# How different our red dwarf stars from yellow dwarf stars? **URL:** \ **Category:** Factual Questions\ **Created:** [April 19, 2014, 2:19am UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467 "2014-04-19T02:19:47Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![buddha\_david](https://avatars.discourse-cdn.com/v4/letter/b/ee7513/32.png) [@buddha\_david](https://boards.straightdope.com/u/buddha_david)\ **Post date:** [April 20, 2014, 1:05am UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467/21 "2014-04-20T01:05:33Z")
> [@Exapno\_Mapcase](#): > > It took about one billion years for life to appear on Earth. It took 3.5 billion years for multicellular life to appear. That’s not immediate. Out of a sample size of one. We have no way of knowing if Earth’s evolutionary life path was faster or slower than the universal norm – although, taking a quick glance around at the current quality of that so-called intelligent life, it was probably slower. 🆒 ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [April 20, 2014, 1:12am UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467/22 "2014-04-20T01:12:38Z")
> [@buddha\_david](#): > > Out of a sample size of one. The one was the one watchwolf49 specifically mentioned, so it doesn’t matter whether it’s the only one or not. ---
**Author:** ![mandala](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mandala/32/95_2.png) [@mandala](https://boards.straightdope.com/u/mandala)\ **Post date:** [April 20, 2014, 3:23am UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467/23 "2014-04-20T03:23:25Z")
Red dwarfs get bluer as they get older and start running out of Hydrogen fuel. As they get bluer, they get hotter and emit more UV. In fact, Proxima Centauri, one heck of a dim red dwarf, is calculated to eventually become 2% as luminous as the Sun a few trillion years from now. This means around the red dwarf, the HZ slowly migrates outward. A planet currently frozen solid may become habitable at that point, and remain habitable for hundreds of billions of years. The other advantages would be that it would not be tidally locked. As red dwarfs grow older they become quieter and cease being flare stars. The planet would benefit from a steady dose of warming radiation, and plenty of UV. One heck of a long wait, sure, but life can indeed get going. If the red dwarfians develop astronomical instruments, they are going to see a giant elliptical galaxy and nothing else in the entire universe. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [April 20, 2014, 7:03pm UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467/24 "2014-04-20T19:03:06Z")
> [@buddha\_david](#): > > Out of a sample size of one. We have no way of knowing if Earth’s evolutionary life path was faster or slower than the universal norm. We have 3 billion data points of a year that passed without the successful development of eukaryotes from its precursors. Now, I admit that it doesn’t tell us a whole lot about the possibilities of all kinds of life everywhere. But it is a reasonably significant clue that starting life from scratch might more probable than building eukaryotes from bacteria and archaebacteria (or whatever). Far from a slam dunk, though, and you’re correct that we don’t know anything about Earth’s path compared to others. For example, no arthropods have ever developed a complex single eye. They took a path that doesn’t lead to it long ago and never looked back (forgive the pun). It’s possible that Earth’s early life took a similarly difficult path towards multicellular life. But Nick Lane’s book Power, Sex, and Suicide points out a number of special developments that are required, and they’re pretty high walls to climb over. They include apoptosis: the ability of a cell to kill itself to help the organism, which is a hard thing for a colony of single-celled organisms to develop. Instead, the possibility for that came as a side effect of the internalization of mitochondria (or so he posits). It’s a rather tricky argument that I can’t do justice to, but it sure was worth reading the book for. (Lane argues that the creation of eukaryotes required an extremely unlikely sequence of events, and given those 3 billion data points, he might be right.) Pardon the tangent. I find it interesting how often topics in that book are (at least tangentially) related to threads here at the Dope. Highly recommended book, esp. for the typical Doper. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [April 20, 2014, 7:22pm UTC](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467/25 "2014-04-20T19:22:51Z")
> [@mandala](#): > > Red dwarfs get bluer as they get older and start running out of Hydrogen fuel. As they get bluer, they get hotter and emit more UV. In fact, Proxima Centauri, one heck of a dim red dwarf, is calculated to eventually become 2% as luminous as the Sun a few trillion years from now. This means around the red dwarf, the HZ slowly migrates outward. A blue dwarf, a class of stars that doesn’t even exist yet, because the universe isn’t old enough. > **[Blue dwarf (red-dwarf stage)](https://en.wikipedia.org/wiki/Blue_dwarf_(red-dwarf_stage))** > > A blue dwarf is a hypothetical class of star that develops from a red dwarf after it has exhausted much of its hydrogen fuel supply. Because red dwarfs fuse their hydrogen slowly and are fully convective (allowing their entire hydrogen supply to be fused, instead of merely that in the core), they are predicted to have lifespans of trillions of years; the Universe is currently not old enough for any blue dwarfs to have formed yet. Their future existence is predicted based on theoretical models. St... [Previous page](https://boards.straightdope.com/t/how-different-our-red-dwarf-stars-from-yellow-dwarf-stars/686467.md?page=1)