Kepler-19b, which orbits the Sun-like star Kepler-19 650 light-years from Earth in the constellation Lyra, has been found to have an 'invisible' world tugging on it.
How do astronomers know, since it's invisible? Kepler-19b alternately runs late and early in its orbit, the first definite detection of a previously unknown planet using this method. No other technique could have found the unseen companion.
Kepler-19 is a 12th-magnitude star and can be seen by backyard telescopes on September evenings.
NASA's Kepler spacecraft locates planets by looking for a star that dims slightly as a planet transits the star, passing across the star's face from our point of view. Transits give one crucial piece of information; the planet's physical size. The greater the dip in light, the larger the planet relative to its star. However, the planet and star must line up exactly for us to see a transit.
The first planet, Kepler-19b, transits its star every 9 days and 7 hours. It orbits the star at a distance of 8.4 million miles, where it is heated to a temperature of about 900 degrees Fahrenheit. Kepler-19b has a diameter of 18,000 miles, making it slightly more than twice the size of Earth. It may resemble a "mini-Neptune," however its mass and composition remain unknown.
If Kepler-19b were alone, each transit would follow the next like clockwork. Instead, the transits come up to five minutes early or five minutes late. Such transit timing variations show that another world's gravity is pulling on Kepler-19b, alternately speeding it up or slowing it down.
The "invisible" world named Kepler-19c, seen in the foreground of this artist's conception, was discovered solely through its gravitational influence on the companion world Kepler-19b - the dot crossing the star's face. Kepler-19b is slightly more than twice the diameter of Earth, and is probably a "mini-Neptune." Nothing is known about Kepler-19c, other than that it exists.
Credit: David A. Aguilar (CfA)
"This invisible planet makes itself known by its influence on the planet we can see," said astronomer Sarah Ballard of the Harvard-Smithsonian Center for Astrophysics (CfA). Ballard is lead author on the study, which has been accepted for publication in The Astrophysical Journal. "It's like having someone play a prank on you by ringing your doorbell and running away. You know someone was there, even if you don't see them when you get outside."
Historically, the planet Neptune was discovered similarly. Astronomers tracking Uranus noticed that its orbit didn't match predictions. They realized that a more distant planet might be nudging Uranus and calculated the expected location of the unseen world. Telescopes soon observed Neptune near its predicted position.
"This method holds great promise for finding planets that can't be found otherwise," stated Harvard astronomer and co-author David Charbonneau.
So far, astronomers don't know anything about the invisible world Kepler-19c, other than that it exists. It weighs too little to gravitationally tug the star enough for them to measure its mass. And Kepler hasn't detected it transiting the star, suggesting that its orbit is tilted relative to Kepler-19b.
"Kepler-19c has multiple personalities consistent with our data. For instance, it could be a rocky planet on a circular 5-day orbit, or a gas-giant planet on an oblong 100-day orbit," said co-author Daniel Fabrycky of the University of California, Santa Cruz (UCSC).
The Kepler spacecraft will continue to monitor Kepler-19 throughout its mission. Those additional data will help nail down the orbit of Kepler-19c. Future ground-based instruments like HARPS-North will attempt to measure the mass of Kepler-19c. Only then will we have a clue to the nature of this invisible world.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Better Brains With Beer
- How A Former Naturopath Can Help Unravel The Trickery of Alternative Medicine
- Brexit, the EU Now Has its Puerto Rico.
- Tidal Disruption Event: Black Hole Eats Star, Beams Signal To Earth
- 9,000 Years: Origin Of Farmed Rice Gets Pushed Back
- Finding All-Hadronic Top - Again
- Psychiatric Diagnoses Not Valid For African-Americans, Says Sociologist
- " And all that science, I don't understand - it's just my job five days a week Pretty sure that..."
- "Good news for asteroid defense (it's not new news, but I only found out about it just now), this..."
- "Okay, first, this planet X, if it exists, always remains outside of Neptune if it exists - you..."
- "UPDATE - most recent paper has semimajor axes of ~380–980 AU, and masses of ~5–20..."
- "A better picture might be obtained by reading this article from an Irish journalist based in Russia..."
- It’s Back to Shots for Flu Prevention
- ACSH Applauds Media Awareness of the Fentanyl Crisis
- Counting Bites Examined, to Help Decrease Food Intake
- The Safe And Unsafe Nutty Treats For Your Pup
- Mr. Potato Head Needs a New Warning Label!
- Shark Finning is Banned in the US; Banning Trade in Fins May Be Next
- Should I stay or should I go?
- New cancer immunotherapy drugs linked to arthritis in some patients
- Simulations foresee hordes of colliding black holes in LIGO's future
- Analysis of genetic repeats suggests role for DNA instability in schizophrenia
- Analysis of media reporting reveals new information about snakebites and how and when they occur