MPSC 2026 Prelims Paper-I · Question 30 of 100

Correct — option (3), 'Statements (a) and (c) are not correct.' Work through the three statements one at a time. Statement (a) claims 61 satellites for Uranus. Uranus has 29 confirmed moons, the most recent of them announced in 2025 from James Webb Space Telescope observations; the count stood at 27 for most of the 2000s and has been in the twenties throughout the modern era. It has never been anywhere near 61, so statement (a) is false. Statement (b) puts Mercury's mean distance from the Sun at 58 million km. The accepted value is about 57.9 million km, or 0.39 astronomical units, so 58 million km is correct to the precision the statement uses, and statement (b) is true. Statement (c) puts Uranus at 4,495 million km from the Sun. That figure is real but belongs to a different planet: 4,495 million km, or about 30 astronomical units, is Neptune's mean distance. Uranus orbits at roughly 2,871 million km, about 19 astronomical units. Statement (c) is therefore false — and it is false in the most instructive way, by attaching a correct number to the wrong planet, which is the standard construction in solar-system questions. So (a) is false, (b) is true, (c) is false. Now read the options carefully, because two of them are framed positively and two negatively. Option (3) says statements (a) and (c) are not correct, which is exactly what has been established, and since there are only three statements it implies (b) is correct, which is also right. It is the only option that survives. Note the deliberate hazard: a candidate who has correctly worked out that only (b) is true, and who is reading quickly for the option that says 'only (b) is correct', will not find it — no such option is printed. The paper forces the conclusion to be expressed the other way round, as a statement about which two are false.

• (1)Only statement (a) is correct. — Wrong twice over. It accepts the claim that Uranus has 61 satellites, which no count of that planet's moons has ever supported — the confirmed total stands at 29 and was 27 for most of the 2000s. And it rejects statement (b), even though 58 million km is the correct mean distance of Mercury from the Sun to the precision given. Option (1) is the exact inversion of the true position on both statements it addresses.
• (2)Only statement (c) is correct. — Accepts 4,495 million km as Uranus's distance from the Sun. The number is a real solar-system figure but it belongs to Neptune, the outermost planet, at about 30 astronomical units; Uranus lies at roughly 2,871 million km, about 19 astronomical units. This option also denies statement (b), which is correct. A candidate who half-remembers 4,495 as 'one of the outer-planet distances' without fixing which planet it belongs to is the intended victim here.
• (4)Statements (b) and (c) are not correct. — The near miss, and the most dangerous option in the set. It is right about statement (c) — 4,495 million km is Neptune's distance, not Uranus's — but wrong about statement (b), since Mercury's mean distance really is about 57.9 million km and the statement's 58 million km is accurate. It also implies that the 61-satellite claim in statement (a) is correct, which it is not. One correct judgement out of three is worth nothing in a question of this construction; every statement must be settled before an option is chosen.

Solar-system numbers are examined because they are finite, checkable and easy to scramble. The two families of figure that recur are orbital distances and moon counts, and they behave very differently. Distances are stable: Mercury sits at about 0.39 astronomical units or 57.9 million km, Venus at 108, Earth at 150, Mars at 228, Jupiter at 778, Saturn at 1,427, Uranus at 2,871 and Neptune at 4,495 million km, and those values have not changed in any exam-relevant way in a century. Because they are stable, the examiner's trick is never to invent a number — it is to move a true number to a neighbouring planet, which is precisely what statement (c) does here. Moon counts are the opposite: they are provisional, they rise as survey telescopes and space telescopes find smaller and fainter objects, and a figure printed in a textbook a decade ago may be out of date. A candidate should therefore hold distances precisely and moon counts only as orders of magnitude — the inner rocky planets have none or almost none, while the giant planets have dozens, and in Saturn's case hundreds.

Uranus is worth knowing for more than its distance. It was discovered by William Herschel in 1781, the first planet found with a telescope rather than known to antiquity; Neptune followed in 1846, and was found by pointing a telescope where mathematics said it should be, after Urbain Le Verrier's calculations from irregularities in Uranus's orbit. Uranus is the planet that lies on its side, its rotational axis tilted by about 98 degrees to its orbital plane, which gives it extreme seasons, and it has a faint ring system. Voyager 2 remains the only spacecraft to have visited it, in 1986, and Neptune, in 1989. In the Marathi column of this paper Uranus appears as प्रजापती, which is the name used in Marathi science writing; Neptune is वरुण. A candidate answering in Marathi must map प्रजापती to Uranus before the numbers in statements (a) and (c) mean anything at all, and confusing प्रजापती with वरुण would make statement (c) appear true.

• Uranus has 29 confirmed moons, the most recent announced in 2025 from James Webb Space Telescope observations; the count was 27 for most of the 2000s. Its five major moons are Miranda, Ariel, Umbriel, Titania and Oberon, named from Shakespeare and Pope rather than from classical mythology.
• Mercury's mean distance from the Sun is about 57.9 million km, or 0.39 astronomical units — the figure of 58 million km given in statement (b) is accurate at that precision. Mercury is the smallest planet and the closest to the Sun.
• Uranus orbits at a mean distance of about 2,871 million km, roughly 19 astronomical units. The figure of 4,495 million km, about 30 astronomical units, is Neptune's mean distance — the outermost planet — which is what makes statement (c) a misattributed true number rather than an invented one.
• Uranus was discovered by William Herschel in 1781, the first planet discovered by telescope. Neptune was found in 1846 after Urbain Le Verrier predicted its position mathematically from perturbations in the orbit of Uranus, and Voyager 2 is the only spacecraft to have visited either planet.
• Uranus's rotational axis is tilted about 98 degrees to its orbital plane, so it effectively rolls along its orbit, producing extreme seasonal cycles. It also has a faint ring system, discovered in 1977 during a stellar occultation.

• A true number attached to the wrong planet. 4,495 million km is a genuine solar-system distance, but Neptune's, not Uranus's; this is the commonest construction in planetary questions and it defeats a candidate who recognises numbers without owning them.
• Trusting a memorised moon count. Satellite totals are revised upward as fainter objects are found, so hold them as orders of magnitude — none for Mercury and Venus, two for Mars, dozens to hundreds for the giants — and never as a fixed figure to be matched exactly.
• Missing a switch from a positive to a negative option framing. Here the candidate works out that only statement (b) is true, but the paper prints no option saying so; the same conclusion appears as 'statements (a) and (c) are not correct', and two of the four options use the negative form.

Solar-system questions in Paper-I take three forms. The first is the ordering or comparison question — arrange planets by distance, size, or period — which is answered from one memorised sequence. The second is the statement-verification question used here, where two or three numerical claims must each be judged true or false and the trap is a correct figure attached to the wrong body. The third is the discovery-and-mission question: who found which planet and when, and which spacecraft has visited it. The preparation that covers all three is a single table of the eight planets with distance, number of moons as an order of magnitude, one distinguishing physical feature and one discovery or mission fact — and the discipline, in the hall, of settling every statement before looking at the options, because negative framings make it easy to choose the mirror image of the right answer.

No directly related past PYQ was found.

• practice — not a real PYQ

  The average distance of the planet Neptune from the Sun is approximately :

  • (a)778 million km
  • (b)1,427 million km
  • (c)2,871 million km
  • (d)4,495 million km

  Answer(d) 4,495 million km — about 30 astronomical units, which makes Neptune the outermost planet of the solar system. The other three figures are the mean distances of Jupiter, Saturn and Uranus respectively, and moving one of them onto the wrong planet is the standard way this fact is turned into a wrong statement.

• practice — not a real PYQ

  Which planet of the solar system was the first to be discovered with the help of a telescope, and by whom ?

  • (a)Uranus, by William Herschel in 1781
  • (b)Neptune, by Johann Galle in 1846
  • (c)Saturn, by Galileo Galilei in 1610
  • (d)Mercury, by Nicolaus Copernicus in 1543

  Answer(a) Uranus, by William Herschel in 1781 — the planets out to Saturn were known to antiquity without instruments, so Uranus was the first genuinely new planet. Neptune came next, in 1846, but only after Urbain Le Verrier had predicted its position from irregularities in the orbit of Uranus, which is a discovery of a different kind.