how would 2 close binary stars of 0.86 solar masses each separated by 5.5 million miles appear from earth and how noticeable would their dimming be when orbiting their barycenter and how long would it last
Two 0.86-solar-mass stars separated by 5.5 million miles would likely look like a very close pair of bright points from Earth unless the system were nearby and resolved by a telescope; by naked eye they would usually blend into a single star-like point. If the orbit is aligned so one passes in front of the other, the dimming would be noticeable only as a periodic dip in brightness, and the eclipse duration would be on the order of about 1 day for a central eclipse in a circular, edge-on orbit.
What they would look like
For a binary with those masses and separation, the stars would orbit each other fairly quickly and stay very close together in the sky. The main visual impression would be:
- As an unresolved source: one steady star-like point.
- Through a telescope: two close points, possibly varying slightly in brightness depending on star type.
- If eclipsing: a repeating light curve with two dips each orbit, one usually deeper than the other if the stars differ in size or surface brightness. Eclipsing binaries are exactly the kind of system where the total light drops periodically as one star blocks the other.
How much dimming
The amount of dimming depends mostly on:
- How edge-on the orbit is.
- Whether the stars are similar in size and brightness.
- Whether the eclipse is total or partial.
If the two stars are roughly similar, a deep eclipse can cut the combined light by something like 25% to 50% in an idealized case, but many real systems are shallower because the stars are not perfectly aligned or not equal in brightness. The brightness decline in eclipsing binaries comes from one star passing in front of the other, and the light-curve shape tells you how big and how aligned the stars are.
How long it lasts
Using the stated separation of 5.5 million miles and the combined mass of 1.72 solar masses, the orbital period is roughly 160 days, and the relative orbital speed is about 22 miles per second. With that scale, a central eclipse would last about 1 day from first to last contact, with the deepest part lasting perhaps several hours depending on the stars’ radii. That estimate is based on the crossing time across the stellar diameters compared with the orbital speed, which is the standard way eclipse duration is estimated in binary systems.
A simple picture
Imagine two fairly ordinary sun-like stars locked in a slow, wide dance. Most of the time they just look like a single steady point of light, but every few months one slides in front of the other and the system briefly fades before returning to normal. That fade would be noticeable in precision brightness measurements, and possibly to the eye only if the dimming were especially deep and the system were bright enough.
One caveat
The exact appearance and dimming can change a lot if either star is larger than the Sun, rotating rapidly, distorted by gravity, or not perfectly edge-on from Earth. So the numbers above are a good order-of-magnitude estimate, not a guaranteed exact light curve.
Brief takeaway
- Appearance: probably a single point to the naked eye, potentially a close pair in a telescope.
- Dimming: noticeable only if the orbit is eclipsing; could be substantial.
- Duration: about 1 day for a full eclipse, with the strongest drop lasting hours.