Astronomy

How (the heck) was this photo of Venus at inferior conjunction (between us and the Sun) taken?

How (the heck) was this photo of Venus at inferior conjunction (between us and the Sun) taken?


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This great answer by @gerrit discussing planetary phases seen in visible light contains the image I've included below. According to the Wikimedia Commons link these are ESO images from the Venus transit 2004 VT-2004 observing campaign.

The ESO, or European Southern Observatory:

Organisation Européenne pour des Recherches Astronomiques dans l'Hémisphere Austral) is a 16-nation intergovernmental research organization for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. (emphasis added)

These images are very high quality, and the last one, dated8/6/04(08-June-2004) appears to be taken at/near inferior conjunction, when Venus is almost directly between the observer and the Sun.

Question: I'd like to understand with what instrument this image was taken, and how the technical challenges imaging Venus with such a small angular separation between it and the Sun were overcome! I did a quick check and during the UTC day of June 8th, 2004, Venus moved from about 0.6 to 1.1 degrees from the Sun as viewed by Earth. How was Venus imaged so nicely? Was this really imaged from the ground through Earth's daytime atmosphere, or from space? In either case, how was a high quality telescope pointed so close to the Sun and shielded from stray light and protected from damage?


below: Phases of Venus, from here.


I think you'll have to live with an incomplete answer. It appears this was taken by an amateur astronomer using a simple 4.5 inch telescope. You can find, on the ESO website, a collection of many images taken during the 2004 transit. On this page, is the image you are asking about (along with some other images by the same person). The credit for that image is given as:

The Phases of Venus

Statis Kalyvas
4.5-inch Mizar telescope
Nikon Coolpix 750
February 27 - June 8, 2004
Thessaloniki, Greece

I'm assuming (because I can't find any reference to state otherwise) that the name "Mizar telescope" is just the personal name Statis Kalyvas gave to his telescope. Although you can see that the equipment was nothing an amateur astronomer couldn't buy. A pretty typical telescope with a standard camera. Nothing "professional" or extremely high tech.

We can probably guess at some other pieces of the puzzle though. From the image below, you can see that the 2004 transit began (from Thessaloniki's local time) at 7:13 AM and ended at 1:25 PM.

Given that the observation period of the transit itself happened during the day, Statis definitely would have needed a solar filter for his telescope, which would have blocked upwards of 99.999% of the light from the Sun, allowing him to view the transit safely.

For the other images leading up to the transit, my guess is that he made his observations during in the evening when the Sun was near the horizon and not very bright (due to much of the light being scattered). Venus should've been higher in the sky than the Sun and still visible at that time. An eyepiece which gives a small field of view would've been useful here.

You can possibly guess that the image was taken near the horizon because a 4.5 inch telescope should have a resolution of $1.21 mathrm{arcsec}$ at best whereas, near conjunction, Venus is almost an arcminute in size. Venus should be well resolved, but it looks a bit fuzzy. This is likely attributed to the high airmass near the horizon. The drastic difference between the clarity of the image on 3/4 and 13/4 (just ten days later) leads me to believe the telescope was capable of better resolution and was simply impeded by the atmosphere near the horizon.


Moon and Venus at dawn June 17, 18, 19

Before sunrise on June 17, 18 and 19, 2020, look for the waning crescent moon near Venus, the brightest planet. Venus is just now emerging from the dawn glare. A less-bright planet wouldn’t be visible so close to the sun, but Venus is exceedingly bright. It’ll be beautiful set against the brightening sky. You might – or might not – spot the Pleiades star cluster before Venus rises into your sky. This dipper-shaped cluster of stars is also just returning to the morning sky. From some parts of the globe, the moon will occult (cover over) Venus on June 19. More about the June 19 occultation of Venus by the moon later in this post.

In another week or two, both Venus and the Pleiades will be much easier to spot in a predawn sky. For now, let the moon guide you to them. The moon’s illuminated side will be pointing right at Venus on the mornings of June 17 and 18. Both will be ascending over your eastern horizon just as the morning darkness is giving way to dawn.

On June 19, look for the very old and very slender moon to be quite close to Venus on the sky’s dome. If you see the moon on June 19, but not Venus, that might be because Venus is behind the moon!

View at EarthSky Community Photos. | The planet Venus was bright in our evening sky in recent months, but it reached inferior conjunction – passing between us and the sun – on June 3. Now, this bright planet is in the east before sunrise. Those with telescopes will find Venus in a waxing crescent phase. Steven Bellavia of Mattituck, New York, caught the crescent Venus through a telescope, in daylight, only 5 days after its inferior conjunction. He wrote: “Venus, 0.9% illuminated, around noon on June 8.” Thank you, Steven!

We provide the approximate rising time for Venus at various latitudes (given an absolutely level horizon in the direction of sunrise):

40 degrees north latitude
Venus rises one hour before sunrise

Equator (0 degrees latitude)
Venus rises 1 1/3 hours before sunrise

35 degrees south latitude
Venus rises 1 1/2 hours before sunrise

Venus transitioned from the evening to morning sky on June 3. That’s when it passed between the Earth and sun at inferior conjunction. Now, Venus sits low in the east at dawn. Generally, when a planet or bright star lurks this low in the glow of morning twilight, it isn’t easily visible, if visible at all.

But dazzling Venus ranks as the third-brightest celestial object to light up the sky, after the sun and moon, respectively. So if you have a clear sky and unobstructed horizon, you will likely see Venus with the unaided eye some 60 to 45 minutes before sunrise. If your sky conditions aren’t great – or trees or buildings block your view to the east – just wait. Venus is now ascending in the east before sunup. It’ll come into view for you in that part of the sky soon.

Daytime occultation of Venus by a crescent moon on June 19, 2020. Times are for the United Kingdom. Image via Pete Lawrence.

Occultation of Venus on June 19. The waning crescent moon is taking aim at the planet Venus as we speak. Relative to the backdrop stars and planets of the zodiac, the moon travels about 1/2 degree (the moon’s own angular diameter) eastward per hour, or about 13 degrees eastward per day. On June 18, a thinner waning crescent moon will be closer to Venus on the sky’s dome than on June 17. Then, on June 19, an even slenderer crescent will meet up with the queen planet, to showcase a close conjunction of nighttime’s two brightest heavenly bodies: the moon and Venus.

On June 19, if you’re at just the right place worldwide, you can watch the moon occult (cover over) Venus, though the event will be taking place almost exclusively in a daytime sky. You’ll probably need binoculars or a telescope to witness the occultation. Venus disappears beneath the moon’s illuminated side and then reappears from behind the moon’s dark side an hour or so later. Use care if using an optical aid, as the moon and Venus won’t be that far from the sun. For your safety, and to enhance the view, have someone block out the sun with an umbrella or some such thing, but otherwise providing an open view of the moon and Venus.

Here in the most of the United States (excepting the extreme northeast U.S.), at dawn on June 19, by the time the moon rises, the occultation will already be over. Thus we’ll see the moon to the east (sunrise side) of Venus. We’ll see Venus exceedingly close to the moon, on the side of the moon that appears darkened and perhaps illuminated by earthshine.

Some people in northeastern North America (Northeast United States and Maritime Provinces of Canada), at dawn June 19, may see the moon – but not Venus – because the moon will be covering Venus and hiding this world from view.

North (above) the dotted curve (Greenland, northwestern Europe and northern Asia) has the June 19th occultation of Venus in a daytime sky. At the far west (left) of the occultation viewing area (northeast North America), the occultation takes place at dawn. Worldwide map via International Occultation Timing Association (IOTA).

From Greenland, northwestern Europe and northern Asia (Russia and Mongolia), this lunar occultation of Venus takes place during the daytime hours on June 19, 2020.

In northeastern North America, you might catch the beginning of the occultation at dawn June 19. For example, on June 19th from St. John’s, Newfoundland, the occultation starts at 4:49 a.m. Newfoundland Daylight Time (NDT), sunrise comes at 5:03 a.m. NDT, and the occultation ends at 5:41 a.m. NDT.

In the looped area over northeast North America, the occultation is in process at moonrise June 19. Although you won’t see the beginning of the occultation from this looped area, you can view the end of the occultation at dawn June 19th. For instance, from Boston, Massachusetts, the end of the occultation occurs at 4:07 a.m. Eastern Daylight Time (EDT), or about an hour before sunrise (5:07 a.m. EDT).

Click on this IOTA page to find out the occultation times in Universal Time (UTC) for your part of the world. You must convert Universal Time to your local time.

Newfoundland Daylight Time = UTC – 2 1/2 hours
Atlantic Daylight Time = UTC – 3 hours
Eastern Daylight Time = UTC – 4 hours

Bottom line: In the predawn/dawn sky on June 17, 18 and 19, 2020, the waning crescent moon will appear near the brightest planet Venus. For some on June 19, the moon will be visible, but not Venus the planet will be behind the moon.


Venus, about 8 hours before January 11 inferior conjunction

Remember the wonderful transit of Venus in June of 2012, when this world – next inward in orbit around the sun – passed directly in front of the sun as seen from Earth? On that day, astronomers would have said that Venus was in inferior conjunction to the sun. Both Venus and the Earth are moving, and so it takes 584 days – or about 1 year, 7 months – for Venus to gain a lap on Earth and pass between us and the sun again. It has now been 584 days since that 2012 transit of Venus, and this inner planet crossed, more or less, between us and the sun today (January 11, 2014). Shahrin Ahmad in Malaysia captured Venus about 8 hours before inferior conjunction.

View larger. | The planet Venus, about 8 hours before the January 11, 2014 inferior conjunction. The daylight hemisphere of the planet is facing almost entirely away from Earth. Photo by EarthSky Facebook friend Shahrin Ahmad in Malaysia. Thank you, Shahrin! Visit Shahrin’s blog and photo gallery.

At this 2014 inferior conjunction of Venus, the planet did not pass directly in front of the sun. A transit of Venus is a very rare event. It won’t happen again until the year 2117. On January 11, Venus passed about 5 degrees N. of the sun as seen from Earth. Shahrin Ahmad wrote:


See Venus at Her Most Ravishing

Venus is HUGE right now but oh-so-skinny as it approaches inferior conjunction on August 15. Like crescents? You’ll never see a thinner and more elegant one, but first you’ll have to find it. Here’s how.

On August 9th, Venus is only 6 days before inferior conjunction when it passes between the Earth and Sun. Shortly before, during and after conjunction, Venus will appear as a wire-thin crescent. The planet will continue moving west of the Sun and rise higher in the morning sky after mid-August with greatest elongation west occurring on October 26, when its phase will fatten to half.
Wikipedia with additions by the author

There’s only one drawback to enjoying Venus at its radically thinnest — it’s very close to the Sun and visible only during the daytime. A look at the diagram above reveals that as Venus and Earth draw closer, the planet also aligns with the Sun. At conjunction on August 15, it will pass 7.9° south of our star, appearing as an impossibly thin crescent in the solar glare. The sight is unique, a curved strand of incandescent wire burning in the blue.

Venus at inferior conjunction on January 10, 2014 shows both the sunlit crescent and cusp extensions caused by sunlight penetrating the atmosphere from behind. During this previous inferior conjunction, Venus passed north of the Sun, so we see the bottom of the crescent illuminated. Credit: Tudorica Alexandru

If you’re patient and the air is steady, you might even glimpse the cusps of the illuminated crescent extending beyond their normal length to partially or even completely encircle Venus’s disk. These thread-like extensions become visible when the planet lies almost directly between us and the Sun. Sunlight scatters off the Venus’s dense atmosphere, causing it to glow faintly along the limb. One of the most remarkable sights in the sky, the sight is testament to the thickness of the planet’s airy envelope.

Going, going, gone! Venus photographed in its beautiful crescent phase on two occasions last week. When the planet reaches inferior conjunction this Saturday (August 15), the crescent will expand to nearly 1 arc minute across. No planet comes closer to Earth than Venus — just 27 million miles this week. Credit: Giorgio Rizzarelli

Today, only 1.7% of the planet is illuminated by the Sun, which shines some 11° to the northwest. The Venusian crescent spans 57 arc seconds from tip to tip, very close to 1 arc minute or 1/30 the width of the Full Moon. Come conjunction day August 15, those numbers will be 0.9% and 58 arc seconds. The angular resolution of the human eye is 1 minute, implying that the planet’s shape might be within grasp of someone with excellent eyesight under a clear, clean, cloudless sky. However — and this is a big however — a bright sky and nearby Sun make this practically impossible.

No worries though. Even 7x binoculars will nail it the trick is finding Venus in the first place. For binocular users, hiding the Sun COMPLETELY behind a building, chimney, power pole or tree is essential. The goddess lurks dangerously close to our blindingly-bright star, so you must take every precaution to protect your eyes. Never allow direct sunlight into your glass. Never look directly at the Sun – even for a second – with your eyes or UV and infrared light will sear your retinas. You can use the map provided, which shows several locations of the planet at 1 p.m. CDT when it’s highest in the sky, to help you spot it.

The Sun’s position is shown for 1 p.m. local daylight time facing due south, while Venus and its corresponding phase is depicted before, at and after conjunction. As Venus moves from left to right south of the Sun, its phase changes from evening crescent (left) to morning crescent from our perspective on Earth. Source: Stellarium with additions by the author

If you’d like to see Venus on a different day or time, download a free sky-charting program like Stellarium or Cartes du Ciel. With Stellarium, open the Sky and Viewing Options menu (F4) and click the Light Pollution Level option down to 𔄙” to show Venus in a daytime sky. Pick a viewing time, note Venus’s orientation with respect to the Sun (which you’ve hidden of course!) and look at that spot in the sky with binoculars. I’ll admit, it’s a challenging observation requiring haze-free skies, but be persistent.

By coincidence, the Moon and Venus will be about the same distance from the Sun and appear as very similar thin crescents around 1 p.m. CDT on August 13. Venus should still be visible using the methods described below, but the Moon will be impossible to see. Source: Stellarium

A safer and more sure-fire way to track the planet down involves using those setting circles on your telescope mount most of us never bother with. First, find the celestial coordinates (right ascension and declination) of the Sun and Venus for the time you’d like to view. For example, let’s say we want to find Venus on August 10 at 2 p.m. Using your free software, you click on the Sun and Venus’s positions for that time of day to get their coordinates, in this case:

Venus – Right ascension 9h 42 minutes, declination +6°.
Sun – RA 9h 22 minutes, dec. +15° 30 minutes

Now subtract the two to get Venus’ offset from the Sun = 20 minutes east, 9.5° south.

Dust off those setting circles (declination shown here, marked off in degrees) and use them to point you to Venus this week. Credit: Bob King

Next, polar align your telescope using a compass and then cover the objective end with a safe mylar or glass solar filter. Center and sharply focus the Sun in the telescope. Now, loosen the RA lock and carefully offset the right ascension 20 minutes east using your setting circle, then re-lock. Do the same with declination, pointing the telescope 9.5° south of the Sun. If you’re polar alignment is reasonably good, when you remove the solar filter and look through the eyepiece, you should see Venus staring back at you from a blue sky. If you see nothing at first, nudge it a little this way and that to bring the planet into view.

Sometimes it takes me a couple tries, but I eventually stumble arrive on target. Obviously, you can also use this technique to spot Mercury and Jupiter in the daytime, too. By the way, don’t worry what the RA and Dec. read on your setting circles when you begin your hunt only the offset’s important.

When inferior conjunction occurs at the same time Venus crosses the plane of Earth’s orbit, we see a rare transit (upper right) like this one on June 5, 2012. Credit: Bob King

This year’s conjunction is one of the best for finding Venus in daylight because it’s relatively far from the Sun. With an orbital inclination of 3.2°, Venus’s position can range up to 8° north and south of the Earth’s orbital plane or ecliptic. Rarely does the planet cross the ecliptic at the same time as inferior conjunction. When it does, we experience a transit of Venus. Transits always come in pairs the last set occurred in 2004 and 2012 the next will happen over 100 years from now in 2117 and 2125.

I hope you’re able to make the most of this opportunity while still respecting your tender retinas. Good luck!


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 &ndash 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
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

Venus nodes

Venus will be at the descending node of its orbit on Friday October 25 (at 2 Universal Time, which by American clocks is 4 or more hours, earlier, in Oct. 24).

Ascending and descending nodes keep happening and may seem among the least exciting pf astronomical events, but they shape the orbits of the moving bodies and set them up for whatever else happens. And it happens that I’ve been working on a bit for my Venus book about that planet’s plane – its inclination and nodes – and have today fashioned this space diagram.

See the end note about enlarging illustrations.

It shows the orbits of Earth in a year and of speedier Venus over seven months. The planets, at the beginnings of the months, are exaggerated 300 times in size and the Sun 5 times.

Earth moves in the ecliptic plane Venus does not. Its plane is at an inclination of 3.4 degrees to the ecliptic. Stalks connect it to the ecliptic plane at intervals of 5 days. Also, Venus’s path is drawn with a thinner line when it is south of the ecliptic.

I chose the year 2020 because, in the 8-year Venus cycle, this is the type of year in which the inferior conjunction with the Sun happens close to descending node. Inferior conjunction is the moment when Venus passes between us and the Sun. Descending node is the moment when Venus slopes southward through the ecliptic plane. Ergo, Venus very nearly passes in front of the Sun literally.

It did so 8 and 16 years previously: the great transits. The cycle slowly evolves, and this time inferior conjunction comes just too soon – two days – before descending node. (The red line for the conjunction points slightly above the Sun the blue line for the node points slightly to the right of the Sun.) Venus will miss the Sun on the northern side.

But the timing of the node passages determines much else. Because descending node is now, the next ascending node will be on 2020 Feb. 15. That will cause Venus’s course next April and May to be seen by us far enough north that it will cross the Pleiades and then reach its northernmost point in the whole cycle. And then to seem to rush down rapidly to the descending node in our picture.

So, back to Venus now, or tomorrow evening.

You can see that Venus is on the ecliptic. And is still almost down on the sunset horizon/ But is inching out into the evening sky, and sharp observers are already monitoring it, or her (I’m having to write a section on that question too).

At the ascending node in February she will be only just past the “First Point of Aries,” which is the ascending node of the ecliptic on the equator.

ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.


Five petals of Venus

To return to the subject of how orbits appear when plotted geocentrically (that is, with the Earth stationary).

This is how Mars’s Earth-based movements appear over a span of two years: one loop toward us at Mars’s opposition, contrasting with a wide swing around the far side of the Sun.

Now Venus: what pattern do its geocentric motions make? The pattern is shaped by the famous Venus cycle.

(By the way, I had this post ready to go a week ago. Then Microsoft struck. I’ve only just got back my internet connection.)

Over 8 years, each phenomenon – each relative position of Earth, Venus, and Sun – occurs 5 times, and then over the next 8 years they repeat 5 times almost identically. For Venus, the tight inward loops are the inferior conjunctions, in which Venus passes between us and the Sun the wide swings are centered on the superior conjunctions, when Venus passes around the far side of the Sun. So the general pattern is (as Anthony Barreiro commented) a “lovely five-petalled rose.” The tight loops are the stamens of the rose, the wide swings are the petals.

When I try to plot a geocentric picture in the same way as the one for Mars, but over eight years (2016-2023) to show the complete rose, it is bewilderingly cluttered: five overlapping tracks, eight-times-twelve little Venus globes at monthly intervals – already too much without the ecliptic-plane grid and other details. So here is the oicture in a more simplified version: still calculated in three dimensions, but, by moving the viewpoint to the north ecliptic pole, it becomes a flat plan of Venus’s path.

Earth is in the middle the vernal-equinox direction is to the right the yellow spots are the Sun at the beginning of each month. The rest is the rhythmic motions of Venus.

You’ll still have trouble deciphering which part of the track is for which year (I’ve used white, cyan, magenta, yellow for 2016, 2017, 2018, 2019, and again for 2020, 2021, 2022, 2023) but it doesn’t matter greatly. You can see the five inferior conjunctions, in their five directions. If you trace across the circle from each loop to the next, you see that they are not adjacent to each other but 2/5 pf the way around, like the five points of a pentagram.

(A pentagram, from the cover picture story of Astronomical Calendar 2015.)

The directions of the five inferior conjunctions determine their differing characters, by determining their places in Venus’s “true” (heliocentric) orbit, which is tilted and slightly elliptical.

2017 Mar 25: in Pisces Venus passes 8 degrees north of the Sun distance from us 0.28 AU (astronomical units, Sun-Earth distance) diameter of Venus’s (mostly dark) disk 60″ (arc seconds).
2018 Oct 26: in Virgo 6° degree south of Sun 0.27 AU 62″.
2020 Jun 3: in Taurus 0.5° north of Sun 0.29 AU 58″.
2022 Jan 9: in Sagittarius 5° north of Sun 0.27 AU 63″.
2023 Aug 13: Cancer-Leo-Hydra border 7° degrees south of Sun 0.29 AU 58″.

March 2017 is the next of those wonderful occasions, like March 2009, when we in the northern hemisphere have a chance to see Venus pass so far north of the Sun that it may be visible near to both sunset and sunrise of the days near, and even the day of, inferior conjunction. And years of the 2023 type are the similar opportunities for south-hemisphere dwellers.

Having brought Venus into conjunction with petals and the southern hemisphere, I may be forgiven for remembering the limerick that rhymes in é[email protected]

There was a young gal from Australia
Who went to a ball as a dahlia.
When the petals unfurled
It was known to the world
That the dress – as a dress – was a failure.


Transit of Venus: What Earth Looks Like From Venus During Rare Sky Show

There is no question that countless numbers of people will be watching the transit of Venus on Tuesday a very striking celestial phenomenon that has been seen only once in the last 129 years and won't happen again until December in the year 2117.

But as we prepare to watch the planet cross the face of the sun from our Earthly vantage point, have you ever wondered what the view would be like if we were on Venus? Obviously, that answer would be "what view?" since Venus is cloaked with a perpetual overcast.

But if it were somehow possible to get a view of the night sky from Venus right now, there would appear a uniquely stunning sight: our home planet Earth.

Flammarion's dream

During the late 19th and early 20th centuries, one of the most popular astronomy writers was Frenchman Nicolas Camille Flammarion. He was a prolific author of more than fifty books, as well as also publishing the magazine L'Astronomie, starting in 1882, as well as maintaining his own observatory at Juvisy-sur-Orge, France. In his 1894 book "Popular Astronomy," Flammarion speculated about the possibility of life on Venus. Then he added:

"The inhabitants of Venus see us shining in their sky like a magnificent star of the first magnitude, soaring in the zodiac, and showing motions similar to those which the planet Mars presents to us."

In fact, the view would be even more magnificent than Flammarion could have ever imagined. [Transit of Venus: A 2012 Observer's Guide (Infographic)]

From Earth, Venus would be at inferior conjunction, passing directly between us and the sun. But as seen from Venus, our Earth would be at opposition to the sun and interestingly, any Venusians looking Earthward would see (assuming they were above the planet's clouds, perhaps riding in a balloon) an object far brighter than any of the neighboring stars.

Viewed from Venus, the Earth would blaze like some stupendously bright bluish-white star in the constellation of Ophiuchus, the serpent holder. Our home planet would appear to blaze at a resplendent magnitude of -6.5. That's nearly five times brighter than Venus would appear for us!

Remember of course, that from Earth, Venus appears most dazzling when it's roughly one-quarter illuminated a crescent shape seen at a distance of about 40 million miles (64 million km). But right now as seen from Venus, Earth is not a crescent but a fully illuminated disk. In addition, our two worlds are now at their closest proximity to each other, at 26.9 million miles (43.2 million km), making the "full Earth" appear about 1.75 times larger than the crescent Venus.

And furthermore, Earth would really would look like the "double planet" that science writers often proclaim it to be, for as seen from Venus, our moon shines like a yellowish-white star of magnitude -2.5 (about the same brightness as Jupiter would look to us) hovering within half a degree to the left of the Earth. As Flammarion noted, "they form a magnificent couple."

There's something for you to dwell upon as you watch the silhouette of Venus slowly cross in front of the sun on Tuesday.


Perpetually in view

Later this month, Venus is going to do something out of the ordinary &mdash remain in view right on through its conjunction with the sun. Normally, the planet becomes lost for a time in the solar glare as it sweeps between us and the sun. This time, however, the tilt of Venus' orbit (3.39 degrees different than that of Earth) will carry Venus widely north of the sun from our vantage point here on Earth.

So, for a few days around the time of Venus' "inferior conjunction," it will be possible to glimpse the planet both as an "evening star" low in the west after sunset and as a "morning star" in the east before sunup. Its slender crescent will measure nearly 1 arcsecond across &mdash about 1/30 the apparent width of the moon and large enough to resolve with 7-power binoculars.

Seen from mid-northern latitudes, the ecliptic (the sun's apparent path through the sky) at this time of year is steeply inclined to the horizon in the early evening. Therefore, Venus descends rapidly, losing about 1.5 degrees each day during March. On March 23 at 3 a.m. EST (0800 GMT), the sun and Venus are in conjunction in "right ascension," with the planet 8.6 degrees due north of the center of the solar disk. (Reminder: Your closed fist held at arm's length is about 10 degrees wide.)

On the evening of March 22 and the morning of March 23, viewers in North America will see Venus about equally well in the evening and morning skies, almost 9 degrees to the upper right of the setting sun and about as far to the upper left of the rising sun. From latitude 40 degrees north, Venus will be 5 degrees above the horizon at sunrise and sunset.

The two diagrams accompanying this story illustrate this effect. Plotted for a North American observer at a latitude of 40 degrees, they show that Venus will be 5 degrees above the horizon at sunset on March 22, yet equally high at sunrise the following morning! Shining at magnitude -4.1, the planet may be seen for a couple of days, centered on these dates, setting after the sun and rising the next morning before it.


Here’s your chance to spot Mercury, as it cosies up to Venus this weekend

Look to the north-west on the evening of Friday 22 May, soon after sunset, to enjoy a spectacular coming together of brilliant Venus and shy and elusive Mercury. The planetary pair are separated in the sky by just 1.3 degrees (77 arcminutes), which is just over two full-Moon diameters. (Another easy-to-demonstrate method of gauging how far this is, is that a finger held out at arm’s length covers approximately one degree.) Given clear skies, with a few caveats, this exciting event can be enjoyed even from light-polluted towns and cities.

Look to the north-western horizon shortly after sunset this evening to see a great conjunction between Venus and Mercury. This is the view from London any about 40 minutes after sunset. Astronomy Now graphic by Greg Smye-Rumsby.

The one fly in the ointment is that the conjunction occurs at an altitude of less than 10 degrees, so you’ll need to have a horizon from the west-north-west around to the north-west (azimuth 290 to 315 degrees check your smartphone’s compass) that’s free from obscuring buildings and trees. If you can secure a good view, then this event should be readily visible with the naked eye, but have a pair of binoculars or a small telescope, operating at a low magnification, to hand in case the early evening is hazy. Sunset in London occurs shortly before 9pm BST (20:00 UT), at 9.14pm in Manchester and just after 9.30pm in Edinburgh. Your smartphone’s weather app can give your local sunset time.

If you have to use binoculars to view the conjunction, then make absolutely sure that the Sun has set below the horizon at your location before sweeping across the sky. If the Sun enters the field of view of any optical aid that you are using, its heat and light can cause catastrophic damage to your eyesight.

Venus will be the first astronomical object to appear in the deepening twilight. Even casual stargazers can’t have failed to notice the blazing ‘evening star’ that has recently seemed an almost permanent fixture in the post-sunset western sky, especially given the fine weather and clear skies most of the UK has been enjoying. The more committed observers will have noticed that the gloss has been coming off Venus’ brilliance as May has progressed, with the planet sinking lower in the sky and its brightness dimming somewhat. Having said this, Venus is still a blazing beacon, shining at magnitude –4.2.

Venus exhibited around a five per cent-illuminated phase on 25 May 2012, similar to that which it shows off this evening. Image: Damian Peach.

It shouldn’t be too long into the evening before Mercury appears alongside Venus, placed to Venus’ left at roughly the same altitude. Mercury has been on the scene for about a week now, itself shining significantly brighter than any star visible from UK shores at this time of year, as it has been climbing steadily away from the north-western horizon. This evening it shines at magnitude –0.5.

The end of civil twilight (when the Sun lies six degrees below the horizon) usually signals the appearance of the brighter stars. In London, this occurs at about 9.40pm BST (20.40 UT) and at 10pm and 10.25pm, from Manchester and Edinburgh, respectively. The planetary pair lie at an altitude just short of eight degrees as seen from London, and just over six and seven degrees as seen from Edinburgh and Manchester, respectively.

During any moments of steady seeing (often fleeting at such a low elevation), it might be possible to glean Venus’ extremely thin crescent disc through a pair of binoculars. Its elongation from the Sun is only 20 degrees and so it exhibits just a 5.3 per cent-illuminated phase some 53 arcminutes in size. A small telescope would be a better bet to see this, as well as resolving Mercury’s 67 per cent-illuminated gibbous phase.

Through a small telescope Venus shows a very slim crescent this evening, while Mercury sports a much smaller gibbous disc. Astronomy Now graphic by Greg Smye-Rumsby.

Experienced observers can observe this conjunction in broad daylight, as Venus and Mercury are actually at their closest of 0.9 degree (53 arcminutes) at around 9am BST (08:00 UT). At this time, the pair lie about 27 degrees above the eastern horizon from London, and culminate due south at an advantageous 65-degree altitude at around 2.15pm BST, when their separation has widened to nearly 56 arcminutes. Viewing astronomical objects that are close to the Sun in broad daylight is fraught with danger, given the risk of damaging your eyes by looking at the Sun, so this is not recommended for casual or inexperienced observers.

On Sunday 24 May, the Moon joins Mercury and Venus in the dusk north-western sky. Astronomy Now graphic by Greg Smye-Rumsby.

If you are clouded out or can’t be free to observe this conjunction, then two evenings later, on Sunday 24 May, look out for when the young crescent Moon muscles in on the scene. It appears above five degrees to the left of Mercury, which is now separated from Venus by just over five degrees.

There’s also a chance on 24 May that you might see Comet SWAN if you have binoculars or a small telescope. AN Graphic by Greg Smye-Rumsby.

Venus now rapidly departs the evening sky on its way to inferior conjunction (between us and the Sun) on 3 June. It’s been a memorable evening apparition and, in what’s a great year for Venus fanciers, the planet returns as a blazing ‘morning star’ in July, for what promises to be a splendid morning apparition that lasts almost until the end of 2020.

Mercury makes further strides in evening visibility to put on a fine evening apparition, centred on a greatest eastern elongation from the Sun on 4 June.

It’s not all that common to see the two innermost, or so-called ‘inferior’ planets, come this close together, so make the most of it should the sky be clear for you.


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