Page 71 - All About Space 68 - 2017 UK

STARGAZER
What’s in the sky?

Jargon buster

Conjunction Declination (Dec) Opposition
A conjunction is an alignment of objects at the same This tells you how high an object will rise in the sky. When a celestial body is in line with the Earth and Sun.
celestial longitude. The conjunction of the Moon and Like Earth’s latitude, Dec measures north and south. During opposition, an object is visible for the whole
the planets is determined with reference to the Sun. A It’s measured in degrees, arcminutes and arcseconds. night, rising at sunset and setting at sunrise. At this
planet is in conjunction with the Sun when it and Earth There are 60 arcseconds in an arcminute and there are point in its orbit, the celestial object is closest to Earth,
are aligned on opposite sides of the Sun. 60 arcminutes in a degree. making it appear bigger and brighter.
Right Ascension (RA) Magnitude Greatest elongation
Right Ascension is to the sky what longitude is to An object’s magnitude tells you how bright it appears When the inner planets, Mercury and Venus, are at
the surface of the Earth, corresponding to east and from Earth. In astronomy, magnitudes are represented their maximum distance from the Sun. During greatest
west directions. It is measured in hours, minutes and on a numbered scale. The lower the number, the elongation, the inner planets can be observed as
seconds since, as the Earth rotates on its axis, we see brighter the object. So, a magnitude of -1 is brighter evening stars at greatest eastern elongations and as
different parts of the sky throughout the night. than an object with a magnitude of +2. morning stars during western elongations.

21 22

AUG AUG
Total solar eclipse Conjunction
visible through the US, between the Moon ©Raymond Shobe
while a partial eclipse is and Mercury in Leo
visible elsewhere and Sextans

26 27

AUG AUG
Conjunction between Conjunction between
the Moon and dwarf Uranus and dwarf
planet Haumea in planet Eris in Pisces and
Virgo and Boötes Cetus

5 6

SEP SEP
Neptune reaches The Moon and Neptune
opposition in Aquarius, make a close approach,
reaching a magnitude passing within 0°44’ of
©NASA of 7.8 each other in Aquarius

12 13 Naked eye
Binoculars
SEP SEP Small telescope
Mercury is at greatest Mercury is at half
elongation west in the phase in the dawn Medium telescope
dawn sky, shining bright sky
at magnitude -0.4 Large telescope

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