# Tag Info

16

Because there are so many planets out there! There just happens to be an entire web page dedicated to calculating that answer. Transits can only be detected if the planetary orbit is near the line-of-sight (LOS) between the observer and the star. This requires that the planet's orbital pole be within an angle of $d_*/a$ (part 1 of the figure below) ...

16

The reason is electron degeneracy pressure. The cores of giant planets are dense enough that the electrons in the gas occupy about $h^3$ of phase space each. The Pauli exclusion principle means that they cannot all occupy low energy/momentum states. This means that even at relatively cool temperatures the gas can still exert considerable pressure due to the ...

14

There are a couple of resources for you to look over the list of CONFIRMED extra-solar planets. Wikipedia is always a nice starting point. Here is a list of the currently 53 known planetary SYSTEMS. And from that page, you can check out numerous other exoplanet details. This article from August 2010 Space.com lists 5 candidates. The definitive site ...

14

Yes. I'm not going to list all the stars here but it's easy to compile such a list. Wikipedia has a list of exoplanetary host stars. If you sort the table by ascending apparent magnitude and decide how bright "naked-eye stars" need to be, you can take as many as you like from the list by taking all the stars with smaller magnitudes. I think magnitude 6 is ...

14

New research is suggesting that solar systems may be inherently unstable. You may have read recently that wandering inter-stellar planets may be more common than stars. The prediction is that planets frequently become ejected from their solar systems early in their formations, and wind up wandering deep space forever. There is a complicated interaction ...

12

Almost all exoplanets observed are near F, G, and K stars. In part, this is because astronomers are looking for earth-like planets, so they look at stars similar to our Sun, but there are also some physical reasons. Sahu et al (2006) have provided some evidence that red dwarfs (class M) are more likely to have planets than other spectral types, though it is ...

10

Given what we know about planetary formation (Link 1, Link 2, Link 3 and Link 4), and the theories around it, it would probably be a safe bet to say that ALL stars end up having some left over material that might become planets. I think the bigger question is how many of those planetary orbits stay stable enough throughout the life of the star? All these ...

10

(I just performed a bit of an edit on your question to have it align more with what I think you are asking as opposed to the overly speculative sentences you had. I hope you don't mind. :) And I will build on Andrew's answer (I hope he doesn't mind).) This is probably related to the question What are the prerequisites for considering any other planet to be ...

10

Stars are divided (this is only an approximate distinction) into Population I, Population II and Population III. Population I stars are the relatively young stars like the Sun that we see around us today, while Population II are older stars that have a low but non-zero metal content (in this context a metal is any element heavier than Helium i.e. those ...

8

The earliest stars did not have planets primarily due to a lack of metals. Metals in this sense is an element (with some extra properties that are not relevant in this context) heavier than helium. The very article that you linked to references this. This leads to the following: Stars without metals tend to not last very long. Metals in a star act to slow ...

7

You are correct that the standard for naming exoplanets is normally the lower-case letter after the star name in the order of discovery. So in our system, Earth would be Sol b. If there are multiple stars in the system, like 16 Cyg (which has 16 Cyg A and B), then the planet's lower-case letter would be appended to the star's, such as 16 Cyg Bb. So the ...

7

Unfortunately, it's highly highly unlikely. We're barely even capable of identifying individual stars within the Andromeda galaxy (and the ones we can identify, if any, are almost all supergiants - these are pretty much the only stars we can identify in the Local Magellanic Clouds, which are closer than Andromeda). Even if we were able to identify individual ...

7

http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar_planets#Direct_imaging A shade used to block out a bright source in order to image a dim source right next to it is called a coronagraph. They are [EDIT: modestly sized] screens attached to the telescope itself, not [EDIT: huge] devices deployed far from the telescope. These are being used ...

7

"Host star", or "host" for short, seems to fit the bill.

6

Not having been at the meeting, here's my take on it. It's becoming saturated in that it's the hot topic right now where there is a lot of funding so everyone is trying to get involved to some level. There is a lot of people competing for limited resouces and there is only so much that can be done with current technology.My wife was recently on a grant ...

5

Scientists can image exoplanets today, using coronagraphs and other techniques: The major difference from Sagan's speculation are the advances in adaptive optics that allow terrestrial observatories to perform in ways that vastly exceed the expectations of Sagan's time. Space-based observatories are awesome, but the sheer size of these instruments is ...

5

This is by no means a settled question; rather it is at the forefront of exoplanet research. There are several ideas out there, and I'll list a few. Migration via drag: In young stellar disks, there may be a bunch of leftover gas that can produce a drag force on planets. By the way, there is a subtle reason this works at all. Because gas will have some ...

5

Though the definition of "confirmed" is not a firm one, and is really an operational matter of peer review and consensus among researchers, the most widely accepted method of confirmation is high-resolution radial velocity analysis: the observation of shifts in the spectrum of the parent star as it is alternately "tugged" towards and away from an observing ...

5

Several answers occurred to me. Timescale. Pop III stars only last a few million years. This article, which is billed as as evidence for a much shorter timescale of planetary formation than previously thought, still quotes 10 million years (caveat: for terrestrial planets, but I didn't find a source right off the bat for gas giants). However, if I'm wrong ...

5

"It is one of the deepest and most detailed images ever taken of a galaxy outside our own." Just imaging those stars required Hubble-level capabilities, and that's child's play compared to exoplanet detection. I don't think that doing even the Doppler-shift spectroscopic method would be feasible for a long time to come. Plus, there's decades of work already ...

5

There is mounting evidence from the Kepler mission that these hot Jupiters migrated in by scattering other planets out. Of the 400-odd systems with multiple planets, almost none of them have a hot Jupiter. Statistically quite significant.

5

Yes this heat is the residual heat from its formation ~ 70 Myr ago. It is currently cooling down, but it should take several billion years to reach temperatures as cold as Jupiter. The structure of this object is really close to Jupiter in fact, even if it's more massive it has roughly the same radius and a similar composition. We can't actually call it a ...

5

The paper The stability and dynamics of planets in tight binary systems (The Astrophysical Journal, 2009-04-01. PDF, 561 KB) probably has more about this topic than you'd ever want to know. I read the abstract. From that, it seems that I was more or less right in my previous comment (see last sentence of the abstract), except that in binary systems, it ...

5

I did some research and I think I can answer my question myself now, after all. I hope you find it interesting. As it turns out, the technology of the Kepler space telescope would indeed allow detection of all Solar system planets except Mercury and probably Mars, i.e. all of them are big enough to be seen by it from a distance of about 2,000 ly. However, ...

4

Transit-based methods and astrometry won't help here (a rogue (not rouge) planet is highly unlikely to move across the line-of-sight between us and neighboring stars more than once), but microlensing events like that (provided there's another star behind the planet and Proxima) are possible. Of course, if you don't make repeated observations, you cannot be ...

4

The atmosphere, if present on the daylight part of the surface, will be also present in the night side, providing mechanisms for heat transport from day side to night side. So if daylight side allows liquid water, the night side will be not much colder than cold places on Earth. Have a look at a paper: Merlis, T. M., & Schneider, T. (2010). ...

4

This question was asked a couple of years ago and things have changed since then. We now know that small planets are found around stars across a broad range of metallicities and that it is only the existence of giant planets that are affected by low metallicity. Nature article here. It was previously thought that small planets were more common around small ...

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