51

To add to Rob's answer, I wanted to expand on where this naming convention comes from. The International Astronomical Union (IAU) is the organization which generally sets conventions and definitions. They're the ones who demoted Pluto to being a dwarf planet in 2006. Anyway, before any exoplanets were found, there existed a convention for naming multiple-...


37

The convention for planetary naming is that the closest planet to the star (if multiple planets are found at the same time) is named "star"b, then "star"c and so on. As correctly pointed out by Zephyr, if the discoveries are more haphazard, the order of discovery takes precedence over distance from the star). So, there is no Trappist-1a. Or you can think of ...


30

A recent study indicates that Cold Jupiters similar to Saturn and Jupiter greatly outnumber Hot Jupiters. The authors studied 18 years worth of data to find long-period exoplanets, that is planets far from their host star. Cold Jupiters, being farther from their host star, have longer periods than Hot Jupiters. Therefore, they need to be observed over a ...


28

The star at the center of TRAPPIST-1 is called 2MASS J23062928-0502285. It was discovered by the Two Micron All-Sky Survey (2MASS), which imaged the whole sky in the infrared between 1997 and 2001. This resulted in a catalog of over 300 million objects. TRAPPIST-1 itself was cataloged in 1999. The name is actually its coordinates in right ascension and ...


26

This is a broad question and too broad for me to answer comprehensively. It should be broken down into doppler methods, transits and direct imaging; and that's before we get to questions of detecting Kuiper belts, radio emission etc. I'll stick for the moment with what I know about detection of planets using the doppler wobble technique. Doppler Technique ...


26

TLDR version: probably not, and claims for the habitability of planets in this system are on shaky ground. Long version follows. Planets So as of Feng et al. (2017), there are four planet candidates around Tau Ceti: Tau Ceti g, minimum mass $1.75^{+0.25}_{-0.40}\ M_\oplus$, semimajor axis $0.133^{+0.001}_{-0.002}\ \mathrm{AU}$ Tau Ceti h, minimum mass $1....


25

From an exoplanet-finding point of view, the Sun has between one and three planets. The major exoplanet-finding techniques in current use involve watching for either periodic Doppler shifts as the planet's gravitational pull causes the star to wobble, or periodic brightness shifts as the planet transits the star. Both require that the planet is large ...


22

It depends on how you define Jupiter analogues. There are several possible factors, including mass, eccentricity and orbital period cutoffs. Given there's no consistent definition, comparison of results between the various papers is difficult. For example, the recent paper by Wittenmyer et al. considers "cool Jupiters" to be planets with masses greater than ...


22

I feel it's a cheap answer but heavy Jupiters can get much denser than Earth because planets with Jupiter's mass stop adding size as they add more mass. A planet with Jupiter's size and 10-12 times Jupiter's mass would be over twice Earth's density. As far as Earth-like planets, there's a cool property of terrestrial planets, more mass means more tightly ...


21

I'd say that HD 189733b is a good candidate for the most extreme known weather on another planet (outside our Solar System). According to some recent news accounts, the atmospheric temperature is believed to be over 1000° C, with 7000 kph winds. (For comparison to the data in Rory Alsop's answer, that's about 1900 meters per second.) And it rains molten ...


21

The distance moduli at 5, 500, 50,000 and 5,000,000 are -4.1, 5.9, 15.9 and 25.9 respectively. We add that to the absolute visual magnitude of the Sun, 4.8, to get apparent magnitudes of 0.7, 10.7, 20.7 and 30.7 respectively. Most planets are detected by the Doppler wobble in the parent star or if the planet transits in front of the parent star. Some are ...


19

No such planet has been announced as having been discovered. The paper only shows evidence for the 7 (really 6 because the 7th can't be officially confirmed with only 1 observation) terrestrial planets and does not make the case for any other planets. The paper doesn't indicate that more planets could exist, but does remark that there are large error bars on ...


18

So far, we don't have anywhere near enough detail to identify weather on planets in other star systems. We even have difficulty working out the size of some of them, so it may be a while till we can get a good idea as to weather. So the answer is going to be in our solar system. As for extremes, we have a couple of options: WIND Saturn and Neptune have ...


18

The answer is Yes.. Planets that don't orbit around a star are known as Rogue Planets. There is nothing preventing a rogue planet from having one or many moons. Not so long ago, the first candidate for a free-floating exoplanet-exomoon system was presented in this paper. It looks like a gas giant several times larger than Jupiter with a sub-Earth mass moon....


18

Trappist-1 was first catalogued by the 2MASS survey about 17 years ago and has the catalogue number 2MASS J23062928-0502285. It was identified as an ultra- low-mass star with a spectral type of M7.5 by Gizis et al. (2000) and Cruz et al. (2003), using a combination of 2MASS and proper motion. The reason it was monitored by the Trappist telescope is that is ...


15

The first part of your question has been asked before: Is Sun a part of a binary system? and the current (lack of) evidence for such a companion is discussed on the relevant wikipedia page about "Nemesis". To summarise: if it were a small companion star, or even a brown dwarf that had been cooling for 4.5 billion years and it had a 26 million year orbit, ...


14

In 2013, the smallest detected exoplanet was Kepler-37-b, which is actually smaller in mass and size than Earth, so we already had a limited ability to detect these size exoplanets. It is worth noting that there wasn't any new technology that allowed this advance, the paper linked to by NASA indicates that the same methods were used as they would usually ...


14

Earlier this year (2016), scientists used the radial velocity method to discover a planet orbiting Proxima Centauri: Proxima Centauri b. It was announced in Anglada-Escudé et al. (2016). Here are some of its basic properties, as reported by the authors of the paper and known as of August 2016: Mass: At least 1.3 Earth masses Semi-major axis: 0.05 AU Maximum ...


14

This is a question that concerns the initial mass function (IMF) - an empirical (that is, defined by observations rather than theory) function that describes the statistical distribution of stellar masses. Edwin Salpeter (1955) was the first to describe the IMF, though if you read Chabrier (2003) there are some reasonably comprehensive explanations of the ...


14

I am beginning to assume that our solar system is not unique and that every star has several planets. Not quite, but indeed a study published in Nature in 2012 found that, based on our observations so far, roughly 17% of stars host Jupiter-mass planets, 52% host "Cool Neptunes" and 62% host Super-Earths. (Note that these percentages do not add up to 100%, ...


14

Yes, there is a limit. Anything with a mass larger than about 13 times that of Jupiter would be called a brown dwarf (a failed star), though whether such an object would consist entirely of gas, or had a rocky/icy core as is probable for most giant planets, is not presently observable. Any larger than about 75 Jupiter masses and we would just call it a star. ...


13

This is actually quite straightforward with digital CCD's (it used to be quite tricky with film cameras as you'd have to carefully develop film that moved past the lens and assess the width of the trail) Get yourself a good telescope - a 12" Dobsonian or above if you want to give yourself a good chance of picking out the fluctuations against the noise ...


13

During high school, I have learned that we are in the solar system and there are some planets orbiting the Sun. Yes that is correct. According to current definitions of what counts as a planet, there are 8 planets orbiting our Sun $-$ Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are also a collection of smaller "Dwarf Planets" ...


13

There is no unique definition of Earth-like and it depends on what characteristics are important in the context of discussion. The most simple one is to just compare radii and masses. That is observationally sensible as radius is directly deducable from transits (assuming stellar size known) and mass is often an accessible properties for transiting planets ...


12

There is no "orbital path" detected, that's why it is a "free-floating planet". There is no radial velocity mesured, but the informations given by its kinematic location show that it belongs to the beta Pictoris group, that is a stellar group. For more dirty details, have a look at the submitted paper on PSO J318.5-22: http://arxiv.org/abs/1310.0457 ...


12

Well done you. I double checked the calculations and couldn't fault what you had done. So I contacted the lead author of the paper about it and here is the response: "After checking the numbers in our paper, I found an error: we actually used a mass of 1.0 MSun for J1407 in our simulations, instead of the 0.9 MSun as stated. This accounts for the difference ...


12

Radial velocity Radial velocity might be able to detect Jupiter in the 5 or 500 light-years cases unless the solar system were oriented close to face-on. There is nevertheless the potential for confusion with the solar activity cycle at a similar period (this issue has come up for a couple of extrasolar Jupiter-analogues), which may require a very long ...


11

This is a fairly loaded question in that it depends heavily on what a "hot Jupiter" actually is defined to be. What is "hot"? What is a "Jupiter"? In reality, there's a continuum of planetary masses and distances from their parent star, and in the literature you'll commonly see references to "hot Neptunes", "hot Saturns," etc. The predominant theory as to ...


Only top voted, non community-wiki answers of a minimum length are eligible