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So you think you found an exoplanet -- a planet around another star? It’s not as simple as pointing a telescope to the sky and looking for a planet that waves back. Scientists gather many observations and carefully analyze their data before they can be even somewhat sure that they’ve discovered new worlds.
Here are 10 things to know about finding and confirming exoplanets.
This is an illustration of the different elements in our exoplanet program, including ground-based observatories, like the W. M. Keck Observatory, and space-based observatories like Hubble, Spitzer, Kepler, TESS, James Webb Space Telescope, WFIRST and future missions.
The vast majority of planets around other stars have been found through the transit method so far. This technique involves monitoring the amount of light that a star gives off over time, and looking for dips in brightness that may indicate an orbiting planet passing in front of the star.
We have two specialized exoplanet-hunting telescopes scanning the sky for new planets right now -- Kepler and the Transiting Exoplanet Survey Satellite (TESS) -- and they both work this way. Other methods of finding exoplanets include radial velocity (looking for a “wobble” in a star's position caused by a planet’s gravity), direct imaging (blocking the light of the star to see the planet) and microlensing (watching for events where a star passes in front of another star, and the gravity of the first star acts as a lens).
Here’s more about finding exoplanets.
To find a planet, scientists need to get data from telescopes, whether those telescopes are in space or on the ground. But telescopes don’t capture photos of planets with nametags. Instead, telescopes designed for the transit method show us how brightly thousands of stars are shining over time. TESS, which launched in April and just began collecting science data, beams its stellar observations back to Earth through our Deep Space Network, and then scientists get to work.
Researchers combing through TESS data are looking for those transit events that could indicate planets around other stars. If the star’s light lessens by the same amount on a regular basis -- for example, every 10 days -- this may indicate a planet with an orbital period (or “year”) of 10 days. The standard requirement for planet candidates from TESS is at least two transits -- that is, two equal dips in brightness from the same star.
Not all dips in a star's brightness are caused by transiting planets. There may be another object -- such as a companion star, a group of asteroids, a cloud of dust or a failed star called a brown dwarf, that makes a regular trip around the target star. There could also be something funky going on with the telescope’s behavior, how it delivered the data, or other “artifacts” in data that just aren’t planets. Scientists must rule out all non-planet options to the best of their ability before moving forward.
Finding the same planet candidate using two different techniques is a strong sign that the planet exists, and is the standard for “confirming” a planet. That’s why a vast network of ground-based telescopes will be looking for the same planet candidates that TESS discovers. It is also possible that TESS will spot a planet candidate already detected by another telescope in the past. With these combined observations, the planet could then be confirmed. The first planet TESS discovered, Pi Mensae c, orbits a star previously observed with the radial-velocity method on the ground. Scientists compared the TESS data and the radial-velocity data from that star to confirm the presence of planet “c.”
Scientists using the radial-velocity detection method see a star’s wobble caused by a planet’s gravity, and can rule out other kinds of objects such as companion stars. Radial-velocity detection also allows scientists to calculate the mass of the planet.
Other space telescopes may also be used to help confirm exoplanets, characterize them and even discover additional planets around the same stars. If the planet is detected by the same method, but by two different telescopes, and has received enough scrutiny that the scientists are more than 99 percent sure it’s a planet, it is said to be “validated” instead of “confirmed.”
After thoroughly analyzing the data, and running tests to make sure that their result still looks like the signature of a planet, scientists write a formal paper describing their findings. Using the transit method, they can also report the size of the planet. The planet’s radius is related to how much light it blocks from the star, as well as the size of the star itself. The scientists then submit the study to a journal.
Scientific journals have a rigorous peer review process. This means scientific experts not involved in the study review it and make sure the findings look sound. The peer-reviewers may have questions or suggestions for the scientists. When everyone agrees on a version of the study, it gets published.
When the study is published, scientists can officially say they have found a new planet. This may still not be the end of the story, however. For example, the TRAPPIST telescope in Chile first thought they had discovered three Earth-size planets in the TRAPPIST-1 system. When our Spitzer Space Telescope and other ground-based telescopes followed up, they found that one of the original reported planets (the original TRAPPIST-1d) did not exist, but they discovered five others --bringing the total up to seven wondrous rocky worlds.
Confirmed planets get added to our official catalog. So far, Kepler has sent back the biggest bounty of confirmed exoplanets of any telescope -- more than 2,600 to date. TESS, which just began its planet search, is expected to discover many thousands more. Ground-based follow-up will help determine if these planets are gaseous or rocky, and possibly more about their atmospheres. The forthcoming James Webb Space Telescope will be able to take a deeper look at the atmospheres of the most interesting TESS discoveries.
Scientists sometimes even uncover planets with the help of people like you: exoplanet K2-138 was discovered through citizen scientists in Kepler’s K2 mission data. Based on surveys so far, scientists calculate that almost every star in the Milky Way should have at least one planet. That makes billions more, waiting to be found! Stay up to date with our latest discoveries using this exoplanet counter.
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A simulated image of NASA’s Nancy Grace Roman Space Telescope’s future observations toward the center of our galaxy, spanning less than 1 percent of the total area of Roman’s Galactic Bulge Time-Domain Survey. The simulated stars were drawn from the Besançon Galactic Model.
The view from your backyard might paint the universe as an unchanging realm, where only twinkling stars and nearby objects, like satellites and meteors, stray from the apparent constancy. But stargazing through NASA’s upcoming Nancy Grace Roman Space Telescope will offer a front row seat to a dazzling display of cosmic fireworks sparkling across the sky.
Roman will view extremely faint infrared light, which has longer wavelengths than our eyes can see. Two of the mission’s core observing programs will monitor specific patches of the sky. Stitching the results together like stop-motion animation will create movies that reveal changing objects and fleeting events that would otherwise be hidden from our view.
Watch this video to learn about time-domain astronomy and how time will be a key element in NASA’s Nancy Grace Roman Space Telescope’s galactic bulge survey. Credit: NASA’s Goddard Space Flight Center
This type of science, called time-domain astronomy, is difficult for telescopes that have smaller views of space. Roman’s large field of view will help us see huge swaths of the universe. Instead of always looking at specific things and events astronomers have already identified, Roman will be able to repeatedly observe large areas of the sky to catch phenomena scientists can't predict. Then astronomers can find things no one knew were there!
One of Roman’s main surveys, the Galactic Bulge Time-Domain Survey, will monitor hundreds of millions of stars toward the center of our Milky Way galaxy. Astronomers will see many of the stars appear to flash or flicker over time.
This animation illustrates the concept of gravitational microlensing. When one star in the sky appears to pass nearly in front of another, the light rays of the background source star are bent due to the warped space-time around the foreground star. The closer star is then a virtual magnifying glass, amplifying the brightness of the background source star, so we refer to the foreground star as the lens star. If the lens star harbors a planetary system, then those planets can also act as lenses, each one producing a short change in the brightness of the source. Thus, we discover the presence of each exoplanet, and measure its mass and how far it is from its star. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
That can happen when something like a star or planet moves in front of a background star from our point of view. Because anything with mass warps the fabric of space-time, light from the distant star bends around the nearer object as it passes by. That makes the nearer object act as a natural magnifying glass, creating a temporary spike in the brightness of the background star’s light. That signal lets astronomers know there’s an intervening object, even if they can’t see it directly.
This artist’s concept shows the region of the Milky Way NASA’s Nancy Grace Roman Space Telescope’s Galactic Bulge Time-Domain Survey will cover – relatively uncharted territory when it comes to planet-finding. That’s important because the way planets form and evolve may be different depending on where in the galaxy they’re located. Our solar system is situated near the outskirts of the Milky Way, about halfway out on one of the galaxy’s spiral arms. A recent Kepler Space Telescope study showed that stars on the fringes of the Milky Way possess fewer of the most common planet types that have been detected so far. Roman will search in the opposite direction, toward the center of the galaxy, and could find differences in that galactic neighborhood, too.
Using this method, called microlensing, Roman will likely set a new record for the farthest-known exoplanet. That would offer a glimpse of a different galactic neighborhood that could be home to worlds quite unlike the more than 5,500 that are currently known. Roman’s microlensing observations will also find starless planets, black holes, neutron stars, and more!
This animation shows a planet crossing in front of, or transiting, its host star and the corresponding light curve astronomers would see. Using this technique, scientists anticipate NASA’s Nancy Grace Roman Space Telescope could find 100,000 new worlds. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR)
Stars Roman sees may also appear to flicker when a planet crosses in front of, or transits, its host star as it orbits. Roman could find 100,000 planets this way! Small icy objects that haunt the outskirts of our own solar system, known as Kuiper belt objects, may occasionally pass in front of faraway stars Roman sees, too. Astronomers will be able to see how much water the Kuiper belt objects have because the ice absorbs specific wavelengths of infrared light, providing a “fingerprint” of its presence. This will give us a window into our solar system’s early days.
This animation visualizes a type Ia supernova.
Roman’s High Latitude Time-Domain Survey will look beyond our galaxy to hunt for type Ia supernovas. These exploding stars originate from some binary star systems that contain at least one white dwarf – the small, hot core remnant of a Sun-like star. In some cases, the dwarf may siphon material from its companion. This triggers a runaway reaction that ultimately detonates the thief once it reaches a specific point where it has gained so much mass that it becomes unstable.
NASA’s upcoming Nancy Grace Roman Space Telescope will see thousands of exploding stars called supernovae across vast stretches of time and space. Using these observations, astronomers aim to shine a light on several cosmic mysteries, providing a window onto the universe’s distant past. Credit: NASA’s Goddard Space Flight Center
Since these rare explosions each peak at a similar, known intrinsic brightness, astronomers can use them to determine how far away they are by simply measuring how bright they appear. Astronomers will use Roman to study the light of these supernovas to find out how quickly they appear to be moving away from us.
By comparing how fast they’re receding at different distances, scientists can trace cosmic expansion over time. This will help us understand whether and how dark energy – the unexplained pressure thought to speed up the universe’s expansion – has changed throughout the history of the universe.
NASA’s Nancy Grace Roman Space Telescope will survey the same areas of the sky every few days. Researchers will mine this data to identify kilonovas – explosions that happen when two neutron stars or a neutron star and a black hole collide and merge. When these collisions happen, a fraction of the resulting debris is ejected as jets, which move near the speed of light. The remaining debris produces hot, glowing, neutron-rich clouds that forge heavy elements, like gold and platinum. Roman’s extensive data will help astronomers better identify how often these events occur, how much energy they give off, and how near or far they are.
And since this survey will repeatedly observe the same large vista of space, scientists will also see sporadic events like neutron stars colliding and stars being swept into black holes. Roman could even find new types of objects and events that astronomers have never seen before!
Learn more about the exciting science Roman will investigate on X and Facebook.
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First off, what is the One-Year Crew? Obviously, they’re doing something for a year, but what, and why?
Two crew members on the International Space Station have just met the halfway point of their year in space. NASA Astronaut Scott Kelly and Russian Cosmonaut Mikhail Kornienko are living in space for 342 days and will help us better understand the effects of microgravity on the human body.
Why 342 days and not 365? Thought you might ask. Due to crew rotation schedules, which involve training timelines and dictate when launches and landings occur, the mission was confined to 342 days. Plenty of time to conduct great research though!
The studies performed throughout their stay will yield beneficial knowledge on the medical, psychological and biomedical challenges faced by astronauts during long-duration spaceflight.
The weightlessness of the space environment has various effects on the human body, including: Fluid shifts that cause changes in vision, rapid bone loss, disturbances to sensorimotor ability, weakened muscles and more.
The goal of the One-Year Mission is to understand and minimize these effects on humans while in space.
The Twins Study
A unique investigation that is being conducted during this year in space is the Twins Study. NASA Astronaut Scott Kelly’s twin brother Mark Kelly will spend the year on Earth while Scott is in space. Since their genetic makeup is as close to identical as we can get, this allows a unique research perspective. We can now compare all of the results from Scott Kelly in space to his brother Mark on Earth.
But why are we studying all of this? If we want to move forward with our journey to Mars and travel into deep space, astronauts will need to live in microgravity for long periods of time. In order to mitigate the effects of long duration spaceflight on the human body, we need to understand the causes. The One-Year mission hopes to find these answers.
Halfway Point
Today, September 15 marks the halfway point of their year in space, and they now enter the final stretch of their mission.
Here are a few fun tidbits on human spaceflight to put things in perspective:
1) Scott Kelly has logged 180 days in space on his three previous flights, two of which were Space Shuttle missions.
2) The American astronaut with the most cumulative time in space is Mkie Fincke, with 382 days in space on three flights. Kelly will surpass this record for most cumulative time in space by a U.S. astronaut on October 16.
3) Kelly will pass Mike Lopez-Alegria’s mark for most time on a single spaceflight (215 days) on October 29.
4) By the end of this one-year mission, Kelly will have traveled for 342 days, made 5,472 orbits and traveled 141.7 million miles in a single mission.
Have you seen the amazing images that Astronaut Scott Kelly has shared during the first half of his year in space? Check out this collection, and also follow him on social media to see what he posts for the duration of his #YearInSpace: Facebook, Twitter, Instagram.
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To start off the summer, the U.S. Postal Service issued a set of stamps showcasing views of the Sun from our Solar Dynamics Observatory!
Since its launch in 2010, the Solar Dynamics Observatory (or SDO) has kept up a near-constant watch on the Sun from its vantage point in orbit around Earth. SDO watches the Sun in more than 10 different types of light, including some that are absorbed by Earth’s atmosphere so can only be seen from space. These different types of light allow scientists to study different parts of the Sun – from its surface to its atmosphere – and better understand the solar activity that can affect our technology on Earth and in space.
The new set of stamps features 10 images from SDO. Most of these images are in extreme ultraviolet light, which is invisible to human eyes.
Let’s explore the science behind some of the stamps!
The dark area capping the northern polar region of the Sun is a coronal hole, a magnetically open area on the Sun from which high-speed solar wind escapes into space. Such high-speed solar wind streams can spark magnificent auroral displays on Earth when they collide with our planet’s magnetic field.
The bright flash on the Sun’s upper right is a powerful solar flare. Solar flares are bursts of light and energy that can disturb the part of Earth’s atmosphere where GPS and radio signals travel.
This view highlights the many active regions dotting the Sun’s surface. Active regions are areas of intense and complex magnetic fields on the Sun – linked to sunspots – that are prone to erupting with solar flares or explosions of material called coronal mass ejections.
These images show a burst of material from the Sun, called a coronal mass ejection. These eruptions of magnetized solar material can create space weather effects on Earth when they collide with our planet’s magnetosphere, or magnetic environment – including aurora, satellite disruptions, and, when extreme, even power outages.
These images show evolving coronal loops across the limb and disk of the Sun. Just days after these images were taken, the Sun unleashed a powerful solar flare.
Coronal loops are often found over sunspots and active regions, which are areas of intense and complex magnetic fields on the Sun.
This view in visible light – the type of light we can see – shows a cluster of sunspots near the center of the Sun. Sunspots appear dark because they are relatively cool compared to surrounding material, a consequence of the way their extremely dense magnetic field prevents heated material from rising to the solar surface.
For more Sun science, follow NASA Sun on Twitter, on Facebook, or on the web.
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"We came all this way to explore the Moon, and the most important thing is that we discovered the Earth." - Apollo 8 astronaut Bill Anders
On Dec. 24, 1968, Anders snapped this iconic photo of "Earthrise" during the historic Apollo 8 mission. As he and fellow astronauts Frank Borman and Jim Lovell became the first humans to orbit the Moon, they witnessed Earth rising over the Moon's horizon. The image helped spark the first #EarthDay on April 22, 1970.
Anders sat down with Dr. Kate Calvin, our chief scientist and senior climate advisor, to chat about the photo, and NASA’s role in studying our home.
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Measuring how much water is in a snowpack is not easy. Scientists are investigating the best combination of sensors for different terrains. More accurate snow measurements will help scientists and decision makers better understand our world’s water supply and better predict floods and droughts.
To follow scientists in the field studying snow, follow #SnowEx on Twitter and Facebook
If #NationalCheeseDay has you thinking about the Moon, you're not alone. 🧀
In 1965, the Ranger 9 probe captured these sharp images of a cratered lunar surface just moments before its planned impact. What we learned paved the way for Apollo. #Apollo50th
That’s a wrap folks! Gucci is signing off. Thank you for all the amazing questions. Didn’t get your question answered? No worries! We’re coming to you live next week in our second Answer Time of 2020, featuring NASA Astronaut Nick Hague. Submit your questions now here: https://nasa.tumblr.com/ask
What do modern cochlear implants and robotic gloves have in common? They were derived from NASA technology. We’ve made it easier to find and use our patented inventions that could help create products that enhance life for people with disabilities.
October is National Disability Employment Awareness Month, which highlights the contributions of American workers with disabilities – many of whom use assistive technology on the job. Take a look at these assistive technologies that are NASA spinoffs.
The Joint Optical Reflective Display (JORDY) device is a headset that uses NASA image processing and head-mounted display technology to enable people with low vision to read and write. JORDY enhances individuals’ remaining sight by magnifying objects up to 50 times and allowing them to change contrast, brightness, and display modes. JORDY's name was inspired by Geordi La Forge, a blind character from “Star Trek: The Next Generation” whose futuristic visor enabled him to see.
Work that led to the modern cochlear implant was patented by a NASA engineer in the 1970s. Following three failed corrective surgeries, Adam Kissiah combined his NASA electronics know-how with research in the Kennedy Space Center technical library to build his own solution for people with severe-to-profound hearing loss who receive little or no benefit from hearing aids. Several companies now make the devices, which have been implanted in hundreds of thousands of people around the world.
Ironhand, from Swedish company Bioservo Technologies, is the world’s first industrial-strength robotic glove for factory workers and others who perform repetitive manual tasks. It helps prevent stress injuries but has been especially warmly received by workers with preexisting hand injuries and conditions. The glove is based on a suite of patents for the technology developed by NASA and General Motors to build the hands of the Robonaut 2 humanoid robotic astronaut.
Neurofeedback technology NASA originally developed to improve pilots’ attention has been the basis for products aimed at helping people manage attention disorders without medication. The devices measure brainwave output to gauge attention levels according to the “engagement index” a NASA engineer created. Then, they show the results to users, helping them learn to voluntarily control their degree of concentration. One such device is a pair of smart glasses from Narbis, whose lenses darken as attention wanes.
A NASA scientist who developed ways to use air pressure to simulate gravity for astronauts exercising in space had the idea to apply the concept for the opposite effect on Earth. After licensing his technology, Alter-G Inc. developed its anti-gravity G-Trainer treadmill, which lets users offload some or all of their weight while exercising. The treadmills can help people recover from athletic or brain injuries, and they allow a safe exercise regimen for others with long-term conditions such as arthritis.
Some of the most exciting assistive technologies to spin off may be yet to come. Delsys Inc. developed electromyographic technology to help NASA understand the effects of long-term weightlessness on astronauts’ muscles and movements. Electromyography detects and analyzes electrical signals emitted when motor nerves trigger movement. Among the company’s customers are physical therapists developing exercise routines to help patients recover from injuries. But some researchers are using the technology to attempt recoveries that once seemed impossible, such as helping paralyzed patients regain movement, letting laryngectomy patients speak, and outfitting amputees with artificial limbs that work like the real thing.
To further enhance the lives of people with disabilities, NASA has identified a selection of patented technologies created for space missions that could spur the next generation of assistive technology here on Earth.
Want to learn more about assistive technologies already in action? Check out NASA Spinoff to find products and services that wouldn’t exist without space exploration.
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We’ve just added two more science missions to our lineup! The two selected missions have the potential to open new windows on one of the earliest eras in the history of our solar system – a time less than 10 millions years after the birth of our sun.
The missions, known as Lucy and Psyche, were chosen from five finalists and will proceed to mission formulation.
Lucy, a robotic spacecraft, will visit a target-rich environment of Jupiter’s mysterious Trojan asteroids. Scheduled to launch in October 2021, the spacecraft is slated to arrive at its first destination, a main asteroid belt, in 2025.
Then, from 2027 to 2033, Lucy will explore six Jupiter Trojan asteroids. These asteroids are trapped by Jupiter’s gravity in two swarms that share the planet’s orbit, one leading and one trailing Jupiter in its 12-year circuit around the sun. The Trojans are thought to be relics of a much earlier era in the history of the solar system, and may have formed far beyond Jupiter’s current orbit.
Studying these Trojan asteroids will give us valuable clues to deciphering the history of the early solar system.
The Psyche mission will explore one of the most intriguing targets in the main asteroid belt – a giant metal asteroid, known as 16 Psyche, about three times farther away from the sun than is the Earth. The asteroid measures about 130 miles in diameter and, unlike most other asteroids that are rocky or icy bodies, it is thought to be comprised of mostly metallic iron and nickel, similar to Earth’s core.
Scientists wonder whether psyche could be an exposed core of an early planet that could have been as large as Mars, but which lost its rocky outer layers due to a number of violent collisions billions of years ago.
The mission will help scientists understand how planets and other bodies separated into their layers early in their histories. The Psyche robotic mission is targeted to launch in October of 2023, arriving at the asteroid in 2030, following an Earth gravity assist spacecraft maneuver in 2024 and a Mars flyby in 2025.
Get even more information about these two new science missions HERE.
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