A 'serious' scientist in 1992 or 1993 had to admit the possibility that planets were really rare, that most stars might not have planets. We've gone from there to here - where most stars have planets.
— Debra Fischer
There may be hundreds of small seed planets - or planetesimals - which grow in the disk of matter around a star.
Kepler's blown the lid off everything we know about extra-solar planets.
Our field is very focused on finding Earth 2.0, and anything we can do to narrow the search is helpful.
Whether a star has planetary companions or not is a condition of its birth. Those with a larger initial allotment of metals have an advantage over those without.
The gas-giant planets in our solar system all have large moons.
Before 1995, the only planets we knew about were the planets in our solar system.
Within the scientific community, there is healthy skepticism. And the question is, 'How do you ever get to a meaningful null result? How long and how hard do SETI scientists have to look for extraterrestrial intelligence and find nothing before they say, 'There is nothing. We are alone.'
If few worlds have microbial life, it dramatically reduces the chances that more complex organisms exist.
I hope that vigorous space exploration continues and that humankind will have a space station that resides between Earth and the moon. Outside the gravitational field of Earth, we could launch robotic spacecraft to other destinations in our solar system.
One of the first thoughts I had, when doing early exoplanet research, was that Earth and its many companions seemed very different from the planetary systems we were detecting.
Once we see stars with three times the metal content of our sun, the planet detection rate goes up to 20 per cent.
Naturally, we think that finding another Earth-like planet is identifying a site that's at least friendly here for the evolution of life. The primary goal of the Kepler mission is to statistically assess the occurrence of these small terrestrial worlds.
As our sensitivity improves, we are finally seeing planets with longer orbital periods, planetary systems that look more like our solar system.
55 Cancri is extraordinarily rich in heavy elements and extraordinarily efficient at making planets - much more so than our sun - and those elements are the very ones you need to make planets that aren't just gas giants.
We now know that stars which are abundant in heavy metals are five times more likely to harbor orbiting planets than are stars deficient in metals.
Ultimately, what we're looking for in the long run is to find other Earth-like planets.
Because Alpha Centauri is so close, it is our first stop outside our solar system. There's almost certain to be small, rocky planets around Alpha Centauri A and B.
Science requires speculation, creativity, and wild ideas.
Prebiotic chemistry on other worlds is going to be common. Plenty of small rocky planets will have similar chemistry. It's almost a given.
The first exoplanet to be found around a sun-like star was discovered in 1995, just two years before I began studying exoplanet detection.
Generally speaking, exoplanets can be any size, and they are found in a wide range of orbits. Some have massive gas atmospheres; others are smaller with an icy or rocky composition.
It can be very hard to know the history of a particular star, but once in a while, we get lucky and find stars with chemical compositions that likely came from in-falling planets.
There's no doubt that the search for planets is motivated by the search for life. Humans are interested in whether or not life evolves on other planets. We'd especially like to find communicating, technological life, and we look around our own solar system, and we see that of all the planets, there's only one that's inhabited.
Diamond planets truly are the most precious.
Computers can't find the unexpected, but people can when they eyeball the data.
When stars form a planet, they come in a bunch.
It now seems logical that all the stars, like our own sun, must have formed with a system of planets around them.
The universe has told us the most common types of planets are small planets, and our study shows these are exactly the ones that are most likely to be orbiting Alpha Centauri A and B.
The building blocks of life are readily available throughout the universe.
Further ahead, I'd like to see tiny spacebots - smaller than your cell phone - travel outside our solar system to the nearest star system, Alpha Centauri. By keeping the mass of those spacebots low, we could more easily accelerate them.
In 1999, my team discovered that the star Upsilon Andromedae was circled by three gas-giant planets - the first distant multiplanet system ever found. That same year, other researchers observed the first 'transit' of an exoplanet - a planet blocking out a small fraction of the starlight as it passes in front of the star.
