Venus

by Dominic Ford, Editor
Last updated: 24 Mar 2020

The planets of the solar system:
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune


Venus recently passed behind the Sun at superior solar conjunction. From Cambridge, however, it will become visible around 20:26 (EDT), 11° above your western horizon, as dusk fades to darkness. It will then sink towards the horizon, setting 1 hour and 26 minutes after the Sun at 21:32.

Venus

The planet Venus, photographed by Ricardo Nunes.

Venus is the second planet from the Sun, orbiting at a distance of 0.723 AU once every 224 days.

It is our neighbour in the solar system, orbiting just inside the Earth's orbit. It is of a similar size to the Earth – around 95% of an Earth-width across – and has similar abundances of chemical elements such as carbon. For this reason, Venus is often considered to be the Earth's 'twin' planet.

Even though Venus orbits closer to the Sun than the Earth, its surface receives less heat from the Sun since it is permanently enshrouded by thick cloud layers. These reflect so much sunlight back into space that they more than compensate for the increased intensity of the Sun's light. They also make it virtually impossible to observe Venus's surface, meaning that the planet presents a bland and largely featureless disk.

Apparitions of Venus

The table below lists apparitions of Venus around the year 2021, computed from NASA's DE430 planetary ephemeris. To show events around other years, use the control below.

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Apparitions of Venus around 2021

Date Event Declination Angular size
Date Event Declination Angular size
12 Jan 2017 11:06 ESTVenus at greatest elongation east8°27'S24.4"
03 Jun 2017 02:11 EDTVenus at greatest elongation west8°13'N23.9"
17 Aug 2018 04:11 EDTVenus at greatest elongation east5°21'S24.3"
06 Jan 2019 01:16 ESTVenus at greatest elongation west16°27'S24.7"
24 Mar 2020 03:45 EDTVenus at greatest elongation east20°35'N23.4"
13 Aug 2020 09:17 EDTVenus at greatest elongation west20°03'N23.4"
29 Oct 2021 10:57 EDTVenus at greatest elongation east26°54'S24.9"
20 Mar 2022 17:35 EDTVenus at greatest elongation west14°53'S24.5"
04 Jun 2023 12:11 EDTVenus at greatest elongation east22°53'N23.6"
23 Oct 2023 20:05 EDTVenus at greatest elongation west6°19'N24.0"
10 Jan 2025 03:31 ESTVenus at greatest elongation east9°28'S24.5"
31 May 2025 16:57 EDTVenus at greatest elongation west7°28'N23.9"

Observing Venus

Because Venus's orbit lies closer to the Sun than the Earth's, it always appears close to the Sun and is lost in the Sun's glare much of the time.

It is observable for a few months each time it reaches greatest separation from the Sun – moments referred to as greatest elongation.

On these occasions, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning star or the evening star.

These apparitions repeat roughly once every 1.6 years, taking place alternately in the morning and evening skies, depending whether Venus lies to the east of the Sun or to the west.

When it lies to the east, it rises and sets a short time after the Sun and is visible in early evening twilight. When it lies to the west of the Sun, it rises and sets a short time before the Sun and is visible shortly before sunrise.

The journey that Venus makes from the evening sky to the morning sky is much quicker than the reverse journey. This is because Venus's orbit is so close to our own, so the points of greatest elongation are much closer to inferior conjunction than to superior conjunction. Click to expand.

After passing behind the Sun, Venus first appears in the evening sky for a few months, lying to the east of the Sun. It then undergoes inferior solar conjunction, passing between the Earth and Sun a few months after reaching greatest prominence in the evening sky. Moving into the morning sky, it then reaches greatest prominence as the 'morning star' a few months later.

The reverse journey, from the morning sky into the evening sky, takes much longer, as Venus travels a long path around behind the Sun. The moment when Venus passes behind the Sun is typically around seven months after reaching greatest prominence in the morning sky. It does not return to the evening sky until around a year after its disappearance from the morning sky.

At each apparition, Venus reaches a maximum separation from the Sun of around 48°. However, some times of the year are more favourable for viewing Venus than others. From Cambridge, it reaches a peak altitude of between 18° and 45° above the horizon at sunset during each evening apparition, depending on the time of year. During morning apparitions, it reaches a peak altitude of between 22° and 44° at sunrise.

This variability over the course of the year is due to the inclination of the ecliptic to the horizon.

The inclination of the ecliptic to the horizon

The inclination of the ecliptic to the horizon changes over the course of the year, affecting how high planets close to the Sun appear in the sky.

At all times, Venus lies close to a line across the sky called the ecliptic. This line traces the path that the Sun takes through the zodiacal constellations every year, and shows the plane of the Earth's orbit around the Sun. Since all the planets circle the Sun in almost exactly the same plane, it also closely follows the planes of the orbits of the other planets, too.

When Venus is widely separated from the Sun, it is separated from it along the line of the ecliptic. But, at different times of year, the ecliptic meets the horizon at different angles at sunset and sunrise. This would translate into Venus being at different altitudes above the horizon, even if its separation from the Sun was constant.

If the ecliptic meets the horizon at a shallow angle, then Venus has to be very widely separated from the Sun to appear much above the horizon. Conversely, if the ecliptic is almost perpendicular to the horizon, Venus may appear much higher in the sky, even if it is actually much closer to the Sun.

The seasonal dependence of this is that at sunset, the ecliptic makes its steepest angle to the horizon at the spring equinox – in March in the northern hemisphere, and in September in the southern hemisphere. Conversely, it meets the horizon at its shallowest angle at the autumn equinox. Because the seasons are opposite in the northern and southern hemispheres, a good apparition of Venus in one hemisphere will usually be badly placed in the other.

At sunrise, these dates are also inverted, so that for morning apparitions of Venus, the ecliptic makes its steepest angle to the horizon at the autumn equinox, and its shallowest angle to the horizon at the spring equinox.

The optimum time for an apparition of Venus

For this reason, the day when Venus reaches its widest separation from the Sun (greatest elongation) is not necessarily the same day when it appears highest in the sky at sunset or sunrise. Venus typically appears highest in the sky a few days or weeks closer to the spring (evening apparitions) or autumn (morning apparitions) equinox than the moment of greatest elongation.

Visual appearance

Seen through binoculars or a telescope, Venus's disk is the largest of any of the planets on account of its closeness to the Earth, reaching a maximum size of 66" at inferior conjunction.

Nonetheless, it remains just too small to be discernible to the naked eye. Even through a telescope, it is not possible to resolve any detail on its surface without specialist equipment, owing to the thick featureless cloud layers which surround it.

However, as it orbits the Sun, Venus shows phases akin to those of the Moon, and these are quite apparent even through a pair of binoculars, especially if image stabilised.


As it orbits the Sun, Venus shows phases like the Moon. When it is closest to the Earth, passing between us and the Sun, Venus appears almost entirely unilluminated. When it passes around the far side of the Sun, its disk appears almost completely illuminated. When it is prominent in the morning or evening sky, Venus is around half phase.

Space missions

Venus was the first planet ever to be visited by a space probe. After a failed Soviet attempt, the first spacecraft to successfully fly past Venus was the American Mariner 2 (1962).

It has since been visited by more than 20 spacecraft, most recently the American Magellan (1989) and European Venus Express (2005).

These have revealed that the planet's surface temperature to be 480°C – the highest average surface temperature of any body in the Solar System, and hot enough to melt lead and to visibly glow red hot. Its atmosphere has been found to be composed primarily of carbon dioxide, with traces of other noxious compounds such as sulphuric acid, which gives its clouds an acidic yellow hue.

These extreme climatic conditions are less a result of Venus's proximity to the Sun, and more a result of the greenhouse effect: Venus has the strongest known greenhouse effect of any body in the Solar System. Current thinking is that the Earth and Venus may have been very similar planets at the time of their formation, but that a point of divergence came early in their history, when oceans formed on the Earth, allowing carbon dioxide to dissolve in the water and become locked up in carbonaceous rocks such as limestone (calcium carbonate). On Venus, this process never happened, and most of its carbon remains in the form of carbon dioxide in its atmosphere.

NORAD ID COSPAR ID Name Launch date Flight ended Owner
NORAD ID COSPAR ID Name Launch date Flight ended Owner
71 1961-002A SPUTNIK 7 04 Feb 1961 26 Feb 1961 Commonwealth of Independent States (former USSR)
80 1961-003A VENERA 1 12 Feb 1961 Commonwealth of Independent States (former USSR)
371 1962-040A SPUTNIK 19 24 Aug 1962 27 Aug 1962 Commonwealth of Independent States (former USSR)
374 1962-041A MARINER 2 26 Aug 1962 United States
381 1962-043A SPUTNIK 20 31 Aug 1962 05 Sep 1962 Commonwealth of Independent States (former USSR)
389 1962-045A SPUTNIK 21 11 Sep 1962 13 Sep 1962 Commonwealth of Independent States (former USSR)
687 1963-044A COSMOS 21 11 Nov 1963 14 Nov 1963 Commonwealth of Independent States (former USSR)
772 1964-014A COSMOS 27 26 Mar 1964 28 Mar 1964 Commonwealth of Independent States (former USSR)
785 1964-016D ZOND 1 01 Apr 1964 Commonwealth of Independent States (former USSR)
1730 1965-091A VENERA 2 12 Nov 1965 Commonwealth of Independent States (former USSR)
1733 1965-092A VENERA 3 16 Nov 1965 01 Mar 1966 Commonwealth of Independent States (former USSR)
1742 1965-094A COSMOS 96 23 Nov 1965 09 Dec 1965 Commonwealth of Independent States (former USSR)
2840 1967-058A VENERA 4 11 Jun 1967 17 Oct 1967 Commonwealth of Independent States (former USSR)
2845 1967-060A MARINER 5 13 Jun 1967 United States
2852 1967-063A COSMOS 167 16 Jun 1967 24 Jun 1967 Commonwealth of Independent States (former USSR)
3642 1969-001A VENERA 5 04 Jan 1969 15 May 1969 Commonwealth of Independent States (former USSR)
3648 1969-002A VENERA 6 09 Jan 1969 16 May 1969 Commonwealth of Independent States (former USSR)
4489 1970-060A VENERA 7 16 Aug 1970 14 Dec 1970 Commonwealth of Independent States (former USSR)
4501 1970-065A COSMOS 359 21 Aug 1970 05 Nov 1970 Commonwealth of Independent States (former USSR)
5912 1972-021A VENERA 8 26 Mar 1972 21 Jul 1972 Commonwealth of Independent States (former USSR)
5919 1972-023A COSMOS 482 30 Mar 1972 04 May 1981 Commonwealth of Independent States (former USSR)
6919 1973-085A MARINER 10 03 Nov 1973 United States
8411 1975-050D VENERA 9 DESCENT CRAFT 07 Jun 1975 21 Oct 1975 Commonwealth of Independent States (former USSR)
7915 1975-050A VENERA 9 BUS 07 Jun 1975 Commonwealth of Independent States (former USSR)
8423 1975-054D VENERA 10 DESCENT CRAFT 13 Jun 1975 24 Oct 1975 Commonwealth of Independent States (former USSR)
7947 1975-054A VENERA 10 BUS 13 Jun 1975 Commonwealth of Independent States (former USSR)
10911 1978-051A PIONEER VENUS ORBITER 19 May 1978 08 Oct 1992 United States
11001 1978-078A PIONEER VENUS PROBE BUS 07 Aug 1978 09 Dec 1978 United States
12103 1978-078D PIONEER VENUS PROBE 1 07 Aug 1978 09 Dec 1978 United States
12104 1978-078E PIONEER VENUS PROBE 2 07 Aug 1978 09 Dec 1978 United States
12105 1978-078F PIONEER VENUS PROBE 3 07 Aug 1978 09 Dec 1978 United States
12106 1978-078G PIONEER VENUS PROBE 4 07 Aug 1978 09 Dec 1978 United States
12027 1978-084C VENERA 11 DESCENT CRAFT 08 Sep 1978 25 Dec 1978 Commonwealth of Independent States (former USSR)
12028 1978-086C VENERA 12 DESCENT CRAFT 13 Sep 1978 21 Dec 1978 Commonwealth of Independent States (former USSR)
15599 1981-106D VENERA 13 DESCENT CRAFT 30 Oct 1981 27 Feb 1982 Commonwealth of Independent States (former USSR)
15600 1981-110D VENERA 14 DESCENT CRAFT 04 Nov 1981 05 Mar 1982 Commonwealth of Independent States (former USSR)
14104 1983-053A VENERA 15 01 Jun 1983 Commonwealth of Independent States (former USSR)
14107 1983-054A VENERA 16 06 Jun 1983 Commonwealth of Independent States (former USSR)
15858 1984-125E VEGA 1 DESCENT CRAFT 15 Dec 1984 08 Jun 1985 Commonwealth of Independent States (former USSR)
15859 1984-125F VEGA 1 BALLOON 15 Dec 1984 08 Jun 1985 Commonwealth of Independent States (former USSR)
15856 1984-128E VEGA 2 DESCENT CRAFT 21 Dec 1984 14 Jun 1985 Commonwealth of Independent States (former USSR)
15857 1984-128F VEGA 2 BALLOON 21 Dec 1984 14 Jun 1985 Commonwealth of Independent States (former USSR)
19969 1989-033B MAGELLAN 03 May 1989 13 Oct 1994 United States
20298 1989-084B GALILEO 17 Oct 1989 20 Sep 2003 United States
25008 1997-061A CASSINI 14 Oct 1997 14 Sep 2017 United States
28391 2004-030A MESSENGER 02 Aug 2004 29 Apr 2015 United States
28901 2005-045A VENUS EXPRESS 09 Nov 2005 European Space Agency
36576 2010-020D AKATSUKI 19 May 2010 Japan

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Warning

Never attempt to view Venus through a telescope or binoculars if the Sun is still above the horizon. A momentary glance at the Sun through such an instrument is sufficient to cause permanent blindness.

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