June 18, 2023

Bakersfield sky in late June 2023, emphasis on the Big Dipper

Saturday, June 18, 2023

Happy Father’s Day to all of the fathers, whether they are fathers by biology or by the role and care they provide in our lives! In three days on June 21, the season of summer will officially begin with the June solstice. Since the astronomical definitions of the seasons (for our calendars) use the precise position of the sun, we can be precise in our start for summer: 7:58 a.m. Pacific Daylight Time. 

The sun reaches its northernmost trek among the stars at that time. June 21 will be our day with the longest length of daylight, so we say it’s the longest “day” of the year, even though a day is actually a full spin of Earth that includes a time of night. The sun’s energy will hit Kern County at its most direct, steepest angle on this day. 

However, the hottest days of summer will be later in the summer because it takes a bit of time for land and water to warm up. This past spring has had an unusual number of very pleasant days where the evenings cooled off enough to open up the windows. I had to turn on the AC on only one day this spring—a big difference from several of the previous years when the AC unit was running steadily by early May! (You know someone’s a long-time resident of Bakersfield if they revel about cool temperatures in May and June.)

In the evening of June 21, the waxing crescent moon, brilliant Venus, and orange-red Mars will form a tight triangle low in the west after sunset. The pairs of Venus and Mars and the moon and Venus will be close enough to fit together in the same field of a pair of binoculars but the hypotenuse of the triangle—the moon to Mars—will probably be too far apart to fit in the same field of the binoculars. The moon will be at first quarter on the night of June 25/26. The following night, the moon will be near Spica, the brightest star of Virgo.  

Venus and Mars have been steadily drawing closer together and reach their closest approach on the last day of the month. At that point they’ll be 3.5 degrees from each other on the sky (almost two knuckles at arm’s length). By the last day of the month, the moon will be a waxing gibbous over half-way across the sky next to Antares, the orange-red heart of Scorpius. 

If you’re looking for a summer project, how about helping the TESS team find exoplanets? The Planet Hunters TESS project uses the superior capability of humans to see patterns in noisy data, much better capability than what we can program a computer to do (so far). TESS stands for “Transiting Exoplanet Survey Satellite”. TESS is the follow-up to the Kepler mission which found thousands of exoplanets. 

Both TESS and Kepler find exoplanets by staring steadily at nearly two hundred thousand stars  at a time to find the very small percentage of exoplanets whose orbits are perfectly aligned with our line of sight. If the exoplanet orbit is aligned with our line of sight, we’ll see the exoplanet pass in between us and the star, temporarily blocking out a tiny fraction of the star’s light—a transit. The bigger the exoplanet, the more of the star’s light is blocked. 

If you make a plot of the star’s brightness over time (a light curve), you’ll see a small dip in the brightness. If the dip in brightness is caused by something orbiting the star, the dip will repeat itself. Now most star systems come in pairs, so it is quite possible that the dip in brightness we see could be caused by another star instead of an exoplanet. 

The stars we’re looking at are quite dim and have some intrinsic variability already and could even have star spots on the surface, akin to the dark sunspots that sometimes form on our sun’s surface. What this all means is that the light curve data can be a bit noisy with random fluctuations and non-exoplanet wiggles and dips in it. 

The transit hunter teams have developed very sophisticated computer software to sift through all of the thousands of light curve data. Of the 5438 exoplanets that have already been found (at the time of writing), about 75% have been found using the transit technique. About 19% have been found by measuring the periodic wobble of a star as a large exoplanet gravitationally tugs on it. The other 6% have been found using other detection techniques. 

Anyway, the computer algorithms are very good at finding the periodic dips but humans are even better. Human brains are superior at finding patterns that the automated computer systems may miss. Planet Hunters volunteers have already found over 100 new planetary systems in the older Kepler data and the TESS team would sure appreciate your help! Please visit the Planet Hunters TESS project web page for more information. You can also do a  Google/Bing search of “Planet Hunters TESS” also works fine.

I hope you’ll be able to experience a truly dark sky filled with thousands of stars this summer!

Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com