Calculate -> Binary star orbit data

Author: Jim Carr

README.md

@@ -56,7 +56,7 @@ If you're interested in this topic, please buy the book! It provides far more de
 
 ### Binary Stars
 
-- [ ] Calculate -> Binary star orbit data
+- [x] Calculate -> Binary star orbit data
 
 ### The Moon
 

src/Main.java

@@ -5,6 +5,7 @@ public static void main(String[] args) {
 		testSun();
 		testPlanet();
 		testComet();
+		testBinary();
 	}
 
 	public static void testDateTime() {
@@ -66,4 +67,10 @@ public static void testComet() {
 		testComet.testPositionOfEllipticalComet();
 		testComet.testPositionOfParabolicComet();
 	}
+
+	public static void testBinary() {
+		TestBinary testBinary = new TestBinary();
+
+		testBinary.testBinaryStarOrbit();
+	}
 }

src/TestBinary.java

@@ -0,0 +1,21 @@
+import astro.practical.lib.PABinary;
+import astro.practical.models.BinaryStarOrbit;
+import astro.practical.test.TestLib;
+
+public class TestBinary {
+    PABinary paBinary;
+    TestLib testLib;
+
+    public TestBinary() {
+        paBinary = new PABinary();
+        testLib = new TestLib();
+    }
+
+    public void testBinaryStarOrbit() {
+        BinaryStarOrbit binaryStarOrbit = paBinary.binaryStarOrbit(1, 1, 1980, "eta-Cor");
+
+        testLib.setTestName("Binary Star Orbit")
+                .Assert(318.5, binaryStarOrbit.positionAngleDeg)
+                .Assert(0.41, binaryStarOrbit.separationArcsec);
+    }
+}

src/astro/practical/data/BinaryInfo.java

@@ -0,0 +1,35 @@
+package astro.practical.data;
+
+import java.util.ArrayList;
+import java.util.List;
+import astro.practical.models.data.BinaryData;
+
+public class BinaryInfo {
+    List<BinaryData> binaryData;
+
+    public BinaryInfo() {
+        binaryData = new ArrayList<>() {
+            {
+                add(new BinaryData("eta-Cor", 41.623, 1934.008, 219.907, 0.2763, 0.907, 59.025, 23.717));
+                add(new BinaryData("gamma-Vir", 171.37, 1836.433, 252.88, 0.8808, 3.746, 146.05, 31.78));
+                add(new BinaryData("eta-Cas", 480.0, 1889.6, 268.59, 0.497, 11.9939, 34.76, 278.42));
+                add(new BinaryData("zeta-Ori", 1508.6, 2070.6, 47.3, 0.07, 2.728, 72.0, 155.5));
+                add(new BinaryData("alpha-CMa", 50.09, 1894.13, 147.27, 0.5923, 7.5, 136.53, 44.57));
+                add(new BinaryData("delta-Gem", 1200.0, 1437.0, 57.19, 0.11, 6.9753, 63.28, 18.38));
+                add(new BinaryData("alpha-Gem", 420.07, 1965.3, 261.43, 0.33, 6.295, 115.94, 40.47));
+                add(new BinaryData("aplah-CMi", 40.65, 1927.6, 269.8, 0.4, 4.548, 35.7, 284.3));
+                add(new BinaryData("alpha-Cen", 79.92, 1955.56, 231.56, 0.516, 17.583, 79.24, 204.868));
+                add(new BinaryData("alpha Sco", 900.0, 1889.0, 0.0, 0.0, 3.21, 86.3, 273.0));
+            }
+        };
+    }
+
+    public BinaryData getBinaryInfo(String name) {
+        BinaryData binaryInfo = binaryData.stream()
+                .filter(p -> p.Name == name)
+                .findFirst()
+                .orElse(new BinaryData("NotFound", 0, 0, 0, 0, 0, 0, 0));
+
+        return binaryInfo;
+    }
+}

src/astro/practical/lib/PABinary.java

@@ -0,0 +1,40 @@
+package astro.practical.lib;
+
+import astro.practical.data.BinaryInfo;
+import astro.practical.models.BinaryStarOrbit;
+import astro.practical.models.data.BinaryData;
+
+public class PABinary {
+    /**
+     * Calculate orbital data for binary star.
+     */
+    public BinaryStarOrbit binaryStarOrbit(double greenwichDateDay, int greenwichDateMonth, int greenwichDateYear,
+            String binaryName) {
+        BinaryInfo binaryInfo = new BinaryInfo();
+
+        BinaryData binaryData = binaryInfo.getBinaryInfo(binaryName);
+
+        double yYears = greenwichDateYear
+                + (PAMacros.civilDateToJulianDate(greenwichDateDay, greenwichDateMonth, greenwichDateYear)
+                        - PAMacros.civilDateToJulianDate(0, 1, greenwichDateYear)) / 365.242191
+                - binaryData.EpochPeri;
+        double mDeg = 360 * yYears / binaryData.Period;
+        double mRad = Math.toRadians(mDeg - 360 * Math.floor(mDeg / 360));
+        double eccentricity = binaryData.Ecc;
+        double trueAnomalyRad = PAMacros.trueAnomaly(mRad, eccentricity);
+        double rArcsec = (1 - eccentricity * Math.cos(PAMacros.eccentricAnomaly(mRad, eccentricity))) * binaryData.Axis;
+        double taPeriRad = trueAnomalyRad + Math.toRadians(binaryData.LongPeri);
+
+        double y = Math.sin(taPeriRad) * Math.cos(Math.toRadians(binaryData.Incl));
+        double x = Math.cos(taPeriRad);
+        double aDeg = PAMacros.wToDegrees(Math.atan2(y, x));
+        double thetaDeg1 = aDeg + binaryData.PANode;
+        double thetaDeg2 = thetaDeg1 - 360 * Math.floor(thetaDeg1 / 360);
+        double rhoArcsec = rArcsec * Math.cos(taPeriRad) / Math.cos(Math.toRadians(thetaDeg2 - binaryData.PANode));
+
+        double positionAngleDeg = PAUtil.round(thetaDeg2, 1);
+        double separationArcsec = PAUtil.round(rhoArcsec, 2);
+
+        return new BinaryStarOrbit(positionAngleDeg, separationArcsec);
+    }
+}

src/astro/practical/models/BinaryStarOrbit.java

@@ -0,0 +1,11 @@
+package astro.practical.models;
+
+public class BinaryStarOrbit {
+    public double positionAngleDeg;
+    public double separationArcsec;
+
+    public BinaryStarOrbit(double positionAngleDeg, double separationArcsec) {
+        this.positionAngleDeg = positionAngleDeg;
+        this.separationArcsec = separationArcsec;
+    }
+}

src/astro/practical/models/data/BinaryData.java

@@ -0,0 +1,39 @@
+package astro.practical.models.data;
+
+public class BinaryData {
+    /** Name of binary system. */
+    public String Name;
+
+    /** Period of the orbit. */
+    public double Period;
+
+    /** Epoch of the perihelion. */
+    public double EpochPeri;
+
+    /** Longitude of the perihelion. */
+    public double LongPeri;
+
+    /** Eccentricity of the orbit. */
+    public double Ecc;
+
+    /** Semi-major axis of the orbit. */
+    public double Axis;
+
+    /** Orbital inclination. */
+    public double Incl;
+
+    /** Position angle of the ascending node. */
+    public double PANode;
+
+    public BinaryData(String name, double period, double epochPeri, double longPeri, double ecc, double axis,
+            double incl, double paNode) {
+        this.Name = name;
+        this.Period = period;
+        this.EpochPeri = epochPeri;
+        this.LongPeri = longPeri;
+        this.Ecc = ecc;
+        this.Axis = axis;
+        this.Incl = incl;
+        this.PANode = paNode;
+    }
+}