Happy Summer Solstice – The Earliest Since 1896

By Milan B

The (Northern) Summer Solstice, today at 2:44 PM PDT, marks the earliest beginning of summer since 1896.

Chart of Solstice dates in Vancouver classified by "type" (the remainder after dividing the year by 4). Years evenly divisible by 4 (type 0 - such as 2016, 2020, 2024) can have early solstices.
Solstice dates in Vancouver classified by “type” (the remainder after dividing the year by 4). Years evenly divisible by 4 (type 0 – such as 2016, 2020, 2024) can have early solstices.

The chart above shows how the quadrennial correction (which the Julian Calendar is solely based on) works well short term, but over a longer period of time (130 years or so), it produces a significant error (one full day). To correct this, the Gregorian Calendar introduces another correction which is to omit leap days in some of the years that centuries begin with (or end, some would say). Years like 1700, 1800, 1900, 2100, 2200, 2300 etc. are chosen for this correction. So, we are in a deep stretch without this centennial correction and the seasons’ start dates will be falling even earlier until late 21st century.

Comet C/2017 T2 near Galaxy M109

Our observing director, Robert Conrad, wrote this post on facebook about comet C/2017 T2 (PANSTARRS).

“Don’t miss the opportunity on the night of June 15th to see comet C/2017 T2 (PANSTARRS) in the same FOV as the bright galaxy Messier 109 and the bright star Gamma Ursa Majoris. View it around 11:00pm when it’s dark and still relatively high in the sky. Good luck! “

The good news is that the comet is still close to M109 on the night of Tuesday June 16th, 2020 and the skies are forecasted to be somewhat clear in Vancouver. It is easy to find in the North-Western skies because of its proximity to Phecda – a bright star in the bowl of the Big Dipper. Recent observations have the comet at magnitude 8.5 so it is visible in small telescopes.

Galaxy M109 next to the Bowl of the Big Dipper at 11:00 pm PDT on June 16th, 2020 from Vancouver
Comet C/2017 T2 (PANSTARRS) is within 1° of Galaxy M109

GA Lite Astronomy Webinars

Join us for our “GA Lite” series of astronomy webinars, a great follow-up to the RASC Virtual General Assembly. The series is scheduled over the two weekends June 13&14  and June 20&21, with more details at

ga2020.rasc-vancouver/schedule-galiteh

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

What else are you going to do with this Vancouver weather forecast?

Barry Shanko Recognized with 2020 RASC President’s Award

Long-time RASC Vancouver member, Barry Shanko, received the President’s Award as announced at the 2020 RASC AGM this afternoon. A hand out of the 2020 RASC awards winners is available but information about the President’s Award is available in the following excerpt.

President’s Award

This award is given at the President’s discretion, usually once a year, to a member (or members) who has/have made an important contribution to the Society.

Mr. Shanko served as speaker coordinator for the Vancouver Centre for 31 years and was active in RASC public outreach efforts in the Vancouver area. In his life he had to overcome many economic and health challenges but became known for his ability to attract outstanding speakers from around Canada and the U.S. for Vancouver Centre events. Unfortunately, Mr. Shanko passed away unexpectedly just before his 60th birthday on 2020 May 2.

RASC Board of Directors Statement on Racial Inequality

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.

Drake’s Birthday, Seager, Roddenberry & the Odds for Extraterrestrial Life


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. 
  • fp = The fraction of those stars with planetary systems.
  • ne = The number of planets, per solar system, with an environment suitable for life.
  • fl = The fraction of suitable planets on which life actually appears.
  • fi = The fraction of life-bearing planets on which intelligent life emerges.
  • fc = 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, fp= 90%,  ne= 0.3,  fl =10%,  fi = 1.0%, fc = 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*  FQ  FHZ FO  FL  FS

Where 

  • N = the number of planets with detectable biosignature gases 
  • N* = number of M stars with I < 13 
  • FQ = fraction of quiet M stars 
  • FHZ = fraction with rocky planets in the HZ 
  • FO = fraction of observable=transiting systems observable with JWST 
  • FL = fraction with life 
  • FS = fraction with detectable spectroscopic signatures

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

N* = 30000,  (FQ FHZ) = 0.15, FO = 0.001, FL = 1.0, FS = 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.

Nova Newsletter for May/June 2020

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

RASC Virtual General Assembly 2020 poster.
Schedule and more info at ga2020.rasc-vancouver.com/schedule-va/

A Springtime Collection of Comets

“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.

Comet C/2019 Y4 Atlas from Cqoutilam on April 14, 2020.
Comet C/2019 Y4 Atlas imaged from Coquitlam BC on April 14, 2020

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.

ObjectMagnitude
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 limit9.0
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.

This image, taken on April 20, 2020, shows fragments of C/2019 Y4 (ATLAS). Image credit: Quanzhi Ye & Man-To Hui.
An image taken on April 20, 2020, shows fragments of C/2019 Y4 ATLAS. Image credit: Quanzhi Ye & Man-To Hui

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.

Graph showing correlation between the brightness of C/2019 Y4 Atlas and BC's COVID-19 cases.
Correlation between the brightness curve of C/2019 Y4 Atlas and BC’s COVID-19 cases

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.

Comet C/2020 F8 Swan
Comet C/2020 F8 Swan with its striking ion tail. Featured as the APOD on April 29th, 2020 . Image Credit: Gerald Rhemann

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.

Comet C/2017 T2 PanSTARRS
Movement of Comet C/2017 T2 PanSTARRS on Nov 20th, 2019 from Coquitlam, BC.

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.

Chart for C/2017 T2 PanSTARRS close to Bode's Galaxy M81 on May 22 at 23:00
From Vancouver C/2017 T2 PanSTARRS will appear close to Bode’s Galaxy M81 & the cigar galaxy M82 on May 22 at 11:00 pm

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.

Comet C/2019 Y1 Atlas
Comet C/2019 Y1 Atlas on April 14th, 2020. Image credit: Roland Fichtl
Light Curve for Comet C/2019 Y1 Atlas
Observed and Predicted Light Curves for Comet C/2019 Y1 Atlas from http://astro.vanbuitenen.nl/comet/2019Y1

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.

Chart for comet C/2019 Y1 Atlas near the Own Nebula M97
Stellarium Chart for C/2019 Y1 Atlas near the Owl Nebula M97 on May 25, 2020 at 11:00 pm as seen from Vancouver. The red circles have diameters of 0.5° and 2°.

How Close was Asteroid 1998 OR2?

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.

Image shift of the asteroid in two overlaid images: One from the Slooh Observatory in Chile and the other from their Observatory in the Canary Islands.

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.

Angular Distance Measurement in Stellarium between two stars

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.

Parallax is the shift in the position of an object relative to the background stars. Image Credit: http://astronomy.nmsu.edu/geas/lectures/lecture11/lecture11.hint00029.html

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.

Parallax Geometry for Calculating the Distance to the Asteroid.

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, ed, is approximately 12,756 km. That allows us to calculate r:

r =  cord_length  / 2
= ed * sin(a/ed) / 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.

Animation of the Asteroid’s Movement over a 20-minute interval from the Canary Islands.

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?