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.

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.

March 1, 2017

On February 22, astronomers announced the discovery of a remarkable planetary system orbiting a relatively nearby star. Planets outside the solar system are called extrasolar planets or exoplanets. The new system has a whopping seven planets, many of which might host conditions favorable for life. The finding was published in the journal Nature.

This artist’s concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances.
Credit: NASA/JPL-Caltech

The system is located some 40 light-years away in the constellation Aquarius, the Water Bearer. One light-year is the distance that light travels in a vacuum in a year, about 5.88 trillion miles (9.46 trillion kilometers). The planets orbit a star called TRAPPIST-1, named in honor of the telescope used in the discovery. TRAPPIST stands for Transiting Planets and Planetesimals Small Telescope. It is a robotic telescope in Chile funded by Belgium. In May 2016, TRAPPIST detected three planets orbiting a type of small, relatively cool star called a red dwarf. In September, the Spitzer Space Telescope, operated by the United States National Aeronautics and Space Administration (NASA), began monitoring the system. With the help of NASA’s Hubble Space Telescope and other ground-based telescope systems, Spitzer confirmed the existence of two of the planets. But Spitzer determined that the third signal detected by TRAPPIST actually came from four planets, not one. Later, the telescope observed traces of a seventh, even more distant, exoplanet.

Even this farthest exoplanet orbits closer to TRAPPIST-1 than Mercury does to the sun, at a distance of only about 5.6 million miles (9.0 million kilometers). For comparison, Earth orbits about 93 million miles (150 million kilometers) from the sun. Because red dwarfs are much smaller and cooler than the sun, however, three of the planets orbit within a region that should be neither too hot nor too cold for liquid water to exist on their surfaces. Most scientists consider liquid water essential for life, so such a region around a star is known as its habitable zone.

The planetary system’s compact size would provide spectacular views only imagined in science fiction. The star TRAPPIST-1 would appear three times as large as the sun does on Earth, bathing the planets with a dim, pinkish light. Because the exoplanets are so close together, an observer standing on one planet could clearly see the other six. Neighboring planets would sometimes appear larger than does the moon in Earth’s sky.

Follow-up studies are already underway. NASA’s renowned planet-hunting satellite Kepler is currently examining the system. All seven planets are about the size of Earth, but Kepler will more precisely calculate their sizes and possibly find more planets. Spitzer has already confirmed that two of the planets are rocky worlds, rather than gaseous planets like Neptune. But Spitzer will continue to examine the system to learn more about the planets’ masses and compositions. In 2018, NASA plans to launch the James Webb Space Telescope. This powerful satellite should be able to detect if any of the exoplanets have atmospheres and determine their compositions. If the atmosphere contains compounds such as methane, oxygen, and ozone, it would be a strong indication that life exists there.

Other Behind the Headlines posts:

• Ten to 30 Alien Planets for Every Person on Earth? (Jan. 13, 2012)
• Amateur Astronomers Discover a Planet with Four Suns (Oct. 17, 2012)
• New Exoplanet Candidates from Ailing Kepler Spacecraft (June 20, 2013)
• Kepler Space Telescope Goes Dark–For Now (Aug. 16, 2013)
• Exoplanet Bonanza from Kepler (Feb. 27, 2014)
• First “Earth-Cousin” Found by Kepler Space Telescope (May 1, 2014)
• “Hello, Aliens? Are You Out There?” (Feb. 13, 2015)
• New Planetary Neighbors (May 11, 2016)
• The Pale Red Dot: Proxima b (Aug. 31, 2016)
  

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?

May 1, 2014

The first Earthlike planet orbiting in the “Goldilocks zone” of a star other than the sun has been found by scientists analyzing data from the Kepler space telescope. The Goldilocks zone is the region around a star in which liquid water can exist. That is, the planet, called Kepler-186f, is not too hot to cause water to evaporate or too cold to cause it to freeze. Scientists believe the most likely place to find life as we know it is on planets or moons that can support liquid water.

“Being in the habitable zone does not mean we know this planet is habitable,” commented Thomas Barclay, a research scientist at the Bay Area Environmental Research Institute at Ames, and co-author of the paper. “The temperature on the planet is strongly dependent on what kind of atmosphere the planet has. Kepler-186f can be thought of as an Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth.”

The newly discovered extrasolar planet is just 10 percent larger than Earth. It orbits a type of star called a red dwarf. Smaller and cooler than the sun, red dwarfs are also the most abundant type of star in our galaxy, the Milky Way. The star, called Kepler-186, is about half the size and mass of the sun. It is about 500 light-years from Earth in the constellation Cygnus. Four other planets orbit Kepler-186.

Extrasolar planets orbit stars other than the sun. This infrared image of the star HR 8799 and its three orbiting planets was taken in 2008. The arrows indicate the directions of the planets’ orbits. (C. Marois et. al/NCR Canada)

Since the first planets outside the solar system were discovered in the 1990′s, scientists have hoped to find a planet that could support life. Because of the limited ability of the instruments used to search for extrasolar planets, almost all of the early planets discovered were very large and orbited very close to their host star. However, Kepler, which was constructed specifically to hunt for exoplanets, expanded the number of known extrasolar planets from just a few hundred to thousands.

To find extrasolar planets, Kepler examined some 150,000 stars in one small section of the galaxy using a technique called the transit method. Away from the distorting interference of Earth’s atmosphere, almost all stars shine at a consistent brightness. But a planet or other body passing in front of star will block some of the star’s light. Kepler looked for this dip in brightness. Unlike most of the first exoplanets discovered, the planets spotted by Kepler are of many sizes and distances from their home star.

Additional World Book articles:

• Kepler, Johannes
• Life (The search for life on other planets)
• In Search of Other Worlds (a Special Report)

February 27, 2014

The number of known exoplanets in the Milky Way Galaxy has nearly doubled, thanks to a new method of confirming planet candidates discovered by the Kepler space telescope. Mission control officials at NASA‘s Ames Research Center in Moffett Field, California, announced that they had identified 715 new planets, which raises the total number of alien planets to some 1,700. The research has also significantly increased the number of smaller exoplanets. About 95 percent of the new planets are smaller than Neptune, which is about 17 times as massive as Earth. Many exoplanets found previously were at least as massive as Jupiter, which is 318 times as massive as Earth. All of the newly discovered planets orbit one of 305 stars in a multiplanet system like the solar system.

Although Kepler’s original planet-hunting days are over–the telescope has been nonoperational since May 2013–mission scientists are still on the job. The new exoplanets were found in data collected during the telescope’s first two years in orbit, from 2009 to 2011. Kepler’s main mission was to search one section of the Milky Way for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Although Kepler searched over 150,000 stars for signs of orbiting planets, its search zone was actually quite small. Scientists estimate that the Milky Way alone has up to 200 billion stars.

All of the newly identified planets orbit a star in a multiplanet system, like the solar system. (NASA)

The new method of identifying planets is called validation by multiplicity. This method, which relies on the logic of probability, allows scientists to identify exoplanets in groups, rather than one by one. NASA officials compared the technique to the behavior of lions and lionesses living on the savannah. “In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates,” the agency explained in a press release. “If you see two of the big cats it could be a lion (star) and a lioness (planet) or two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride (star and its planets).”

Additional World Book articles:

• Binary star
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)

June 20, 2013

Kepler space telescope has turned up another 503 potential exoplanets, mission control officials at NASA‘s Ames Research Center in Moffett Field, California, announced recently. This brings to 3,216 the number of planet candidates detected by the orbiting probe since its launch in March 2009. Further investigation has confirmed that 132 of those objects are, in fact, extrasolar planets.

Unfortunately, Kepler’s planet-hunting days may be over. Since mid-May, Kepler has been nonoperational because of an equipment malfunction. At that time, mission controllers discovered that one of the craft’s reaction wheels was not working. These devices keep the craft aimed precisely in the right direction. Kepler, which needs three reaction wheels to operate properly, now has only two. Originally, the telescope carried a spare, but that device was put into service when another of the reaction wheels quit working in 2012.

A planet about the size of Saturn, known as Kepler-35b, orbits a binary star (pair of stars) in an artist's illustration of a planetary system discovered by Kepler.

Kepler’s main mission is to search one section of the Milky Way Galaxy for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Kepler has searched over 150,000 stars for signs of orbiting planets.

Additional World Book articles:

• Binary star
• Planet
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)