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64 votes
Accepted

Serious alternate form of the Drake Equation, or graffiti?

Given the font, it's xkcd 384, The Drake Equation. The two $X$'s are the other $f$ terms from the original Drake equation, while the $B_S$ is "amount of bullshit you're willing to buy from Frank ...
Rob's user avatar
  • 2,035
48 votes

How did the Milky Way quasar not disrupt life on Earth?

An active galactic nucleus doesn't emit energy equally in all directions. It may form "jets", and if you are looking into the AGN at the right angle, and then nucleus is active enough, then ...
James K's user avatar
  • 119k
21 votes

Could rogue planets harbor life?

There's also the possibility that a rogue giant planet may have a moon with a subsurface ocean of liquid water due to tidal heating in an orbit close enough to its parent planet. E.g. if Jupiter was a ...
John's user avatar
  • 1,548
16 votes

Whats the probability of a hazardous impact for human life on Mars?

We actually have a very good idea of this because the Mars Reconnaissance Orbiter has been orbiting Mars for over a decade. The MRO is, basically, a spy satellite around Mars and is continually taking ...
Mark Olson's user avatar
  • 7,630
16 votes

What is the probability of life having developed or going to develop in our solar system another time?

The answer is, it could be non-zero (some would argue it must be non-zero), but since we don't know what the probability of life emerging on Earth was, it is impossible to quantify. This is why this ...
ProfRob's user avatar
  • 149k
16 votes

How did the Milky Way quasar not disrupt life on Earth?

How much dangerous a quasar at Sag A* could be? A Fermi-inspired estimation: Assume it is 1000x the luminosity of the Milky way. This is rather at the high end (as per Wiki) and rounding out its ...
fraxinus's user avatar
  • 2,839
13 votes

Could rogue planets harbor life?

In short, if a rogue planet has enough internal heat and retains enough of that internal heat by a thick atmosphere or within a miles-deep ice crust, it could be warm enough for liquid water and thus ...
M. A. Golding's user avatar
13 votes

How did the Milky Way quasar not disrupt life on Earth?

I think the source of confusion here is that the two sources you mention implicitly have different definitions of what quasar is. Firstly, to our current understanding, quasars are not a well-defined ...
vvotan's user avatar
  • 290
13 votes
Accepted

Why can't a half-illuminated planet support life at all?

The phenomenon you are referring to is called "tidal locking", it occurs when the orbital period or one revolution of the planet is roughly equal to the time it takes to rotate in on its ...
Arjun's user avatar
  • 1,256
12 votes

Why can't a half-illuminated planet support life at all?

Pierrehumbert (2010) modelled the possible climates of Gliese 581g. Although that planet has since been shown to probably not exist, the model of a planet with similar characteristics should still ...
gerrit's user avatar
  • 2,033
11 votes

What if we are looking for the wrong signs of life on other planets?

What if we are looking for the wrong signs of life on other planets? Are there any fields of astronomy that look beyond the "near-Earth" life comparisons and look for life in other (...
userLTK's user avatar
  • 23.9k
10 votes
Accepted

What is the underwater temperature of Europa?

No, nothing on Europa could possibly be photosynthesizing as we know it. Jupiter doesn't emit light, and what it reflects from the sun is not enough, plus there's no significant amount of carbon ...
Nathanael Vetters's user avatar
10 votes
Accepted

Is extra-planetary phosphine actually a new discovery?

You're correct; extraterrestrial phosphine is not actually a new discovery. As you said, we've known for decades (see e.g. Ridgway et al. 1976) that phosphine can and does exist in some gas giant ...
HDE 226868's user avatar
  • 36.3k
9 votes

Could any known, living organisms on Earth survive on Mars?

I've read lichens have been shown to survive in a Mars-like atmosphere, tested by NASA. This other article says they can survive vacuum and radiation http://www.astrobio.net/extreme-life/lichen-on-...
Pablo's user avatar
  • 1,081
9 votes

How did the Milky Way quasar not disrupt life on Earth?

A lot of answers here talking about jets, but that only applies to perhaps the very high energy (gamma ray) emission. Most of the luminous quasars we see are not seen via their jets but are extremely ...
ProfRob's user avatar
  • 149k
8 votes

Proxima as Supernova

Proxima Centauri can't explode as supernova as it is about 2 orders of magnitude too small and light. But if a supernova were to happen from that distance? How bright would it be? You can use the ...
Ingolifs's user avatar
  • 4,157
7 votes
Accepted

The Solar System formation

I'll touch on a few of these because I disagree with some of those ideas. There are approx. 2000 planetary systems discovered, and all of them, except the Solar System, have angular momentum ...
userLTK's user avatar
  • 23.9k
7 votes
Accepted

How did the Milky Way quasar not disrupt life on Earth?

Quasars emit their energy along a pair of antipodal jets. Those jets have an angular width of no more than about 2.5 milliarcseconds, which is about $5.5\times 10^{-7}$ degrees, or $10^{-8}$ radians, ...
zibadawa timmy's user avatar
6 votes

Can aliens possibly be around us?

There are a number of misconceptions here. First, most of the visible stars that we see are much closer than you think. Most are within a few hundred light-years. With telescopes you can see more ...
James K's user avatar
  • 119k
6 votes
Accepted

Could Mars have oil?

Planet solidifying. No molten core iron -> no magnetosphere -> solar wind strips atmosphere. Without atmosphere to cycle in exposed water also leaves. Why did Mars freeze solid & Earth has not (...
tomc's user avatar
  • 463
6 votes
Accepted

Plant on large Asteroid?

It might depend on what qualifies as a plant. A thin film of rugged mold for example . . . just maybe. The tricky part is that asteroids are too small to retain an atmosphere and you need an ...
userLTK's user avatar
  • 23.9k
6 votes

Consequences of strong wind on an alien Planet on the possibility of life

We know that life can start and evolve quite well on a planet with 250 mph winds: You're living on one. The jet stream can reach this speed in the Earth's atmosphere. Beyond that it is speculation. ...
James K's user avatar
  • 119k
6 votes

Most powerful microscope on Mars?

Having checked the older rovers, the highest resolution microscope on Mars is in the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument. ...
James K's user avatar
  • 119k
6 votes

How did the Milky Way quasar not disrupt life on Earth?

You misinterpreted the article. the Milky Way recently (by cosmic standards) went through a quasar stage in its evolution. That does seem to indicate that the Milky Way turned into a quasar, but in ...
RonJohn's user avatar
  • 409
5 votes

What if we are looking for the wrong signs of life on other planets?

We only have a sample of 1 - the Earth - for analysis or proposition of potential life-compatible conditions on other planets. Only carbon-based life can exist in this universe. Boron and Silicon are ...
QEDlin Saltum's user avatar
5 votes
Accepted

What planets and moons have we seeded with life (if any)?

This would seem to be constrained to planets and moons earth has landed on or impacted at all, as we have no way of telling after the fact whether a lander was perfectly sterilized. That list is as ...
Pulchritude's user avatar
5 votes
Accepted

Can life on earth be supported by only a Red Dwarf star or a White Dwarf(state still hot not cooled enough yet)?(Provided it is near to the star)

Certainly a red-dwarf star can have enough energy for a planet around it to be in the goldilocks zone. There are some difficulties with red-dwarf stars and Earth like planets. The planet would ...
userLTK's user avatar
  • 23.9k
5 votes

For colonization purposes, what is so good about Titan?

There is nowhere in the solar system except for parts of Earth where humans have any hope of surviving without heavy technological support. There is next to no free oxygen anywhere, nowhere has a ...
Steve Linton's user avatar
  • 10.3k
5 votes

What is the probability of life having developed or going to develop in our solar system another time?

There's nothing wrong with asking a question to which the answer is "nobody knows" -- so long as you are willing to accept that the answer is essentially "nobody knows". The only ...
David Hammen's user avatar
  • 33.7k

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