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Mercury Is Sailing Across the Sun—Here’s How to Watch

On May 9, the innermost planet crosses the sun’s face, an event seen from Earth just 13 to 14 times a century.

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Mercury crossing the sun.


The tiny planet Mercury is making a big splash on May 9, when it glides across the face of the sun for the first time in 10 years.

The black silhouette of the planet will take about seven and a half hours to make its trek across the solar disk, an event known as a transit. The sky show lasts from 7:12 a.m. ET until 2:42 p.m. ET.

Weather permitting, the best seats will be on the East Coast of North America as well as the bulk of South America and Western Europe, where the entire transit will happen during daylight hours. For those on the West Coast of the Americas, the transit will already be under way at sunrise, and for viewers in most of Africa, Eastern Europe, and the bulk of Asia, the transit will still be in progress at sunset.

Folks in East Asia, Australia, and New Zealand will miss out entirely, since the whole transit will happen when these regions face away from the sun.

Safe viewing of the sun’s disk is paramount at all times—never look directly at the sun without proper protection or you risk damaging your eyes. Not that you’d be able to see much with your naked eyes, anyway. From Earth, the black dot of Mercury will be just 1/158 the width of the solar disk, so you will need relatively high-powered visual aids to watch the transit.

Watch the Mercury transit live here.


For people using backyard telescopes, be sure to attach a solar filter that fits on the instrument’s front end. You can also use high-powered binoculars and white cardboard to create a magnified projection of the event.

And of course this transit can be enjoyed by anyone with an internet connection, thanks to live webcasts that will showcase the entire event. Both Virtual Telescope and Slooh.com promise to have coverage from beginning to end on Monday.

Transit of Mercury

Mercury, which appears to be only 1/158 of the sun's diameter, will be seen as

a small black speck crossing the sun's disk on May 9, 2016, over a 7.5-hour period.

 

N

Transit

begins

7:12 a.m.

8 a.m.

E

W

10 a.m.

12 p.m.

2 p.m.

Mercury at transit midpoint

10:57 a.m.

2 p.m.

Transit

ends

2:42 p.m.

S

MONICA SERRANO, NG STAFF

SOURCE: FRED ESPENAK

Transit of Mercury

Mercury, which appears to be only 1/158

of the sun's diameter, will be seen as

a small black speck crossing the sun's disk on May 9, 2016, over a 7.5-hour period.

Transit

begins

7:12 a.m.

N

8 a.m.

E

W

10 a.m.

Mercury

at transit midpoint

10:57 a.m.

12 p.m.

Mercury

at transit midpoint

10:57 a.m.

2 p.m.

Transit

ends

2:42 pm

S

MONICA SERRANO, NG STAFF

SOURCE: FRED ESPENAK

Rare Encounter

While Mercury does pass between Earth and the sun every four months or so, we only get to see it transit when everything lines up just right. The small planet’s orbit is tilted compared to the plane of Earth’s orbit, so most of the time the swift “messenger of the gods” passes above or below the sun's disk from our line of sight. It's the same reason we do not see solar eclipses every month.

Only the two innermost planets, Mercury and Venus, can transit the sun for Earth-based viewers. While Mercury transits happen 13 to 14 times a century, Venusian transits are even rarer, happening on average only once a century. The last Venus transit occurred in 2012, and we won’t see another one until 2117.

Mercury Crossing

For about seven hours and 30 minutes, Mercury will move across the face of the sun. The transit will be observable from most places on Earth for the first time in nearly 10 years.

ARCTIC Ocean

NORTH

AMERICA

ASIA

EUROPE

Atlantic

Ocean

30°N

Entire transit

visible

PACIFIC Ocean

AFRICA

EQUATOR

Indian

Ocean

SOUTH

AMERICA

Transit in progress

at sunrise

Transit in progress

at sunset

AUST.

30°S

AUSTRALIA

3,000 mi

Transit not

visible

Transit not

visible

3,000 km

SCALE AT THE EQUATOR

ANTARCTICA

150°E

180°

150°W

120°

90°

60°

30°W

30°E

60°

90°

120°

MATTHEW W. CHWASTYK, NG STAFF

SOURCE: FRED ESPENAK, NASA/GSFC

Mercury Crossing

For about seven hours and 30 minutes, Mercury will move across the face of the sun. The transit will be observable from most places on Earth for the first time in nearly 10 years.

Entire

transit

visible

Transit in

progress

at sunrise

EQUATOR

Transit in

progress

at sunset

Transit

not

visible

Transit

not

visible

180°

120°

60°W

60°E

120°

MATTHEW W. CHWASTYK, NG STAFF

SOURCE: FRED ESPENAK, NASA/GSFC

Headline

Intro

Intro

Note or units or whatever

Inner headline

Inner text. Paragraph with any kind of information commented in the graphic.

NG STAFF

SOURCE: NATGEO

Don’t fret if you miss this transit of Mercury—you will get another chance in 2019. But after that, we won’t see another such event until 2032. North Americans will have an even longer dry spell to contend with after 2019, as they will have to wait until 2049 for the next Mercury transit visible from that part of the globe.

The most interesting part of a transit for many astronomers is the black drop effect, an optical illusion that happens when the planet either just enters or starts to leave the sun’s disk.

When Mercury’s leading edge first touches the sun, the planet appears to grow a narrow neck connecting it to the edge of the sun, making the silhouette look like a teardrop. This strange apparition happens again just as Mercury becomes engulfed by the sun’s disk.

Seeing a planet creep across our sun also offers a chance to see one of the ways scientists hunt down planets around distant stars. As a distant planet moves in front of its host star as viewed from Earth, our telescopes can detect the very slight dips in the brightness. From this data, astronomers are able to calculate the size, orbit, and even some physical properties of these alien worlds.

So far, NASA’s Kepler mission has been able to successfully identify and confirm 1,041 exoplanets across the galaxy using transit events like what we will be seeing up close with Mercury on May 9.

This story was updated on May 9 at 9:30 am ET.

Follow Andrew Fazekas, the Night Sky Guy, on Twitter, Facebook, and his website.

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