See Mercury at its best meet Mars in the dawn sky – Astronomy Now Online

Posted: November 18, 2019 at 6:42 pm

Innermost planet Mercury puts on its best morning display of the year for Northern Hemisphere observers from late November to early December. Skywatchers in the British Isles should find a location offering an unobstructed view of the southeast horizon about 45minutes before sunrise to get the best views. This looping animation shows the changing configuration of Mercury, Mars and Virgos brightest star, Spica, from 18November through 3December at dawn. Note the span of a fist at arms length (about 10) for scale, but the Moons apparent size on 24 and 25November has been enlarged for clarity. AN animation by Ade Ashford.Mercurys transit of the Sun on 11November is still fresh in the memory, but it doesnt take long for the innermost planets orbital motion to carry it far enough west of the Sun to be visible low above the southeastern horizon in dawn twilight. Mercury attains its greatest westerly elongation of 20degrees on the UK morning of 28November. In fact, for Northern Hemisphere observers, the remainder of the month into early December offers Mercurys best morning viewing prospects for the entire year.

Any opportunity to get a glimpse of this elusive and fast-moving planet is well worth getting up a little earlier for, particularly when as now you get a chance to see Mars nearby at the same time. As with any observation made in the eastern sky during dawn twilight, timing is everything: you need to view late enough that Mercury gets a chance to rise high enough above the horizon murk, but not so late that impending sunrise makes the sky too bright to see it. (Never look anywhere near the Sun after it has risen.)

Observers in the British Isles need to find a location that offers an unobscured view of the southeast horizon about three-quarters of an hour before sunrise between now and the first week of December. Our interactive online Almanac gives you the time of sunrise for your nearest town or city, so just subtract 45minutes from that.The slim crescent of the 27-day-old waning Moon lies slightly less than 4degrees above magnitude +1.7 Mars at UK dawn on Sunday, 24November 2019, hence the pair will fit in the same field of view of 10 and lower magnification binoculars. On this morning, the Red Planet sits midway between magnitude -0.2 Mercury and first-magnitude star Spica in Virgo. Note that the Moons apparent size has been enlarged for clarity in this illustration. AN graphic by Ade Ashford.Mercury is located in the constellation of Libra for the period illustrated in the animation at the top of the page. The planet lies about 9degrees (almost the span of a fist held at arms length) above the southeast horizon at the optimal viewing time between 23November and the beginning of December. The Red Planet sits midway between Mercury and the first-magnitude star Spica, the brightest in the constellation of Virgo, at UK dawn on 24November.

Magnitude +1.7 Mars remains in Virgo until the morning of 1December when it crosses the constellation border to join Mercury in Libra. Mercury brightens more than fourfold from magnitude +1 to -0.6 during the 18November to 3December observing window. If clear, dont miss the binocular highlights of 24 and 25November at dawn when the old waning crescent Moon lies 4 above Mars and 3 to the lower left of Mercury, respectively.

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See Mercury at its best meet Mars in the dawn sky - Astronomy Now Online

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