Welcome to Astronomy Stack Exchange

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:

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

Just questions...

Good answers are voted up and rise to the top.

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

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?

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?

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.

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.

• Specific issues with astronomy
• Real problems or questions that youâ€™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.

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?

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

+10 question voted up
+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
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
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.

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!

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.

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

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

 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