Join us on Sunday, June 7th at 11:00 am, for the RASC Virtual GA!

Live streamed on the RASC YouTube channel.

youtube.com/c/rascanada

The talks are free, open to the public, and family friendly.

The Board of Directors of the Royal Astronomical Society of Canada met recently, and unanimously approved the following statement:

In response to recent events, The Royal Astronomical Society of Canada wishes to state that it supports peaceful protests and dialogue across the world aimed at addressing longstanding issues of racial inequality, and in particular anti-Black discrimination and violence. The Society is dedicated to equality of opportunity and treatment for all, regardless of race, sex, gender identity or expression, sexual orientation, national or ethnic origin, religion or religious belief, age, marital status, and disabilities. We are opposed to all forms of unlawful and unfair discrimination.

by Venus Observer, Milan B.

In two days (June 3rd, 2020), our twin sister planet will pass between us and the Sun. This brings fond memories of the similar passes in June 2004 and June 2012, which both resulted in transits across the solar disk, but this time around, Venus will just miss the solar disk by a quarter of a degree on its passage from northern to southern ecliptic latitudes.

This 8 year cycle of Venus was known even to ancient Mayas. In 8 Earths years, Venus will make 13 orbits around the Sun and since both planets orbit the sun in the same direction, there will be 13 – 8 = 5 synodic periods of Venus looking from planet Earth. Any Fibonacci fans out there?

During 5 synodic periods Venus will go through 5 inferior conjunctions. Only one of these five is close to the Sun in the current epoque, two will be midway to the maximum distance which is just under 9 degrees and the remaining two will be very close to the maximum angular distance from the Sun.

5 synodic periods of Venus actually falls short of 8 years by 2 and a half days. With this, all inferior conjunctions will slowly move earlier in the year within each series. The 2020 conjunction, happening on June 3rd, is part of the June-May series, as was the 2004 transit, which occurred on June 8th and the 2012 transit, which occurred on June 5th.

With this years conjunction being a near miss, the question becomes: when will Venus next be so close to the solar disk? The visualisation below shows about 130 years of inferior conjunctions and each of the five seasons is labelled by the pair of months that it occurs in during the 21st century.

As the Jun-May series conjunctions (the green series above) are slowly moving away from the Sun and will not result in any transits for many centuries, we will need to turn to another series to bring us the next sequence of close passes and transits. The Jan-Dec series conjunctions, which are currently far from the solar disk are slowly inching (in astronomical terms) towards the Sun and also regressing from mid January (in early 2000’s) into early December (in the early 2100’s) which will result in another pair of transits, this time the December transits of 2117 and 2125.

From the chart above it becomes apparent that after the June 2020 conjunction, Venus will not venture so close to the Sun (from Earths perspective) for another 97 years, until the 2117 transit. Hopefully, some of the younger generations will get a chance to see this remarkable astronomical event.

Frank Drake is 90 years old today (May 28, 2020), making it a good day to ponder the odds for extraterrestrial life. Drake, an astrophysicist, has been involved in the search for extraterrestrial intelligence, including the founding of SETI, for decades. One of his best-known contributions was the development of the Drake Equation in 1961. The equation was originally intended to promote discussion between Drake and his colleagues on extraterrestrial life. The equation is still alive and relevant today with new revisions being proposed, debates on the values for its parameters, and a continuing appreciation of it from the general public. On the occasion of Frank Drake’s birthday, here is the Drake Equation plus two others inspired by it.

The Drake Equation estimates the number of communicating civilizations in the cosmos or more simply, the odds of finding intelligent life. The equation calculates the number of communicating civilizations by multiplying together estimates of several parameters. SETI’s web page displays the Drake equation as:

Where

• N = The number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable.
• R* = The rate of formation of stars suitable for the development of intelligent life. 
• f_p = The fraction of those stars with planetary systems.
• n_e = The number of planets, per solar system, with an environment suitable for life.
• f_l = The fraction of suitable planets on which life actually appears.
• f_i = The fraction of life-bearing planets on which intelligent life emerges.
• f_c = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
• L = The length of time such civilizations release detectable signals into space.

A wide range of values have been proposed for each parameter but a modern optimistic estimate has

R=7, f_p= 90%,  n_e= 0.3,  f_l =10%,  f_i = 1.0%, f_c = 1.0%, L = 10,000,000

which yields N = 189 civilizations in our galaxy.

The Drake Equation provides an estimate of the number of civilizations whose electromagnetic emissions are detectable. Astronomer Sara Seager proposed an equation that based on detecting planets whose biosignature gases can be detected. Biosignature gases, produced by living organisms, accumulate in a planet’s atmosphere to levels that can be detected with a remote space telescope. The Seager equation is:

N =  N^*  F_Q  F_HZ F_O  F_L  F_S

Where 

• N = the number of planets with detectable biosignature gases 
• N^* = number of M stars with I < 13 
• F_Q = fraction of quiet M stars 
• F_HZ = fraction with rocky planets in the HZ 
• F_O = fraction of observable=transiting systems observable with JWST 
• F_L = fraction with life 
• F_S = fraction with detectable spectroscopic signatures

Seager’s estimates for these parameters for M stars in the TESS/JWST survey are

N^* = 30000,  (F_Q F_HZ) = 0.15, F_O = 0.001, F_L = 1.0, F_S = 0.5

Which yields N = 2 civilizations.

Sara Seager is giving an “Update on NASA’s TESS Exoplanet Mission” at the RASC Virtual General Assembly. Live streamed on Sunday June 7th, 2020 on the RASC YouTube channel www.youtube.com/c/rascanada.

Sara Seager posted a YouTube video honouring Drake and the influence he had on her own research.

A form of Drake’s equation was used by Gene Roddenberry to pitch Star Trek in 1964. Roddenberry was trying to justify the large number of inhabited planets in the show. He did not have a copy of the equation so he made up his own variant

with no explanation of the parameters. It is said that Frank Drake later pointed out to Roddenberry that a value raised to the first power is merely the value itself when he visited the Star Trek set.

Happy 90th Birthday to Frank Drake, a pioneer in the search for life elsewhere in the universe.

I found it interesting to compare images of two Pinwheel galaxies despite the difference in targets and imaging setups.

The Pinwheel Galaxy, M101 in Messier’s catalogue, is a beautiful face-on spiral galaxy that is popular with astrophotographers. Tonight at 11:00 pm from Vancouver, it is at an altitude of 84°- almost straight up – in the constellation Ursa Major. This is a great location for visual observing or imaging to minimize atmospheric disturbance.  I collected image data of M101 in 2014 with a small 100 mm refractor.

Another pinwheel from Messier’s catalogue is M83, also known as the Southern Pinwheel. It is visible at the same time but its altitude is just 10° above the southern horizon in the constellation Hydra when viewed from Vancouver. That location makes M83 a difficult target so I decided to use a remote telescope in Chile at latitude 30°S.  From Chile, M83 reaches 89° when transiting the meridian at 02:16 am UTC.

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Click on the image to open a larger view.

Two very different setups were used to collect the imaging data. The M101 data was collected using my own equipment from Coquitlam, BC:

• Skywatcher 100ED pro refractor
• Nikon D5100 DSLR
• Total Exposure:  30 min with 20 subframes at 90 sec and ISO 1600
• Heavy light pollution (sqm: 18.5, Bortle class 7)

The M83 data was from the Telescope.live remote CH-1 telescope in Chile:

• Planewave CDK24 (60 cm, F6.5)
• FLI ProLine PL900 (3056 x 3056)
• Total Exposure: 90 min with  9 Luminance and 3 each of Red, Green, Blue subframes at 300 sec and 1 x binning.
• Pristine Dark skies at an elevation of 1500 m (sqm: 21.8, Bortle class 1) – same skies as the Gemini South telescope.

So it is not at all surprising that the M83 image is better with 6X more aperture and 3X longer exposure.

The two galaxies are both face-on spirals, appear somewhat similar, and are close to the same visual magnitude but some of their physical properties are quite different as shown in the table below.

	M101	M83
Constellation	Ursa Major	Hydra
Visual magnitude	7.86	7.54
Angular Size	28′.8 × 26′.9	12′.9 × 11′.5
Distance	1.8 Mly	14.7 Mly
Diameter	170,000 ly	55,000 ly
Radial velocity	241 ± 2 km/s	508 km/s
Number of Supernovae	4	6

M83 has spawned a large number of supernova explosions — six in total that we have observed (SN 1923A, SN 1945B, SN 1950B, SN 1957D, SN 1968L, and SN 1983N).  Only 4 supernovae have been observed in M101 but SN 2011fe, a Type Ia supernova, reached magnitude 9.9 in 2011 and was visible in binoculars.

M83 is thought to have a double nucleus at its core. The paper  “Double nucleus in M83” provides evidence of a second hidden nucleus that is more massive than the visible nucleus.

Our NOVA Newsletter for Mar-Apr 2020 is available as a pdf file. An archive of older issues can be found on our Newsletter page. The contents include:

A Close, Unheralded Neighbour by J. Karl Miller

President’s message by Gordon Farrell

AAVSO Custom Chart Plotter – A Game Changer by Robert Conrad

RASC Virtual General Assembly 2020 by the RASC Vancouver GA Committee

“The Hour arrived—and it became
A wandering mass of shapeless flame,
A pathless Comet, and a curse,
The menace of the Universe!”

Lord Byron, “Seventh spirit” from the dramatic poem Manfred, 1817.

Throughout history and across cultures comets have be viewed with dread, fear, and awe. They have been branded with such titles as “the Harbinger of Doom” and “the Menace of the Universe“. Nowadays, we look forward to observing them and hope for a comet bright enough to view with our naked eyes.

This spring features a fine collection of bright comets. It is doubtful that any will reach naked-eye visibility so a small telescope or binoculars are recommended for observing them.

A comet’s brightness is measured on a scale called visual or apparent magnitude. The following table is a refresher on some common magnitudes for those not familiar with this scale. Notice the scale is backwards where small magnitude indicates brighter objects.

Object	Magnitude
Venus (brightest planet)	-4.6
Sirius (brightest star)	-1.4
Polaris (the North Star)	2.0
Naked-eye limit (city/urban) Faintest star seen from a city location	3.0
Naked-eye limit (dark sky)	6.0
Binocular limit	9.0
Small Telescope limit (100 mm refractor)	11.0

C/2019 Y4 Atlas

C/2019 Y4 Atlas had stargazers looking forward with anticipation to the next great naked-eye comet. Its rapid brightening in Feb 2020 led to speculation that it would become a naked-eye comet that might even be visible in daylight.

“a comet may be visible with the naked eye in late April and early May. It’s even possible that it could get bright enough that it’s visible at twilight while the sun is still up”

Thrillist: https://www.thrillist.com/news/nation/comet-atlas-c19-y4-headed-near-earth-2020

But it was a bit of a let down to learn that images taken in early April showed its nucleus starting to disintegrate.

C/2019 Y4 Atlas is still relatively bright at magnitude 9.5 and is in a good position for viewing. It appears about 30° above the horizon in the northwest at 11 pm. It is headed lower and dimming so the next few weeks may be our last chance to observe it.

With tongue in cheek, one can see “evidence” that comet C/2019 Y4 Atlas was a “harbringer of doom”: It appeared and started to rapidly brighten just before the number of cases of COVID-19 in BC started to ramp up; The comet’s peak brightness corresponds closely with the peak of COVID-19 cases; and The curves for the comet’s brightness and the number of new COVID-19 cases have both shown signs of flattening. Perhaps its recent dimming should be interpreted as a foreshadowing that the worst of COVID-19 is over 😉

C/2020 F8 SWAN

Comet C/2020 F8 SWAN may be the brightest comet of 2020 – if you able to observe it from the southern hemisphere. It is already bright at 7.0 mag and is expected to brighten to magnitude 3.5 as it continues to approach the Sun during May.

It has developed a striking tail. In the Northern Hemisphere, it is only visible extremely low in the sky in late May. It will re-appear in the morning sky in August but by then is expected to have dimmed down to mag 11.

C/2017 T2 PanSTARRS

The comet C/2017 T2 PanSTARRS has been a steady performer. It became brighter than mag 10 on New Year’s Day 2020 and is currently at magnitude 8.2 as it makes its way from Camelopardalis toward the Big Dipper. It reaches perihelion, its closest point the Sun, on May 4th.

It is expected to be at its maximum brightness of 8.0 on May 15th. For a special treat, a few days later on the nights of May 22nd and 23rd, the comet will pass within 2° of the galaxies M81 and M82. It should remain bright until July and is well-positioned for viewing from Vancouver during the next few months.

On June 4th, the comet will be easy to find as it passes less than 1° from Dubhe, the brightest star in the Big Dipper.

C/2020 Y1 Atlas

Another comet that is well positioned for observing from Vancouver is C/2020 Y1 Atlas. It is following a similar path to C/2017 T2 PanSTARRS, heading higher in Northern sky.

It is currently around 7.9 mag and has continued to brightening even though it reached perihelion on Mar 15. Its observed brightness has consistently being higher that the initial predictions as shown in its light curve where blue and black dots are visual and photometric CCD observations from COBS or the MPC, and the gray curve is based on the original MPEC or MPC predictions. Software like Stellarium and SkySafari appear to be displaying the magnitude for this comet from the initial predictions – as a result, the comet might appear much brighter in the sky than it does in the simulated views from the software.

Lets hope it stays bright longer as it will be within 0.5° of the Owl Nebula M97 and within 2° of the galaxy M108 on May 25 at 11:00 pm PDT as seen from Vancouver – that should make a nice photo op.

The large asteroid 1998 OR2 safely made a close flyby of Earth on April 29, 2020. Its size is estimated to be between 1.8 and 4.1 km, making it capable of doing some serious damage and NASA classifies it as a large “potentially hazardous asteroid”. But its orbit has been carefully tracked and this asteroid poses no possibility of impact for at least the next 200 years. How close did it come? I tried to find out by measuring its parallax from two remote observatories and applying my rusty high-school trigonometry – the result was a distance value within 0.8% of NASA’s estimate.

Slooh hosted a live viewing of this asteroid on April 28. 2020 just before its closest flyby of Earth. They had two of their remote telescopes pointed at the asteroid: one located in the Canary Islands and another near Santiago in Chile. As expected the position of the asteroid, with respect to the background stars, appeared to shift in images taken by each telescope. This image shift is known as parallax. To make the shift more obvious, I grabbed an image from each telescope and aligned them with the Gimp (free image processing software similar to Photoshop). The asteroid appears as a slightly elongated oval compared to the background stars because of its rapid apparent motion during each exposure.

I noticed that the angular distance of the shift is about the same as the distance between a couple of stars just above the comet. So I fired up Stellarium and used its Angle Measure tool to measure the distance between the two stars. This turned out to be 4’ 30.84” or 0.0013131 when converted to radians.

With that measurement, the distance to the asteroid can be calculated with a bit of parallax math. The animated image below illustrates how the asteroid can shift in position with respect to the background stars when observed from two separated sites.

The geometry for our case is shown in the not-to-scale diagram below where the circle represents the Earth. Notice that the observing sites in the Canary Islands and in Chile are separated by less than the diameter of the Earth.

We want to calculate d – the distance to the asteroid. The definition of the trig tan function, tan(p) = r / d, can be re-arranged as

d =  r  /  tan(p)

to do so.

The parallax angle, p, is known from our prior use of Stellarium’s Angle Measure tool – it is 1/2 the measured shift in the asteroid’s position or ½ * 0.0013131 = 0.0006565 radians.

The value of r is 1/2 of the chord length between the Slooh observatory in Chile and the observatory in the Canary Islands. The arc length, a, between these two sites (along the surface of the Earth) is easy to find, Google reports it to be about 8912 km. The general formula for calculating the length of a chord from an arc-length on a circle is

chord_length = diameter * sin( arc_length / diameter )

The circle, in this case, is the Earth whose diameter, e_d, is approximately 12,756 km. That allows us to calculate r:

r =  cord_length  / 2
= e_d * sin(a/e_d) / 2
= 12756 * sin(8912 / 12756) / 2
=  4,102 km

Plugging these values of p and r into the parallax equation provides an estimate of the distance, d, to the asteroid.

d =  r / tan(p)
= 4102 / tan(0.0006565)
= 6,248,285 km

This value is within 0.8% of NASA’s estimate of 6.3 million km for the distance at closest approach – not too bad.

When observed from a single site, asteroid 1998 OR2 appears to move quickly across the field of background stars because it is relatively close to Earth. The animation below shows how much the asteroid moved during a 20-minute interval when observed from the Canary Islands Observatory.

I believe that the velocity of the asteroid could be calculated from this animation along with the distance estimate.  Is anyone up for tackling that calculation?

by Milan B.

All non-circumpolar stars have seasons of visibility. They depend on how far the star is from the Equator (the declination), but also how far the star is from the ecliptic. Sirius, being a Southern Hemisphere star and lying around 17 degrees below the equator also lies quite a bit below the ecliptic. This celestial geometry results in Sirius’ visibility season stretching roughly between September 1^st and May 1^st (the following year) for observers near 49 degrees North.

So, we have a few days left for this year’s season and to many it may be obvious how fast Sirius is disappearing in the SW sky twilight these days. All non-circumpolar stars are rising and setting just under four minutes earlier each day, throughout the year, but is this season finale unfolding faster for Sirius than other stars? 

The end of season for Sirius coincides with another celestial phenomenon, this one by our own star – the Sun. Around this time of the year the days are lengthening at fast pace as we just past the spring Equinox in March. The sunsets are falling about a minute and a half later each day in April as the Sun is climbing higher in the Northern Hemisphere heading towards the June Solstice. The table below shows how the difference between the time Sirius sets and the sunset shrinks dramatically in the month of April.

Date	Sirius Setting at	Sunset	Difference	Altitude of Sirius at Sunset
April 1	23:57	19:45	4h 12min	23.7o
April 11	23:17	20:00	3h 17min	21.3o
April 21	22:38	20:15	2h 23min	17.2o
May 1	21:58	20:28	1h 30min	11.6o

How dramatic the change is between April 1^st and May 1^st could be seen in the images taken from Sky Safari. Both images show the SW-W sky at the time of civil dusk, when the Sun is about 6 degrees below the horizon and when the brighter stars become visible.

On April 1^st the altitude of Sirius at Civil dusk is 22.4^o

On May 1^st the altitude of Sirius at Civil dusk is only 6.1^o

In normal times I would say: go out and enjoy the last few days of Sirius visibility in the evening SW sky, but we are in different times. Hopefully, next year in April, we will be able to do this without breaking any rules.

Cosmonaut Yuri Gagarin became the first human in space on board Vostok 1 on the morning of April 12, 1961.

The event is celebrated as Yuri’s Night around the world each April. The 2020 celebration is a virtual World Space Party at https://party.yurisnight.net/ due to the covid-19 pandemic. The Yuri’s Night webcast on youtube will connect Yuri’s Night fans around the world to dozens of astronauts, celebrities, musicians, space professionals and more in a huge celebration of humanity & human spaceflight worldwide.

“Circling the Earth in my orbital spaceship I marveled at the beauty of our planet. People of the world, let us safeguard and enhance this beauty — not destroy it!”

— Yuri Gagarin

Cosmonauts were chosen not only for their excellence in training but also for their short stature because the cockpit was small. Gagarin was 1.57 meters or 5 feet 2 inches tall.

Legend says that Gagarin had to relieve himself on the way to the launch pad. Modern (male) cosmonauts have done so as well: They leave the bus and relieve themselves at the left back wheel of the bus. A new space suit design might mean and end to this tradition.

Vostok 1 made one complete orbit of the Earth that took 108 minutes. The first American in space was Alan Shepard’s aboard the Freedom 7 Mercury capsule. Shepard’s craft entered space, but was not capable of achieving orbit.

Gagarin ejected from the space capsule when it was still 7 km from the ground. He then deployed a parachute at 2.5 km in altitude.

A farmer and her daughter came upon Gagarin after his landing. Dressed in his orange spacesuit and dragging his parachute, he told them “don’t be afraid, I am a Soviet like you, who has descended from space and I must find a telephone to call Moscow!”

A crater on the Moon is named for Gagarin, as is asteroid 1772 Gagarin.

The following infographic from space.com has more on how the first human spaceflight worked.