Star Rounds

Look up at a blue sky and you see no stars. They have not gone anywhere. The Sun is simply too bright, and the constellations are still right above you. This app turns your phone into a light. Point it and a spotlight falls on the sky; inside that circle the stars and constellation lines appear. It works in daylight, at night, and straight down through the ground. Every constellation you light up is recorded in your star atlas. Filling all 88 is the game. ■ Find "Find Gemini!" Swing your phone around, shine the light, and press when you think you have it. Miss, and a beam stretches to the right answer. All 88 constellations, plus the Sun, Moon and planets. You can also search by name. Tap ⌕, type in English or Japanese, and a beam points the way. ■ Travel Fly to the constellation you are lighting. You pass rings of distance on the way: the Moon, the Sun, Jupiter's orbit, Neptune's orbit, Voyager 1, the Oort cloud — hundreds of light years out. When you arrive, you circle the whole group of stars. The familiar shape comes apart in front of you. It turns out that shape belonged to one single vantage point: Earth. ■ Every star has something you did not know • The light of Betelgeuse reaching your eye now left the star in 1476 • Rigel truly shines 50,000 times brighter than the Sun, yet from 860 light years it is only magnitude 0.1 • Antares is 296 times the Sun's width — put it where the Sun is and it would swallow Earth's orbit • Mintaka and Bellatrix are joined by a single line, and stand 950 light years apart ■ Turn time and season Tap "Six months on" and the constellations now hidden behind the Sun rise into the night. Or move the dials yourself, in ten-minute steps and half a year. ■ No network Your location stays on the device. Every position is calculated on board, so the app works with no signal at all. ■ Inside 8,404 naked-eye stars, all 88 constellations with lines and boundaries, 333 proper star names, the Sun, Moon and seven planets, distances for 2,368 stars. English and Japanese.