Transit of Mercury facts for kids

The transit of Mercury on May 9, 2016. Mercury is visible to the lower left of center. A sun spot is visible above center.

Mercury crossing the Sun as seen by the rover Curiosity on Mars (June 3, 2014).

A transit of Mercury happens when the planet Mercury passes directly in front of the Sun. From Earth, Mercury looks like a tiny black dot moving across the Sun's bright face. This happens because Mercury is closer to the Sun than Earth is, and sometimes it lines up perfectly between us and the Sun.

Transits of Mercury are special events that don't happen very often. They can only be seen from Earth in May or November. The last few transits were on May 7, 2003; November 8, 2006; May 9, 2016; and November 11, 2019. The next one will be on November 13, 2032. A typical transit lasts for several hours. These events are much more common than transits of Venus, happening about 13 or 14 times every 100 years. This is because Mercury orbits the Sun much faster and is closer to it.

On June 3, 2014, the Mars rover Curiosity watched Mercury cross the Sun. This was the first time a planet crossing the Sun was seen from a place other than Earth!

Why We Study Transits

Mercury's path around the Sun is inside Earth's path. This means Mercury can sometimes come between the Sun and Earth. When Mercury is at a special point in its orbit called a node, and it lines up with the Sun and Earth, we see a transit. During a transit, Mercury crosses the Sun's disk. These events can last up to 7 hours and 50 minutes.

Studying transits of Mercury helps scientists learn many things about the planet and its orbit. Here are some examples:

• Measuring the Solar System: Transits help us figure out the true distances between planets and the Sun.
• Understanding Earth's Spin: They can help scientists study how Earth's rotation changes over time.
• Learning About Other Planets: By watching Mercury, scientists can even learn about the mass of Venus.
• Checking the Sun's Size: Transits can help us see if the Sun's size changes over long periods.
• The Black Drop Effect: Scientists also study a strange effect called the "black drop effect" during transits. This effect makes the planet seem to stretch and connect to the edge of the Sun, making it hard to tell the exact start and end times of the transit.

When Transits Happen

Transits of Mercury only happen when Earth is lined up with a special point (a node) in Mercury's orbit. Right now, this alignment happens around May 8 (when Mercury is moving "down" in its orbit) and November 10 (when it's moving "up"). During May transits, Mercury looks a bit bigger (about 12 arcseconds wide) than during November transits (about 10 arcseconds wide).

Transits of Mercury happen in a regular pattern. For example, transits often repeat after 13, 33, 46, or 217 years.

• An interval of 13 years is common for both May and November transits.
• An interval of 33 years is also expected for both May and November transits.
• A transit that follows a similar path across the Sun will happen 46 years later.
• A transit that follows almost the exact same path across the Sun will happen 217 years later.

Scientists can predict when transits of Mercury will happen for many years into the future. You can find these predictions from places like NASA.

How We Watch Transits

Mercury is very small when it crosses the Sun. It's only about 12 arcseconds wide, which is too tiny to see without a telescope. When observing a transit, people usually record the exact times when Mercury's disk touches the edge of the Sun. These moments are called "contacts."

There are four contacts:

• 1st contact: When Mercury first touches the Sun's outer edge.
• 2nd contact: When Mercury is fully inside the Sun's disk.
• 3rd contact: When Mercury starts to leave the Sun's disk.
• 4th contact: When Mercury completely leaves the Sun's disk.

The 2nd and 3rd contacts are usually easier to see clearly. However, effects like the "black drop effect" can make it tricky to get super accurate timings.

Partial Transits

A simulated view of the November 15, 1999 transit of Mercury across the Sun.

Sometimes, Mercury only seems to "graze" the Sun during a transit. This can happen in a couple of ways:

• Full for some, partial for others: From some parts of the world, Mercury might fully cross the Sun. But from other parts, it might only partly cross. The transit on November 15, 1999, was like this. Most of the world saw a full transit, but people in Australia, New Zealand, and Antarctica saw only a partial one.
• Partial for some, missed by others: In other rare cases, Mercury might only partly cross the Sun for some observers, while for others, it misses the Sun entirely! This happened on May 11, 1937, where a partial transit was seen in southern Africa and Asia, but no transit was visible in Europe.

History of Observations

The very first time a transit of Mercury was observed was on November 7, 1631. A scientist named Pierre Gassendi watched it. He was surprised by how small Mercury looked compared to the huge Sun. Another famous astronomer, Johannes Kepler, had predicted that transits of Mercury and Venus would happen.

Pictures from the November 15, 1999, transit were featured on Astronomy Picture of the Day (APOD). The May 9, 2016, transit was also highlighted on APOD three times!

The 1832 Transit

The Shuckburgh telescope at the Royal Observatory, Greenwich in London was used to watch the 1832 Mercury transit. Scientists used it to measure the planet's size and record the event. They noticed a strange effect, describing it as if Mercury was "sunk below the sun's surface."

The 1907 Transit

For the 1907 Mercury transit, several telescopes were used at the Paris Observatory. These included large reflectors and smaller refractors, all set up on a terrace to get the best view.

Timeline of Transits

The table below lists all the transits of Mercury that have happened since 1605, and some that will happen in the future. The times are given in UTC (Coordinated Universal Time).

Past Transits of Mercury
Date of mid-transit	Time (UTC)			Notes
	Start	Mid	End
1605 Nov 1	18:47	20:02	21:18
1615 May 3	06:44	10:09	13:33
1618 Nov 4	11:10	13:42	16:14
1628 May 5	14:23	17:32	20:40
1631 Nov 7	04:39	07:20	10:01	First observed transit by Pierre Gassendi.
1644 Nov 9	22:55	00:57	02:58
1651 Nov 3–4	23:09	00:52	02:35	Observed by Jeremy Shakerly in Surat.
1661 May 3	13:08	16:54	20:40	Happened on the day King Charles II of England was crowned.
1664 Nov 4	15:54	18:32	21:10
1674 May 7	22:01	00:16	02:31
1677 Nov 7	09:33	12:11	14:48	Observed by Edmund Halley to measure solar parallax.
1690 Nov 10	03:59	05:43	07:27
1697 Nov 3	03:40	05:42	07:43
1707 May 5	19:37	23:32	03:27	Observed by Abraham Sharp.
1710 Nov 6	20:40	23:22	02:03
1723 Nov 9	14:27	16:59	19:30
1736 Nov 11	09:11	10:30	11:49
1740 May 2	21:42	23:02	00:21
1743 Nov 5	08:15	10:30	12:45
1753 May 6	02:19	06:13	10:06	Scientists worldwide organized observations.
1756 Nov 7	01:28	04:10	06:54
1769 Nov 9–10	19:23	21:46	00:10	Observed by Charles Green and James Cook in New Zealand.
1776 Nov 2	21:03	21:36	22:09
1782 Nov 12	14:42	15:16	15:50	Observed from Cambridge, U.K.
1786 May 4	03:01	05:41	08:21
1789 Nov 5	12:53	15:19	17:44
1799 May 7	09:10	12:50	16:31	Observed by Capel Lofft in England.
1802 Nov 9	06:16	08:58	11:41	Observed by William Herschel and Capel Lofft.
1815 Nov 12	00:20	02:33	04:46
1822 Nov 5	01:04	02:25	03:45
1832 May 5	09:04	12:25	15:47
1835 Nov 7	17:35	20:08	22:41
1845 May 8	16:24	19:37	22:49	Observed by William Lassell.
1848 Nov 9	11:07	13:48	16:28
1861 Nov 12	05:21	07:19	09:18	Partially observed from Malta.
1868 Nov 5	05:28	07:14	09:00
1878 May 6	15:16	19:00	22:44	Observed from Greenwich Observatory.
1881 Nov 6–7	22:19	00:57	03:36	Observed by John Tebbutt.
1891 May 8–9	23:57	02:22	04:47
1894 Nov 10	15:58	18:35	21:11	Observed from Sidmouth, Devon.
1907 Nov 14	10:24	12:07	13:50	Observed from Johannesburg.
1914 Nov 7	09:57	12:03	14:09	Seen by several observers across the U.K.
1924 May 8–9	21:44	01:41	05:38
1927 Nov 10	03:02	05:46	08:29
1937 May 11	08:53	08:59	09:06	Only seen as a partial transit in Southern Africa, Southern Arabia, South Asia, and Western Australia.
1940 Nov 11–12	20:49	23:21	01:53	Observed from New South Wales.
1953 Nov 14	15:37	16:54	18:11	Observed from the Royal Observatory at the Cape of Good Hope.
1957 May 5–6	23:59	01:14	02:30
1960 Nov 7	14:34	16:53	19:12
1970 May 9	04:19	08:16	12:13
1973 Nov 10	07:47	10:32	13:17
1986 Nov 13	01:43	04:07	06:31
1993 Nov 6	03:06	03:57	04:47	This short transit was only visible from the South Pole.
1999 Nov 15	21:15	21:41	22:07	Partial transit in Australia, Antarctica, and New Zealand's South Island.
2003 May 7	05:13	07:52	10:32
2006 Nov 8	18:12	20:41	23:10
2016 May 9	11:12	14:57	18:42	The whole transit was seen in South America, eastern North America, and western Europe. Parts of it were seen everywhere else except Australia and far eastern Asia.
2019 Nov 11	12:35	15:20	18:04
Future Transits of Mercury
Date of mid-transit	Time (UTC)			Notes
	Start	Mid	End
2032 Nov 13	06:41	08:54	11:07
2039 Nov 7	07:17	08:46	10:15
2049 May 7	11:03	14:24	17:44
2052 Nov 8–9	22:53	01:29	04:06
2062 May 10–11	18:16	21:36	01:00
2065 Nov 11–12	17:24	20:06	22:48
2078 Nov 14	11:42	13:41	15:39
2085 Nov 7	11:42	13:34	15:26
2095 May 8–9	17:20	21:05	00:50
2098 Nov 10	04:35	07:16	09:57
2108 May 12	01:40	04:16	06:52
2111 Nov 14–15	22:15	00:53	03:30
2124 Nov 15	16:49	18:28	20:07

See Also

• Mercury Passing Before the Sun, a 1914 painting
• Transit of Mercury from Mars
• Transit of minor planets
• Transit of Venus
• Vulcan (hypothetical planet)

Images for kids

• 

  Transit of Mercury on November 11, 2019

• 

  Transit of Mercury on November 8, 2006 with sunspots #921, 922, and 923