18 votes
Accepted

Are main-sequence G9 stars habitable?

Stars themselves are not "habitable", but any star could have a "habitable zone". Generally the term "habitable zone" refers to the zone around a star in which water ...
James K's user avatar
  • 121k
16 votes

How would ocean tides work on a tidally-locked planet?

Since the tidal bulge is always in the same place, how would that affect ocean tides? The concept of tidal bulge is a useful fiction, but fiction nonetheless. For an object in an eccentric orbit, the ...
David Hammen's user avatar
  • 33.9k
15 votes
Accepted

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 ...
James K's user avatar
  • 121k
15 votes

Were any other planets in the solar system previously habitable?

The idea that planets age and go from being viable to dead is an old one (and typical for old science fiction), but not really supported by modern science. Rather, both planets and the sun evolve over ...
Anders Sandberg's user avatar
13 votes

Confusion over habitable zone

The reason you get a too cold temperature for Earth is of course because you ignored the greenhouse effect. The atmospheric composition strongly affects the actual temperature of planets, which ...
Anders Sandberg's user avatar
9 votes
Accepted

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 ...
Rory Alsop's user avatar
  • 5,063
9 votes
Accepted

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 ...
M. A. Golding's user avatar
8 votes
Accepted

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. ...
userLTK's user avatar
  • 24k
8 votes
Accepted

Given proper temperature and luminosity, Is the Circumstellar Habitable Zone larger for larger stars?

Yes. When our Sun expands into a humungous red giant in a few billion years, the habitable zone will indeed increase in size with it. It is expected to evolve into an AGB (asymptotic giant branch) ...
4NT4R3S's user avatar
  • 899
8 votes

Why do red dwarf (M-type) stars give off such violent flares and CMEs, out of proportion to their size and temperature?

Magnetic activity in the form of magnetically powered flares, hot X-ray emitting coronal, UV-bright chromospheres and starspots is driven by an interior stellar dynamo. Whilst the details of how this ...
ProfRob's user avatar
  • 152k
7 votes

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". ...
John Duffield's user avatar
7 votes

Is the Michael H. Hart range for the Habitable Zone (Goldlocks Zone) still used?

A number of contemporary researchers in this field consider Hart's model plain erroneous at the lower temperatures (i.e. upper range on the AU), among them David Catling who reasons that the main ...
the gods from engineering's user avatar
7 votes
Accepted

Orbital period of a planet orbiting Delta Pavonis in habitable zone

From the Keplerian-Newtonian two-body approximation (which is more than good enough for most fictional worldbuilding), eccentricity doesn't matter for orbital period. When the mass of the satellite is ...
notovny's user avatar
  • 4,788
6 votes

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 ...
userLTK's user avatar
  • 24k
6 votes

Were any other planets in the solar system previously habitable?

Most modern science generally agrees that it's not impossible for Mars to have once had microbial life, whether on its surface or underground. It's why so many probes, orbiters, landers, and rovers ...
KEY_ABRADE's user avatar
6 votes

Can such planet orbit 61 Cygni A within a habitable zone?

There are two issues here: is the orbit stable in the A-B binary system, and is the planet within the life zone. The 61 Cygni A-B orbit has a mean separation of 84 AU with a periapsis of 44 AU. That ...
Anders Sandberg's user avatar
6 votes

Is Venus in our sun's habitable zone?

What are the inner and outer edges of the Sun's circumstellar habitable zone or Goldilocks zone? Here is a link to a list of about a dozen estimates made in the last 60 years, some using complex ...
M. A. Golding's user avatar
6 votes

Why do red dwarf (M-type) stars give off such violent flares and CMEs, out of proportion to their size and temperature?

You would think that M-type dwarfs would be among the more magnetically stable stars due to their low temperature and mass, but they aren't. This is because such low-mass red dwarf stars are ...
4NT4R3S's user avatar
  • 899
5 votes
Accepted

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. ...
userLTK's user avatar
  • 24k
5 votes
Accepted

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. ...
ProfRob's user avatar
  • 152k
5 votes

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, ...
Anders Sandberg's user avatar
5 votes

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 ...
pela's user avatar
  • 38.2k
5 votes
Accepted

Can a tidally locked planet sustain a magnetic field

tl;dr: It should be possible for tidally locked planets to have magnetic fields under certain condiitions which are not all known at the moment. Tidally locked planets and moons rotate. Their ...
M. A. Golding's user avatar
4 votes

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 ...
ProfRob's user avatar
  • 152k
4 votes

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 ...
James K's user avatar
  • 121k
4 votes

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 ...
Rob's user avatar
  • 2,646
4 votes
Accepted

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 ...
Max0815's user avatar
  • 1,862
4 votes
Accepted

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 ...
SpaceCore's user avatar
  • 3,003

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