Updated

Updated · Space.com · Jul 31

Mercury and Jupiter Meet Within 0.6 Degrees on Aug. 15 as Venus Reaches 46-Degree Elongation

Updated

Updated · Space.com · Jul 31

Mercury and Jupiter Meet Within 0.6 Degrees on Aug. 15 as Venus Reaches 46-Degree Elongation

Q: Will the blinding dawn twilight completely hide the ultra-close, rare encounter between Mercury and Jupiter this August?

No. The dawn glare will make the August 15 Mercury-Jupiter conjunction hard to see, but it should not completely hide it for many observers. The pairing is genuinely close and unusual: the two planets will be less than 0.6 degrees apart, with some sky guides putting the gap at about 33 arcminutes, roughly the apparent width of the full moon. That means if you can pick up one planet, the other should be very nearby in the same binocular field. The real problem is altitude, not brightness alone. Both planets will sit very low in the east-northeast in bright pre-sunrise twilight. Mercury is actually brightening through early August after reaching greatest western elongation on Aug. 2, and Jupiter is brighter still, but both are competing with the Sun’s glare near the horizon. A flat, unobstructed eastern horizon will be crucial. Observers have the best chance about 30 to 50 minutes before local sunrise, before the sky gets too washed out but after the planets have climbed a little. Binoculars are widely recommended, though they should only be used once the Sun is still safely below the horizon. In very clear skies, experienced observers may catch the pair with the naked eye, but many people in hazy or urban conditions may miss it. So the encounter is not likely to be completely erased by twilight, but it will be a difficult, horizon-sensitive sight rather than an easy showpiece.

Q: Why is Venus mysteriously fading into the horizon's glare just as it reaches its maximum distance from the sun?

Venus is not actually dimming; it is being pushed into brighter horizon twilight because of geometry. On Aug. 15, Venus reaches greatest eastern elongation, about 46 degrees from the sun, which normally favors evening viewing. But elongation alone does not determine how high a planet appears after sunset. This August, Venus is moving along a southerly track, giving it a more negative declination. That places it lower in the west-southwest for Northern Hemisphere observers as the month goes on. The result is that, even while Venus is still brilliantly bright and at a favorable angle from the sun, it sits closer to the horizon after sunset. Near the horizon, the sky remains brighter, atmospheric haze is thicker, and the planet sets sooner into lingering twilight. So observers perceive Venus as fading into the glare, even though its intrinsic brightness remains extremely strong. Its telescopic appearance also helps explain the timing. Around greatest elongation, Venus looks roughly half illuminated. That phase is normal for Venus at this point in its orbit and does not outweigh the stronger effect of its low altitude and brighter background sky. In short, Venus’s “disappearance” is a perspective effect: maximum angular separation from the sun does not guarantee maximum visibility if the planet’s southerly declination keeps it low and immersed in twilight.

3 articles · Updated · Space.com · Jul 31

Less than 0.6 degrees will separate Mercury and Jupiter before sunrise on Aug. 15, creating a tight dawn conjunction low in the east-northeast.
The pairing will be hard to spot because both planets sit only 12 degrees west of the sun and rise about 65 minutes before sunrise; binoculars may be needed in bright twilight.
Jupiter emerges into view from Aug. 12 and stays within 4 degrees of Mercury from Aug. 13 through Aug. 17, then climbs higher into better morning visibility.
Venus remains August’s brightest evening planet, reaching greatest elongation of 46 degrees on Aug. 15 even as it sinks lower into the west-southwest twilight.
Saturn is the month’s best telescopic target, rising late evening, while Mars brightens only slowly despite Earth closing in by about 425,800 miles a day.