# Tag Info

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### Do blue giants have a habitable zone?

Just because a planet is in the "Habitable zone" doesn't mean it is habitable. A planet is said to be in the habitable zone if it is possible for liquid water to exist on the surface. A planet may be ...
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### Why the Circumstellar Habitable Zone is defined as it is, if life could be possible outside of it?

From your first link, the definition is: "The circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support ...
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### How far from Betelgeuse is its habitable zone?

Nobody knows the limits of the Sun's habitable zone, or how broad or narrow it is. Here is a link to a list of various estimates of the inner, or outer, or both, edges of the circumstellar habitable ...
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### How much light would be reflected from Jupiter to Europa (in Europas night)?

It's a pretty straight forward calculation of 3 factors. Distance from the sun, apparent size and albedo. I'm going to compare Jupiter to our full moon, since we're all familiar with that. ...
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### Detecting habitable planets

It isn't the only way, Aaron. See the Wikipedia Methods of detecting exoplanets article. The first method listed is radial velocity. That's where we measure the Doppler shift of the star's "wobble". ...
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### What kind of star would allow for life like our Sun/Earth and then go nova?

In the real universe, stars that go supernova are very large stars that are short lived, or, they could be white dwarfs that accrue matter and overcome the Chandrasekhar limit. Very large stars, 8 ...
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### Which spiral arm of the Milky Way is Kepler-62 in?

The Kepler space telescope had a field of view along the so called Orion arm, or spur, of the galaxy. The same structure which we ourselves are inside. It basically looks along a line where the star ...
• 10.7k
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### Ramifications of black hole stellar system

For those who haven't seen it: The basic answer is that a planet can orbit a black hole. There are stable circum-black-hole orbits, just as there are stable orbits around just about any celestial ...
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### Help in determining the features of an unusual, fictional star system

First it will be important to consider the term 'relativistic speed'. If by that you mean something like 0.1c, it will only change the colour of the stars as you mentioned in the bounty description. ...
• 1,534
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### Distance from the sun can equal a hospitable planet?

It's actually the opposite. Venus, Mars and I'll include the Earth as well, are likely getting more solar energy per square meter, not less, over time, even as they slowly move away from the sun. ...
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### Detecting habitable planets

Yes and yes. Transit detection is only effective for that (small) fraction of planets that pass between the star and our line of sight. Most planets will go undetected by this method. Also correct. ...
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### How far from Betelgeuse is its habitable zone?

Habitable zones, defined in terms of equilibrium temperature, scale with the square root of the luminosity of the star. So whatever the habitable zone limits $[a_{inner},a_{outer}]$ are for the Sun, ...
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### Astrophysics Ph.D. thesis on intergalactic rogue planets and their habitability; how active is this field of research?

This became too long for a comment, but shouldn't be considered a definite answer: Until recently, almost every rogue planet was found with microlensing, meaning that they're only observable for a ...
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### What is space temperature around Earth?

Assume you have a spherical blackbody. The solar flux at the radius of the Earth is given to a good approximation by $L/4\pi d^2$, where $d = 1$ au. This is $f=1367.5$ W/m$^2$ (though note the ...
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### Which would be safer: removing hydrogen or adding hydrogen to our sun?

My kneejerk reaction is that your only option is to remove a chunk of mass from the outer part of the Sun. The Sun will respond (on a Kelvin-Helmholtz timescale), by contracting and becoming less ...
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### Why bother looking for Earth-like planets?

The possibility of exploring exoplanets is so remote it is not a factor. We are interested in Earth-like planets as there is only one type of planet that we know can support life, and that is the ...
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### Could a Jovian or Saturnian moon keep its atmosphere if the system was within the habitable zone?

To your first question... from this paper, we can see that there are 3 types of atmospheric escape: Jeans Escape: Temperature and escape velocity factors determine the gasses and the amount that's ...
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### Could a Jovian or Saturnian moon keep its atmosphere if the system was within the habitable zone?

1st Q: It's been said that an astronomical body can keep it's atmosphere if the escape velocity is more than six times the average speed of the molecules. Gravity isn't the only factor that permits ...
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### Are there any planets or objects orbiting in Goldilocks zone?

From the Wikipedia article Circumstellar habitable zone, which is just another name for the Goldilocks zone: Estimates for the habitable zone within the Solar System range from 0.38 to 10.0 ...
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### Is it dangerous to look at an L-type brown dwarf from too close?

A typical L-type brown dwarf is about 1200-2200 K in surface temperature and is about the size of Jupiter. Using the Stefan-Boltzmann law, we can deduce that the hottest brown dwarfs have a luminosity ...
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### Is axial tilt critical for life?

I agree with David Hammen. Hyperphysics is mostly a very good site but they dropped the ball on that page IMHO. Hope you don't mind a partially speculative answer, but here goes: Why does it ...
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### Simple life on asteroids

If you take a slowly rotating asteroid with a large basin of trapped water, some solved minerals, and may be some gases, close to the asteroid's surface, to get an environment similar to a black ...
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### Galactic Habitable Zone

I'll be honest. I looked up Galactic Habitable Zone on Wikipedia. The idea was introduced in 1986 and expanded upon in the book "Rare Earth" by Brownlee and Ward. Essentially the idea is that in the ...
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### What percentage of gas giant exoplanets are in the habitable zone?

Of the gas giants, the number of "hot Jupiters" is about the same as the number of "hot Neptunes." A little under 9% of known gas giants are in the habitable zones. An article by John Wenz has the ...
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### What percentage of gas giant exoplanets are in the habitable zone?

I was curious about the figure given in Mick's answer (~9%), so I did some data-crunching of my own. I looked at the NASA Exoplanet Archive, in particular the table of confirmed planets. I was ...
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