October 11, 2019

Every year in the first week of October, the Nobel Foundation in Sweden awards Nobel Prizes to artists, economists, scientists, and peace workers who—in keeping with the vision of the Swedish chemist and industrialist Alfred Nobel—have conferred the greatest benefit to humankind. Today, World Book looks at the first three prizes, in the scientific categories of physiology or medicine, physics, and chemistry.

Nobel Prize medal (Credit: Nobel Foundation)

On Monday, October 7, 2019, the Nobel Prize in physiology or medicine was given jointly to the scientists William G. Kaelin, Jr., Sir Peter J. Ratcliffe, and Gregg L. Semenza for their work showing how cells adapt to the changing availability of oxygen. Kaelin, Ratcliffe, and Semenza identified the molecular machinery that allows cells to respond to changes in oxygen levels. Their discoveries offer promising new strategies in the treatment of such diseases and maladies as anemia, cancer, heart attacks, and strokes.

William G. Kaelin, Jr., was born in New York and is a professor of medicine at the Dana-Farber Cancer Institute in Boston and at the Brigham and Women’s Hospital at Harvard Medical School. Peter J. Ratcliffe of the United Kingdom is the director of clinical research at the Francis Crick Institute in London and director of the Target Discovery Institute at the University of Oxford. Gregg L. Semenza, also from New York, is a professor of genetic medicine at Johns Hopkins University in Baltimore, Maryland.

On Tuesday, October 8, the Nobel Foundation announced the prize for physics had been awarded to the Canadian-American cosmologist James Peebles and to the Swiss scientists Michel Mayor and Didier Queloz for their work on explaining the evolution of the universe and for discovering distant exoplanets (planets beyond our solar system). Among other things, Peebles theorized how matter in the young universe swirled into galaxies. In 1995, Mayor and Queloz discovered an exoplanet orbiting a star elsewhere in our home galaxy, the Milky Way, enhancing the study of planetary systems beyond our own that could support life.

James Peebles is the Albert Einstein professor of science at Princeton University in New Jersey. Michel Mayor is an astrophysicist and professor emeritus of astronomy at the University of Geneva. Didier Queloz is a professor of physics at the Cavendish Laboratory at Cambridge University, and at the University of Geneva.

On Wednesday, October 9, the Nobel Foundation announced that John B. Goodenough of the United States, M. Stanley Whittingham of the United Kingdom, and Akira Yoshino of Japan would share the prize for chemistry for developing and refining rechargeable lithium-ion batteries. The lightweight, rechargeable, and powerful batteries are used in everything from mobile phones to laptop computers and electric vehicles. They can also store great amounts of energy from solar and wind power, further enabling the possibility of a fossil fuel-free future.

At 97 years old, John B. Goodenough is the oldest ever recipient of the Nobel Prize. He is currently the Virginia H. Cockrell Chair in Engineering at the University of Texas at Austin. M. Stanley Whittingham is a distinguished professor at Binghamton University, State University of New York. Akira Yoshino is an honorary fellow at Tokyo’s Asahi Kasei Corporation and a professor at Meijo University in Nagoya, Japan.

September 13, 2019

Last week, on September 6, an up-and-coming space agency fell just short of its goal. About 1 mile (1.5 kilometers) above the moon’s surface, the India Space Research Organization (ISRO) lander Vikram deviated from its landing course and disappeared from radio contact. Vikram was to be the crowning stage of Chandrayaan-2 (Mooncraft-2), ISRO’s second lunar mission.

This artist’s depiction shows Chandrayaan-2′s lunar lander, Vikram, approaching the moon. Credit: © Raymond Cassel, Shutterstock

India was endeavoring to become the fourth country to make a soft landing (a landing that does not destroy the craft) on the surface of the moon, after the United States, the former Soviet Union, and China. Vikram would have been the first lander near the moon’s south pole, a region full of water ice and other minerals that could one day be the site of a permanent base. Vikram would have deployed a rover to explore the landing site. The Chandrayaan-2 orbiter, which had launched Vikram, located the lander on the surface of the moon a few days after its disappearance. ISRO reported that Vikram had apparently made a “hard landing,” and the lander did not respond to contact attempts.

Before the recent failure, ISRO had been riding a wave of success. In 2008, the agency deployed its first lunar satellite, Chandrayaan-1. Chandrayaan-1 mapped the moon’s surface for about a year. The satellite also released a hard lander that impacted the lunar surface. In 2013, ISRO launched the Mars Orbiter Mission, called Mangalyaan (Marscraft). The satellite overcame a minor engine failure to reach Martian orbit in September 2014.

ISRO’s failed soft landing on the moon comes on the heels of another prominent lunar failure. In April 2019, the lander Beresheet (In the Beginning), developed by the Israeli company SpaceIL, slammed into the moon when its main engine cut out unexpectedly. SpaceIL had hoped to become the first private company to place a lander on the moon’s surface. It had been one of the competitors for the Google Lunar X Prize. The contest would have awarded $20 million to the first company to achieve a soft landing on the moon. But none of the competitors attempted a landing, even after several deadline extensions, so the prize was withdrawn. The Israeli project cost about $100 million, a fraction of what a similar mission by the United States National Aeronautics and Space Administration (NASA) would have cost, but it took greater risks and ultimately failed.

The process of landing is the most dangerous phase of a lander’s mission. Many different systems must work perfectly for the lander to bring itself to a halt on the surface. Any malfunction is usually catastrophic. At other points in a mission, such as in transit to or in orbit around another body, engineers have plenty of time to identify and work around problems with a spacecraft. But this cannot be done in the time-sensitive environment of landing.

April 12, 2019

On Wednesday, April 10, scientists with the Event Horizon Telescope (EHT) team published a photograph of the invisible—or at least the area around the invisible. The EHT captured an image of an event horizon (the surface of a black hole) for the first time. The EHT is a global collection of radio telescopes that work together as one giant telescope. As its name implies, the EHT was created to observe an event horizon, a mission that has at last been accomplished. The EHT began its quest in 2006, and has since greatly expanded its network.

On April 10, 2019, scientists with the Event Horizon Telescope team released this first ever image of a black hole—or at least the event horizon surrounding a black hole. Credit: EHT Collaboration/ESO

A black hole is a region of space whose gravitational force is so strong that nothing can escape from it, not even light. The event horizon is the “point of no return” for a black hole: Anything that crosses this horizon is sucked into the black hole forever. Because light cannot escape a black hole, all black holes are invisible and cannot be directly photographed. But physicists predicted that an image of the area surrounding a black hole would reveal a halo of high-energy matter and radiation around a circular shadow.

The boxed area in this image shows the black hole at the core of the M87 galaxy.
Credit: NASA/CXC/Villanova University/J. Neilsen

Heino Falcke, a German astrophysicist now at Radboud University in the Netherlands, discovered that this halo would emit radio waves detectable on Earth. He helped found the EHT to photograph event horizons through these radio waves. The collection of ground-based radio telescopes participating in the EHT project stretches from Hawaii to Europe and all the way south to Antarctica. Several dozen of the world’s leading observatories and universities contribute to the project.

The EHT observed a supermassive black hole at the center of a huge galaxy called Messier 87, or M87, some 55 million lightyears from Earth. A supermassive black hole is a type of black hole with a mass from 1 million to billions of times the mass of our solar system’s  sun. Many galaxies have a supermassive black hole near their centers. The supermassive black hole at the center of M87 is one of the largest ever discovered, some 6.5 billion times the mass of our sun. The diameter of its event horizon is roughly the size of our entire solar system.

It took an enormous effort to produce the image released this April. Two years ago, in April 2017, eight radio telescopes of the EHT simultaneously observed the M87 black hole for 10 days. The observations had to be precisely synchronized (scheduled) by atomic clock to combine and match up their images. In total, the observatories collected more than 5 petabytes of data, equal to the text of 88 million print editions of the World Book Encyclopedia. (A petabyte is 1,000 terabytes. A terabyte is a measure of computer information or memory equal to about 1 trillion bytes). This was so much information that it was faster to fly the data by airplane between the laboratories that analyzed the data than to transfer it over the internet. An American computer scientist named Katie Bouman developed a special algorithm to combine the data from the eight telescopes into a single image.

Just like the detection of gravitational waves three years ago, this work promises to revolutionize astronomy. Each year, new observatories join the EHT, strengthening its resolution (image sharpness). The EHT has observed black holes other than the one at the core of M87, including the one at the center of our own Milky Way galaxy, Sagittarius A*. EHT scientists think they will be able to produce an image of that event horizon soon. Scientists might also be able to sharpen the image of the M87 black hole in the coming months.

August 9, 2018

Astronomers at the Carnegie Institution for Science in Washington, D.C., recently discovered a new batch of moons orbiting Jupiter, the largest planet in our solar system. The new group of 12 moons—which bring’s Jupiter’s moon total to an astounding 79—includes an oddball, however: one is going “the wrong way.”

Ganymede is the largest of Jupiter’s moons. Astronomers recently found 12 new and much smaller moons orbiting Jupiter, bringing the planet’s solar system-leading total to 79. Credit: NASA

Led by astronomer Scott Sheppard, the Carnegie team had been looking for “Planet Nine,” a hypothetical major planet in the Kuiper belt, a band of objects in the outer regions of our solar system. In March 2017, Jupiter moved into the astronomers’ search area. The telescope the team was using was uniquely suited for finding small or faraway objects: it could block out light from larger nearby heavenly bodies. Sheppard took time away from Planet Nine to poke around Jupiter, and his curiosity was rewarded with the discovery of 12 new moons. The first two bodies orbit close to Jupiter, and were quickly confirmed as moons. The other 10 skew farther out from the mighty planet and were not announced as moons until July 17, 2018.

Callisto, another large moon of Jupiter, has a diameter of almost 3,000 miles (4,800 kilometers), many times the size of Jupter’s newly discovered moons. Credit: NASA

The new moons are small, some less than a mile (several hundred meters) in diameter. Their orbital characteristics tell scientists a lot about them. Nine of the 10 newest moons orbit in retrograde, meaning in the opposite direction of the rotation of Jupiter. This leads the astronomers to think they formed from objects captured by Jupiter’s hefty gravitational pull. Most moons form with their parent planet and have prograde orbits, meaning they orbit in the same direction as the host planet. But captured objects often have retrograde orbits. Sheppard’s team thinks these nine moons are parts of captured objects broken up by collisions over millions or billions of years.

The tenth of the newest moons, however—which Sheppard calls Valetudo, a great-granddaughter of the Roman mythological god Jupiter—travels in a prograde orbit. It dives through the orbits of the other nine moons, putting it on an eventual collision course. When moon finally meets moon, the impact will either destroy the bodies or make them even smaller.

January 4, 2018

Astronomers at the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) observatory at the summit of the dormant volcano Haleakala in Hawaii recently detected a mysterious object speeding through our solar system. This by itself was not unusual. One of the main missions of the Pan-STARRS project is to detect near-Earth objects in space that could possibly collide with our planet. However, researchers quickly realized that this space rock did not move like the asteroids and comets they routinely encounter. Astronomers quickly learned that this object was a visitor from beyond our solar system—the first interstellar asteroid ever observed.

This artist’s impression shows `Oumuamua the interstellar asteroid. Credit: ESO/M. Kornmesser

Scientists at NASA’s Center for Near-Earth Object Studies (CNEOS) in Pasadena, California, determined the object was an asteroid, now officially designated as A/2017 UI. Its composition and its unusual path through our solar system showed it was from outer space. Researchers at Pan-STARRS named the asteroid `Oumuamua, which is a Hawaiian word that means messenger.

`Oumuamua appeared only as a faint spot on the Pan-STARRS telescope as it zipped through our solar system at up to 196,000 miles per hour (355,431 kilometers per hour). But later images from other observatories showed that `Oumuamua was 1,300 feet (400 meters) long and about 10 times as long as it was wide, and spinning rapidly. `Oumuamua’s elongated cigar shape is a rarity among space objects. Most asteroids are compact and lumpy after having been battered by countless random collisions with other objects on their long journeys through space. `Oumuamua is also dark red, a color created as its rocky surface was bombarded by high-energy cosmic rays for millions or perhaps billions of years. A/2017 UI traveled in a retrograde orbit (opposite that of the planets) around the sun on its way toward the constellation Pegasus.

Some researchers suggested that `Oumuamua was more than just an interstellar oddity, and that it was perhaps a message from a distant alien civilization. They pointed out that “a cigar or needle shape is the most likely architecture for an interstellar spacecraft, since this would minimize friction and damage from interstellar gas and dust.” Several groups scanned `Oumuamua for alien radio transmissions, including researchers at the Green Bank Telescope in West Virginia, the William Herschel Telescope in Spain’s Canary Islands, and the European Southern Observatory’s Very Large Telescope in Chile. No alien messages were found, and the consensus was that `Oumuamua was odd but completely natural. Scientists suspect that the so-called “space cucumber” has an icy core—as do most comets—beneath its hard carbonic shell.

October 27, 2017

On August 17, a faint chirp from instruments at the Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States set off a mad scramble in observatories around the world to catch a glimpse of something never before observed: the cosmic collision of two neutron stars (an event called a kilonova). In the extraordinary events that followed, the signal initially detected by LIGO was picked up by as many as 70 Earth and space-based telescopes, providing a remarkably detailed picture of one of the most violent, cataclysmic events in the universe. The significant observation was announced by LIGO scientists on October 16.

This artist’s representation shows two neutron stars colliding, a cataclysmic event known as a kilonova. Astronomers witnessed a kilonova for the first time on Aug. 17, 2017. Credit: © Robin Dienel, Carnegie Institution for Science

LIGO is a pair of facilities built to detect gravitational waves, types of radiation created by the movement of matter through space. LIGO consists of three detectors—two near Richland, Washington, and one in Livingston, Louisiana. The LIGO detectors are designed to find gravitational waves created by such violent cosmic events as collisions between black holes, objects with gravitational forces so strong that nothing can escape them. The first gravitational waves were detected by LIGO on Sept. 14, 2015. The waves were generated by colliding black holes billions of light-years away from Earth.

The recent kilonova observation was significant for several reasons. It was the first time LIGO had detected the weaker gravitational wave generated by a collision between neutron stars, the smallest and densest types of known stars. The kilonova signal was also detected at the European Gravitational Observatory (EGO) interferometer, called Virgo, located near Pisa, Italy. With data from multiple observatories, astronomers were able to determine the starting point of the gravitational wave. As word of the signal spread, dozens of other telescopes on Earth and in space were trained on the location to detect other kinds of energy from the cosmic collision. Astronomers were able to observe the resulting fireball in visible light from telescopes. Other telescopes recorded the gamma rays, radio waves, ultraviolet rays, and X rays generated from the collision. It was the first time such a cosmic event had been seen by astronomers, witnessed in wavelengths across the electromagnetic spectrum.

The gravitational wave signal detected by LIGO came from two neutron stars orbiting each other about 130 million light-years away. Each neutron star had slightly more mass than our own sun, but all that mass was crammed into a sphere only about 20 miles (32 kilometers) in diameter. The doomed stars circled each other 30 times a second as they neared to within about 200 miles (320 kilometers) of each other. The orbit increased to about 2,000 times per second just before they collided in an impact that released a tremendous burst of energy. What happened next is uncertain. Scientists think that after the stars collided they may have formed a heavier neutron star or collapsed into a black hole.

Some telescopes were able to spot a faint flash in the night sky. That flash was generated in the fireball of the collision as radioactive heavy chemical elements were blown away at nearly one-fifth the speed of light. Scientists had long theorized that such catastrophic celestial collisions were necessary to forge heavy chemical elements, such as gold, platinum, and uranium. The spectrum of light coming from the observed collision of neutron stars helped confirm this theory. They calculated that the explosion created about 100 times the mass of Earth in gold. Scientists now believe such collisions of neutron stars are common in the universe. They believe that most heavy element atoms in the universe are formed in such kilonova events.

October 13, 2017

Yesterday, on Thursday, October 12, a house-sized asteroid buzzed Earth, passing within the orbit of the moon and uncomfortably close to hundreds of orbiting communications and weather satellites. Officials at the United States National Aeronautics and Space Administration (NASA) insisted there was never any danger of a collision. They first discovered the space rock, called 2012 TC4, five years ago and have been following it ever since. The close shave by TC4 posed no threat, but it did provide NASA with an opportunity to test systems that detect orbiting objects and to develop plans to respond to a potentially catastrophic impact.

This illustration depicts the safe flyby of asteroid 2012 TC4 as it passes by Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Technicians from NASA and the European Space Agency’s Near-Earth Object program measured TC4 to be about 50 to 100 feet (15 to 30 meters) in diameter. It is traveling through space at about 16,000 miles (25,800 kilometers) per hour. At its closest, it will pass by southern Australia a mere 27,300 miles (44,000 kilometers) above the surface, just beyond the 22,400-mile (36,000-kilometer) plane of Earth’s most remote geosynchronous (fixed-orbit) satellites.

This illustration shows the path of asteroid 2012 TC4 as it passes within the moon’s orbit of Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Technicians at the space agencies determined that TC4 makes an elongated orbit around the sun every 609 days. They calculate that TC4 will pass close to Earth again in 2050 and 2079. For now, the calculations show that there is no danger of TC4 striking Earth. However, should TC4’s orbit be deflected by even a small amount, the chances of an impact could increase. Officials say there is a 1-in-750 chance that TC4 could strike Earth sometime after 2050. Those are long odds, to be sure, but NASA scientists continue to track TC4 nonetheless, as well as 12 other asteroids with a greater risk of impact.

Scientists know that Earth has been struck by asteroids and meteors repeatedly over the past 4.5 billion years. NASA experts estimate that objects the size of TC4 fly past Earth about three times per year. They point out, however, that the chances of a serious asteroid impact anytime soon are remote. But even the experts are occasionally taken by surprise. The Chelyabinsk meteor, a chunk of rock similar in size to TC4, fell into Earth’s atmosphere and exploded over the city of Chelyabinsk in southeastern Russia on Feb. 15, 2013. The impact frightened thousands of people and took NASA and other space-observing agencies by surprise. They did not see that one coming.

September 19, 2017

Cassini is gone. For more than 13 years, the space probe revealed the secrets of Saturn. It ended its mission in a blaze of glory on Friday, September 15, crashing into the planet it had studied for so long.

Cassini photographed Saturn illuminated from behind by the sun. This panoramic view was created by combining 165 images taken by Cassini’s wide-angle camera over nearly three hours on Sept. 15, 2006. Credit: NASA/JPL/Space Science Institute

Cassini was a spacecraft sent to Saturn to study the planet and its rings and satellites. The United States National Aeronautics and Space Administration (NASA) launched Cassini on Oct. 15, 1997. The craft began orbiting Saturn on July 1, 2004. Engineers and scientists at NASA’s Jet Propulsion Laboratory built Cassini. The Italian Space Agency provided a large antenna and several other elements of the spacecraft. The craft was named for the Italian-born French astronomer Giovanni Domenico Cassini, who made major discoveries about Saturn in the late 1600’s.

Cassini regularly provided spectacular revelations about the Saturn system. It discovered lakes of liquid hydrocarbons on Saturn’s moon Titan, the first lakes observed outside of Earth. The probe also discovered vertical structures in Saturn’s rings, structures rising high above the equatorial plane.

This artist’s conception shows Cassini diving between Saturn and the planet’s innermost ring. Credit: NASA/JPL-Caltech

Perhaps its most important discovery, however, was the detection of favorable conditions for life within the icy moon Enceladus. Measurements from Cassini revealed that a global ocean of liquid water lies beneath Enceladus’s icy crust. Furthermore, the probe imaged—and even flew through—plumes of ice crystals created by geysers at the moon’s surface. Cassini determined that these geysers were powered by hydrothermal activity in the ocean floor and that the plume contained hydrocarbon compounds. With these discoveries, Enceladus leapt to the top of the list of other places in the solar system where life might have developed.

This photograph of Saturn’s northern hemisphere was among the last taken by NASA’s Cassini spacecraft on Sept. 13, 2017. Credit: NASA/JPL-Caltech/Space Science Institute

Nearing 20 years in space, Cassini was running low on fuel. Mission planners directed Cassini to hurtle into Saturn’s clouds. Scientists were concerned that if the probe ran out of propellant and orbited uncontrollably within the Saturn system, it could have crashed into Titan or Enceladus. If this had occurred, any microbes from Earth surviving on Cassini’s surface could have contaminated these moons. Cassini sent back data and images right up to its final plunge into Saturn’s atmosphere.

Saturn will be without a visiting spacecraft from Earth for some time. With NASA trying to develop both the James Webb Space Telescope and the Space Launch System within its tight budget, planetary exploration has fallen by the wayside. Such probes take at least 5 to 10 years to plan and build. Then, it would take another six years or so for a spacecraft to reach Saturn. Therefore, any follow-up probe to Saturn would be at least a dozen years in the future.

Cassini may be gone, but its impact on the study of Saturn will continue to be felt for many years. Over 3,000 scientific papers have already been published based on data gathered by Cassini, and more are on the way. Current and future scientists will be using data gathered by Cassini to make new discoveries about the ringed planet for decades to come.

March 2, 2017

Time operates on an epic scale among the stars and galaxies of outer space. Some stars exist for millions of years but then suddenly undergo rapid changes and explode within months. In October 2013, an international team of scientists led by Ofer Yaron, an astrophysicist at the Weizmann Institute of Science in Israel, detected and studied a supernova that occurred in a distant galaxy within three hours of the explosion’s light first reaching Earth. Thanks to the timely observations, the team was able to learn a lot about the star and the explosion that consumed it. The team published its findings in February 2017 in the journal Nature Physics.

Supernova 1604 was a star that exploded in our own galaxy. The supernova blasted off the shell of gas and dust seen in this false-color composite image. The shell continues to expand at around 2,000 kilometers (1,200 miles) per second. The German astronomer Johannes Kepler observed the explosion in 1604. Credit: NASA/ESA/JHU/R. Sankrit & W. Blair

A supernova is an exploding star that can become billions of times as bright as our sun before gradually fading from view. At its brightest, a supernova may outshine an entire galaxy. The explosion throws a large cloud of gas into space at speeds of up to 10 percent of the speed of light, which is 186,282 miles (299,792 kilometers) per second. The mass of the expelled material may exceed 10 times the sun’s mass. Most supernovae reach their peak brightness in one to three weeks and shine intensely for several months.

A red supergiant called V838 Monocerotis glows at the center of a dust cloud in this photograph taken by the Hubble Space Telescope. In 2002, the star gave off a brilliant flash of light, becoming 600,000 times as bright as the sun. The flash illuminated dust thrown off the star during a previous outburst. Credit: NASA/ESA/H.E. Bond (STScI)

The exploding star examined by Yaron and his associates was a red supergiant. Such stars are dozens of times larger than our sun, which is a main sequence star or yellow dwarf. Red supergiants have relatively short life spans, however, existing for “only” millions of years. In contrast, our sun is expected to live some 10 billion years. All stars produce energy through the process of nuclear fusion, a joining of two atomic nuclei (cores) to produce a larger nucleus. Fusion releases a huge amount of energy. Most stars fuse hydrogen or helium, but a supergiant quickly (over millions of years) burns through its fuel supply and begins to fuse heavier elements together in its core. At this point, a supergiant’s days are numbered. Each new level of fusion chips away at its core, slowly killing the star. At a critical point, the star quickly fuses its available silicon into iron. Once the core fills with iron, the star will collapse and rebound in an explosive supernova.

Click to view larger image
A huge star creates chemical elements by nuclear fusion, the joining of two atomic nuclei to make a larger nucleus. In the outermost shell, hydrogen nuclei fuse, creating helium. In the next shell, helium fuses to make carbon and oxygen. Fusion creates successively heavier elements in shells closer to the core, where iron is produced. The shells in this diagram are not drawn to scale. Credit: WORLD BOOK diagram

Based on the patterns of light emitted by the supernova in question, Yaron and the team discovered that the star had blown off a layer of material into space about a year before the explosion. They suspect that this layer has to do with a change in fusion fuel at the star’s core shortly before it went supernova. The transition itself was violent, setting off a chain reaction within the star that shot a layer of star matter into space ahead of the supernova.

The discovery was made with the help of an ever-improving array of automated survey telescopes. Such telescopes capture images of a certain portion of the night sky. A computer then compares the images against earlier pictures of the same section of sky, looking for changes. If it detects any, the computer alerts a human astronomer to investigate the findings.

Astronomers are eagerly awaiting the next supernova to occur in the Milky Way. They estimate that a supernova occurs once every 100 years or so in our galaxy, but they are not always visible to Earth-bound observers. The last local supernova seen on Earth occurred in 1604, when German astronomer Johannes Kepler observed what he thought was a new star in the night sky. The most recent intragalactic (within our galaxy) supernova occurred around 1900, but its light was obscured by dust. Scientists were only able to study it 100 years later with instruments such as the orbiting Chandra X-Ray Observatory and the National Radio Astronomy Observatory’s Very Large Array near Socorro, New Mexico. If we’re lucky enough for the next supernova to be close (but not too close), we can learn more about the largest stars and the brilliant ends of their lives.

August 31, 2016

On August 24, scientists from the European Southern Observatory (ESO) announced that they had discovered an extrasolar (beyond our solar system) planet, or exoplanet, that may harbor conditions favorable to life. This exoplanet, called Proxima b, orbits Proxima Centauri, the star closest to the sun. Astronomers have nicknamed Proxima b the “pale red dot,” a play on Earth’s appearance as a “pale blue dot” in a distant photo taken by the Voyager 1 space probe in 1990. Astronomers believe that Proxima Centauri, a red dwarf star, will cast its close-orbiting planet in a pale red glow. The search for a planet orbiting Proxima Centauri, which began just seven months ago, was dubbed the “Pale Red Dot” campaign.

This artist’s impression shows the red dwarf star Proxima Centauri, the closest star to our solar system, on the red horizon of Proxima b, a planet scientists think could support life. The double star Alpha Centauri AB appears to the upper right of Proxima Centauri. Credit: ESO/M. Kornmesser

Proxima Centauri is part of a three-star system called Alpha Centauri. Two of the stars, Centauri A and Centauri B, are roughly the size of the sun and orbit each other. Proxima Centauri is a much smaller red dwarf star and orbits the larger pair of stars every million years or so.

Proxima b (nicknamed the “pale red dot” by astronomers) and its orbit around Proxima Centauri are compared with the same region of our own solar system. Proxima Centauri is smaller and cooler than the sun, and Proxima b orbits much closer to its star than Mercury orbits the sun. A planet in the green habitable zone could possibly have liquid water, which could possibly support life. Credit: ESO/M. Kornmesser/G. Coleman

The newly discovered exoplanet, Proxima b, is at least 1.3 times the size of Earth. Its size indicates that it is probably a rocky planet, like Earth and Mars. It orbits Proxima every 11 Earth days (Mercury, the closest planet to the sun, completes a year every 88 Earth days). If Proxima Centauri were a star like our sun, the planet would be little more than a charred husk. But red dwarf stars are small and relatively cool. Consequently, it is possible that liquid water could exist on the exoplanet’s surface. Scientists call this region around a star, where temperatures are suitable for liquid water, its habitable zone. Liquid water is a necessary building block for life as we know it.

If red dwarf stars can harbor habitable worlds, then the odds that life exists elsewhere in the universe increase significantly. Red dwarfs make up about 70 percent of the stars in the universe. They also burn slowly and steadily, for up to 10 trillion years. In contrast, the sun has a stable lifespan of only 10 billion years. As a result, if favorable conditions exist, life could have countless chances to form over countless eons.

Astronomers still have a lot to learn about Proxima b and whether it can host life. It might lack an atmosphere or get bombarded by powerful X ray blasts from Proxima. The James Webb Space Telescope (JWST), to be launched in 2018, should answer some of these questions. It will be able to determine the exoplanet’s composition and whether it has an atmosphere. JWST will also gather more information on the planet’s size and makeup. Future space telescopes may even be powerful enough to see the “pale red dot” directly.

Most exoplanets are too far away to be explored by spacecraft from Earth. They orbit stars many light-years away. A light-year is the distance light travels in a year, or about 5.88 trillion miles (9.46 trillion kilometers). Nothing can travel faster than the speed of light. Proxima Centauri, however, is just 4.2 light-years away, tantalizingly close in astronomical terms. But the fastest spacecraft ever created have reached just tiny fractions of the speed of light. Using such technology, a traditional space probe would still take thousands of years to reach the system.

A private initiative called Breakthrough Starshot, however, has proposed launching a tiny spacecraft to the system that would take as little as 20 years to get there. The probe would be only a gram or two (the equivalent of less than an ounce on Earth) and be propelled by large Earth-based lasers to 20 percent of the speed of light. There are many technical hurdles to be overcome, however, and the group does not anticipate launching a probe for at least another 20 years, but there is hope that the planet could be explored close-up before 2100. Soon, we may get to say hello to our closest potential neighbor. Will it say hi back?