Space & astronomy · the experiment
Rebuild the most stretched orbit
You hold the two neutron stars of PSR J0653+0443 and their 79-day period. Your job: give the orbit its shape, then check what that shape implies.
1 · Stretch the orbit
Beginner
Over its 79-day orbit, where does the pulsar spend nearly all its time?
The period is fixed at 79.084 days. Set the eccentricity so that the pulsar goes from −90° to +90° around its companion in 46 minutes.
2 · Slow down at the far end
At closest approach, the two stars are 0.83 solar radii apart and moving at 1,140 km/s. The ratio of the farthest to the closest distance is (1 + e)/(1 − e), about 262.
Intermediate
How fast are they moving at the farthest point of the orbit?
3 · Go back to the old record
Before this pair, the most stretched orbit known for any pair of stars had an eccentricity of 0.985.
Expert
Same period, same mass, eccentricity 0.985: how long would the passage from −90° to +90° last?
Check it: bring the eccentricity back to 0.985 and read the passage time.
4 · Turn the ellipse
Relativity makes the ellipse turn: its closest point advances by 0.0178° per year. The paper writes this advance along the orbit as proportional to the angle θ travelled around the companion, not to the time elapsed.
Expert
What share of one full orbit's advance happens during the 46-minute passage, from −90° to +90°?
Orbit rebuilt
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