Skip to main content
Astronomy

Welcome to Astronomy Stack Exchange

site icon

Astronomy Stack Exchange is a question and answer site for astronomers and astrophysicists. It's built and run by you as part of the Stack Exchange network of Q&A sites. With your help, we're working together to build a library of detailed answers to every question about astronomy.

We're a little bit different from other sites. Here's how:

Ask questions, get answers, no distractions

This site is all about getting answers. It's not a discussion forum. There's no chit-chat.

Just questions...

...and answers.

Good answers are voted up and rise to the top.

The best answers show up first so that they are always easy to find.

The person who asked can mark one answer as "accepted".

Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.

Is the Sun visible from Proxima Centauri to human eyes?

14

I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?

2 Answers

4

Alpha Centauri A and B happen to be rather similar to Sol, and their absolute magnitudes are 4.38 and 5.71 respectively (Wikipedia). Add them together and you get absolute magnitude 4.10 (the scale is logarithmic, and backward). Sol, with absolute magnitude 4.83, should look 0.73 magnitude dimmer than αCen at the same distance, so magnitude +0.46, quite bright.

3

The key to this is the so called Absolute Magnitude, which represents the visual magnitude from a distance of 10 parsecs (about 32 light years). The sun is much brighter than Proxima Centauri. It has an absolute magnitude of 4.8, and at a distance of 4 light years (the distance of Proxima), it would be be somwhat brighter than 1st mag, and so very easily visible with the unaided eye.

Get answers to practical, detailed questions

Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.

Ask about...

  • Specific issues with astronomy
  • Real problems or questions that you’ve encountered
  • Experimental and theoretical problems in astronomy, astrophysics, cosmology, and planetary science
  • Astronomical equipment, both professional and amateur
  • The use of space probes, telescopes, and rovers for astronomical purposes
  • Certain resource requests

Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.

Questions that need improvement may be closed until someone fixes them.

Don't ask about...

Tags make it easy to find interesting questions

All questions are tagged with their subject areas. Each can have up to 5 tags, since a question might be related to several subjects.

Click any tag to see a list of questions with that tag, or go to the tag list to browse for topics that interest you.

Is the Sun visible from Proxima Centauri to human eyes?

14

I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?

You earn reputation when people vote on your posts

Your reputation score goes up when others vote up your questions, answers and edits.

+10 question voted up
+10 answer voted up
+15 answer is accepted
+2 edit approved

As you earn reputation, you'll unlock new privileges like the ability to vote, comment, and even edit other people's posts.

Reputation Privilege
15 Vote up
50 Leave comments
125 Vote down (costs 1 rep on answers)

At the highest levels, you'll have access to special moderation tools. You'll be able to work alongside our community moderators to keep the site focused and helpful.

Reputation Privilege
500 Vote to close, reopen, or migrate questions
1000 Edit other people's posts
2000 Access to moderation tools
see all privileges

Improve posts by editing or commenting

Our goal is to have the best answers to every question, so if you see questions or answers that can be improved, you can edit them.

Use edits to fix mistakes, improve formatting, or clarify the meaning of a post.

Use comments to ask for more information or clarify a question or answer.

You can always comment on your own questions and answers. Once you earn 50 reputation, you can comment on anybody's post.

Remember: we're all here to learn, so be friendly and helpful!

9

Alpha Centauri A and B happen to be rather similar to Sol, and their absolute magnitudes are 4.38 and 5.71 respectively (Wikipedia). Add them together and you get absolute magnitude 4.10 (the scale is logarithmic, and backward). Sol, with absolute magnitude 4.83, should look 0.73 magnitude dimmer than αCen at the same distance, so magnitude +0.46, quite bright.

edit

The difference between magnitude 0.4 (your answer) and magnitude 0.46 (my answer) is accounted for by the distance between Proxima and Alpha A/B, which I ignored for simplicity. It's not a factor of 1.4. - Anton Sherwood Aug 27, 2016 at 3:56

add a comment

Unlock badges for special achievements

Badges are special achievements you earn for participating on the site. They come in three levels: bronze, silver, and gold.

In fact, you can earn a badge just for reading this page:

 Informed Read the entire tour page
 Student First question with score of 1 or more
 Editor First edit
 Good Answer Answer score of 25 or more
 Civic Duty Vote 300 or more times
 Famous Question Question with 10,000 views

see all badges

Sign up to get started

Sign up

Signing up allows you to:

  • Earn reputation when you help others with questions, answers and edits.
  • Select favorite tags to customize your home page.
  • Claim your first badge:  Informed
Looking for more in-depth information on the site? Visit the Help Center

Astronomy Stack Exchange is part of the Stack Exchange network

Like this site? Stack Exchange is a network of 182 Q&A sites just like it. Check out the full list of sites.

Stack Exchange