101. On the moon’s surface are large dark patches called seas – because this is what people once believed they were. They are, in fact, lava flows from ancient volcanoes.
102. Quasars are the most distant known objects in the Universe. Even the nearest is billions of light years away.
103. The brightest quasar is 3C 273, 2 billion light years away.
104. The brightest stars in the night sky are not actually stars, but the planets Jupiter, Venus, Mars and Mercury.
105. Jupiter’s moon Europa may have oceans of water beneath its dry surface and it is a major target in the search for life in the Solar System.
106. There may be 20 trillion galaxies in the Universe.
107. Galaxies are often found in a group or clusters. One cluster may have 30 or so galaxies in it.
108. In the 1970s the US Vikings 1 and 2 and the Soviet Mars 3 and 5 probes all reached the surface of Mars.
109. The Solar System has nine planets including Pluto, but Pluto may be an escaped moon or an asteroid not a planet.
110. The Milky Way belongs to a cluster of 30 galaxies called the Local Group, which is 7 million light years across.
111. The Virgo Cluster is 50 million light years away and is made up of 1000 galaxies.
112. For a satellite or a spacecraft to stay in orbit 200 km above the earth, it has to fly over 8 km/sec.
113. When a spacecraft reaches 140% of the orbital velocity i.e. 11.2 km/sec, it is going fast enough to break free of the Earth’s gravity. This is called escape velocity.
114. Saturn’s rings are sets of thin rings of ice, dust and tiny rocks, which orbit the planet around its equator.
115. A tablespoon of neutron star would weigh about ten billion tones.
116. The earth actually takes 365.24219 days to orbit the Sun, which is called one Solar Year. To compensate for the missing 0.242 days, the western calendar adds an extra day in February every fourth (leap) year, but misses out three leap years every four centuries.
117. X-Rays cannot reach the earth’s atmosphere, so astronomers can only detect them using space telescopes such as ROSAT.
118. The Sun has sunspots, the dark spots on the Sun’s photosphere (surface), 2000°C cooler than the rest of the surface.
119. After the big bang, there was antimatter, the mirror image of matter. Antimatter and matter destroyed each other when they met, thus they annihilated. Matter just won, but the Universe was left almost empty.
120. The afterglow of the Big Bang can still be detected as microwave background radiation coming from all over space.
121. Dishes in the space telescopes have to be made accurate two billionths of a millimeter.
122. You can see another galaxy with the naked eye: the Andromeda Galaxy, 2.2 million light years away.
123. Dried up riverbeds show that Mars probably once had water in its surface. There is sometimes ice at the poles and maybe water underground.
124. For a satellite to fly off into the space, its momentum should be greater than the pull of gravity of the earth.
125. The future of the Universe may depend on how much dark matter there is. If there is too much, its gravity will eventually stop the Universe’s expansion – and make it shrink again.