variety of areas.

Women achieve great things around the world every day. However, not many women craft an algorithm to create the first-ever picture of a black hole. American computer scientist Katie Bouman worked on compiling the first images of an event horizon—the “surface” of a black hole. A black hole is a region of space whose gravitational force is so strong that nothing can escape from it. At the event horizon, the pull of gravity becomes so strong that nothing known can escape. Capturing the event horizon was considered an amazing feat of astronomical imaging. Bouman has helped us understand the universe’s greatest mystery.

Katherine Louise Bouman was born May 9, 1989, in West Lafayette, Indiana. While in high school, she volunteered at Purdue University, conducting imaging research. She attended the University of Michigan from 2007 to 2011, where she graduated summa cum laude (with highest distinction) with a bachelor’s degree in electrical engineering. She received her Ph.D. degree in electrical engineering and computer science from the Massachusetts Institute of Technology (MIT) in 2017.

Bouman joined the Event Horizon Telescope (EHT) project in 2013. The EHT is a global network of ground-based telescopes established to produce images of black hole event horizons. At MIT, she worked to develop the mathematical framework used to assemble images of black holes from radio telescope data. She led the development of the Continuous High-Resolution Image Reconstruction using Patch priors (CHIRP) algorithm. An algorithm is a step-by-step mathematical procedure, often carried out by a computer. The CHIRP algorithm takes images of one object from multiple sources and uses computer vision techniques to produce a single sharper image of the object. Computer vision is the use of computers to recognize patterns in images, a major topic in artificial intelligence.

In 2017, radio telescopes participating in the EHT project observed the M87 galaxy. The following year, Bouman headed one of the four EHT teams that used the data gathered to produce possible images of the supermassive black hole astronomers suspected to be at the center of M87, called M87*. Two teams, including Bouman’s, used algorithms similar to CHIRP. Two other teams used an algorithm traditionally used in radio astronomy. The teams then checked their images against one another.

In 2019, EHT released the combined image of M87*. At that time, two photographs of Bouman garnered significant media attention. The first showed her reaction as her team’s results were compiled for the first time. The second showed her posing with the hard drives of data used to compile the image of M87*. This photograph drew comparisons to a 1969 image of the American computer scientist Margaret Hamilton standing next to a stack of volumes containing the printed computer code for the Apollo lunar missions.

This artist’s illustration imagines the view from the surface of one of the planets in the TRAPPIST-1 planetary system. Astronomers think that some of the planets in this system may have a substantial ocean of water, a necessary ingredient for life.
Credit: NASA/JPL-Caltech

One of the most stunning astronomical discoveries of the last decade was an entire system of exoplanets, relatively close to Earth, that have the potential to host life. During a Dec. 13, 2022 conference, astronomers reported preliminary findings about the system gathered by the powerful new James Webb Space Telescope (JWST).  

This artist’s illustration shows what the TRAPPIST-1 planetary system may look like. The planetary system has seven planets that rapidly orbit close to the parent star. Three of the planets orbit within the habitable zone of the star where liquid water can exist on a planet’s surface.
Credit: NASA/JPL-Caltech

TRAPPIST-1 is a red dwarf star about 40 light-years from Earth in the constellation Aquarius. One light-year equals the distance light travels in a vacuum in a year, about 5.88 trillion miles (9.46 trillion kilometers). TRAPPIST-1 is notable for having seven orbiting planets. Astronomers classify the planets as terrestrial, meaning they have Earthlike qualities. All of them orbit the star within or near a region that astronomers call the habitable zone. That is, in that region in which liquid water can exist on a planet’s surface. Scientists consider liquid water to be an essential ingredient for life. 

The first three planets in the TRAPPIST-1 system were discovered in 2015. These were discovered by astronomers using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) robotic telescope pair, located at La Silla Observatory in Chile and Oukaïmeden Observatory in Morocco. Scientists using the Spitzer Space Telescope and the Very Large Telescope in Chile announced in 2017 that they had confirmed the discovery of those three planets and had discovered four more planets. 

The potential of these planets to host conditions favorable for life made the TRAPPIST-1 system a major target for the JWST. This advanced satellite observatory was launched in December of 2021 and began conducting scientific observations in mid-2022. Earlier that year, JWST characterized the atmosphere of the giant exoplanet WASP-96b as a proof-of-concept, setting the stage for TRAPPIST-1 observations.  

The preliminary results from two of the TRAPPIST-1 planets confirm that they do not have hydrogen atmospheres. They may have no atmospheres, or they may have atmospheres composed of other gases, including carbon dioxide, methane, and water vapor. Such atmospheres could make these planets hospitable for life. 

Because these exoplanets are so small, even the powerful JWST needs to view the system for extended periods to gather accurate data. But the system’s diminutive proportions will speed up the observation process. JWST detects minute changes to the star’s light as each planet passes in front of it. The seven planets whirl around TRAPPIST-1 with orbital periods of 1.5 to 18.8 Earth days. In contrast, Earth’s orbital period (also called a year) is about 365 days, and Mercury’s is 88 Earth days. (Because TRAPPIST-1 is a small, cool star, these tight orbits still lie within or near its habitable zone.) Astronomers are confident that they will have a good “family portrait” of the TRAPPIST-1 within a year.  

JWST has already racked up impressive observations after just a half-year of activity. With its study of TRAPPIST-1, it will help bring astronomers closer to answering one of the most fundamental questions in science: are we living things on Earth alone in the universe, or not? 

A hidden star catalog on an ancient manuscript attributed to Hipparchus
Credit: Early Manuscripts Electronic Library/Lazarus Project, University of Rochester

Scholars studying Biblical texts have made an almost unimaginable find—fragments of a lost star catalog compiled by the ancient astronomer Hipparchus. Hipparchus’s work represents the earliest known project to catalog the entire night sky. The find is an example of a palimpsest—a manuscript that has been written over with other writings. The discovery was announced in the fall of 2022. 

The lost fragments were discovered by researchers examining a text taken from the library of St. Catherine’s Monastery, a Greek Orthodox monastery on the Sinai peninsula in Egypt. That text was written during the Middle Ages, a period of history that lasted form about the 400’s through the 1400’s. 

The text was written not on paper, but on a specially prepared animal skin called parchment. However, parchment and other materials could be rare in the Middle Ages. For this reason, scribes sometimes scraped the surface of the parchment, clearing the page for a new manuscript. In many cases, the scraped away writing can still be detected, forming a type of hidden manuscript called a palimpsest. 

In 2012, a biblical scholar asked his college students to study the text beneath the manuscript, hoping to find earlier Christian writings. But one student spotted an astronomical passage often attributed to the ancient Greek mathematician Eratosthenes. 

In 2017, researchers at the University of Rochester in New York analyzed the pages using multi-spectral imaging. They took 42 photos of each page at various wavelengths of light. A computer algorithm then combined the various images to search for hidden markings. The researchers discovered myths about the stars’ origins compiled by Eratosthenes, along with a poem about the constellations. 

During the COVID-19 pandemic, the house-bound scholar passed the time re-examining the images. He was surprised to find what appeared to be stellar coordinates, numbers that can be used to measure the position of a star in the night sky.  

Using radiocarbon dating, the coordinates were determined to be written in the 400’s or 500’s A.D. However, the way they were written suggested that they might have been copied from Hipparchus. Moreover, astronomers know that the stars appear to change position over time due to a wobble in Earth’s axis, an effect called precession. The coordinates were so detailed that scholars could thus determine that they were taken in 129 B.C., during Hipparchus’s life. 

The oldest surviving star catalog comes from a work called the Almagest by the astronomer Ptolemy, compiled in the 100’s A.D. Hipparchus’s earlier catalog is mentioned in ancient sources. But with no surviving evidence, it was thought to be lost forever or even never to have existed. 

The new discovery sheds an amazing light on Hipparchus’s work. Compiled nearly 2,000 years before the invention of the telescope, his catalog would have required countless hours of measurement with a sighting tube or a device called an armillary sphere. For now, only a few fragments remain, but scientists hope that they will help to identify other fragments of Hipparchus’s work in other manuscripts. 

An artist’s im­pres­sion of Plan­et GJ 367b.
Credit: SPP 1992 (Patricia Klein)

Do you know someone who listens to heavy metal music? Maybe you have friends who like to wear black clothing and bang their heads to loud tunes. Perhaps you have an uncle who’s into Ozzy Osbourne or Van Halen. You may know someone who’s pretty metal, but that person is probably an absolute creampuff compared with the heavy metal planet recently discovered by German scientists.

The planet, designated GJ367b, is an exoplanet, a planet orbiting a star beyond our solar system. It orbits a red dwarf star some 31 light-years from Earth in the southern constellation Vela, the Sails. One light-year is this distance light travels in one year, about 5.88 trillion miles (9.46 trillion kilometers).

At about 3/4 the size of Earth, GJ367b is the smallest exoplanet yet discovered. But, that does not mean that it is a lightweight. The exoplanet has a density of 8 grams per cubic centimeter, compared with about 5.5  grams per cubic centimeter for Earth. This extreme density suggests that GJ367b is the most metallic planet yet discovered. It probably consists mostly of an iron core, perhaps surrounded by a thin layer of rock.

The planet’s density is not its only extreme characteristic. The planet orbits extremely close to its parent star, whipping around the red dwarf every eight hours. If you lived on GJ367b, you might be able to celebrate your birthday about three times each Earth day. You probably wouldn’t like the weather, though. Daytime temperatures reach a sizzling 1500 °C (2700 °F). That’s almost hot enough to melt the planet’s metal. In fact, GJ367b may have an atmosphere composed of evaporated rock.

That scientists were able to learn so much about such a small planet shows just how far the hunt for exoplanets has advanced. Scientists discovered GJ367b using the Transiting Exoplanet Sky Survey (TESS) telescope, announcing the discovery in December. The TESS telescope identifies exoplanets by measuring changes in a star’s light as an orbiting planet transits (passes in front of) it. Scientists hope to learn even more about this heavy metal world with the launch of the James Webb Space Telescope.

January 8, 2020

Late last year, on Dec. 18, 2019, the European Space Agency (ESA) launched the CHEOPS telescope into space, where it will study the composition of exoplanets. Exoplanets, or extrasolar planets, orbit stars other than our sun. The CHEOPS telescope was launched aboard a Russian-made Soyuz rocket from the Guiana Space Center on the northern coast of South America. CHEOPS—pronounced KAY ops—is an acronym for Characterizing Exoplanets Satellite. If the acronym sounds familiar, Cheops was also the Greek name of the ancient Egyptian king Khufu, who constructed the Great Pyramid at Giza.

A Soyuz rocket carrying the ESA’s CHEOPS telescope lifts off from the Guiana Space Center on Dec.18, 2019. Credit: ESA/S. Corvaja

CHEOPS is small for a satellite, measuring just 5 feet (1.5 meters) long. The craft turns within a polar orbit that allows it to fly between night and day. Its back, covered in solar panels, receives continuous sunshine, while the telescope and camera on the other side is always peering into dark, sunless, and limitless space.

This artist’s impression shows CHEOPS with its back to the sun and the telescope pointed into dark space. Credit: ESA/C. Carreau

The CHEOPS mission is not to discover new exoplanets, but rather to learn more about the exoplanets we already know exist. CHEOPS will study exoplanets larger than our own Earth but smaller than the planet Neptune. Scientists want to know if these intermediate sized exoplanets are more like “super-Earths”—large rocky worlds—or “mini-Neptunes”—small gas giants. By studying an exoplanet’s atmosphere, diameter, mass, and other properties, CHEOPS can determine its composition and whether or not it might be able to support life. Astronomers have discovered over 4,000 exoplanets so far, but there are likely hundreds of billions more to be found.

CHEOPS will use the transit method to study exoplanets. It will aim its camera at a star and capture periodic dips in the star’s light output. These dips occur when an exoplanet passes in front of—or transits—a star in relation to CHEOPS’s point of view.

CHEOPS is a stepping stone between the first exoplanet observatories, such as Kepler and COROT, and the powerful observatories of the near future. The United States National Aeronautics and Space Administration (NASA) James Webb Space Telescope (JWST), scheduled for launch in 2021, will be able to determine the gases present in the atmospheres of some exoplanets and even record low detail images of those gases. The European Southern Observatory’s Extremely Large Telescope (ELT) will also be able to image rocky exoplanets and characterize their atmospheres after it is completed in 2025. The ELT is a ground-based observatory being built in the Atacama Desert of northern Chile. Kepler and COROT prepared the way for CHEOPS, and the JWST and ELT will further examine the most promising CHEOPS targets as scientists continue the hunt for extraterrestrial life.

May 11, 2016

Yesterday, May 10, we met over a thousand of Earth’s neighbors for the first time. Princeton University researcher Timothy Morton and a team of other scientists analyzed data returned by the U.S. National Aeronautics and Space Administration (NASA) satellite Kepler and detected over 1,200 more planets orbiting other stars, nearly double the amount previously known. The group announced the discoveries in a NASA press conference and published their results in The Astrophysical Journal.

The space telescope Kepler (Credit: NASA/Kepler mission/Wendy Stenzel)

Kepler is a space-based telescope originally designed to search for Earth-sized planets orbiting sunlike stars. Scientists refer to planets beyond our solar system as extrasolar planets or exoplanets. The telescope watched many stars simultaneously for small changes in brightness that might be caused by a passing planet. Kepler’s main goal was to find small, rocky planets—called terrestrial (Earthlike) planets—that orbit within their star’s habitable zone. In this region, temperatures allow for the existence of liquid water, which many scientists think is essential for life. The mission also helped scientists understand the variety of planetary systems that exist around sunlike stars. Kepler still hunts for planets today, albeit with a modified mission due to hardware failure on the craft.

Morton and his team developed a method to statistically analyze the likelihood that a promising return from Kepler could be caused by something other than an exoplanet, such as another star. If the probability of such a false positive was less than 1 percent, then the team reasoned that the result came from an exoplanet. Rather than use new observations, the team looked at over 4,000 objects of interest previously identified by the telescope. Of those objects, 1,284 were confirmed to be exoplanets (not counting the 984 already confirmed by other methods) and 428 were deemed false positives.

The new method will likely revolutionize the search for exoplanets. Before this study, astronomers have had to manually confirm all promising results returned by Kepler using Earth-based observatories, an expensive, time-consuming process. Now, they can use the Morton team’s method as a first pass, automatically confirming the most likely signals as exoplanets and ruling out the least likely ones. They can then spend their valuable research time on determining whether the trickier signals were caused by orbiting exoplanets.

Of the 1,200 newly discovered exoplanets, over 500 could potentially be rocky planets like Earth and Mars. Of these, nine orbit in their star’s habitable zone. In the future, astronomers will use even more powerful telescopes to study these exoplanets to try to answer one of astronomy’s greatest questions: are we alone in the universe, or is there other life out there?