Population

Climate change is a serious problem requiring immediate attention. We need to reduce greenhouse gas emissions into our atmosphere as fast as possible. Half measures will not do. We are rapidly running out of time before the quality of life for all humans on planet Earth declines, especially for the economically disadvantaged.

A precipitous decline in biological diversity due to habitat loss and extinction of species is of greater concern, and yet it gets very little attention in the mainstream media. While climate change will render large areas of the Earth uninhabitable, biodiversity loss will lead to a partial or complete collapse of the ecosystem humans depend upon for food.

Getting even less attention is the cause of both of these problems: overpopulation. If you were born in 1973, the world’s human population is now twice what it was then. If you were born in 1952, there are three times as many people alive now than there were then. We have a climate emergency and a biodiversity emergency because we have a population emergency. The number of humans on this planet needs to decline, and the only humane way to accomplish that is to have fewer children. It is that simple.

And, yet, we often see this or that news article lamenting the fact that the birth rate in this or that country is too low. That’s crazy! A low birth rate should be a cause for celebration given the current state of the world and its environment. Certainly, a low birth rate does lead to some economic challenges, but these pale in comparison to the challenges we will face if population (and consumption) continue to grow.

As a humanist, I believe that we should do all we can to alleviate and eliminate human suffering. It is our highest moral calling. To be sure, some human suffering is inevitable and necessary when an individual makes poor decisions and suffers the consequences before hopefully making a mid-course correction. But the kind of suffering I am talking about is suffering that is imposed upon a person through no fault of their own, be it the cruelty of other human beings, or the cruelty of nature.

In this light we can see that our economic systems, governments, and most religions are utterly failing us. Nothing short of drastic changes will solve these problems. May wisdom, intelligence, ingenuity, and compassion guide us, rather than fear, ignorance, hatred, and dogma.

There is an organization dedicated to stabilizing human population throughout the world by lowering the birth rate: Population Connection. I encourage you to support their work as I do.

YearPopulationGrowth Factor
20207,794,798,7391.0
20197,713,468,1001.0
20187,631,091,0401.0
20177,547,858,9251.0
20167,464,022,0491.0
20157,379,797,1391.1
20147,295,290,7651.1
20137,210,581,9761.1
20127,125,828,0591.1
20117,041,194,3011.1
20106,956,823,6031.1
20096,872,767,0931.1
20086,789,088,6861.1
20076,705,946,6101.2
20066,623,517,8331.2
20056,541,907,0271.2
20046,461,159,3891.2
20036,381,185,1141.2
20026,301,773,1881.2
20016,222,626,6061.3
20006,143,493,8231.3
19996,064,239,0551.3
19985,984,793,9421.3
19975,905,045,7881.3
19965,824,891,9511.3
19955,744,212,9791.4
19945,663,150,4271.4
19935,581,597,5461.4
19925,498,919,8091.4
19915,414,289,4441.4
19905,327,231,0611.5
19895,237,441,5581.5
19885,145,426,0081.5
19875,052,522,1471.5
19864,960,567,9121.6
19854,870,921,7401.6
19844,784,011,6211.6
19834,699,569,3041.7
19824,617,386,5421.7
19814,536,996,7621.7
19804,458,003,5141.7
19794,380,506,1001.8
19784,304,533,5011.8
19774,229,506,0601.8
19764,154,666,8641.9
19754,079,480,6061.9
19744,003,794,1721.9
19733,927,780,2382.0
19723,851,650,2452.0
19713,775,759,6172.1
19703,700,437,0462.1
19693,625,680,6272.1
19683,551,599,1272.2
19673,478,769,9622.2
19663,407,922,6302.3
19653,339,583,5972.3
19643,273,978,3382.4
19633,211,001,0092.4
19623,150,420,7952.5
19613,091,843,5072.5
19603,034,949,7482.6
19592,979,576,1852.6
19582,925,686,7052.7
19572,873,306,0902.7
19562,822,443,2822.8
19552,773,019,9362.8
19542,724,846,7412.9
19532,677,608,9602.9
19522,630,861,5623.0
19512,584,034,2613.0
19502,536,431,0183.1

References
World Population Prospects 2019, United Nations.
Worldometers.info; 17 January, 2020; Dover, Delaware, U.S.A.

Satellite and Meteor Crossings 2019 #2

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.

I’ve put together a video montage of satellites I serendipitously recorded between August 9, 2019 and December 22, 2019.  Many of the satellite crossings are moving across the fields as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.

Satellites in higher orbits take longer to cross the field. In the next video, the originally geosynchronous satellite OPS 1570 (IMEWS-3, “Integrated Missile Early Warning System”) is barely visible until it exhibits an amazing sunglint around 3:41:22 UT.

I caught one meteor on October 6, 2019 at 9:57:43 UT. Field location was UCAC4 515-043597. The meteor was a Daytime Sextantid, as determined using the method I described previously in There’s a Meteor in My Image. The meteor even left a brief afterglow—a meteor train!

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Bastien and Bastienne…and Beethoven?

Musical mystery, or compositional coincidence?  Wolfgang Amadeus Mozart wrote the music for his one-act opera Bastien and Bastienne in 1768, at the age of 12.  The short Overture to Bastien and Bastienne bears a remarkable resemblance to the opening theme of Beethoven’s Eroica symphony, composed between 1802 and 1804.  Although the keys are different (Mozart’s overture is in G major and Beethoven’s symphony is in E♭ major), could it be that Beethoven had Mozart’s theme in mind while he composed his 3rd symphony?  It is unlikely that Bastien and Bastienne was known to Beethoven, as that music received its first public performance in 1890.  Perhaps, just a coincidence.  Great minds think alike, it appears.

Overture to Bastien and Bastienne, Statatskapelle Dresden, Sir Colin Davis, RCA 74321-56698-2
Symphony No. 3, “Eroica”, Chicago Symphony Orchestra, Sir Georg Solti, London 430 792-2

An Astronomy Retirement Community

Are any of you nearing retirement (as I am) or already retired who might be interested in moving to an astronomy-oriented retirement community? If you are, I encourage you to join the moderated Groups.io discussion group Dark-Sky Communities at

https://groups.io/g/Dark-Sky-Communities

I am working to establish such a community and would value your input and assistance. That work involves extensive research, networking, writing articles in various publications to reach a wider audience, finding a suitable developer, and seeking benefactors.

Some characteristics of the community I envision include:

  1. Rural location with a dark night sky, but not too far from a city with decent medical facilities, preferably to the northeast or northwest;
  2. Location with an abundance of clear nights and mild winters, probably in Arizona, New Mexico, or West Texas;
  3. Lighting within the community that does not interfere with astronomical activities, strictly enforced;
  4. Community is owned and operated by a benefit corporation or cooperative that will rent a house or apartment to each resident;
  5. Observatories will be available for rental by interested residents who will equip them;
  6. Pro-am collaborative research opportunities will be developed and nurtured;
  7. A community observatory and a public observatory for astronomy outreach will be constructed and maintained;
  8. Lodging will be available for visitors and guests;
  9. There will be opportunities for on-site income operating and maintaining the community or, alternatively, a reduction in monthly rental fees.

Many of us have spent a significant amount of time and energy over the years trying to rein in light pollution in our respective communities and in the wider world, with varying degrees of success. Those efforts should continue, but the grim reality is that light pollution is continuing to get worse almost everywhere.

The opportunity to live in a community of varied interests but with a common appreciation for the night sky and a natural nighttime environment will appeal to many of us. Furthermore, a dark-sky community will afford us opportunities to show the world at large a better way to live.

Traditionally, in the United States at least, if one wants to live under a dark and starry night sky, your only options are to purchase land and build a house on it, or purchase an existing rural home. Not only is buying and maintaining rural real estate unaffordable or impractical for many, many would prefer to live in a rural community, provided that the night sky and nighttime environment are vigorously protected. Rental will also make it easier to move into and out of the community as circumstances change.

Zodiacal Light 2020

In 2020, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin (42° 58′ N, 90° 08′ W).

Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:

January 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12
Zodiacal Light 6:28 – 7:07 p.m. West
13
Zodiacal Light 6:29 – 7:29 p.m. West
14
Zodiacal Light 6:30 – 7:30 p.m. West
15
Zodiacal Light 6:31 – 7:31 p.m. West
16
Zodiacal Light 6:32 – 7:32 p.m. West
17
Zodiacal Light 6:33 – 7:33 p.m. West
18
Zodiacal Light 6:34 – 7:34 p.m. West
19
Zodiacal Light 6:35 – 7:35 p.m. West
20
Zodiacal Light 6:36 – 7:36 p.m. West
21
Zodiacal Light 6:37 – 7:37 p.m. West
22
Zodiacal Light 6:38 – 7:38 p.m. West
23
Zodiacal Light 6:39 – 7:39 p.m. West
24
Zodiacal Light 6:41 – 7:41 p.m. West
25
Zodiacal Light 6:42 – 7:42 p.m. West
26 27 28 29 30 31  
February 2020
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10
Zodiacal Light 7:00 – 7:17 p.m. West
11
Zodiacal Light 7:01 – 8:01 p.m. West
12
Zodiacal Light 7:03 – 8:03 p.m. West
13
Zodiacal Light 7:04 – 8:04 p.m. West
14
Zodiacal Light 7:05 – 8:05 p.m. West
15
Zodiacal Light 7:06 – 8:06 p.m. West
16
Zodiacal Light 7:07 – 8:07 p.m. West
17
Zodiacal Light 7:09 – 8:09 p.m. West
18
Zodiacal Light 7:10 – 8:10 p.m. West
19
Zodiacal Light 7:11 – 8:11 p.m. West
20
Zodiacal Light 7:12 – 8:12 p.m. West
21
Zodiacal Light 7:13 – 8:13 p.m. West
22
Zodiacal Light 7:15 – 8:15 p.m. West
23
Zodiacal Light 7:16 – 8:16 p.m. West
24
Zodiacal Light 7:17 – 8:17 p.m. West
25 26 27 28 29

March 2020
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11
Zodiacal Light 8:37 – 9:37 p.m. West
12
Zodiacal Light 8:38 – 9:38 p.m. West
13
Zodiacal Light 8:39 – 9:39 p.m. West
14
Zodiacal Light 8:41 – 9:41 p.m. West
15
Zodiacal Light 8:42 – 9:42 p.m. West
16
Zodiacal Light 8:43 – 9:43 p.m. West
17
Zodiacal Light 8:45 – 9:45 p.m. West
18
Zodiacal Light 8:46 – 9:46 p.m. West
19
Zodiacal Light 8:47 – 9:47 p.m. West
20
Zodiacal Light 8:49 – 9:49 p.m. West
21
Zodiacal Light 8:50 – 9:50 p.m. West
22
Zodiacal Light 8:51 – 9:51 p.m. West
23
Zodiacal Light 8:53 – 9:53 p.m. West
24
Zodiacal Light 8:54 – 9:54 p.m. West
25
Zodiacal Light 8:55 – 9:55 p.m. West
26 27 28
29 30 31        

April 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9
Zodiacal Light 9:17 – 9:51 p.m. West
10
Zodiacal Light 9:19 – 10:19 p.m. West
11
Zodiacal Light 9:20 – 10:20 p.m. West
12
Zodiacal Light 9:22 – 10:22 p.m. West
13
Zodiacal Light 9:23 – 10:23 p.m. West
14
Zodiacal Light 9:25 – 10:25 p.m. West
15
Zodiacal Light 9:27 – 10:27 p.m. West
16
Zodiacal Light 9:28 – 10:28 p.m. West
17
Zodiacal Light 9:30 – 10:30 p.m. West
18
Zodiacal Light 9:31 – 10:31 p.m. West
19
Zodiacal Light 9:33 – 10:33 p.m. West
20
Zodiacal Light 9:35 – 10:35 p.m. West
21
Zodiacal Light 9:36 – 10:36 p.m. West
22
Zodiacal Light 9:38 – 10:38 p.m. West
23
Zodiacal Light 9:40 – 10:40 p.m. West
24
Zodiacal Light 9:41 – 10:41 p.m. West
25
26 27 28 29 30    
September 2020
SUN MON TUE WED THU FRI SAT
    1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16
Zodiacal Light 4:05 – 5:05 a.m. East
17
Zodiacal Light 4:06 – 5:06 a.m. East
18
Zodiacal Light 4:07 – 5:07 a.m. East
19
Zodiacal Light 4:09 – 5:09 a.m. East
20
Zodiacal Light 4:10 – 5:10 a.m. East
21
Zodiacal Light 4:11 – 5:11 a.m. East
22
Zodiacal Light 4:13 – 5:13 a.m. East
23
Zodiacal Light 4:14 – 5:14 a.m. East
24
Zodiacal Light 4:15 – 5:15 a.m. East
25
Zodiacal Light 4:16 – 5:16 a.m. East
26
Zodiacal Light 4:17 – 5:17 a.m. East
27
Zodiacal Light 4:19 – 5:19 a.m. East
28
Zodiacal Light 4:20 – 5:20 a.m. East
29
Zodiacal Light 4:27 – 5:21 a.m. East
30      

October 2020
SUN MON TUE WED THU FRI SAT
        1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16
Zodiacal Light 4:41 – 5:41 a.m. East
17
Zodiacal Light 4:42 – 5:42 a.m. East
18
Zodiacal Light 4:43 – 5:43 a.m. East
19
Zodiacal Light 4:44 – 5:44 a.m. East
20
Zodiacal Light 4:46 – 5:46 a.m. East
21
Zodiacal Light 4:47 – 5:47 a.m. East
22
Zodiacal Light 4:48 – 5:48 a.m. East
23
Zodiacal Light 4:49 – 5:49 a.m. East
24
Zodiacal Light 4:50 – 5:50 a.m. East
25
Zodiacal Light 4:51 – 5:51 a.m. East
26
Zodiacal Light 4:52 – 5:52 a.m. East
27
Zodiacal Light 4:53 – 5:53 a.m. East
28
Zodiacal Light 4:55 – 5:55 a.m. East
29
Zodiacal Light 5:24 – 5:56 a.m. East
30 31

November 2020
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13 14
Zodiacal Light 4:13 – 5:13 a.m. East
15
Zodiacal Light 4:15 – 5:15 a.m. East
16
Zodiacal Light 4:16 – 5:16 a.m. East
17
Zodiacal Light 4:17 – 5:17 a.m. East
18
Zodiacal Light 4:18 – 5:18 a.m. East
19
Zodiacal Light 4:19 – 5:19 a.m. East
20
Zodiacal Light 4:20 – 5:20 a.m. East
21
Zodiacal Light 4:21 – 5:21 a.m. East
22
Zodiacal Light 4:22 – 5:22 a.m. East
23
Zodiacal Light 4:23 – 5:23 a.m. East
24
Zodiacal Light 4:24 – 5:24 a.m. East
25
Zodiacal Light 4:25 – 5:25 a.m. East
26
Zodiacal Light 4:26 – 5:26 a.m. East
27
Zodiacal Light 4:27 – 5:27 a.m. East
28
Zodiacal Light 5:17 – 5:28 a.m. East
29 30          

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Meteor Shower Calendar 2020

Here’s our meteor shower calendar for 2020.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2020.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Here’s a printable PDF file of the meteor shower calendar shown below:

Happy meteor watching!

January 2020
SUN MON TUE WED THU FRI SAT
      1
DLM QUA
2
DLM QUA
3
DLM QUA
4
DLM QUA
5
DLM QUA
6
DLM QUA
7
DLM QUA
8
DLM QUA
9
DLM QUA
10
DLM QUA GUM
11
DLM QUA GUM
12
DLM QUA GUM
13
DLM GUM
14
DLM GUM
15
DLM GUM
16
DLM GUM
17
DLM GUM
18
DLM GUM
19
DLM GUM
20
DLM GUM
21
DLM GUM
22
DLM GUM
23
DLM
24
DLM
25
DLM
26
DLM
27
DLM
28
DLM
29
DLM
30
DLM
31
DLM ACE
 
February 2020
SUN MON TUE WED THU FRI SAT
            1
DLM ACE
2
DLM ACE
3
DLM ACE
4
DLM ACE
5
ACE
6
ACE
7
ACE
8
ACE
9
ACE
10
ACE
11
ACE
12
ACE
13
ACE
14
ACE
15
ACE
16
ACE
17
ACE
18
ACE
19
ACE
20
ACE
21 22
23 24 25
GNO
26
GNO
27
GNO
28
GNO
 
March 2020
SUN MON TUE WED THU FRI SAT
1
GNO
2
GNO
3
GNO
4
GNO
5
GNO
6
GNO
7
GNO
8
GNO
9
GNO
10
GNO
11
GNO
12
GNO
13
GNO
14
GNO
15
GNO
16
GNO
17
GNO
18
GNO
19
GNO
20
GNO
21
GNO
22
GNO
23
GNO
24
GNO
25
GNO
26
GNO
27
GNO
28
GNO
29 30 31        
April 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12 13 14
LYR
15
PPU LYR
16
PPU LYR
17
PPU LYR
18
PPU LYR
19
ETA PPU LYR
20
ETA PPU LYR
21
ETA PPU LYR
22
ETA PPU LYR
23
ETA PPU LYR
24
ETA PPU LYR
25
ETA PPU LYR
26
ETA PPU LYR
27
ETA PPU LYR
28
ETA PPU LYR
29
ETA LYR
30
ETA LYR
   
May 2020
SUN MON TUE WED THU FRI SAT
          1
ETA
2
ETA
3
ELY ETA
4
ELY ETA
5
ELY ETA
6
ELY ETA
7
ELY ETA
8
ELY ETA
9
ELY ETA
10
ELY ETA
11
ELY ETA
12
ELY ETA
13
ELY ETA
14
ARI ELY ETA
15
ARI ETA
16
ARI ETA
17
ARI ETA
18
ARI ETA
19
ARI ETA
20
ARI ETA
21
ARI ETA
22
ARI ETA
23
ARI ETA
24
ARI ETA
25
ARI ETA
26
ARI ETA
27
ARI ETA
28
ARI ETA
29
ARI
30
ARI
31
ARI
           
June 2020
SUN MON TUE WED THU FRI SAT
  1
ARI
2
ARI
3
ARI
4
ARI
5
ARI
6
ARI
7
ARI
8
ARI
9
ARI
10
ARI
11
ARI
12
ARI
13
ARI
14
ARI
15
ARI
16
ARI
17
ARI
18
ARI
19
ARI
20
ARI
21
ARI
22
JBO ARI
23
JBO ARI
24
JBO ARI
25
JBO
26
JBO
27
JBO
28
JBO
29
JBO
30
JBO
       
July 2020
SUN MON TUE WED THU FRI SAT
      1
JBO
2
JBO
3
CAP
4
CAP
5
CAP
6
CAP
7
CAP
8
CAP
9
CAP
10
CAP
11
CAP
12
CAP SDA
13
CAP SDA
14
CAP SDA
15
CAP SDA PAU
16
CAP SDA PAU
17
PER CAP SDA PAU
18
PER CAP SDA PAU
19
PER CAP SDA PAU
20
PER CAP SDA PAU
21
PER CAP SDA PAU
22
PER CAP SDA PAU
23
PER CAP SDA PAU
24
PER CAP SDA PAU
25
PER CAP SDA PAU
26
PER CAP SDA PAU
27
PER CAP SDA PAU
28
PER CAP SDA PAU
29
PER CAP SDA PAU
30
PER CAP SDA PAU
31
PER CAP SDA PAU
 
August 2020
SUN MON TUE WED THU FRI SAT
            1
PER CAP SDA PAU
2
PER CAP SDA PAU
3
KCG PER CAP SDA PAU
4
KCG PER CAP SDA PAU
5
KCG PER CAP SDA PAU
6
KCG PER CAP SDA PAU
7
KCG PER CAP SDA PAU
8
KCG PER CAP SDA PAU
9
KCG PER CAP SDA PAU
10
KCG PER CAP SDA PAU
11
KCG PER CAP SDA
12
KCG PER CAP SDA
13
KCG PER CAP SDA
14
KCG PER CAP SDA
15
KCG PER CAP SDA
16
KCG PER SDA
17
KCG PER SDA
18
KCG PER SDA
19
KCG PER SDA
20
KCG PER SDA
21
KCG PER SDA
22
KCG PER SDA
23
KCG PER SDA
24
KCG PER
25
KCG
26 27 28
AUR
29
AUR
30
AUR
31
AUR
         
September 2020
SUN MON TUE WED THU FRI SAT
    1
AUR
2
AUR
3
AUR
4
AUR
5
SPE AUR
6
SPE
7
SPE
8
SPE
9
DSX SPE
10
STA DSX SPE
11
STA DSX SPE
12
STA DSX SPE
13
STA DSX SPE
14
STA DSX SPE
15
STA DSX SPE
16
STA DSX SPE
17
STA DSX SPE
18
STA DSX SPE
19
STA DSX SPE
20
STA DSX SPE
21
STA DSX SPE
22
STA DSX
23
STA DSX
24
STA DSX
25
STA DSX
26
STA DSX
27
STA DSX
28
STA DSX
29
STA DSX
30
STA DSX
     
October 2020
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Venus: Future Earth?

In terms of bulk properties, Venus is the most Earthlike planet in the solar system. The diameter of Venus is 95% of Earth’s diameter. The mass of Venus is 82% of Earth’s mass. It has a nearly identical composition.

But…the average surface temperature of Venus is 735 K (863˚ F) and the surface atmospheric pressure is 91 times greater than Earth’s—equivalent to the pressure 3,000 ft. below the ocean’s surface. The present atmosphere of Venus is composed of 96.5% carbon dioxide (CO2) and 3.5% nitrogen (N2), plus a number of trace elements and compounds.

Venus was not always so inhospitable. What happened?

The cratering record suggests that nearly all of Venus has been resurfaced within the last 300 – 800 Myr. Before that, Venus probably was much more hospitable, even habitable, perhaps. The Pioneer Venus large probe and infrared spectral observations from Earth of H2O and HDO (deuterated isotope of water) indicate that the deuterium-to-hydrogen ratio in the Venusian atmosphere is 120 – 157 times higher than in water on Earth, strongly suggesting that Venus was once much wetter than it is today and that it has lost much of the water it once had to space. (Hydrogen is lighter than deuterium and therefore more easily escapes to space.) In addition to deuterium abundance, measuring the isotopic abundance ratios of the noble gases krypton and xenon would help us better understand the water history of Venus. These cannot be measured remotely and requires at-Venus sampling.

Venus receives 1.92 times as much solar radiation as the Earth, and this was undoubtedly a catalyst for the runaway greenhouse effect that transformed the Venusian climate millions of years ago.

We know that CO2 is a potent greenhouse gas, but anything that increases the amount of water vapor (H2O) in the atmosphere leads to global warming as well. As do clouds.

Climate modeling shows us that that the hothouse on the surface of Venus today is due to CO2 (66.6%), the continual cloud cover (22.5%), and what little water vapor remains in the atmosphere (10.9%).

Interestingly, if all the CO2 and N2 in the Earth’s crust were somehow liberated into the atmosphere, our planet would have an atmosphere very similar to Venus.

Venus is the easiest planet to get to from Earth, requiring the least amount of rocket fuel. There is so much we still don’t understand about how Venus transformed into a hellish world, and we would be well-advised to learn more about Venus because it may inform us about Earth’s future as well.

Tessera terrain covers about 7% of the surface of Venus. These highly deformed landforms, perhaps unique in the solar system, may allow us to someday sample the only materials that existed prior to the great resurfacing event.

COLORIZED TOPOGRAPHIC DATA OVERLAID UPON FORTUNA TESSERA TERRAIN IMAGE
In this radar image, blue represents the lowest elevations, white the intermediate elevations, and red the highest elevations. Source: Emily Lakdawalla, https://www.planetary.org/blogs/emily-lakdawalla/2013/02071317-venus-tessera.html .

If living organisms ever developed on Venus, the only place they could still survive today is 30 miles or so above the surface where the atmospheric temperature and pressure are similar to the surface of the Earth.

Even four billion years ago, Venus may have been too close to the Sun for life to develop, but if it did, Venus probably remained habitable up to at least 715 Myr ago.

Now for the bad news. All main-sequence stars, including our Sun, slowly brighten as they age, and their habitable zones move outward from their original locations. Our brightening Sun will eventually render the Earth uninhabitable, certainly within the next two billion years, and our water could be lost to the atmosphere and then space within the next 13o million years, leading to a thermal runaway event and an environment similar to that of Venus. Human-induced climate change could make the Earth uninhabitable for humans and many other species long before that.

One indication that water is being lost to space and surface warming is occurring is water vapor in the stratosphere. The more water vapor that is in the stratosphere, the more water is being forever lost to space and the greater the surface warming. Careful and continuous monitoring of water vapor levels in the Earth’s stratosphere is important to our understanding of climate change on Earth.

To conclude, Arney and Kane write:

“Venus teaches us that habitability is not a static state that planets remain in throughout their entire lives. Habitability can be lost, and the runaway greenhouse is the final resting place of once watery worlds.”

References

Arney, G., & Kane, S. 2018, arXiv e-prints, arXiv: 1804.05889

Bézard, B., & de Bergh, C. 2007, J. Geophys. Res., 112, E04S07, doi: 10.1029/2006JE002794.

Ostberg, C., & Kane, S. R. 2019, arXiv e-prints,arXiv: 1909.07456

Way, M.J. 2019, EPSC Abstracts, 13, EPSC-DPS2019-1846-1

Way, M. J., Del Genio, A. D., Kiang, N. Y., et al. 2016, Geophys. Res. Lett., 43, 8376

Smaller Portions, Please

Some facts about U.S.:

  • The average adult weighs 15 pounds more than 20 years ago
  • 40% of adults and 20% of children are obese
  • The average adult is eating ~300 calories more per day than in the 1970s
  • Beginning in 2015, more money is spent eating out than eating at home
  • Restaurant portion sizes have quadrupled since the 1950s

It’s true, we’re eating away from home more often, and the portion sizes we’re being served at restaurants are usually larger than they need to be. Have you ever had a totally satisfying meal at a restaurant that doesn’t leave you feeling like a beached whale afterwards? A well-prepared and well-presented meal does not have to be large to be loved.

Large portion sizes at restaurants are particularly a problem for those of us who are conditioned to eat everything on our plate, and who don’t like to take leftovers home.

Restauranteurs, please step up to the plate and fight obesity by making your standard portion sizes smaller. If a customer wants a larger portion, they should have to ask for it.

References

Briefing: The obesity epidemic. (October 18, 2019). The Week, 19(946), 12.

Keith Bechtol at UW Space Place

We are so very fortunate here in southern Wisconsin to have evening public lectures the 2nd Tuesday every month of the year at the University of Wisconsin Space Place, expertly organized by Jim Lattis. On Tuesday, November 12th, Clif Cavanaugh (retired physics and astronomy professor at the UW in Richland Center) and I made the trek (as we often do) from Spring Green-Dodgeville to the Space Place in Madison. This month, we were treated to an excellent presentation by Keith Bechtol, an Observational Cosmologist in the Physics Department at UW-Madison. His topic was The Big Picture: Science with Astronomical Surveys. Keith is an early career scientist with a bright future. His presentation was outstanding.

I’d like to share with you some of the highlights.

Before the talk, which is mostly about the Large Synoptic Survey Telescope (LSST), currently under construction in Chile and expected to see first light in 2020, I asked Keith about whether LSST would be renamed the Vera Rubin Telescope as was announced at AAS 234 in St. Louis this past summer. As it turns out, Keith has been a vocal advocate for naming LSST after Vera Rubin, though no final decision has yet been made.

Before I get into notes from the talk, I wanted to share with you the definition of the word synoptic in case you are not familiar with that word. The Oxford English Dictionary defines the word synoptic as “furnishing a general view of some subject; spec. depicting or dealing with weather conditions over a large area at the same point in time.” But rather than the traditional meteorological definition, here we are referring to a wide-field survey of the entire night sky visible from Cerro Pachón in Chile, latitude 30˚ S.

Keith first talked about how astronomical imaging is currently advancing along two fronts. The first is high-resolution imaging, as recently illustrated with first image of the event horizon of a black hole from the Event Horizon Telescope, where an amazing resolution of around 25 microarcseconds was achieved.

In general, the larger the telescope aperture, the smaller the field of view.

The Hubble Space Telescope’s Ultra Deep Field is only 3.1 arcminutes square

A survey telescope, on the other hand, must be designed to cover a much larger area of the sky for each image.

Not only can a survey telescope detect “anything that changes” in the night sky, but it also allows us to probe the large-scale structure of our universe. Three still-mysterious entities that are known to affect this large-scale structure are dark energy, dark matter, and neutrinos. Keith indicates that “these names are placeholders for physics we don’t yet fully understand.”

Dark energy, which is responsible for driving galaxies apart at an accelerating rate, is unusual in that it maintains a constant density as the universe expands. And its density is very low.

Supernovae are a very useful tool to probe the dark-energy-induced accelerating expansion of the universe, but in any particular galaxy they are exceedingly rare, so by monitoring large areas of the sky (ideally, the entire sky), we can discover supernovae frequently.

The mass distribution of our universe subtly affects the alignment and shapes of distant galaxies through a phenomenon known as weak gravitational lensing. Understanding these distortions and correlations requires a statistical approach looking at many galaxies across large swaths of sky.

Closer to home, small galaxies that have come too close our Milky Way galaxy are pulled apart into stellar streams that require a “big picture” approach to discover and map. The dark matter distribution in our Milky Way galaxy plays an important role in shaping these stellar streams—our galaxy contains about ten times as much dark matter as normal matter.

With wide-field surveys, not only do we need to cover large areas of sky, but we also want to be able to see the faintest and most distant objects. That latter property is referred to as “going deeper”.

The LSST will provide a dramatic increase in light gathering power over previous survey instruments. The total number of photons collected by a survey instrument per unit time is known as the étendue, a French word, and it is the field of view (in square degrees) × the effective aperture (in m2) × the quantum efficiency (unitless fraction). The units of étendue are thus m2deg2. Note that the vertical axis in the graph below is logarithmic, so the LSST will have a significantly higher étendue than previous survey instruments.

The largest monolithic mirrors in the world are fabricated at the Steward Observatory Mirror Lab at the University of Arizona in Tucson. The largest mirrors that can be produced there are 8.4 meters, and LSST has one of them.

Remember the Yerkes Observatory 40-inch refractor, completed in 1897? It has held the record as the largest lens ever used in an astronomical telescope. Until now. A 61.8-inch lens (L-1) and a 47.2-inch (L-2) have been fabricated for use in the LSST camera.

L-1, the largest lens ever produced, is the front lens of the LSST camera

LSST will utilize a camera that is about the size of a car. It is the largest camera ever built for astronomy.

The LSST camera will produce 3.2 gigapixel images. You would need to cover about half a basketball court with 4K TV screens to display the image at full resolution.

An image will be produced every 15 seconds throughout the night, every clear night, and each patch of sky will be reimaged every three nights. That is a HUGE amount of data! ~10 Tb of data each night. Fiber optical cable will transport the data from Cerro Pachón to the National Center for Supercomputing Applications in Urbana, Illinois, where it will be prepared for immediate use and made publicly available to any interested researcher. The amount of data is so large that no one will be downloading raw data to their local computer. They will instead be logging in to the supercomputer and all processing of the data will be done there, using open source software packages.

There are many data processing challenges with LSST data needing to be solved. Airplane, satellite, and meteor trails will need to be carefully removed. Many images will be so densely packed with overlapping objects that special care will be needed separating the various objects.

One LSST slide that Keith presented showed “Solar System Objects: ~ 6 million” and that piqued my interest, given my ongoing research program of observing stellar occultations by asteroids and trans-Neptunian objects for IOTA. Currently, if you endeavor to observe the highest probability occultation events from a fixed observatory location each night, you will be lucky to record one positive event for every ten negative events (no occultation). The reason for this is that our knowledge of the orbital elements of the small bodies of the solar system is not yet precise enough to accurately predict where stellar occultation events will occur. Gaia DR3, scheduled for the latter half of 2021, should significantly improve the precision of small body orbits, and even though LSST does not have nearly the astrometric precision of Gaia, it will provide many valuable astrometric data points over time that can be used to refine orbital elements. Moreover, it is expected that LSST will discover—with its much larger aperture than Gaia—at least 10 times the number of asteroids and trans-Neptunian objects that are currently known.

During the question and answer period after the lecture, I asked Keith what effect the gigantic increase in the number of satellites in Earth orbit will have on LSST operations (global broadband internet services provided by organizations like SpaceX with its Starlink constellation). He stated that this definitely presents a data processing challenge that they are still working on.

An earlier version of Keith’s presentation can be found here. All images in this article except the first (OED) come from Keith’s presentation and have not been altered in any way.

References

Bechtol, Keith, “The Big Picture: Science with Astronomical Surveys” (lecture, University of Wisconsin Space Place, Madison, November 12, 2019).

Bechtol, Ellen & Keith, “The Big Picture: Science and Public Outreach with Astronomical Surveys” (lecture, Wednesday Night at the Lab, University of Wisconsin, Madison, April 17, 2019; University Place, Corporation for Public Broadcasting, PBS Wisconsin).

Jones, R. L., Jurić, M., & Ivezić, Ž. 2016, in IAU Symposium, Vol. 318, Asteroids: New Observations, New Models, ed. S. R. Chesley, A. Morbidelli, R. Jedicke, & D. Farnocchia, 282–292. https://arxiv.org/abs/1511.03199 .

Oxford English Dictionary Online, accessed November 17, 2019, https://www.oed.com/ .

Remembering Comet Holmes

Twelve years ago today, Comet Holmes (17P) brightened from magnitude 16.5 to 2.6, forming a right triangle with Mirfak (α Persei) and δ Persei, opposite to Algol. Here is what I wrote in The Sky This Week at that time.


TSTW 10/25/07

Comet Holmes Bursts on the Scene!

Who ever said astronomy isn’t exciting? Sure, much of what we observe in the cosmos seems predictable and unchanging—but then something unexpected happens and we are scrambling to get a front-row seat and our lives are thrown into an exhilarating tizzy for a few hours or days. Whether it be an unexpected auroral display, a meteor fireball, a nova, supernova, or comet, the result is the same: it is exciting to be an astronomer, to be attuned to a universe that existed long before we were born and that will be here long after we are gone. That, to me, is comforting.

Very early Wednesday, October 24, a 16th-magnitude short-period comet presently in Perseus by the name of Holmes brightened about 14 magnitudes from 16.5 to 2.6 in little more than 12 hours: a brightness increase of 363,000 times! While such a cometary outburst was unexpected, it is not unprecedented. From time to time, solar heating (greatest when a comet is near perihelion) must cause pressure to build up inside a comet as subsurface ices volatilize. Eventually, the pressure builds up until it explodes through the surface of the comet, spewing gas and dust into space and exposing fresh material to solar radiation. Sometimes, this process is so violent that the comet breaks into multiple fragments.

Comet Holmes (17P) is one of the so-called “short period” comets, meaning it orbits the Sun in less than 200 years or has been observed at more than one perihelion passage. Comet Holmes orbits the Sun every 6.9 years, ranging from just inside the main part of the asteroid belt (2.1 AU) to the orbit of Jupiter (5.2 AU). No doubt Comet Holmes’ original orbit has been substantially altered by the gravitational influence of Jupiter. Comet Holmes is presently 2.5 AU from the Sun (230 million miles) and 1.6 AU from the Earth (150 million miles), having just passed perihelion on May 4, 2007.

Comet Holmes was discovered during its last outburst, which occurred on November 6, 1892 by English amateur astronomer Edwin Holmes (1839-1919). It was observed again in 1906, but was then lost until being recovered in 1964. It has since been observed near perihelion at every return.

The recent outburst of Comet Holmes may be one for the record books. I am not aware of any other comet outburst being recorded where the comet brightened by as much as 14 magnitudes in less than a day! Fortunately, the first two nights after the outburst the sky was beautifully clear here. The first night, October 24, Comet Holmes looked like a star to the unaided eye. In binoculars, it looked like a tiny yellow or orange planetary nebula, only slightly bigger than a star, and of uniform brightness. The following night, October 25, it still looked like a star to the unaided eye, but in binoculars it was larger than the previous night. The total brightness had not diminished. In the telescope, the comet was truly spectacular, made all the more amazing considering how the comet was only 43° away from the closest full moon of the year! The round coma contained a bright off-center fan-shaped wedge with a brilliant tiny pointlike nucleus. There was definitely evidence of concentric, spiraling shells of material opening outward from the center of the coma to the outermost parts of the coma.

You have just got to get out to see this comet! And as often as possible! Here is an ephemeris for Dodgeville for the coming week.


TSTW 11/1/07

Comet Holmes (17P)

Comet Holmes slowly moves towards Mirfak this week, an impressive binocular and telescopic object in Perseus. It is easily visible to the unaided eye, too, as a small fuzzball on the Capella-side of Perseus.

Sunlight and solar wind particles are hitting the comet on the north-northeast side, and photographs show the comet is sharp edged there. The opposite, south-southwest side is ragged, with ionized gas streamers spreading out in that direction in long-exposure photographs.

Whatever tail the comet has is pretty much hidden behind it, as our viewing angle (known as the phase angle) diminishes from 15° to 13° this week. The phase angle is the Sun – Comet – Earth angle. A phase angle of 0° would mean we are looking directly down the tail (least favorable, maximum foreshortening). A phase angle of 90° would mean we are looking perpendicular to the tail (most favorable, no foreshortening).

Prime time for observing the comet is pretty much all night, with the comet transiting the celestial meridian at 2:05 a.m. CDT at the beginning of the week, and at 12:30 a.m. CST by the end of the week. Look at it every clear night, because surprising changes can and do occur. Don’t miss it! It may be a while until something like this happens again. The last time Comet Holmes went into a major outburst was 115 years ago!