By Dale Hawkins
"The 'Dog Days' of Summer"
Sky Watch keeping an eye on the horizon
Share
Tweet
The Ancient Greeks, Romans, and Egyptians called the hottest days of summer the ‘Dog Days’ of summer. To me they’re a sizable chunk of the ‘Hundred Days of Hell.’ To explain:
Those of you who know me are aware of my serious aversion to heat. I respect the sun as being vital to all life on earth, but we are far from being close friends. Thus, you can well understand that summer is my least favorite season. While you’re enjoying the Mountain Festival and getting a suntan, I’m hunkered down in my air conditioned ‘igloo’ cooling my heals until astronomy time arrives. Fortunately, I’m a retired submariner and can therefore psychologically manage such a lifestyle (although I’m keenly aware of the human opportunity cost of my sequestration).
My condition is of course not unique. In fact, I come by my problem honestly; my mother is the same way (although I’m happy to say that my daughter is normal, thanks to a healthy dose of Costa Rican genes).
I have designated the ‘Hundred Days of Hell’ as extending from Flag Day (June 14) to the autumnal equinox (usually September 22nd or 23rd). One hundred days; that’s not much longer than a descent submarine patrol. No doubt that’s one reason I enjoy following Dodger baseball; no one game is critical – it’s how well you come out after 163 games that counts!
When fall arrives, most people lament the demise of yet another summer. However, I and my fellow commiseraters start to really come alive. By late September, there’s only a week left of the Major League Baseball regular season with playoff berths at stake, and the politicos are really cranked up with election fever. Yes, there will still be some hot days ahead, but we can sneer at them, for the nights will be longer than the days.
When you’re toughing out a long-term assignment, it’s psychologically important to break down progress into smaller pieces. Marking these occasions can help the team (even teams of only one) to keep the proper amount of energy focused on the proper goal (‘Any excuse to party!’). In baseball, it’s the ‘All-Star break;’ in the Submarine Force, we call it ‘Hump Day.’
I manufacture all manner of milestones to help me mark progress toward the goal of the Equinox! A number involve the rising and setting of various stars. For instance, it has been noted that at first light (04:04) on the morning after my birthday (June 18th), the star Capella appears above the houses from my backyard.
This brings us back to dogs. What do dogs have to do with all of this!? Well, I’ll tell you...
Sirius was an important star to the Ancient Egyptians, Greeks, Romans, and no doubt other ancient civilizations. It’s the brightest star in our nighttime sky. At 8.6 light-years, it’s also one of the closest. Perhaps most significantly, the appearance of Sirius was used to predict when the Nile River would flood, which was critical to agricultural and other planning.
There is a period during which Sirius is invisible to the unaided eye because it is too close to the sun. On July third, Sirius is in conjunction with the sun (that is, as close as it appears to get to the sun for this orbit). This marks the first ‘Dog Day of Summer.’ As the earth moves around the sun, Sirius appears to move away. It starts to become visible low in our morning twilight on or about August eleventh, marking the end of the Dog Days of Summer.
The name Sirius means “dog star,” by which it is known throughout a surprising number of cultures. Thus, we still speak of the “Dog Days of Summer.” The ancients believed that the intense light of Sirius, the brightest star in our sky after the sun, added its own heat to the sun’s, thus making for hotter days. That’s an interesting notion, but they clearly had no real idea of how far away Sirius really is! It’s awesome--and humbling–to realize how much more we now know than the best of the Ancients.
All eyes have of course been on Pluto. Here’s some of the latest. However, as I mentioned in my last article, we need to be patient. New Horizons cannot move its instruments or its antenna; the whole spacecraft has to be turned. That means that at any given moment the probe is either gathering information or sending it back to us–not both. That’s why we gave it massive storage capability.
New Horizons phoned home after passing Pluto and Charon as scheduled and reported all is well. It also downloaded the high-resolution image of Plutonian mountains that you see here just to prove it could really do it and to give us a tiny taste of much that is yet to come.
For the time being, the probe will continue to gather data (including images) as it recedes from the Plutonian system, after which it will take about sixteen (16!) months to download all of its files to us.
The images New Horizons has sent back are of course stunning– naturally; aren’t they always? We’re so used to NASA sending back stunning images that we fail to be stunned anymore! Curiosity is still exploring Mars, Cassini is still surveying the Saturnian system, and Dawn is sending back ever-higher resolution images of Ceres as it spirals into an ever-tightening orbit. It’s no surprise that the New Horizons mission is performing “nominally.” But mark this in your book: With the success of Dawn and New Horizons, NASA has completed the initial survey of our Solar System.
What amazes me, as an electronics engineer, is our ability to communicate with these spacecraft. Johns Hopkins’ Applied Physics Laboratory (JHAPL) is of course to be congratulated on constructing an excellent spacecraft and executing a near-flawless mission. However, a key link, and nearly unsung hero in this adventure, is JPL’s Deep Space Tracking Network.
Why does it take sixteen months to download New Horizons’ data? Because it’s very far away and the probe has a very small power supply (since it’s so far from the sun, New Horizons cannot use solar electricity for power; it must use a radioisotope thermoelectric generator (RTG). Even though it has a way-cool-sounding name and uses plutonium for power, it only puts out the power of three 60-watt-light bulbs. That’s precious little power for beaming messages half-way across the Solar System!
New Horizons is now some five billion kilometers from the earth, which means radio signals take well over four hours to get from there to here. Now, that’s what I call a stretch! To even make it possible for the probe to download its precious cargo over such a distance with so little power means two big things:
1. New Horizons must take its sweet time (When one is trying to whisper instructions on how to build an aircraft–in the dark–you take it nice and slow!); and...
2. The antennas back on the earth must be huge and be connected to extremely sensitive radio receivers.
New Horizons will indeed take its sweet time–sixteen months. NASA/JHAPL will release updates on a nearly continuous basis throughout this download period, and well beyond as they continue to process information.
What really fascinates me is the array of huge dish antennae and their associated electronics that are capable of listening to New Horizons and the other space probes careening around the Solar System. Operated by Caltech’s Jet Propulsion Laboratory in Pasadena, most of the antennae are located at Fort Erwin, north of Barstow.
As Dr. Carl Sagan so eloquently put it, our Deep Space Tracking Network deciphers spacecraft signals that have “less energy than that of a snowflake striking the ground,” yielding images and data that stagger the imagination.
You can stay abreast of the New Horizons download at http://www.pluto\jhuapl.edu. Of special interest will be the decision on which Kuiper Belt object the probe will visit next, which is expected by the end of the year.
Saturn rules the night sky throughout August. Its rings remain broadly tilted toward us. Saturn is also approaching quadrature on August 21st; that is, Saturn, the sun and the earth form a ninety degree angle. This means that Saturn casts an off-center shadow across Saturn’s rings, which makes for a more three-dimensional appearance.
August 12-13: With the moon nicely hidden, the Perseid Meteor Shower should be a goodie this year. Its peak (usually at least one hundred meteors per hour) is predicted for approximately 1a.m. (local time) on Thursday morning Aug. 13. With no moon, that’s about as optimal as you can get! The Perseids are the remnant debris of Comet109/P Swift-Tuttle, which will be back to see us in 2122.
August 22: Join us at Aviator Park at the Tehachapi Airport for our first annual star party! Our focus will be on the first-quarter moon, Saturn, and how to use telescopes and binoculars. See you there!
Sunrise/Sunset: 6:03 a.m./7:57 p.m.
