Model · Sun and Ross 128
Two stars, closing at 31 km/s.
The Sun and Ross 128 are not standing still. Ross 128 is falling toward us at an angle, and the gap that every message has to cross is shrinking. It has also swung out of the one narrow band of sky where Earth can be seen crossing the Sun.
- Distance now
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- Closing speed
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- Closest in
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- They lost sight of Earth
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Model
Pick a year
Drag through time. In recorded history the view is edge-on to Earth's orbit, so you can watch Ross 128 cross the thin band from which Earth is seen passing the Sun. In deep time the map looks down on that plane, with the Sun at the centre.
- Distance
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- Light delay, one way
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- Reply, at the earliest
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- Moving
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- Our Sun in their sky
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- Their star in ours
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- Height above Earth's orbit
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- Can they see Earth cross the Sun?
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- Sun · us
- Ross 128 · them
- Earth transit zone: from here, Earth can be seen crossing the Sun
- the chosen year
Moments
What the drift means
Dates come from the model below. Click one to jump to it.
How this is modelled
Ross 128's measured position, parallax and proper motion (Gaia DR3) and radial velocity (−31.0 km/s, Pulkovo compilation) give its velocity relative to the Sun: 37.9 km/s in total, 31.0 of it straight toward us. The model moves it in a straight line at that velocity and measures everything from the Sun. Gravity from the Galaxy and from passing stars is left out, which is fine for tens of thousands of years and drifts by a few tenths of a light year over a hundred thousand.
The Earth transit zone is the band within 0.266° of the plane of Earth's orbit, the Sun's radius seen from 1 au. A world inside it sees Earth cross the Sun once a year. The model holds that plane fixed at its J2000 orientation, as Kaltenegger & Faherty (Nature, 2021) did; they found Ross 128 inside the zone from about 1040 BCE to 1120 CE, and this model gives 1142 BCE to 1119 CE. Letting the plane wobble as it really does moves the start to about 1390 BCE and leaves the end where it is.
Closest approach: this model gives 6.34 ly about 71,000 years from now. García-Sánchez et al. (2001), with older data and a galactic potential, found 6.23 ly at about the same time. Brightness uses absolute magnitudes 4.83 for the Sun and 13.53 for Ross 128 and ignores dust. Story time is real time plus 70,491 days; the stars move on real time, so "now" here is the story's present, 2219.
Source: lib/drift.js. The 2219 signal · Pulsar ledger