THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet <http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A> 70 Falmouth Street Portland, Maine 04103 43.6667° N 70.2667° W Altitude: 10 feet below sea level Founded January 1970 Julian Date: 2459054.16 2019-2020: CLXXXIV THE DAILY ASTRONOMER Friday, July 24, 2020 Remote Planetarium 71: Week 15 Quiz and Weekly Skywatch Exoplanets and aliens were this week's topics. Or, more correctly, exoplanets and the search for aliens were this week's topics. Naturally, those will be the question topics, as well. Five questions from each article. We won't ask quiz questions based on the quiz we posted on Monday. *1. What does SETI stand for?* (No choices for this question.) *2. In terms of light-time, how far away is the most distant human-made object?* a. 20.6 light hours b. three light weeks c. seven light months d. 1.1 light years *3. Radio broadcasts transmitted from Earth travel through space at __________________* a. the speed of sound b. one quarter light speed c. one half light speed d. light speed *4. Which of the following chemical signatures might indicate the presence of life on an exo-planets? (Could be more than one.)* a. water vapor b. methane c. molecular oxygen d. iron *5. How can astronomers determine the chemical constituents of an exo-planet's atmosphere?* a. they can't. They can make an educated guess about the chemicals based on the planet's mass. b. the chemicals present in the parent star are always present in the exo-planet's atmosphere c. the star's light passes through the atmosphere, the gases of which absorb light at different wavelengths. This spectrum is used to identify the gases present in the atmosphere. d. none of the above. *6. What value can one estimate through use the Drake Equation?* a. the number of advanced civilizations in the Milky Way Galaxy b. the number of aliens in the solar system c. the ratio of stars with aliens to those without d. the percentage of planets capable of harboring life *7. What is the rate of star formation in the Milky Way Galaxy?* a. 3 solar masses a year b. 5 solar masses a year c. 8 solar masses a year d. 11 solar masses a year *8. The Milky Way Galaxy likely contains approximately how many potentially habitable worlds?* a. 10 million b. 200 million c. 1.6 billion d. 40 billion *9. What is defined as a "habitable zone?" of a star?* a. a region in which temperatures are neither too high nor too low b a region from the star's surface to 100 AU (astronomical units) c. a region in which water could gather as a liquid on a planet's surface d. both a and c e. all of the above f. none of the above *10. A scientist derives a N value of 10 million in the Drake Equation. Consequently, the galaxy would have to have _______________ advanced civilizations.* a. 10 million b. less than 10 million c. more than 10 million d. none of the above *11. Where is the nearest exo-planet?* a. 4.2 light years away b. 8.1 light years away c. 11.2 light years away d. 20 light years away *12. How far away is the most distant exo-planet yet discovered? (The finding is still a matter of dispute.)* a. 8,000 light years b. 14,000 light years c. 38,000 light years d. 2.2 million light years *13. How many exo-planets have been directly imaged so far?* a. none b. 5 c. 15 d.24 *14. Which one of the following is NOT a main types of planet orbit within a binary star system?* a. S type b. P type c. T type d. W type *15. According to a 2019 survey, approximately how many binary star systems have planets within a 1600 light year radius?* a. 50 b. 85 c. 123 d. 176 *ANSWERS* *1. What does SETI stand for? * The Search for Extraterrestrial Intelligence. *2. In terms of light-time, how far away is the most distant human-made object?* a. 20.6 light hours The Voyager 1 craft, launched in September 1977, is nearly 150 times farther from the Sun than Earth. A light beam leaving Earth would require slightly less than 21 hours to reach the Voyager 1 spacecraft. Considering that Proxima Centauri, the closest star system to the Sun, is 4.2 light years away, humans haven't yet attained the technological development necessary for interstellar travel. *3. Radio broadcasts transmitted from Earth travel through space at __________________* d. light speed All electromagnetic radiation travels at light speed when propagating through a vacuum. Radio broadcasts form a "shell" that expands away from our planet through outer space. Alien astronomers observing from any star system within that shell could detect these signals and realize that life exists on our planet. *4. Which of the following chemical signatures might indicate the presence of life on an exo-planet? (Could be more than one.)* a. water vapor b. methane c. molecular oxygen Based on our knowledge of Earth's atmosphere, we know that methane and molecular oxygen are both indicative of metabolic activity. As water is vital to every life form, the presence of water vapor on an exo-planet might indicate that the planet contains the conditions that are conducive to life's development. *5. How can astronomers determine the chemical constituents of an exo-planet's atmosphere?* c. the star's light passes through the atmosphere, the gases of which absorb light at different wavelengths. This spectrum is used to identify the gases present in the atmosphere. Each molecule absorbs light at specific wavelengths. By examining the absorption lines, astronomers can identify the gases present in an exo-planet's atmosphere. *6. What value can one estimate through use the Drake Equation?* a. the number of advanced civilizations in the Milky Way Galaxy The Drake Equation combines our knowledge of stars and planets with speculations about life's resilience. *7. What is the rate of star formation in the Milky Way Galaxy?* a. 3 solar masses a year On average, three solar masses of material become incorporated into stars each year. That value is not necessarily equal to three stars. They could form more stars that are less massive than the Sun. *8. The Milky Way Galaxy likely contains approximately how many potentially habitable worlds?* d. 40 billion An immense number. Realize that the year 1988 was a billion seconds ago. If we went back in time one billion minutes, we'd be in the year AD 119! If even a small fraction of those worlds actually contained life, we'd have millions of life-bearing worlds in our galaxy. *9. What is defined as a "habitable zone?" of a star?* a. a region in which temperatures are neither too high nor too low c. a region in which water could gather as a liquid on a planet's surface d. both a and c The habitable zone is the area around a star which might have conditions conducive to life's development. A planet would need to be close enough to its parent star so as to receive ample heat and light, but not so close that the temperatures render the planet inhospitable. *10. A scientist derives a N value of 10 million in the Drake Equation. Consequently, the galaxy would have to have _______________ advanced civilizations.* d. none of the above The N value derived from the Drake Equation is mostly guesswork that has no bearing on the actual value of the galaxy's advanced civilizations. Another scientist could derive a value of 20 million and another 3 million. We don't have nearly enough information available to know how many advanced civilizations exist in the Milky Way *11. Where is the nearest exo-planet?* a. 4.2 light years away Astronomers have found two planets around Proxima Cenaturi, the closest star to the Sun. Although one of these planets is within the star's habitable zone, it is also subjected to strong stellar winds that might render it inhospitable to life. *12. How far away is the most distant exo-planet yet discovered? (The finding is still a matter of dispute.)* d. 2.2 million light years It is possible that the microlensing event PA-99-N2 was caused by a planet microlensing the light of a more distant star. Some astronomers wonder, however, if the foreground object was instead brown dwarf. However, this object could be the most distant exo-planet yet detected. *13. How many exo-planets have been directly imaged so far?* d.24 Directly imaged exo-planets follow wide orbits around their parent stars. Also, these stars are relatively close to Earth. With one exception, all these directly imaged planets are less than 1000 light years from Earth. *14. Which one of the following is NOT a main types of planet orbit within a binary star system?* d. W type A planet following an S-type orbit revolves around only one of the stars within a binary system. A planet following a P-type orbit revolves around both stars. A planet following a T-orbit is located at either one of the L-points within the orbit of the secondary star. *15. According to a 2019 survey, approximately how many binary star systems have planets within a 1600 light year radius?* d. 176 Planets are likely very common, even within multiple star systems. ______________________________________________________________ *SKYWATCH HOTLINE # 3:* July 24 – 30, 2020 On July 24 the Sun will rise at 5:22 a.m. and set at 8:12 p.m, giving us 14 hours and 50 minutes of daylight, a 36 minute decrease since the summer solstice. On July 30, the Sun will rise at 5:29 a.m. and set at 8:06 p.m, providing us with 14 hours and 37 minutes of daylight. The Sun is passing through the constellation Cancer the Crab this week. By week’s end it will almost be directly in front of the Praesepe Star Cluster. At week's beginning the moon will be progressing through the waxing crescent phase. The moon will reach the first quarter point on July 27th. On that date, the moon will rise at 1:25 p.m. and set at 12:17 a.m. the following morning. The moon will then pass through the waxing gibbous phase toward the end of the week. The moon will be full on August 3rd. *Mercury* rises around 3:55 a.m at week’s beginning and will be visible briefly in the eastern pre-dawn sky before being obscured by the intensifying twilight, Mercury reached greatest western elongation on July 20th and will now appear to move closer to the Sun. *Venus,* as always the brightest planet, currently occupies the Taurus constellation and will rise at 2:25 a.m. at week’s beginning. The optimal time to view Venus is between 3 - 5 a.m, when the brilliant planet remains visible against the pre-dawn glow. It was at its maximum brightness of the year on July 10th. Though slightly dimmer now at magnitude -4.3, Venus will still be 15 times brighter than Sirius. *Mars* rises by 11:19 p.m. As it is currently located almost precisely on the celestial equator within the constellation Cetus, Mars rises nearly due east and will remain an eastern evening sky object through the rest of the night. At magnitude -0.9, Mars is now brighter than any night sky star except Sirius, which is not currently visible. Mars will continue to rise earlier and grow brighter as it approaches its next opposition on October 13, 2020. *Jupiter *reached opposition on July 14th and will now slowly move away from Earth and grow gradually dimmer. However, at magnitude -2.6, Jupiter outshines all the stars and planets, save Venus. It will rise in the eastern sky at 7:30 p.m. at the beginning of the week and it will set just before 4:30 a.m. Jupiter reaches opposition again on August 19, 2021. *Saturn *reached opposition on July 20th and attained its maximum brightness at that time. Saturn is also now moving away from Earth and will become dimmer as a consequence. However, at magnitude 0.1, Saturn remains brighter than Vega and will rise at 7:54 p.m. at week’s beginning. Both Jupiter and Saturn are currently passing through the constellation Sagittarius the Archer. Yet again Comet NEOWISE is the celestial object of the week! Named for the Near-Earth Object Wide-Field Infrared Survey Explorer that astronomers used to discover this icy interloper on March 27th. Though dimmer at magnitude 2.5, Comet NEOWISE is higher in the northwestern evening sky and can be see south of the Big Dipper. The Comet is fading as it moves away from Earth. The comet reached perigee, its closest point to Earth, on July 23. On that date it passed 64 million miles from our home planet. [image: skychart.png] We’re expecting the peaks of two minor meteor showers this week: the alpha Capricornids on July 26th and the July Gamma Draconids on July 28th. Both events should produce fewer than 10 meteors an hour at maximum. The July Gamma Draconid radiant is located about 12 degrees north of Vega, the brightest star in Lyra the Harp. The Perseid meteor shower has begun, but not in earnest. The Perseids peak on August 11th. The brightest fly over of the International Space Station occurs this week on July 28th. The ISS will rise at 10:08:51 p.m. and attain its maximum altitude of 79 degrees at 10:14:19 p.m. At that time the ISS will shine at magnitude -3.8, more than three and a half times brighter than Jupiter! The International Space Station then will vanish into the shadow at 10:14:47 p.m. During this passage, the ISS will appear to slice across the Big Dipper’s handle, Draco the Dragon and Cygnus the Swan. [image: PassSkyChart2.png] To subscribe or unsubscribe from the Daily Astronomer: https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A= <https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A=1>