An unusually strong portfolio can certainly help, particularly if your art integrates into your overall narrative and figures to be a part of your future. The less it stands out, and the more it’s just a side activity, the less effect it will be likely to have. In some cases, a supplement may have a negative effect - no one likes to have their time wasted reviewing work which doesn’t meet standards, or which doesn’t really fit in to an applicant’s overall narrative. Even a very strong portfolio will be unlikely to overcome major academic deficiencies, however.
Is art important enough to your long term plan that you would consider applying to the Brown-RISD joint program? A RISD-caliber portfolio would definitely stand out at the Ivies and similar highly selective colleges. The idea of bringing your art into astrophysics research is appealing, and could definitely help you stand out.
Here’s a couple of video clips from students in the Brown-RISD program who have combined art with science quite effectively:
http://motionographer.com/2014/05/30/xiangjun-shi-why-do-i-study-physics/
http://browncreativemind.com/conversations/lizzie-kripkie-brownrisd-dual-degree/
I would also be rigorous in making sure that your portfolio is really of sufficiently high quality to stand out. Many applicants have an opinion of their talents that isn’t necessarily backed up by their work. I’ve seen a lot of kids delude themselves, and ignore advice, plunging ahead under the mistaken belief that they will be recognized as the next great talent. External awards help, but art is highly subjective. Is your art at the level of Scholastic Arts and Writing National Portfolio work, or YoungArts finalist level? That would definitely stand out.
Many of the top award winners and portfolio applicants are kids who come from schools with nationally known programs, and who have been exposed to teachers who understand what goes into making a good portfolio - places like Dreyfoos School for the Arts, Miami DASH, GW Carver, etc. Having professional advice definitely makes a difference, as does assembling a well-presented portfolio. Lighting and photography make a difference.
There is a RISD adjunct professor (who also teaches at the RISD pre-college program) named Clara Lieu who charges a fairly nominal fee to critically review portfolios. She’s worked with tons of pre-college kids, and has good insights on where many students tend to go off track.
https://claralieu.■■■■■■■■■■■■■/college-art-portfolio-video-critiques/
If you are applying this year then you are way behind the curve. If you are applying for next year, and if art is a major part of your narrative and future plans, then I would really work to put together a top notch portfolio. It takes a lot of time, and many people underestimate that.